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1
Mjör, Ivar A. "Dentin permeability: the basis for understanding pulp reactions and adhesive technology". Brazilian Dental Journal 20, n. 1 (2009): 3–16. http://dx.doi.org/10.1590/s0103-64402009000100001.
Abstract (sommario):
Permeability involves the passage of fluids, ions, molecules, particulate matter and bacteria into and through a substance or tissue under different and varying conditions. The permeability of the dentin is essential to support the physiology and reaction patterns of the pulp-dentin organ. Nutrients and impulses are transported from the pulp via the odontoblast process and the contents of its tubules maintain the dentin as a vital tissue. However, the main interest of this paper focuses on penetration from the outside towards the pulp rather than from the pulp towards the outside. The present overview centers on the dentinal tubules; how they are formed and how they change as a result of normal and abnormal function, age, and pathological processes and the effect of these processes on the permeability of dentin. Particular attention is focused on the patency of the dentinal tubules.This overview is largely based on the author’s own research, clinical insights and active participation in continuing dental education over the last 50 years. It is not a review of the literature related to the permeability of dentin. Rather it presents interpretation of results related to the permeability of dentin based on experience and opinions acquired over a lifetime in dental research.
2
Gevkaliuk, N. O., I. M. Martyts, V. M. Mykhailiuk, M. Y. Pynda, V. Y. Pudiak e V. Y. Krupei. "Quantity and diameter of dentinal tubules of human teeth and teeth of experimental animals according to scanning electron microscopy data". Regulatory Mechanisms in Biosystems 14, n. 4 (24 novembre 2023): 609–16. http://dx.doi.org/10.15421/022388.
Abstract (sommario):
Insight into the interrelation between the structure and mechanical properties of dentin of a tooth is crucial for prevention and treatment of oral cavity diseases. The study of the structure of dental dentin is important for understanding the pathogenetic mechanisms of the spread of cariogenic microflora in progressive dental caries to the pulp and periodontium, as well as for the interpretation of the results of studies of dental dentin-adhesive materials. The in vitro research presented here involved the examination of coronal dentin in 46 intact teeth from rats, cats, dogs, and humans at various distances from the pulp chamber, with a focus on the quantity and diameter of dentinal tubules. The calculations were based on the analysis of 155 scanning electron microscope photographs of the enamel surface and pulp chamber wall. The researchers calculated the quantity and diameter of dentinal tubules per unit area, which they measured at various distances from the pulp chamber. It was found that dentinal tubules are the widest near the pulp chamber wall, where the average diameter ranged from 1.7 to 2.8 µm. The highest values were found in premolars of young humans and the lowest - in the incisors of rats. In the middle portion of the dentin, the diameter of dentinal tubules ranged from 1.0 to 13.3 µm, while at the periphery, it was 0.6–0.9 µm. The highest density of dentinal tubules per unit area was found closest to the pulp horn, and the lowest was in the enamel region. Near the pulp chamber wall, the average density of dentinal tubules ranged from 50 000 to 90 000/mm², in the middle of the dentin, it ranged from 37 000 to 50 000/mm², and at the periphery, it ranged from 10 000 to 25 000/mm². All examined teeth exhibited straight dentinal tubules, except for the rats’ incisors, which showed local irregularities. A comparison was made based on the quantity and width of dentinal tubules in the examined animals and humans.
3
Dauphin, Y., e C. T. Williams. "Chemical composition of enamel and dentine in modern reptile teeth". Mineralogical Magazine 72, n. 1 (febbraio 2008): 247–50. http://dx.doi.org/10.1180/minmag.2008.072.1.247.
Abstract (sommario):
AbstractElemental distribution maps by wavelength-dispersive electron microprobe of enamel and dentine in modern crocodile teeth illustrate variations in both minor and major elements. Mg has the largest difference between the enamel and dentine, being enriched in the dentine. Mg, Ca and P are not homogeneously distributed in the dentine, but their distribution reflects changes during growth of the teeth. These variations in compositional differences of teeth from modern samples potentially can assist in establishing growth rates in fossil teeth samples, and thereby provide information on the physiology of extant species.
4
Augustin, Paul, Lüthy e Schärer. "Perfusing dentine with horse serum or physiologic saline: its effect on adhesion of dentine bonding agents". Journal of Oral Rehabilitation 25, n. 8 (agosto 1998): 596–602. http://dx.doi.org/10.1046/j.1365-2842.1998.00276.x.
5
Pashley, DH. "Dentin-Predentin Complex and Its Permeability: Physiologic Overviwe". Journal of Dental Research 64, n. 4 (aprile 1985): 613–20. http://dx.doi.org/10.1177/002203458506400419.
6
Kabartai, F., T. Hoffmann e C. Hannig. "The physiologic sclerotic dentin: A literature-based hypothesis". Medical Hypotheses 85, n. 6 (dicembre 2015): 887–90. http://dx.doi.org/10.1016/j.mehy.2015.09.016.
7
Baldión, Paula A., Myriam L. Velandia-Romero e Jaime E. Castellanos. "Odontoblast-Like Cells Differentiated from Dental Pulp Stem Cells Retain Their Phenotype after Subcultivation". International Journal of Cell Biology 2018 (2018): 1–12. http://dx.doi.org/10.1155/2018/6853189.
Abstract (sommario):
Odontoblasts, the main cell type in teeth pulp tissue, are not cultivable and they are responsible for the first line of response after dental restauration. Studies on dental materials cytotoxicity and odontoblast cells physiology require large quantity of homogenous cells retaining most of the phenotype characteristics. Odontoblast-like cells (OLC) were differentiated from human dental pulp stem cells using differentiation medium (containing TGF-β1), and OLC expanded after trypsinization (EXP-21) were evaluated and compared. Despite a slower cell growth curve, EXP-21 cells express similarly the odontoblast markers dentinal sialophosphoprotein and dentin matrix protein-1 concomitantly with RUNX2 transcripts and low alkaline phosphatase activity as expected. Both OLC and EXP-21 cells showed similar mineral deposition activity evidenced by alizarin red and von Kossa staining. These results pointed out minor changes in phenotype of subcultured EXP-21 regarding the primarily differentiated OLC, making the subcultivation of these cells a useful strategy to obtain odontoblasts for biocompatibility or cell physiology studies in dentistry.
8
Sharma, Priyanka, Shalini Garg, Abhishek Dhindsa, Neetu Jain, Sakshi Joshi e Anil Gupta. "Effect of chlorhexidine gluconate as hemostatic agent in healing and repair after mineral trioxide aggregate vital pulp therapy in young permanent teeth – A clinical study". Indian Journal of Physiology and Pharmacology 65 (25 febbraio 2022): 222–28. http://dx.doi.org/10.25259/ijpp_302_2021.
Abstract (sommario):
Objectives: The aim of the study was to evaluate the clinical success of mineral trioxide aggregate (MTA) partial pulpotomy as a definitive procedure in deeply carious permanent posterior teeth using 0.12% chlorhexidine (CHX) gluconate or normal saline as hemostatic agents. Materials and Methods: A pilot randomized control clinical trial was conducted on subjects with a deep carious lesion on 20 immature posterior teeth of subjects (10.8 ± 2.62 years). Caries and the superficial layer of exposed pulp were removed and then flushed with 0.12% CHX or saline solution. Gray MTA was placed, followed by resin-modified glass ionomer and composite. Results: 12 months follow-up showed 100% clinical and 90% radiographical success in both groups. Dentine Bridge was formed 90% in both the study and control group, which showed MTA partial pulpotomy is an effective procedure (P = 0.000). Conclusion: MTA partial pulpotomy using 0.12% CHX gluconate as a hemostatic agent for the treatment of deeply carious immature permanent posterior teeth appears to increase the radiographic rate of formation of dentin bridge as compared to the normal saline.
9
Benoît, R. "Analyse génétique et physiologique". Revue d'Orthopédie Dento-Faciale 52, n. 4 (ottobre 2018): 351–72. http://dx.doi.org/10.1051/odf/2018029.
Abstract (sommario):
Les gènes du développement ont d'abord été mis en évidence chez la drosophile en 1950 (gène HOM), puis chez la souris en 1970 (gènes Hox). Ces gènes codent pour la mise en place de « champs », puis de populations cellulaires, puis de « systèmes composites ». Au cours de l'évolution, le cerveau et les cellules des crêtes neurales sont responsables, par l'intermédiaire de ces gènes et de leurs protéines du développement des divers systèmes composites du crâne et de la face et de leurs fonctions. Nous isolerons le système dentaire, le système musculaire, avec le système squelettique comme soutien avant intégration. Par des exemples cliniques différents nous proposerons une analyse génétique et fonctionnelle.
10
Shadab, Munwar Baloch, Sana Javed Khoso, Faiz Muhammad Khoso, Sajid Ali Majeedano e Fida Baloch. "The Physiological Role of Parathyroid Hormone and Serum Calcium in Odontogenesis Stunting Children; Cross-sectional Analysis of Children Attending Dental OPD and Paediatric Ward at LUMHS". Annals of PIMS-Shaheed Zulfiqar Ali Bhutto Medical University 13, n. 4 (9 gennaio 2024): 472–76. http://dx.doi.org/10.48036/apims.v13i4.1001.
Abstract (sommario):
Objectives: To determine serum PTH and serum calcium levels among children with delayed eruption of permanent teeth, attending the dental OPD at LUMHS.
Methodology: A cross-sectional study was conducted with the assistance of the Physiology Department, LUMHS, in collaboration with the Clinical Ward, Pediatric and Dental Wards, and D-R Lab, LUMHS, from March to August 2022. Children up to 18 years old, corresponding to the period of active odontogenesis and growth, diagnosed with odontogenesis stunting characterized by delayed or disrupted tooth development, as confirmed by clinical examination and radiographic imaging, visiting the dental outpatient department (OPD) were included. Blood samples for PTH and serum calcium levels were obtained with the informed consent of parents. Parathyroid Hormone was considered normal from 10 to 55 picograms/ml.
Results: A total of 250 children were studied, with an overall mean age of 12.24 ± 12.0 years. Males comprised 60.4%, and females were 39.6%. Most cases (28.4%) had dentine score 0, 24.8% had dentine score I, 24.8% had dentine score II, 18.8% had dentine score IV, while only 3.2% had dentine score II. Mean parathyroid hormone levels were significantly associated with higher dentine scores (p < 0.05). Although mean parathyroid hormone levels were statistically insignificant according to children's age (p < 0.05).
Conclusion: A decrease in levels of parathyroid hormones and calcium has been observed to contribute to the delay in the eruption of primary teeth. Additionally, factors such as stunted growth and deficiencies in parathyroid hormones and calcium levels further exacerbate this delay, highlighting the importance of adequate nutrition in dental development.
11
Dupont, Mariève, Jean-Philippe Drouin-Chartier e Geneviève Mailhot. "Nutrition, santé osseuse et dentaire : de la physiologie à la pratique". Nutrition Science en évolution: La revue de l'Ordre professionnel des diététistes du Québec 17, n. 1 (2019): 4. http://dx.doi.org/10.7202/1062450ar.
12
Gug, Hye Ri, Yeoung-Hyun Park, Su-Jin Park, Ji Yeon Jang, Ji-Hyun Lee, Dong-Seol Lee, Won-Jun Shon e Joo-Cheol Park. "Novel strategy for dental caries by physiologic dentin regeneration with CPNE7 peptide". Archives of Oral Biology 143 (novembre 2022): 105531. http://dx.doi.org/10.1016/j.archoralbio.2022.105531.
13
D’Incau, Emmanuel, François Rouzé l’Alzit, Pierre-Hadrien Decaup e Arnaud Soenen. "Vieillissement de l’occlusion dentaire". Revue d'Orthopédie Dento-Faciale 54, n. 1 (febbraio 2020): 57–71. http://dx.doi.org/10.1051/odf/2020007.
Abstract (sommario):
La mise au point de mesures préventives et curatives efficaces passe par la connaissance du vieillissement des organes et de leurs fonctions. Ce principe s’applique à l’occlusion dentaire dont il est important de connaître le vieillissement. L’objectif principal de cet article est de revenir, sous forme de revue narrative, sur cette problématique d’abord dans un contexte physiologique puis dans un contexte pathologique.
14
You, Jason C., Kavitha Muralidharan, Chia-Hsuan Fu, Jin Park, Umberto Tosi, Xiaohong Zhang e Jeannie Chin. "Distinct patterns of dentate gyrus cell activation distinguish physiologic from aberrant stimuli". PLOS ONE 15, n. 5 (14 maggio 2020): e0232241. http://dx.doi.org/10.1371/journal.pone.0232241.
15
Saber, Shehab-El Din Mohammed, e Farid Sabry El-Askary. "The Outcome of Immediate or Delayed Application of a Single-Step Self-Etch Adhesive to Coronal Dentin Following the Application of Different Endodontic Irrigants". European Journal of Dentistry 03, n. 02 (aprile 2009): 83–89. http://dx.doi.org/10.1055/s-0039-1697412.
Abstract (sommario):
ABSTRACTObjectives: The aim of this study was to evaluate the outcome of immediate or delayed bonding of a single-step self-etch adhesive to coronal dentin after the application of different endodontic irrigants.Methods: Thirty five human molars were used. The coronal dentin was irrigated with either 0.9% physiologic saline (NS), 2% Chlorhexidine gluconate (CHX) or 2.5% commercially used sodium hypochlorite (NaOCl). Compositecylinders were bonded with the coronal dentin using the Clearfil S3 bond, which was applied either immediatelyor after one week storage time following the irrigation procedures. Shear bond strength testing was performed at a cross-head speed of 0.5 mm/min, and the resin/dentin interface was evaluated using SEM.Results: Irrigation with NS, CHX, or NaOCL followed by immediate adhesive application resulted in a reduction in the shear bond strength values recorded and this was statistically significant in comparison with the control group (P<.05). However, delaying the adhesive application resulted in a statistically significant (P<.05) improvement in the shear bond strength recorded in specimens irrigated with NS and CHX only.Conclusions: Delaying the bonding procedures for one week appeared to be beneficial in improving the shear bond strength of Clearfil S3 bond with coronal dentin especially when NS and CHX were used as endodontic irrigants. NaOCL proved to be an incompatible irrigating solution when used prior to the application of such adhesive. (Eur J Dent 2009;3:83-89)
16
Isokawa, Masako, Giuliano Avanzini, David M. Finch, Thomas L. Babb e Michel F. Levesque. "Physiologic properties of human dentate granule cells in slices prepared from epileptic patients". Epilepsy Research 9, n. 3 (settembre 1991): 242–50. http://dx.doi.org/10.1016/0920-1211(91)90058-n.
17
Atabek, D., H. Sillelioğlu, Ç. Çinar e A. Ölmez. "Maturogenesis of an Early Erupted Immature Permanent Tooth: A Case Report With 7-Year Follow-Up". Journal of Clinical Pediatric Dentistry 39, n. 3 (1 marzo 2015): 262–67. http://dx.doi.org/10.17796/1053-4628-39.3.262.
Abstract (sommario):
The main objective of treatment of an undeveloped tooth (immature) is to provide vital pulp therapy to allow continued development of root dentin. A case report is presented that demonstrates the use of calcium hydroxide (CaOH2) as an indirect pulp-copping material for the purpose of continued maturogenesis of an early-erupted permanent tooth with severe mobility and almost-begun root formation. Seven-year radiographic and clinical follow-up demonstrated a vital pulp and physiologic root development without any endodontic failure clinically or radiographicaly.
18
Orthlieb, Jean-Daniel, Anne Giraudeau, Marion Jeanny, Jean-Philippe Ré e Armelle Manière-Ezvan. "Regards sur l’insuccès occlusal". L'Orthodontie Française 87, n. 1 (marzo 2016): 13–22. http://dx.doi.org/10.1051/orthodfr/2016011.
Abstract (sommario):
Le succès est matérialisé par la pérennité d’un résultat thérapeutique esthétique et fonctionnel. L’insuccès occlusal «post-orthodontique» pourrait se traduire par une instabilité dentaire, un inconfort fonctionnel jusqu’à une plainte dentaire ou musculo-articulaire. L’analyse de l’occlusion recherche les anomalies occlusales à potentialités pathogènes répertoriées en anomalies de calage, anomalies de centrage, anomalies de guidage. La grande capacité de tolérance de l’appareil manducateur rend difficile la définition de la frontière entre physiologie et pathologie, mais il est nécessaire de disposer de repères que l’on peut résumer ainsi : – calage : contact occlusal de la cuspide mésio-linguale des premières molaires maxillaires (en classe I, II ou III) et contacts occlusaux entre les canines antagonistes; – centrage : absence de décentrage transversal entre OIM et ORC; – guidage : absence d’interférence postérieure, absence d’interférence antérieure (verrouillage).
19
Martin-Gonzalez, Jenifer, Juan J. Segura-Egea, Antonio Pérez-Pérez, Daniel Cabanillas-Balsera e Víctor Sánchez-Margalet. "Leptin in Dental Pulp and Periapical Tissues: A Narrative Review". International Journal of Molecular Sciences 23, n. 4 (11 febbraio 2022): 1984. http://dx.doi.org/10.3390/ijms23041984.
Abstract (sommario):
Leptin is a non-glycosylated 16 kDa protein synthesized mainly in adipose cells. The main function of leptin is to regulate energy homeostasis and weight control in a central manner. There is increasing evidence that leptin also has systemic effects, acting as a link between innate and acquired immune responses. The expression of leptin and its receptor in human dental pulp and periradicular tissues have already been described, as well as several stimulatory effects of leptin protein expression in dental and periodontal tissues. The aim of this paper was to review and to compile the reported scientific literature on the role and effects of leptin in the dental pulp and periapical tissues. Twelve articles accomplished the inclusion criteria, and a comprehensive narrative review was carried out. Review of the available scientific literature concluded that leptin has the following effects on pulpal and periapical physiology: 1) Stimulates odontogenic differentiation of dental pulp stem cells (DPSCs), 2) Increases the expression of dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (DMP-1), odontoblastic proteins involved in odontoblastic differentiation and dentin mineralization, 3) Stimulates vascular endothelial growth factor (VEGF) expression in human dental pulp tissue and primary cultured cells of human dental pulp (hDPCs), 4) Stimulates angiogenesis in rat dental pulp cells, and 5) Induces the expression of interleucinas 6 and 8 in human periodontal ligament cells (hPDLCs). There is evidence which suggests that leptin is implicated in the dentin mineralization process and in pulpal and periapical inflammatory and reparative responses.
20
Shetty, Karthik, Keerthana Kunaparaju, Ankita Kanotra, Anushka Arora e Ishani Saluja. "Non-Surgical Management of an Anterior Tooth with Internal Inflammatory Resorption: A Case Report". Indian Journal of Forensic Medicine & Toxicology 15, n. 3 (2 giugno 2021): 5380–85. http://dx.doi.org/10.37506/ijfmt.v15i3.16347.
Abstract (sommario):
Background: According to the Glossary of the American Association of Endodontists, resorption is definedas a condition associated with either a physiologic or a pathologic process resulting in the loss of dentin,cementum, or bone. It may present internally (pulpal origin) or externally (periodontal origin). Internalresorption is a rare, insidious, resorptive pathological process, starting from the pulp extending into thesurrounding dentin. Treatment is mainly focused on arresting the cellular activity accounting for theresorptive process.Methodology: A patient presented with an upper front tooth that was tender on percussion and a history oftrauma in her childhood which resulted in Ellis class II fracture of the tooth. Pulp sensibility testing showeda negative response suggestive of a non-vital tooth. A non-surgical endodontic therapy was carried out underthe microscope with calcium hydroxide dressings followed by the three-dimensional obturation techniqueusing thermoplasticized Gutta percha.Conclusion: The current case report discusses the etiology and symptoms of internal inflammatoryresorption, the contribution of cone beam computed tomography imaging in its diagnosis, and a step wiseprotocol for the three dimensional obturation of the resorptive lesion.
21
Kinney, J. H., M. Balooch, S. J. Marshall, G. W. Marshall e T. P. Weihs. "Atomic Force Microscope Measurements of the Hardness and Elasticity of Peritubular and Intertubular Human Dentin". Journal of Biomechanical Engineering 118, n. 1 (1 febbraio 1996): 133–35. http://dx.doi.org/10.1115/1.2795939.
Abstract (sommario):
An atomic force microscope was used to measure the hardness and elasticity of fully-hydrated peritubular and intertubular human dentin. The standard silicon nitride AFM tip and silicon cantilever assembly were replaced with a diamond tip and stainless steel cantilever having significantly higher stiffness. Hardness was measured as the ratio of the applied force to the projected indentation area for indentations with depths from 10–20 nm. The sample stiffness was measured by imaging specimens in a force-modulated mode. Hardness values of 2.3 ± 0.3 GPa and 0.5 ± 0.1 GPa were measured for the peritubular and intertubular dentin, respectively. Stiffness imaging revealed that the elastic modulus of the peritubular dentin was spatially homogeneous; whereas, there was considerable spatial variation in the elasticity of the intertubular dentin. The atomic force microscope can be used to measure the mechanical properties of fully hydrated calcified tissues at the submicron level of spatial resolution, thus augmenting more traditional depth sensing probes.
22
Stringer, J. L., e E. W. Lothman. "Maximal dentate gyrus activation: characteristics and alterations after repeated seizures". Journal of Neurophysiology 62, n. 1 (1 luglio 1989): 136–43. http://dx.doi.org/10.1152/jn.1989.62.1.136.
Abstract (sommario):
1. The dentate gyrus was activated by trains of stimulation to either the contralateral CA3 region or the ipsilateral angular bundle. Responses were monitored with recordings of extracellular field potentials and extracellular potassium ([K+]o. Maximal dentate activation was identified by the appearance of bursts of large-amplitude (20-40 mV) population spikes associated with a secondary rise in [K+]o and an abrupt negative shift of the DC potential. 2. Several parameters were defined to characterize features of maximal dentate activation. These included 1) time to onset of maximal dentate activation, 2) duration of maximal dentate activation, 3) stimulus threshold for maximal dentate activation, 4) threshold for afterdischarge production, and 5) afterdischarge durations. The time to onset of maximal dentate activation and the duration of maximal dentate activation depended on the stimulus intensity until, above a certain stimulus intensity, both parameters reached constant values. The total period of maximal dentate activation (during both stimulation and afterdischarge) was constant. 3. The characteristics of maximal dentate activation were then determined in kindled animals and compared with age-matched controls. Kindled animals had a significant increase in the total duration of maximal dentate activation and a decrease in the ratio of afterdischarge threshold to the threshold for maximal dentate activation to 1 from a ratio in control animals of 6. 4. In a set of urethan-anesthetized animals, the characteristics of maximal dentate activation before and after 36 stimuli were determined. One hour after the last of 36 stimulus-evoked seizures, there was a trend towards a decrease in the threshold for maximal dentate activation and in the time to its onset.(ABSTRACT TRUNCATED AT 250 WORDS)
23
Buckmaster, Paul S. "Does a Unique Type of CA3 Pyramidal Cell in Primates Bypass the Dentate Gate?" Journal of Neurophysiology 94, n. 1 (luglio 2005): 896–900. http://dx.doi.org/10.1152/jn.01216.2004.
Abstract (sommario):
The predominant excitatory synaptic input to the hippocampus arises from entorhinal cortical axons that synapse with dentate granule cells, which in turn synapse with CA3 pyramidal cells.Thus two highly excitable brain areas—the entorhinal cortex and the CA3 field—are separated by dentate granule cells, which have been proposed to function as a gate or filter. However, unlike rats, primates have “dentate” CA3 pyramidal cells with an apical dendrite that extends into the molecular layer of the dentate gyrus, where they could receive strong, monosynaptic, excitatory synaptic input from the entorhinal cortex. To test this possibility, the dentate gyrus molecular layer was stimulated while intracellular recordings were obtained from CA3 pyramidal cells in hippocampal slices from neurologically normal macaque monkeys. Stimulus intensity of the outer molecular layer of the dentate gyrus was standardized by the threshold intensity for evoking a dentate gyrus field potential population spike. Recorded proximal CA3 pyramidal cells were labeled with biocytin, processed with diaminobenzidine for visualization, and classified according to their dendritic morphology. In response to stimulation of the dentate gyrus molecular layer, action potential thresholds were similar in proximal CA3 pyramidal cells with different dendritic morphologies. These findings do not support the hypothesis that dentate CA3 pyramidal cells receive stronger synaptic input from the entorhinal cortex than do other proximal CA3 pyramidal cells.
24
Bragin, A., G. Jando, Z. Nadasdy, M. van Landeghem e G. Buzsaki. "Dentate EEG spikes and associated interneuronal population bursts in the hippocampal hilar region of the rat". Journal of Neurophysiology 73, n. 4 (1 aprile 1995): 1691–705. http://dx.doi.org/10.1152/jn.1995.73.4.1691.
Abstract (sommario):
1. This paper describes two novel population patterns in the dentate gyrus of the awake rat, termed type 1 and type 2 dentate spikes (DS1, DS2). Their cellular generation and spatial distribution were examined by simultaneous recording of field potentials and unit activity using multiple-site silicon probes and wire electrode arrays. 2. Dentate spikes were large amplitude (2-4 mV), short duration (< 30 ms) field potentials that occurred sparsely during behavioral immobility and slow-wave sleep. Current-source density analysis revealed large sinks in the outer (DS1) and middle (DS2) thirds of the dentate molecular layer, respectively. DS1 and DS2 had similar longitudinal, lateral, and interhemispheric synchrony. 3. Dentate spikes invariably were coupled to synchronous population bursts of putative hilar interneurons. CA3 pyramidal cells, on the other hand were suppressed during dentate spikes. 4. After bilateral removal of the entorhinal cortex, dentate spikes disappeared, whereas sharp wave-associated bursts, reflecting synchronous discharge of the CA3-CA1 network, increased several fold. 5. These physiological characteristics of the dentate spikes suggest that they are triggered by a population burst of layer II stellate cells of the lateral (DS1) and medial (DS2) entorhinal cortex. 6. We suggest that dentate spike-associated synchronized bursts of hilar-region interneurons provide a suppressive effect on the excitability of the CA3-CA1 network in the intact brain.
25
Yin, Ying, Qun Wang, Wen Sun, Yuli Wang, Ning Chen e Dengshun Miao. "p27kip1deficiency accelerates dentin and alveolar bone formation". Clinical and Experimental Pharmacology and Physiology 41, n. 10 (ottobre 2014): 807–16. http://dx.doi.org/10.1111/1440-1681.12276.
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Kelty, Taylor J., Todd R. Schachtman, Xuansong Mao, Kolter B. Grigsby, Thomas E. Childs, T. Dylan Olver, Paige N. Michener, Rachel A. Richardson, Christian K. Roberts e Frank W. Booth. "Resistance-exercise training ameliorates LPS-induced cognitive impairment concurrent with molecular signaling changes in the rat dentate gyrus". Journal of Applied Physiology 127, n. 1 (1 luglio 2019): 254–63. http://dx.doi.org/10.1152/japplphysiol.00249.2019.
Abstract (sommario):
Effective treatments preventing brain neuroinflammatory diseases are lacking. Resistance-exercise training (RT) ameliorates mild cognitive impairment (MCI), a forerunner to neuroinflammatory diseases. However, few studies have addressed the molecular basis by which RT abates MCI. Thus experiments were performed to identify some molecular changes occurring in response to RT in young, female Wistar rats. To induce MCI, intraventricular lipopolysaccharide (LPS) injections were used to increase dentate gyrus inflammation, reflected by significantly increased TNF-α (~400%) and IL-1β (~1,500%) mRNA ( P < 0.0001) after 6 wk. Five days after LPS injections, half of LPS-injected rats performed RT by ladder climbing for 6 wk, 3 days/wk, whereas half remained without ladders. RT for 6 wk increased lean body mass percentage ( P < 0.05), individual muscle masses (gastrocnemius and tibialis anterior) ( P < 0.05), and maximum lifting capacity ( P < 0.001). The RT group, compared with sedentary controls, had 1) ameliorated spatial learning deficits ( P < 0.05), 2) increased dentate gyrus phosphorylation of IGF-1R, protein kinase B, and GSK-3β proteins ( P < 0.05), components of downstream IGF-1 signaling, and 3) increased dentate gyrus synaptic plasticity marker synapsin protein ( P < 0.05). Two follow-up experiments (without LPS) characterized dentate gyrus signaling during short-term RT. Twenty-four hours following the third workout in a 1-wk training duration, phosphorylation of ERK1/2 and GSK-3β proteins, as well as proliferation marker protein, PCNA, were significantly increased ( P < 0.05). Similar changes did not occur in a separate group of rats following a single RT workout. Taken together, these data indicate that RT ameliorates LPS-induced MCI after RT, possibly mediated by increased IGF-1 signaling pathway components within the dentate gyrus.NEW & NOTEWORTHY The data suggest that resistance-exercise training restores cognitive deficits induced by lipopolysaccharides and can activate associated IGF-1 signaling in the dentate gyrus. Our data show, for the first time, that as few as three resistance-exercise workouts (spread over 1 wk) can activate IGF-1 downstream signaling and increase proliferation marker PCNA in the dentate gyrus.
27
Colgin, Laura Lee, Don Kubota, Fernando A. Brucher, Yousheng Jia, Erin Branyan, Christine M. Gall e Gary Lynch. "Spontaneous Waves in the Dentate Gyrus of Slices From the Ventral Hippocampus". Journal of Neurophysiology 92, n. 6 (dicembre 2004): 3385–98. http://dx.doi.org/10.1152/jn.00478.2004.
Abstract (sommario):
Spontaneous negative-going potentials occurring at an average frequency of 0.7 Hz were recorded from the dentate gyrus of slices prepared from the temporal hippocampus of young adult rats. These events (here termed “dentate waves”) in several respects resembled the dentate spikes described for freely moving rats during immobile behaviors and slow-wave sleep. Action potentials were observed on the descending portion of the in vitro waves and, as expected from this, whole cell recordings established that the waves were composed of depolarizing currents. Dentate waves appeared to be locally generated within the granule cell layer and were greatly reduced by antagonists of AMPA-type glutamate receptors or by lesions to the entorhinal cortex. Simultaneous recordings indicated that the waves were often synchronized in the inner and outer blades of the dentate gyrus. Knife cuts through the perforant path and the commissural/associational system did not eliminate synchronization, leaving electrotonic propagation via gap junctions as its probable cause. In accord with this, cuts that separated the two blades of the dentate eliminated synchronization between them, and a compound that inhibits gap junctions reduced wave activity. Dentate waves were regularly accompanied by sharp waves in field CA3 and were reduced in size by the acetylcholinesterase inhibitor, physostigmine. It is hypothesized that dentate waves occur when spontaneous glutamate release from dentate afferents produces action potentials in neighboring granule cells that then summate electrotonically into a population event; once initiated, the waves propagate, again electrotonically, and thereby engage a significant portion of the granule cell population.
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Buckmaster, Paul S., e F. Edward Dudek. "Network Properties of the Dentate Gyrus in Epileptic Rats With Hilar Neuron Loss and Granule Cell Axon Reorganization". Journal of Neurophysiology 77, n. 5 (1 maggio 1997): 2685–96. http://dx.doi.org/10.1152/jn.1997.77.5.2685.
Abstract (sommario):
Buckmaster, Paul S. and F. Edward Dudek. Network properties of the dentate gyrus in epileptic rats with hilar neuron loss and granule cell axon reorganization. J. Neurophysiol. 77: 2685–2696, 1997. Neuron loss in the hilus of the dentate gyrus and granule cell axon reorganization have been proposed as etiologic factors in human temporal lobe epilepsy. To explore these possible epileptogenic mechanisms, electrophysiological and anatomic methods were used to examine the dentate gyrus network in adult rats that had been treated systemically with kainic acid. All kainate-treated rats, but no age-matched vehicle-treated controls, were observed to have spontaneous recurrent motor seizures beginning weeks to months after exposure to kainate. Epileptic kainate-treated rats and control animals were anesthetized for field potential recording from the dentate gyrus in vivo. Epileptic kainate-treated rats displayed spontaneous positivities (“dentate electroencephalographic spikes”) with larger amplitude and higher frequency than those in control animals. After electrophysiological recording, rats were perfused and their hippocampi were processed for Nissl and Timm staining. Epileptic kainate-treated rats displayed significant hilar neuron loss and granule cell axon reorganization. It has been hypothesized that hilar neuron loss reduces lateral inhibition in the dentate gyrus, thereby decreasing seizure threshold. To assess lateral inhibition, simultaneous recordings were obtained from the dentate gyrus in different hippocampal lamellae, separated by 1 mm. The perforant path was stimulated with paired-pulse paradigms, and population spike amplitudes were measured. Responses were obtained from one lamella while a recording electrode in a distant lamella leaked saline or the γ-aminobutyric acid-A receptor antagonist bicuculline. Epileptic kainate-treated and control rats both showed significantly more paired-pulse inhibition when a lateral lamella was hyperexcitable. To assess seizure threshold in the dentate gyrus, two techniques were used. Measurement of stimulus threshold for evoking maximal dentate activation revealed significantly higher thresholds in epileptic kainate-treated rats compared with controls. In contrast, epileptic kainate-treated rats were more likely than controls to discharge spontaneous bursts of population spikes and to display stimulus-triggered afterdischarges when a focal region of the dentate gyrus was disinhibited with bicuculline. These spontaneous bursts and afterdischarges were confined to the disinhibited region and did not spread to other septotemporal levels of the dentate gyrus. Epileptic kainate-treated rats that displayed spontaneous bursts and/or afterdischarges had significantly larger percentages of Timm staining in the granule cell and molecular layers than epileptic kainate-treated rats that failed to show spontaneous bursts or afterdischarges. In summary, this study reveals functional abnormalities in the dentate gyri of epileptic kainate-treated rats; however, lateral inhibition persists, suggesting that vulnerable hilar neurons are not necessary for generating lateral inhibition in the dentate gyrus.
29
Schweitzer, J. S., P. R. Patrylo e F. E. Dudek. "Prolonged field bursts in the dentate gyrus: dependence on low calcium, high potassium, and nonsynaptic mechanisms". Journal of Neurophysiology 68, n. 6 (1 dicembre 1992): 2016–25. http://dx.doi.org/10.1152/jn.1992.68.6.2016.
Abstract (sommario):
1. The dentate gyrus has been proposed to be a gate for entry of neuronal activity into the hippocampus. This function would give it a critical role in the propagation of seizure activity in that region. The hallmark of epileptiform activity in the dentate itself, often referred to as "maximal dentate activation" (MDA), has not been reproduced previously in vitro. 2. With the use of rat hippocampal slices, bath [Ca2+] was decreased, and [K+] was increased concurrently to simulate conditions found during intense neuronal activity in vivo. Both evoked and spontaneous field bursts were observed in the dentate granule cell layer under these conditions. These bursts were similar to MDA, consisting of a prolonged negative shift in extracellular potential with large-amplitude population spikes. 3. In 0.5 mM bath [Ca2+], single stimuli applied to the perforant path could evoke prolonged field bursts in the dentate only when bath [K+] was > or = 9 mM. However, repetitive stimulation (10 Hz) of the perforant path could elicit similar dentate responses when bath [K+] was as low as 5 mM. 4. In 0.5 mM bath [Ca2+], interictal-type bursts appeared spontaneously in CA1 and CA3 when bath [K+] was > or = 5 mM but were lost when [K+] was > 9 mM. Spontaneous seizurelike activity in the dentate required a higher minimum bath [K+] (9 mM) and persisted at [K+] of 11 mM. 5. Stimulation-evoked field bursts in the dentate altered epileptiform activity in CA3. At bath [K+] insufficient to cause spontaneous CA3 bursts, CA3 was activated transiently when prolonged field bursts occurred in the dentate. At higher bath [K+] in which spontaneous CA3 bursts did occur, they were depressed during the dentate bursts. 6. Deletion of Ca2+ from the bath; the addition of 30 microM each of bicuculline methiodide, D,L-2-amino-5-phosphonopentanoate (AP-5), and 6,7-dinitroquinoxaline-2,3-dione (DNQX); or the combination of both manipulations did not block antidromically evoked or spontaneous prolonged field bursts in the dentate. Thus the mechanisms maintaining and propagating these events did not require fast amino acid-mediated synaptic transmission. 7. The concurrent alteration of [K+] and [Ca2+] required to produce prolonged field bursts in the dentate underscores the positive feedback relationship between neuronal excitation and extracellular ionic concentrations, whereas the ability of synaptic stimulation to trigger nonsynaptic seizurelike events such as these prolonged field bursts may be relevant to the transition from interictal to ictal activity in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)
30
Doherty, James, e Raymond Dingledine. "Regulation of Excitatory Input to Inhibitory Interneurons of the Dentate Gyrus During Hypoxia". Journal of Neurophysiology 77, n. 1 (1 gennaio 1997): 393–404. http://dx.doi.org/10.1152/jn.1997.77.1.393.
Abstract (sommario):
Doherty, J. and R. Dingledine. Regulation of excitatory input to inhibitory interneurons of the dentate gyrus during hypoxia. J. Neurophysiol. 77: 393–404, 1997. The role of metabotropic glutamate receptors (mGluRs) and adenosine receptors in hypoxia-induced suppression of excitatory synaptic input to interneurons residing at the granule cell–hilus border in the dentate gyrus was investigated with the use of whole cell electrophysiological recording techniques in thin (250 μm) slices of immature rat hippocampus. Minimal stimulation evoked glutamatergic excitatory postsynaptic currents (EPSCs) in dentate interneurons in 68 ± 4% (mean ± SE) of trials during stimulation in the dentate granule cell layer (GCL) and 48 ± 3% of trials during stimulation in CA3. Hypoxic episodes, produced by switching the perfusing solution from 95% O2-5% CO2 to a solution containing 95% N2-5% CO2 for 3–5 min, rapidly and reversibly decreased the synaptic reliability, or probability of evoking an EPSC, from either input without reducing EPSC amplitude, consistent with a presynaptic suppression of transmitter release. The mGluR antagonist (+)-α-methyl-4-carboxyphenylglycine [(+)MCPG; 500 μM] did not alter synaptic reliability or mean EPSC amplitude in either pathway. However, (+)MCPG significantly attenuated hypoxic suppression of input from both pathways, suggesting that mGluRs activated by release of glutamate partially mediate hypoxic suppression of EPSCs to dentate interneurons. The mGluR agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 100 μM) rapidly decreased the reliability of excitatory transmission from both the GCL (19 ± 5% of control) and CA3 (39 ± 15% of control). ACPD also increased the frequency of spontaneous EPSCs and evoked a slow inward current in dentate interneurons. Exogenous adenosine (10–300 μM) decreased synaptic reliability for both pathways and reduced the frequency of spontaneous EPSCs, but did not cause a decrease in the mean amplitude of evoked EPSCs, consistent with a presynaptic suppression of excitatory input to dentate interneurons. Conversely, the selective adenosine A1 receptor antagonists 8-cyclopentyl-1,3-dipropylxanthine (200 nM to 1 μM) and N6-cyclopentyl-9-methyladenine (1 μM) enhanced excitatory input to dentate interneurons by increasing synaptic reliability for both the GCL and CA3 inputs. Adenosine A1 receptor antagonists did not, however, reduce hypoxic suppression of excitatory input to dentate interneurons. These results indicate that hypoxia induces a presynaptic inhibition of excitatory input to dentate interneurons mediated in part by activation of mGluRs, but not adenosine A1 receptors, whereas both mGluRs and adenosine A1 receptors can depress excitatory input to dentate interneurons during normoxic stimulation. Regulation of excitatory input to dentate interneurons provides a mechanism to shape excitatory input to the hippocampus under both normal and pathological conditions.
31
Ishikawa, K., E. D. Eanes e M. S. Tung. "The Effect of Supersaturation on Apatite Crystal Formation in Aqueous Solutions at Physiologic pH and Temperature". Journal of Dental Research 73, n. 8 (agosto 1994): 1462–69. http://dx.doi.org/10.1177/00220345940730081101.
Abstract (sommario):
The importance of supersaturation in the dynamics of apatite precipitation from aqueous solutions is well-established. To determine whether this parameter has a comparable impact on the concomitant development of the textural properties of this phase, such as crystal size and shape, we investigated mineral accretion in synthetic solutions seeded with 0.67 g/L apatite over a range of supersaturations at pH 7.4 and 37°C. A dual specific-ion electrode-controlled titration method was used to maintain the seeded reactions under the following solution conditions: 1.0 to 1.8 mmol/L Ca2+, 0.67 to 1.2 mmol/L total phosphate (PO 4), Ca/PO4 (initial) = 1.5, 143 mmol/L KNO3, and 10 mmol/L HEPES. Samples were collected for chemical and textural analyses when the seed apatite was reduced by new accretions to 1/2,1/4,1/8,1/16, and 1/32 of the total solids in suspension. All new accretions were found to be apatitic. At the lowest supersaturation, accretion occurred primarily by growth of the seed crystals. However, at the highest supersaturation examined, the crystals at the end of the experiments were actually smaller, on average, than the original seeds, even though the total mass increased 32-fold. The results suggest that proliferation of new crystals supplanted growth of the seed crystals as supersaturation was increased. The results also suggest that differences in tissue fluid supersaturation may contribute to the large disparity in dimensions between dentin and enamel apatite crystals.
32
Лещева, E. Leshcheva, Ипполитов, I. Ippolitov, Ипполитов, Yuriy Ippolitov, Моисеева e N. Moiseeva. "The role of carbohydrate-protein biopolymers and hyaluronic acid at the resistance formation of hard dental tissues against pathological processes of carious and non-carious genesis". Journal of New Medical Technologies. eJournal 8, n. 1 (5 novembre 2014): 0. http://dx.doi.org/10.12737/7378.
Abstract (sommario):
At the series of histochemical studies hypothesis of existence of a "cationic protein" in human tooth structure and set of its amino acids components and hyaluronic acid has been checked. Taking into account histogenesis and cytogeny of tooth structure and the earlier results received from the epidermis and multilayer partly keratinous epithelium of the oral mucosa, special studies had been created, based on the original equipment preparation of paraffin sections, and thin sections of the whole teeth and modified histochemical identification technology of carbohydrate-protein biopolymers in hard dental tissues. Histological slides are prepared from extracted for orthodontic indications teeth. Sectioned and examined thin sections of teeth has investigated in transmitted light for issues related to topochemistry of carbohydrate-protein biopolymers and hyaluronic acid concerning the distribution in structures of enamel, dentin, predentin, cellular and acellular cement. Identified carbohydrate-protein biopolymers and substances of protein nature objectively fill inter prismatic enamel areas, dentin tubules and their walls, localized in the cement structure of tooth and its soft tissues forming a physiologi-cal barrier to microorganisms and their metabolic products as in the demineralizing processes as for the mechan-ical interventions during the vital activity and medical interventions.
33
Xiong, Zhi-Qi, e Janet L. Stringer. "Extracellular pH Responses in CA1 and the Dentate Gyrus During Electrical Stimulation, Seizure Discharges, and Spreading Depression". Journal of Neurophysiology 83, n. 6 (1 giugno 2000): 3519–24. http://dx.doi.org/10.1152/jn.2000.83.6.3519.
Abstract (sommario):
Since neuronal excitability is sensitive to changes in extracellular pH and there is regional diversity in the changes in extracellular pH during neuronal activity, we examined the activity-dependent extracellular pH changes in the CA1 region and the dentate gyrus. In vivo, in the CA1 region, recurrent epileptiform activity induced by stimulus trains, bicuculline, and kainic acid resulted in biphasic pH shifts, consisting of an initial extracellular alkalinization followed by a slower acidification. In vitro, stimulus trains also evoked biphasic pH shifts in the CA1 region. However, in CA1, seizure activity in vitro induced in the absence of synaptic transmission, by perfusing with 0 Ca2+/5 mM K+medium, was only associated with extracellular acidification. In the dentate gyrus in vivo, seizure activity induced by stimulation to the angular bundle or by injection of either bicuculline or kainic acid was only associated with extracellular acidification. In vitro, stimulus trains evoked only acidification. In the dentate gyrus in vitro, recurrent epileptiform activity induced in the absence of synaptic transmission by perfusion with 0 Ca2+/8 mM K+medium was associated with extracellular acidification. To test whether glial cell depolarization plays a role in the regulation of the extracellular pH, slices were perfused with 1 mM barium. Barium increased the amplitude of the initial alkalinization in CA1 and caused the appearance of alkalinization in the dentate gyrus. In both CA1 and the dentate gyrus in vitro, spreading depression was associated with biphasic pH shifts. These results demonstrate that activity-dependent extracellular pH shifts differ between CA1 and dentate gyrus both in vivo and in vitro. The differences in pH fluctuations with neuronal activity might be a marker for the basis of the regional differences in seizure susceptibility between CA1 and the dentate gyrus.
34
Buckmaster, P. S., E. Tam e P. A. Schwartzkroin. "Electrophysiological correlates of seizure sensitivity in the dentate gyrus of epileptic juvenile and adult gerbils". Journal of Neurophysiology 76, n. 4 (1 ottobre 1996): 2169–80. http://dx.doi.org/10.1152/jn.1996.76.4.2169.
Abstract (sommario):
1. Naturally occurring inherited epilepsy is common among Mongolian gerbils, providing an opportunity to identify neurological factors that correlate with seizure behavior. In the present study we examine the ontogeny of seizure behavior and compare the electrophysiology and anatomy of the dentate gyrus in epileptic and nonepileptic gerbils. 2. Behavioral seizure testing revealed that young gerbils do not begin having seizures until they are 2 mo of age, at which time seizure incidence across animals is at its highest level. Most seizure-positive juvenile gerbils became epileptic adults, but 30% outgrew their epileptic condition. 3. The number of somatostatin- and parvalbumin-immunoreactive neurons in the dentate gyrus and Ammon's horn was counted, with the use of quantitative stereological techniques, in juvenile and adult gerbils. No significant differences were detected between epileptic and nonepileptic groups. 4. In dentate gyrus field potential responses to perforant path stimulation, adult epileptic gerbils showed enhanced paired-pulse inhibition at short (30 ms) interstimulus intervals and enhanced facilitation at intermediate (70 ms) intervals compared with nonepileptic controls. These differences were most pronounced when stimuli were delivered at faster (1.0 Hz) rather than slower (0.1 Hz) rates. 5. Compared with seizure-negative juveniles, seizure-positive juveniles showed the same pattern of paired-pulse response abnormalities as epileptic adults. However, seizure-positive juveniles had a lower threshold for maximal dentate activation than epileptic adults. 6. These results demonstrate similar functional abnormalities in the dentate gyri of epileptic adult gerbils and in juvenile gerbils before they experience multiple seizures. Such findings suggest that abnormalities in functional inhibition of the dentate gyrus network precede and therefore might contribute to overt seizure activity.
35
Sathyanarayanan, Kothandaraman, Lingeswaran Poornima e Keerthi V. Narayan. "Non-Surgical Endodontic Management of External Root Resorption in a Permanent Maxillary Central Incisor Tooth - A 3 Year Follow-Up of a Rare Case Scenario". Journal of Evolution of Medical and Dental Sciences 10, n. 30 (26 luglio 2021): 2350–53. http://dx.doi.org/10.14260/jemds/2021/481.
Abstract (sommario):
Resorption of the tooth represents a multifactorial and a perplexing problem for all clinicians resulting in complete or partial loss of tooth structure. The present clinical demonstration describes management of the permanent maxillary left central incisor (tooth number #21) affected by external root resorption involving the mesial and distal surface of middle one-third of the root. Conventional nonsurgical endodontic treatment followed by MTA (Mineral trioxide aggregate) obturation (PRoRoot MTA, Dentsply, Tulsa Dental Specialties) was planned. The root canal of the affected teeth was debrided with Dual Rinse HEDP (Medcem Weinfelden, Switzerland) containing etidronate powder and chemomechanical preparation of the root canal was performed with XP endo shaper file system (FKG Dentaire, SA, Switzerland). Thirtysix months’ post-operative follow-up revealed complete healing of the external root resorption defect with no clinical and radiological signs and symptoms. In the present case simple non-surgical endodontic management of severe external root resorption was done in a permanent maxillary tooth by using a continuous chelation irrigation technique, intracanal medicament followed by obturation with bio-ceramic material produced satisfactory results in contrast to the recommended surgical management. Resorption of the tooth being a multifactorial and a perplexing problem for all clinicians results in complete or partial loss of tooth structure. According to the Glossary of Endodontic terms, Resorption is defined as a condition associated with either a physiologic or a pathologic process resulting in the loss of dentine, cementum, and/or bone.1 Traditionally resorption can present either as internal or as external resorption.2 External root resorption occurs on the outer surface of the root and are of dissimilar nature such as external surface resorption, external inflammatory root resorption, ankylosis, and external replacement resorption, the most common being external inflammatory root resorption.3 According to the Glossary of Endodontics, “Inflammatory resorption is defined as an internal or external pathologic loss of tooth structure and possibly bone, resulting in a defect; occurs as the result of microbial infection; characterized radiographically by radiolucent areas along the root”.1 It may result due to dental trauma, forceful orthodontic tooth movement, long standing infection of the pulp or periodontal tissues. External resorption presents as a major resorptive condition of the root without any clinical signs and symptoms.2 The non-surgical management of external inflammatory root resorption is based on its aetiology, which needs to be eliminated
36
MacIver, M. Bruce, e Sheldon H. Roth. "Barbiturate effects on hippocampal excitatory synaptic responses are selective and pathway specific". Canadian Journal of Physiology and Pharmacology 65, n. 3 (1 marzo 1987): 385–94. http://dx.doi.org/10.1139/y87-065.
Abstract (sommario):
Barbiturate actions on excitatory synaptic responses in CA 1 and dentate regions of hippocampal slices were studied to determine whether different effects occur on anatomically distinct synaptic pathways. Pentobarbital facilitated transmission between stratum radiatum inputs and CA 1 neurons at low concentrations (0.02–0.08 mM) and produced postsynaptic depression at higher concentrations. Only depression was observed for stratum oriens inputs to CA 1 and perforant path inputs to dentate granulae neurons. The (+) isomer of pentobarbital was approximately four times more potent than the (−) isomer of racemic mixture. Phenobarbital (0.04–0.12 mM) produced only depression of synaptic responses in CA 1 and dentate pathways. Comparison of effect on field excitatory postsynaptic potentials and population spike responses indicated that the barbiturates act at selective and pathway-specific sites. The results provide further evidence for specific cellular and membrane recognition sites for barbiturate action.
37
Verdelis, K., L. Lukashova, J. T. Wright, R. Mendelsohn, M. G. E. Peterson, S. Doty e A. L. Boskey. "Maturational changes in dentin mineral properties". Bone 40, n. 5 (maggio 2007): 1399–407. http://dx.doi.org/10.1016/j.bone.2006.12.061.
38
Pan, Enhui, e Janet L. Stringer. "Role of Potassium and Calcium in the Generation of Cellular Bursts in the Dentate Gyrus". Journal of Neurophysiology 77, n. 5 (1 maggio 1997): 2293–99. http://dx.doi.org/10.1152/jn.1997.77.5.2293.
Abstract (sommario):
Pan, Enhui and Janet L. Stringer. Role of potassium and calcium in the generation of cellular bursts in the dentate gyrus. J. Neurophysiol. 77: 2293–2299, 1997. Epileptiform activity, which appears to be endogenous, has been recorded in the granule cells of the dentate gyrus before the onset of synchronized seizure activity and has been termed cellular bursts. It has been postulated that an increase in input to the dentate gyrus causes a local increase in extracellular K+ concentration ([K+]o) and a decrease in [Ca2+]o that results in this cellular bursting. The first test of this hypothesis is to determine whether the cellular bursts appear in ionic conditions that occur in vivo before the onset of synchronized epileptic activity. This hypothesis was tested in vitro by varying the ionic concentrations in the perfusing solution and recording changes in the granule cells of the dentate gyrus. Intra- and extracellular recordings were made in the dentate gyri of hippocampal slices prepared from anesthetized adult Sprague-Dawley rats. Increasing the extracellular potassium or decreasing the extracellular calcium of the perfusing solution caused three forms of spontaneous activity to appear: depolarizing potentials, action potentials, and cellular bursts. Increasing potassium or decreasing calcium also caused the granule cells to depolarize and reduced their input resistance. No synchronized extracellular field activity was detected. Simultaneously increasing potassium and decreasing calcium caused cellular bursts to appear at concentrations recorded in vivo before the onset of synchronized reverberatory seizure activity.
39
Chen, Huan-Xin, e Steven N. Roper. "PKA and PKC Enhance Excitatory Synaptic Transmission in Human Dentate Gyrus". Journal of Neurophysiology 89, n. 5 (1 maggio 2003): 2482–88. http://dx.doi.org/10.1152/jn.01031.2002.
Abstract (sommario):
cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) are two major modulators of synaptic transmission in the CNS but little is known about how they affect synaptic transmission in the human CNS. In this study, we used forskolin, a PKA activator, and phorbol ester, a PKC activator, to examine the effects of these kinases on synaptic transmission in granule cells of the dentate gyrus in human hippocampal slices using whole-cell recording methods. We found that both forskolin and phorbol ester increased the frequency of spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs) but left the amplitude unaffected. Inactive forskolin and phorbol ester had no effect on sEPSCs in human dentate granule cells. Prior application of forskolin occluded the effects of phorbol ester on mEPSC frequency. Tetanic stimulation applied to the perforant path induced short-term depression in dentate gyrus granule cells. Both forskolin and phorbol ester significantly enhanced this short-term depression. Taken together, these results demonstrate that PKA and PKC are involved in up-regulation of excitatory synaptic transmission in human dentate granule cells, primarily by presynaptic mechanisms. In addition, the occlusion experiments suggest that the two kinases may share a common signal pathway.
40
Alhourani, Ahmad, Kenneth N. Fish, Thomas A. Wozny, Vivek Sudhakar, Ronald L. Hamilton e R. Mark Richardson. "GABA bouton subpopulations in the human dentate gyrus are differentially altered in mesial temporal lobe epilepsy". Journal of Neurophysiology 123, n. 1 (1 gennaio 2020): 392–406. http://dx.doi.org/10.1152/jn.00523.2018.
Abstract (sommario):
Medically intractable temporal lobe epilepsy is a devastating disease, for which surgical removal of the seizure onset zone is the only known cure. Multiple studies have found evidence of abnormal dentate gyrus network circuitry in human mesial temporal lobe epilepsy (MTLE). Principal neurons within the dentate gyrus gate entorhinal input into the hippocampus, providing a critical step in information processing. Crucial to that role are GABA-expressing neurons, particularly parvalbumin (PV)-expressing basket cells (PVBCs) and chandelier cells (PVChCs), which provide strong, temporally coordinated inhibitory signals. Alterations in PVBC and PVChC boutons have been described in epilepsy, but the value of these studies has been limited due to methodological hurdles associated with studying human tissue. We developed a multilabel immunofluorescence confocal microscopy and a custom segmentation algorithm to quantitatively assess PVBC and PVChC bouton densities and to infer relative synaptic protein content in the human dentate gyrus. Using en bloc specimens from MTLE subjects with and without hippocampal sclerosis, paired with nonepileptic controls, we demonstrate the utility of this approach for detecting cell-type specific synaptic alterations. Specifically, we found increased density of PVBC boutons, while PVChC boutons decreased significantly in the dentate granule cell layer of subjects with hippocampal sclerosis compared with matched controls. In contrast, bouton densities for either PV-positive cell type did not differ between epileptic subjects without sclerosis and matched controls. These results may explain conflicting findings from previous studies that have reported both preserved and decreased PV bouton densities and establish a new standard for quantitative assessment of interneuron boutons in epilepsy. NEW & NOTEWORTHY A state-of-the-art, multilabel immunofluorescence confocal microscopy and custom segmentation algorithm technique, developed previously for studying synapses in the human prefrontal cortex, was modified to study the hippocampal dentate gyrus in specimens surgically removed from patients with temporal lobe epilepsy. The authors discovered that chandelier and basket cell boutons in the human dentate gyrus are differentially altered in mesial temporal lobe epilepsy.
41
Yu, Tzu-Ping, e Cui-Wei Xie. "Orphanin FQ/Nociceptin Inhibits Synaptic Transmission and Long-Term Potentiation in Rat Dentate Gyrus Through Postsynaptic Mechanisms". Journal of Neurophysiology 80, n. 3 (1 settembre 1998): 1277–84. http://dx.doi.org/10.1152/jn.1998.80.3.1277.
Abstract (sommario):
Yu, Tzu-Ping and Cui-Wei Xie. Orphanin FQ/nociceptin inhibits synaptic transmission and long-term potentiation in the rat dentate gyrus through postsynaptic mechanisms. J. Neurophysiol. 80: 1277–1284, 1998. Orphanin FQ/nociceptin (OFQ), a recently characterized natural ligand for the opioid receptor-like 1 (ORL1) receptor, shares structural similarity to the endogenous opioids. Our previous study found that OFQ, like classical opioids, modulated synaptic transmission and long-term potentiation (LTP) in the hippocampal CA1 region, suggesting a modulatory role for OFQ in synaptic plasticity involved in learning and memory. In the present study we investigated the action of OFQ in the dentate gyrus and explored possible underlying cellular mechanisms. Field potential recordings showed that OFQ significantly inhibited excitatory synaptic transmission and LTP induction in the dentate lateral perforant path. In the presence of OFQ, the excitatory postsynaptic potential (EPSP) slope-population spike (E-S) curve was shifted to the right, and no significant change was found in paired-pulse facilitation, suggesting a postsynaptic mechanism responsible for the inhibition of synaptic transmission. Under whole cell voltage-clamp conditions, bath application of OFQ activated K+ currents in most granule cells tested at a holding potential of −50 mV, suggesting that OFQ could reduce the excitability of dentate granule cells by hyperpolarizing cell membranes. OFQ also inhibited the amplitude of N-methyl-d-aspartate (NMDA) receptor–mediated excitatory postsynaptic currents (EPSCs) without affecting α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor–mediated EPSCs. This inhibition was not blocked by opioid receptor antagonists. Furthermore, the inward currents evoked by focal application of NMDA to granule cells were suppressed by OFQ in a dose-dependent manner, suggesting that OFQ may suppress LTP by inhibiting the function of postsynaptic NMDA receptors. These results demonstrate that OFQ may negatively modulate synaptic transmission and plasticity in the dentate gyrus through postsynaptic mechanisms, including hyperpolarization of granule cells as well as inhibition of the function of postsynaptic NMDA receptors/channels in dentate granule cells.
42
Francis, M. J. O., J. P. Gage e R. Smith. "Abnormally low lysine in insoluble dentine from patients with osteogenesis imperfecta". Bone 6, n. 4 (1985): 275. http://dx.doi.org/10.1016/8756-3282(85)90011-0.
43
Chapman, C. E., G. Spidalieri e Y. Lamarre. "Activity of dentate neurons during arm movements triggered by visual, auditory, and somesthetic stimuli in the monkey". Journal of Neurophysiology 55, n. 2 (1 febbraio 1986): 203–26. http://dx.doi.org/10.1152/jn.1986.55.2.203.
Abstract (sommario):
Single-unit recordings were obtained from 404 neurons in the dentate and interposed nuclei in two monkeys trained to perform simple movements of the elbow in response to three different sensory cues: a light, a tone, and a small, brief perturbation of the trained forearm. Both flexion and extension movements were investigated. Those dentate neurons that showed a clear modulation before the onset of movement (149 of 318 cells recorded) were classified as stimulus related or movement related on the basis of an analysis of the timing of the initial change in discharge. Seventy-one percent of these dentate neurons (106/149) were classified as stimulus related, and 21% (31/149) were classified as movement related. Within the stimulus-related group 87% responded selectively to only one or two of the sensory cues (selective stimulus-related neurons), most often the teleceptive cues, whereas the remaining 13% responded nonselectively to all three cues (nonselective stimulus-related neurons). Interposed neurons, in contrast, showed principally movement-related discharge, and this represented the initial change in discharge in 89% of the neurons. Eleven percent of the interposed cells showed a selective response to the somesthetic cue. The discharge of 28 out of 91 dentate neurons tested with both flexion and extension movements varied with the direction of movement. Few dentate neurons (9%) were found to display any direction sensitivity when considering the discharge preceding the onset of movement, and none of these showed a reciprocal pattern. The discharge of a greater proportion of neurons (24%) was direction sensitive during movement and was occasionally reciprocal. In the same monkeys, however, 78% of the neurons in the neighboring interposed nucleus were direction sensitive, and one-quarter of these displayed reciprocal patterns of discharge. Thus, the discharge of dentate neurons, occurring well in advance of a conditioned movement, cannot specify direction in this simple reaction-time (RT) task. The sensory responses of selective stimulus-related dentate cells ended near the onset of movement but were time locked to the stimulus and not to the movement. When a neuron was responsive to two of the cues the response did not vary with the modality of the stimulus apart from changes in the latency. The initial sensory response was usually followed by later “secondary” changes in discharge that were temporally related to the movement.(ABSTRACT TRUNCATED AT 250 WORDS)
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Simmons, M. L., G. W. Terman, C. T. Drake e C. Chavkin. "Inhibition of glutamate release by presynaptic kappa 1-opioid receptors in the guinea pig dentate gyrus". Journal of Neurophysiology 72, n. 4 (1 ottobre 1994): 1697–705. http://dx.doi.org/10.1152/jn.1994.72.4.1697.
Abstract (sommario):
1. Activation of kappa 1-opioid receptors inhibits excitatory transmission in the hippocampal dentate gyrus of the guinea pig. The present studies used both anatomic and physiological approaches to distinguish between a pre- and postsynaptic localization of these receptors. 2. The entorhinal cortex was lesioned unilaterally to cause degeneration of perforant path afferents to the dentate molecular layer, and kappa 1-opioid binding sites were measured by labeling with the selective agonist, [3H]-U69593. Binding density was reduced significantly in the dentate gyrus molecular layer ipsilateral to the lesion compared with the contralateral molecular layer and with sham-lesioned controls. 3. Paired-pulse facilitation is a neurophysiologic paradigm that has been used to differentiate pre- and postsynaptic sites of action for agents that inhibit excitatory neurotransmission. U69593 reduced the amplitude of single population spikes and increased the degree of paired pulse facilitation. The potentiation of paired-pulse facilitation was maintained when the stimulation intensity was increased to compensate for the inhibition of excitatory transmission. These effects of kappa 1-receptor activation were similar to those seen after presynaptic inhibition of excitatory neurotransmitter release and support the hypothesis that U69593 presynaptically inhibits excitatory amino acid release in the dentate gyrus. 4. Local application of glutamate by pressure ejection in the dentate molecular layer evoked field excitatory postsynaptic potentials that mimicked those evoked by electrical stimulation of the perforant path. Both responses were sensitive to the non-N-methyl-D-aspartate glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione. U69593 inhibited responses evoked by perforant path stimulation but had no effect on responses evoked by glutamate application.(ABSTRACT TRUNCATED AT 250 WORDS)
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Silver-Thorn, M. B., e T. P. Joyce. "Finite Element Analysis of Anterior Tooth Root Stresses Developed During Endodontic Treatment". Journal of Biomechanical Engineering 121, n. 1 (1 febbraio 1999): 108–15. http://dx.doi.org/10.1115/1.2798031.
Abstract (sommario):
Vertical tooth root fractures are diagnostically challenging, frustrating, and an increasingly common cause of failure of tooth restoration. These vertical root fractures have been associated with many causes, including the endodontic process itself. To investigate these endodontic causes, various phases of crown replacement for an anterior tooth were modeled using nonlinear, plane strain finite element (FE) analysis. Stresses developed during obturation, post positioning, crown placement, and masticatory and occlusal loading of the restored tooth were estimated using this analysis method. The minimum (compressive) principal stress was greatest during obturation of cones 1 and 2, and during mastication of the restored tooth. Although these stresses were significant (−150 to −280 MPa), they did not exceed the compressive strength of dentin. The maximum (tensile) principal stresses, 160 to 300 MPa, were also observed during obturation of cones 1 and 2. These peak stresses exceed the dentin tensile strength.
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Stringer, J. L., J. M. Williamson e E. W. Lothman. "Induction of paroxysmal discharges in the dentate gyrus: frequency dependence and relationship to afterdischarge production". Journal of Neurophysiology 62, n. 1 (1 luglio 1989): 126–35. http://dx.doi.org/10.1152/jn.1989.62.1.126.
Abstract (sommario):
1. Electrical-stimulus trains activated hippocampal circuits in urethan-anesthetized rats. Responses were monitored with recordings of extracellular potentials and with measurements of the extracellular potassium ([K+]o). Stimulating electrodes were placed in the CA3 region contralateral to the recording electrode (cCA3) and in the ipsilateral angular bundle (AB) while recording in the CA1 pyramidal-cell layer or the granule-cell layer of the dentate gyrus. Patterns of maximal activation were identified. 2. In the CA1 region, maximal activation was indicated by the presence of 10- to 15-mV population spikes, a smooth rise in [K+]o of 5-6 mM above base-line levels of 3 mM, and a negative shift of the sustained DC potential of 2-4 mV. The dentate gyrus was considered to be maximally activated when bursts of large-amplitude (20-40 mV) population spikes were present. These population spikes were associated with a secondary rise in [K+]o to 6-8 mM above base line and an abrupt negative shift of the DC potential of 5-8 mV. 3. Maximal activation depended on the stimulus intensity, frequency, and duration. Trains of 10-Hz stimuli were used to determine the lowest stimulus intensity needed to elicit complete activation in CA1 and in the dentate gyrus. At this intensity, afterdischarges were not produced, and these responses could be elicited repeatedly. 4. By the use of this threshold stimulus intensity, cCA3 stimulation produced a rapid and progressive augmentation of CA1 responses until maximal activation was reached. In comparison, stimulation of the AB could produce the same end result, but the appearance of CA1 population spikes was delayed. Stimulation of the AB produced a steady increase in the evoked granule-cell population spike until the appearance of the paroxysmal large-amplitude population spikes. In contrast, cCA3 stimulation produced two positive evoked responses in the dentate gyrus before the paroxysms of population spikes began. 5. The frequency dependence of the responses was determined by giving stimulus trains ranging from 2 to 100 Hz. Stimulation of cCA3 produced population spikes in CA1 up to 100 Hz that were all associated with the same peak rise in [K+]o. AB stimulation only produced CA1 responses with stimulation frequencies between 15 and 25 Hz. The paroxysmal dentate population spikes were generated by stimulus frequencies between 15 and 30 Hz with both AB and cCA3 stimulation. 6. Unilateral colchicine injections caused a loss of dentate granule cells and a loss of maximal dentate activation on the side of the injection.(ABSTRACT TRUNCATED AT 400 WORDS)
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Karst, Henk, e Marian Joëls. "Effect of Chronic Stress on Synaptic Currents in Rat Hippocampal Dentate Gyrus Neurons". Journal of Neurophysiology 89, n. 1 (1 gennaio 2003): 625–33. http://dx.doi.org/10.1152/jn.00691.2002.
Abstract (sommario):
We investigated the effect of chronic stress on synaptic responses of rat dentate granule cells to perforant path stimulation. Rats were subjected for 3 wk to unpredictable stressors twice daily or to control handling. One day after the last stressor, hippocampal slices were prepared and synaptic responses were determined with whole-cell recording. At that time, adrenal weight was found to be increased and thymus weight as well as gain in body weight were decreased in the stressed versus control animals, indicative of corticosterone hypersecretion during the stress period. In slices from rats with basal corticosteroid levels (at the circadian trough, under rest), no effect of prior stress exposure was observed on synaptic responses. However, synaptic responses of dentate granule cells from chronically stressed and control rats were differently affected by in vitro activation of glucocorticoid receptors, i.e., 1–4 h after administration of 100 nM corticosterone for 20 min. Thus the maximal response to synaptic activation of dentate cells at holding potential of −70 mV [when N-methyl-d-aspartate (NMDA) receptors are blocked by magnesium] was significantly enhanced after corticosterone administration in chronically stressed but not in control animals. In accordance, the amplitude of α-amino-3-hydroxy-5-methylisolazole-4-propionic acid (AMPA) but not of NMDA receptor-mediated currents was increased by corticosterone in stressed rats, over the entire voltage range. Corticosterone treatment also decreased the time to peak of AMPA currents, but this effect did not depend on prior stress exposure. The data indicate that following chronic stress exposure synaptic excitation of dentate granule cells may be enhanced when corticosterone levels rise. This enhanced synaptic flow could contribute to enhanced excitation of projection areas of the dentate gyrus, most notably the CA3 hippocampal region.
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Lensu, Sanna, Tomi Waselius, Markku Penttonen e Miriam S. Nokia. "Dentate spikes and learning: disrupting hippocampal function during memory consolidation can improve pattern separation". Journal of Neurophysiology 121, n. 1 (1 gennaio 2019): 131–39. http://dx.doi.org/10.1152/jn.00696.2018.
Abstract (sommario):
Hippocampal dentate spikes (DSs) are short-duration, large-amplitude fluctuations in hilar local field potentials and take place while resting and sleeping. During DSs, dentate gyrus granule cells increase firing while CA1 pyramidal cells decrease firing. Recent findings suggest DSs play a significant role in memory consolidation after training on a hippocampus-dependent, nonspatial associative learning task. Here, we aimed to find out whether DSs are important in other types of hippocampus-dependent learning tasks as well. To this end, we trained adult male Sprague-Dawley rats in a spatial reference memory task, a fixed interval task, and a pattern separation task. During a rest period immediately after each training session, we either let neural activity to take place as usual, timed electrical stimulation of the ventral hippocampal commissure (vHC) to immediately follow DSs, or applied the vHC stimulation during a random neural state. We found no effect of vHC stimulation on performance in the spatial reference memory task or in the fixed interval task. Surprisingly, vHC stimulation, especially contingent on DSs, improved performance in the pattern separation task. In conclusion, the behavioral relevance of hippocampal processing and DSs seems to depend on the task at hand. It could be that in an intact brain, offline memory consolidation by default involves associating neural representations of temporally separate but related events. In some cases this might be beneficial for adaptive behavior in the future (associative learning), while in other cases it might not (pattern separation). NEW & NOTEWORTHY The behavioral relevance of dentate spikes seems to depend on the learning task at hand. We suggest that dentate spikes are related to associating neural representations of temporally separate but related events within the dentate gyrus. In some cases this might be beneficial for adaptive behavior in the future (associative learning), while in other cases it might not (pattern separation).
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Chattipakorn, Siriporn C., e Lori L. McMahon. "Strychnine-Sensitive Glycine Receptors Depress Hyperexcitability in Rat Dentate Gyrus". Journal of Neurophysiology 89, n. 3 (1 marzo 2003): 1339–42. http://dx.doi.org/10.1152/jn.00908.2002.
Abstract (sommario):
Previously we have shown that strychnine-sensitive glycine-gated chloride channels (GlyRs) are functionally expressed by CA1 pyramidal cells and GABAergic interneurons in mature rat hippocampal slices. We now report that glycine application to dentate granule cells and hilar interneurons recorded in acute slices from adolescent rats elicits a strychnine-sensitive current similar to glycine-mediated currents recorded in area CA1, indicating that GlyRs are also present on neurons in the dentate gyrus. This finding suggests that GlyRs have a widespread distribution in the hippocampal region. The physiological role of GlyRs in forebrain is unclear, but it is possible that these receptors mediate neuronal inhibition, similar to γ-aminobutyric acid-A (GABAA) receptors and thus could be a novel target for antiepileptic therapy. Therefore we tested the hypothesis that activation of inhibitory GlyRs could suppress neuronal hyperexcitability in dentate, a brain region vulnerable to epileptic activity. In whole-cell current-clamp recordings of granule cells, we observed a membrane potential hyperpolarization followed by cessation of the action potential firing pattern in hyperexcitable slices induced by elevated extracellular K+ or by blocking GABAA receptors with bicuculline. The GlyR antagonist, strychnine, prevented the antiepileptic effect of glycine. These results demonstrate that glycine, acting at GlyRs, elicits neuronal inhibition in dentate. Further, our findings suggest the possibility that these receptors could be a therapeutic target for the treatment of epilepsy.
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Messaoudi, Elhoucine, Kjetil Bårdsen, Bolek Srebro e Clive R. Bramham. "Acute Intrahippocampal Infusion of BDNF Induces Lasting Potentiation of Synaptic Transmission in the Rat Dentate Gyrus". Journal of Neurophysiology 79, n. 1 (1 gennaio 1998): 496–99. http://dx.doi.org/10.1152/jn.1998.79.1.496.
Abstract (sommario):
Messaoudi, Elhoucine, Kjetil Bårdsen, Bolek Srebro, and Clive R. Bramham. Acute intrahippocampal infusion of BDNF induces lasting potentiation of synaptic transmission in the rat dentategyrus. J. Neurophysiol. 79: 496–499, 1998. The effect of acuteintrahippocampal infusion of brain-derived neurotrophic factor (BDNF) on synaptic transmission in the dentate gyrus was investigated in urethan-anesthetized rats. Medial perforant path-evoked field potentials were recorded in the dentate hilus and BDNF-containing buffer was infused (4 μl, 25 min) immediately above the dentate molecular layer. BDNF led to a slowly developing increase of the field excitatory postsynaptic potential (fEPSP) slope and population spike amplitude. The potentiation either reached a plateau level at ∼2 h after BDNF infusion or continued to increase for the duration of experiment; the longest time point recorded was 10 h. Mean increases at 4 h after BDNF infusion were 62.2 and 224% for the fEPSP slope and population spike, respectively. No changes in responses were observed in controls receiving buffer medium only or buffer containing cytochrome C. BDNF-induced potentiation developed in the absence of epileptiform activity in the hippocampal electroencephalogram or changes in recurrent inhibition on granule cells as assessed by paired-pulse inhibition of the population spike. We conclude that exogenous BDNF induces a lasting potentiation of synaptic efficacy in the dentate gyrus of anesthetized adult rats.