Journal articles: 'Neonatal rat spinal cord'

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Walker, Suellen M., B. David Westin, Ronald Deumens, Marjorie Grafe, and Tony L. Yaksh. "Effects of Intrathecal Ketamine in the Neonatal Rat." Anesthesiology 113, no. 1 (July 1, 2010): 147–59. http://dx.doi.org/10.1097/aln.0b013e3181dcd71c.

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Background Systemic ketamine can trigger apoptosis in the brain of rodents and primates during susceptible developmental periods. Clinically, spinally administered ketamine may improve the duration or quality of analgesia in children. Ketamine-induced spinal cord toxicity has been reported in adult animals but has not been systematically studied in early development. Methods In anesthetized rat pups, intrathecal ketamine was administered by lumbar percutaneous injection. Changes in mechanical withdrawal threshold evaluated dose-dependent antinociceptive and carrageenan-induced antihyperalgesic effects in rat pups at postnatal day (P) 3 and 21. After intrathecal injection of ketamine at P3, 7, or 21, spinal cords were examined for apoptosis (Fluoro-Jade C and activated caspase-3), histopathologic change, and glial responses (ionized calcium-binding adapter molecule 1 and glial fibrillary acid protein). After maximal doses of ketamine or saline at P3 or P21, sensory thresholds and gait analysis were evaluated at P35. Results Intrathecal injection of 3 mg/kg ketamine at P3 and 15 mg/kg at P21 reverses carrageenan-induced hyperalgesia. Baseline neuronal apoptosis in the spinal cord was greater at P3 than P7, predominantly in the dorsal horn. Intrathecal injection of 3-10 mg/kg ketamine in P3 pups (but not 15 mg/kg at P21) acutely increased apoptosis and microglial activation in the spinal cord and altered spinal function (reduced mechanical withdrawal threshold and altered static gait parameters) at P35. Conclusions Because acute pathology and long-term behavioral change occurred in the same dose range as antihyperalgesic effects, the therapeutic ratio of intrathecal ketamine is less than one in the neonatal rat. This measure facilitates comparison of the relative safety of spinally administered analgesic agents.

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Fok-Seang, J., and RH Miller. "Astrocyte precursors in neonatal rat spinal cord cultures." Journal of Neuroscience 12, no. 7 (July 1, 1992): 2751–64. http://dx.doi.org/10.1523/jneurosci.12-07-02751.1992.

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Miller, R. H., and V. Szigeti. "Clonal analysis of astrocyte diversity in neonatal rat spinal cord cultures." Development 113, no. 1 (September 1, 1991): 353–62. http://dx.doi.org/10.1242/dev.113.1.353.

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Within the mammalian CNS, astrocytes appear to be a heterogeneous class of cells. To assay the number of distinct types of astrocytes in the rat spinal cord, cell lineage and phenotypic analyses were carried out on cultures from newborn rat spinal cord and five distinct types of astrocytes were observed. Proliferating precursors for each class of astrocyte were isolated by low density culture and shown to give rise to 5 distinct and morphologically homogeneous clusters of GFAP + astrocytes. Immunocytochemical analysis with antibodies A2B5 and Ran-2, which identify different glial lineages in optic nerve cultures, demonstrated that many clusters included both A2B5+ and A2B5- cells. Similarly, many clusters also possessed a mixture of Ran-2+ and Ran-2-cells, suggesting that in spinal cord cultures, in contrast to optic nerve cultures, expression of these antigens is regulated by individual cells rather than by cell lineage. Single-cell cloning studies, revealed that the abundance and proliferative capacity of individual astrocyte precursors differed depending on the type of astrocyte. To assay the effects of a complex cellular environment on the composition of astrocyte clones, lineage analysis was performed in complete spinal cord cultures using a replication deficient retrovirus. Although similar morphologically homogeneous clones of cells to those seen with single-cell clones were observed, the proliferative capacity and relative abundance of the distinct astrocyte precursors differed from that seen in single-cell cloning studies. Together these observations suggest that in spinal cord, gliogenesis is considerably more complex than in the optic nerve and that cultures of newborn rat spinal cord contain multiple, distinct populations of astrocytes.

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Peng, Yuan Bo, Qing Dong Ling, M. A. Ruda, and Daniel R. Kenshalo. "Electrophysiological Changes in Adult Rat Dorsal Horn Neurons After Neonatal Peripheral Inflammation." Journal of Neurophysiology 90, no. 1 (July 2003): 73–80. http://dx.doi.org/10.1152/jn.01019.2002.

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Neonatal peripheral inflammation has been shown to produce profound anatomical changes in the dorsal horn of adult rats. In this study, we explored whether parallel physiological changes exist. Neonatal rats were injected with complete Freund's adjuvant (CFA) into the left hind paw. At 8–10 wk of age, single dorsal horn neurons were recorded in response to graded intensities of mechanical stimuli delivered to the receptive field. In addition, cord dorsum potentials, produced by electrical stimuli delivered to the left sciatic nerve at 2.5× threshold, were recorded bilaterally from L2 to S3. There were significant increases in background activity and responses to brush and pinch in neonatal rats that were treated with CFA, as compared with control rats. Further analysis showed similar significant changes when dorsal horn neurons were categorized into wide dynamic range (WDR), high-threshold (HT), and low-threshold (LT) groups. The receptive field was significantly larger in neonatally treated rats as compared with control rats. Additionally, there was a significant increase in the response to a 49°C heat stimulus in neonatally treated rats as compared with control rats. There was also a trend for the amplitudes of N1, N2, and P waves of the cord dorsum potential to increase and latencies to decrease in neonatally treated rats, but no significant differences were detected between different levels of the spinal cord (L2 to S3). These data further support the notion that anatomical and physiological plasticity changes occurred in the spinal cord following early neonatal CFA treatment.

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Sugaya, K., and W. C. De Groat. "Micturition reflexes in the in vitro neonatal rat brain stem-spinal cord-bladder preparation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 266, no. 3 (March 1, 1994): R658—R667. http://dx.doi.org/10.1152/ajpregu.1994.266.3.r658.

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An in vitro neonatal (1-7 day) rat brain stem-spinal cord-bladder (BSB) preparation was used to examine the central control of micturition. Isovolumetric bladder contractions occurred spontaneously or were induced by electrical stimulation of the ventrolateral brain stem, spinal cord, bladder wall (ES-BW), or by perineal tactile stimulation (PS). Transection of the spinal cord at the L1 segment increased the amplitude of ES-BW- and PS-evoked contractions, and subsequent removal of the spinal cord further increased spontaneous and ES-BW-evoked contractions but abolished PS-evoked contractions. Hexamethonium (1 mM), a ganglionic blocking agent, mimicked the effect of cord extirpation. Tetrodotoxin (1 microM) blocked ES-BW- and PS-evoked contractions but enhanced spontaneous contractions. Bicuculline methiodide (10-50 microM), a gamma-aminobutyric acid A receptor antagonist, increased the amplitude of spontaneous, ES-BW- and PS-evoked contractions. These results indicate that PS-evoked contractions are mediated by spinal reflex pathways, whereas spontaneous and ES-BW-evoked contractions that are elicited by peripheral mechanisms are subject to a tonic inhibition dependent on an efferent outflow from the spinal cord. PS-evoked micturition is also subject to inhibitory modulation arising from sites rostral to the lumbosacral spinal cord. Although electrical stimulation of bulbospinal excitatory pathways can initiate bladder contractions in the neonatal rat, these pathways do not appear to have an important role in controlling micturition during the first postnatal week.

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Ma, Junxuan, Vaibhav Patil, Abhay Pandit, Leo R. Quinlan, David P. Finn, Sibylle Grad, Mauro Alini, and Marianna Peroglio. "In Vitro Model to Investigate Communication between Dorsal Root Ganglion and Spinal Cord Glia." International Journal of Molecular Sciences 22, no. 18 (September 8, 2021): 9725. http://dx.doi.org/10.3390/ijms22189725.

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Chronic discogenic back pain is associated with increased inflammatory cytokine levels that can influence the proximal peripheral nervous system, namely the dorsal root ganglion (DRG). However, transition to chronic pain is widely thought to involve glial activation in the spinal cord. In this study, an in vitro model was used to evaluate the communication between DRG and spinal cord glia. Primary neonatal rat DRG cells were treated with/without inflammatory cytokines (TNF-α, IL-1β, and IL-6). The conditioned media were collected at two time points (12 and 24 h) and applied to spinal cord mixed glial culture (MGC) for 24 h. Adult bovine DRG and spinal cord cell cultures were also tested, as an alternative large animal model, and results were compared with the neonatal rat findings. Compared with untreated DRG-conditioned medium, the second cytokine-treated DRG-conditioned medium (following medium change, thus containing solely DRG-derived molecules) elevated CD11b expression and calcium signal in neonatal rat microglia and enhanced Iba1 expression in adult bovine microglia. Cytokine treatment induced a DRG-mediated microgliosis. The described in vitro model allows the use of cells from large species and may represent an alternative to animal pain models (3R principles).

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Greer, J. J., Z. al-Zubaidy, and J. E. Carter. "Thyrotropin-releasing hormone stimulates perinatal rat respiration in vitro." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 271, no. 5 (November 1, 1996): R1160—R1164. http://dx.doi.org/10.1152/ajpregu.1996.271.5.r1160.

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In the present study, we test whether thyrotropin-releasing hormone (TRH) stimulates respiratory frequency in perinatal rats by acting at regions of the medulla responsible for respiratory rhythmogenesis, the pre-Botzinger complex. We also test whether TRH stimulates respiration in the fetal rat at a time shortly after the inception of respiratory rhythmogenesis [embryonic days (E) 17-18]. Two in vitro experimental models were utilized: the isolated brain stem-spinal cord preparation from fetal (E17-E18) and neonatal [postnatal days (P) 0-2] rats and the medullary slice preparation isolated from neonatal rats (P1-P2). Bath application of TRH caused a dose-dependent, reversible increase (maximum increase approximately 60%) in the frequency of respiratory rhythmic neural discharge generated by brain stem-spinal cord [half-maximal effective concentration (EC50) approximately 9 nM] and medullary slice (EC50 approximately 2.5 nM) neonatal rat preparations. Pressure injection of TRH unilaterally into the region of the pre-Botzinger complex of the neonatal medullary slice caused an approximately 28% increase in the frequency of respiratory discharge. Application of TRH to the medium bathing fetal rat brain stem-spinal cord preparations caused an approximately threefold increase in respiratory discharge frequency. We conclude that TRH stimulates respiratory discharge frequency from the time near inception of respiratory motor discharge and acts directly at the pre-Botzinger complex.

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Pulford, Bruce E., Andrea R. Mihajlov, Howard O. Nornes, and L. Ray Whalen. "Effects of Cultured Adrenal Chromaffin Cell Implants on Hindlimb Reflexes of the6-OHDA Lesioned Rat." Journal of Neural Transplantation and Plasticity 5, no. 2 (1994): 89–102. http://dx.doi.org/10.1155/np.1994.89.

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The effects of implantation of cultured adrenal medullary cells on the recovery of neurotransmitter specific reflex activity were studied in the rat spinal cord using electrophysiological testing methods. Cell suspensions of cultured neonatal adrenal medullary chromaffin (AM) cells (which produce catecholamines), or Schwann (Sc) cells (controls) were implanted into the lumbar region of the spinal cord 2 weeks after catecholamine (CA) denervation by intracisternal injection of 6-hydroxydopamine (6-OHDA). All cells were taken from 7 day neonates and cultured for 10 days in the presence of nerve growth factor (NGF). Three months after implantation, the extent of implant-associated recovery of reflex activity was determined by measuring electromyogram (EMG) activity and force associated with the long latency component of the hindlimb withdrawal reflex (which is CA modulated). After the electrophysiological testing, rats were anesthetized, and the spinal cords were rapidly removed and frozen. Spinal cords were sectioned longitudinally, and implanted cells were visualized using glyoxylic acid techniques. Labelled sections were examined to determine cell survival. Results indicate that 1) chromaffin cells survive for 3 months in the segments of the cord into which they have been implanted and 2) rats implanted with AM cells have significantly more forceful withdrawal reflexes than those that received Sc cells or received no implant after lesioning.

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Maclean, Jason N., Kristine C. Cowley, and Brian J. Schmidt. "NMDA Receptor-Mediated Oscillatory Activity in the Neonatal Rat Spinal Cord Is Serotonin Dependent." Journal of Neurophysiology 79, no. 5 (May 1, 1998): 2804–8. http://dx.doi.org/10.1152/jn.1998.79.5.2804.

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MacLean, Jason N., Kristine C. Cowley, and Brian J. Schmidt. NMDA receptor-mediated oscillatory activity in the neonatal rat spinal cord is serotonin dependent. J. Neurophysiol. 79: 2804–2808, 1998. The effect of serotonin (5-HT) receptor blockade on rhythmic network activity and on N-methyl-d-aspartate (NMDA) receptor-induced membrane voltage oscillations was examined using an in vitro neonatal rat spinal cord preparation. Pharmacologically induced rhythmic hindlimb activity, monitored via flexor and extensor electroneurograms or ventral root recordings, was abolished by 5-HT receptor antagonists. Intrinsic motoneuronal voltage oscillations, induced by NMDA in the presence of tetrodotoxin (TTX), either were abolished completely or transformed to long-lasting voltage shifts by 5-HT receptor antagonists. Conversely, 5-HT application facilitated the expression of NMDA-receptor–mediated rhythmic voltage oscillations. The results suggest that an interplay between 5-HT and NMDA receptor actions may be critical for the production of rhythmic motor behavior in the mammalian spinal cord, both at the network and single cell level.

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Kremer, E., and A. Lev-Tov. "GABA-Receptor–Independent Dorsal Root Afferents Depolarization in the Neonatal Rat Spinal Cord." Journal of Neurophysiology 79, no. 5 (May 1, 1998): 2581–92. http://dx.doi.org/10.1152/jn.1998.79.5.2581.

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Kremer, E. and A. Lev-Tov. GABA-receptor–independent dorsal root afferents depolarization in the neonatal rat spinal cord. J. Neurophysiol. 79: 2581–2592, 1998. Dorsal root afferent depolarization and antidromic firing were studied in isolated spinal cords of neonatal rats. Spontaneous firing accompanied by occasional bursts could be recorded from most dorsal roots in the majority of the cords. The afferent bursts were enhanced after elevation of the extracellular potassium concentration ([K+]e) by 1–2 mM. More substantial afferent bursts were produced when the cords were isolated with intact brain stems. Rhythmic afferent bursts could be recorded from dorsal roots in some of the cords during motor rhythm induced by bath-applied serotonin and N-methyl-d-aspartate (NMDA). Bilaterally synchronous afferent bursts were produced in pairs of dorsal roots after replacing the NaCl in the perfusate with sodium-2-hydroxyethansulfonate or after application of the γ-aminobutyric acid-A (GABAA) receptor antagonist bicuculline with or without serotonin (5-HT) and NMDA. Antidromic afferent bursts also could be elicited under these conditions by stimulation of adjacent dorsal roots, ventrolateral funiculus axons, or ventral white commissural (VWC) fibers. The antidromic bursts were superimposed on prolonged dorsal root potentials (DRPs) and accompanied by a prolonged increase in intraspinal afferent excitability. Surgical manipulations of the cord revealed that afferent firing in the presence of bicuculline persisted in the hemicords after hemisection and still was observed after removal of their ventral horns. Cutting the VWC throughout its length did not perturb the bilateral synchronicity of the discharge. These findings suggest that the activity of dorsal horn neurons is sufficient to produce the discharge and that the bilateral synchronicity can be maintained by cross connectivity that is relayed from side to side dorsal to the VWC. Antagonists of GABAB, 5-HT2/5-HT1C, or glutamate metabotropic group II and III receptors could not abolish afferent depolarization in the presence of bicuculline. Depolarization comparable in amplitude to DRPs, could be produced in tetrodotoxin-treated cords by elevation of [K+]e to the levels reported to develop in the neonatal rat spinal cord in response to dorsal root stimulation. A mechanism involving potassium transients produced by neuronal activity therefore is suggested to be the major cause of the GABA-independent afferent depolarization reported in our study. Possible implications of potassium transients in the developing and the adult mammalian spinal cord are discussed.

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Le Gal, Jean-Patrick, Laurent Juvin, Laura Cardoit, and Didier Morin. "Bimodal Respiratory–Locomotor Neurons in the Neonatal Rat Spinal Cord." Journal of Neuroscience 36, no. 3 (January 20, 2016): 926–37. http://dx.doi.org/10.1523/jneurosci.1825-15.2016.

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Bell, James A., and Errol B. de Souza. "Functional corticotropin-releasing factor receptors in neonatal rat spinal cord." Peptides 9, no. 6 (November 1988): 1317–22. http://dx.doi.org/10.1016/0196-9781(88)90198-2.

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Pinco, M., and A. Lev-Tov. "Modulation of monosynaptic excitation in the neonatal rat spinal cord." Journal of Neurophysiology 70, no. 3 (September 1, 1993): 1151–58. http://dx.doi.org/10.1152/jn.1993.70.3.1151.

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1. The effects of high-frequency (5-50 Hz) stimulation of dorsal root afferents on monosynaptic excitation of alpha motoneurons was studied in the in vitro spinal cord preparation of the neonatal rat, using sharp-electrode intracellular recordings. 2. Double pulse stimulation of dorsal root afferents induced severe depression of testing excitatory postsynaptic potentials (EPSPs) at each of the tested interstimulus intervals (15 ms-5 s). After perfusion of the preparation with low-calcium, high-magnesium Krebs saline, the amplitude of the conditioning EPSPs was markedly decreased and the testing EPSPs exhibited substantial facilitation that was maximal at the 20-ms interval and that was accompanied by depression at intervals > or = 60-100 ms. 3. Short-duration stimulus trains applied to dorsal root afferents normally induced tetanic depression of the intracellularly recorded monosynaptic EPSPs. Switching the bathing solution to low-calcium, high-magnesium saline decreased the control EPSP and induced facilitation and then tetanic potentiation (TP) of the EPSPs within the applied train. The magnitude of potentiation (% potentiation) of these EPSPs depended on the interpulse interval of the short stimulus train and on the degree of attenuation of the unpotentiated control EPSP after the solution was changed from normal- to low-calcium Krebs solution. 4. Long-duration stimulus trains applied to dorsal root afferents at 5-10 Hz induced marked depression of monosynaptic EPSPs during the train. The depression was alleviated after cessation of the tetanic stimulation and was followed in some cases by slight posttetanic potentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

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Cowley, Kristine C., Eugene Zaporozhets, Jason N. MacLean, and Brian J. Schmidt. "Is NMDA Receptor Activation Essential for the Production of Locomotor-Like Activity in the Neonatal Rat Spinal Cord?" Journal of Neurophysiology 94, no. 6 (December 2005): 3805–14. http://dx.doi.org/10.1152/jn.00016.2005.

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Previous work has established that in vitro bath application of N-methyl-d-aspartic acid (NMDA) promotes locomotor activity in a variety of vertebrate preparations including the neonatal rat spinal cord. In addition, NMDA receptor activation gives rise to active membrane properties that are postulated to contribute to the generation or stabilization of locomotor rhythm. However, earlier studies yielded conflicting evidence as to whether NMDA receptors are essential in this role. Therefore in this study, we examined the effect of NMDA receptor blockade, using d-2-amino-5-phosphono-valeric acid (AP5), on locomotor-like activity in the in vitro neonatal rat spinal cord. Locomotor-like activity was induced using 5-hydroxytryptamine (5-HT), acetylcholine, combined 5-HT and NMDA receptor activation, increased K+ concentration, or electrical stimulation of the brain stem and monitored using suction electrode recordings of left and right lumbar ventral root discharge. We also studied the effect on locomotor capacity of selectively suppressing NMDA receptor–mediated active membrane properties; this was achieved by removing Mg2+ ions from the bath, which in turn abolishes voltage-sensitive blockade of the NMDA receptor channel. The results show that, although NMDA receptor activation may seem essential for locomotor network operation under some experimental conditions, locomotor-like rhythms can nevertheless be generated in the presence of AP5 if spinal cord circuitry is exposed to appropriate levels of non–NMDA receptor–dependent excitation. Therefore neither NMDA receptor–mediated nonlinear membrane properties nor NMDA receptor activation in general is universally essential for locomotor network activation in the in vitro neonatal rat spinal cord.

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Hamurtekin, Emre, Bethany L. Fitzsimmons, Veronica I. Shubayev, Marjorie R. Grafe, Ronald Deumens, Tony L. Yaksh, and Suellen M. Walker. "Evaluation of Spinal Toxicity and Long-term Spinal Reflex Function after Intrathecal Levobupivaciane in the Neonatal Rat." Anesthesiology 119, no. 1 (July 1, 2013): 142–55. http://dx.doi.org/10.1097/aln.0b013e31828fc7e7.

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Abstract Background: Neuraxial anesthesia is utilized in children of all ages. Local anesthetics produce dose-dependent toxicity in certain adult models, but the developing spinal cord may also be susceptible to drug-induced apoptosis. In postnatal rodents, we examined the effects of intrathecal levobupivacaine on neuropathology and long-term sensorimotor outcomes. Methods: Postnatal day 3 (P3) or P7 rat pups received intrathecal levobupivacaine 2.5 mg/kg (0.5%) or saline. Mechanical withdrawal thresholds and motor block were assessed. Spinal cord tissue analysis included apoptosis counts (activated caspase-3, Fluoro-Jade C) at 24 h, glial reactivity at 7 days, and histopathology in cord and cauda equina at 24 h and 7 days. Long-term spinal function in young adults (P35) was assessed by hind limb withdrawal thresholds, electromyography responses to suprathreshold stimuli, and gait analysis. Results: Intrathecal levobupivacaine produced spinal anesthesia at P3 and P7. No increase in apoptosis or histopathological change was seen in the cord or cauda equina. In the P3 saline group, activated caspase-3 (mean ± SEM per lumbar cord section 6.1 ± 0.3) and Fluoro-Jade C (12.1 ± 1.2) counts were higher than at P7, but were not altered by levobupivacaine (P = 0.62 and P = 0.11, two-tailed Mann–Whitney test). At P35, mechanical withdrawal thresholds, thermal withdrawal latency, and electromyographic reflex responses did not differ across P3 or P7 levobupivacaine or saline groups (one way ANOVA with Bonferroni comparisons). Intrathecal bupivacaine at P3 did not alter gait. Conclusion: Single dose intrathecal levobupivacaine 0.5% did not increase apoptosis or produce spinal toxicity in neonatal rat pups. This study provides preclinical safety data relevant to neonatal use of neuraxial local anesthesia.

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Cowley, K. C., and B. J. Schmidt. "Regional Distribution of the Locomotor Pattern-Generating Network in the Neonatal Rat Spinal Cord." Journal of Neurophysiology 77, no. 1 (January 1, 1997): 247–59. http://dx.doi.org/10.1152/jn.1997.77.1.247.

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Cowley, K. C. and B. J. Schmidt. Regional distribution of the locomotor pattern-generating network in the neonatal rat spinal cord. J. Neurophysiol. 77: 247–259, 1997. The regional distribution of spinal cord networks producing locomotor-like, as well as non-locomotor-like, activity was studied with the use of an in vitro neonatal rat preparation. Rhythmic activity was induced by bath application of either serotonin (5-HT), acetylcholine (ACh), N-methyl-d,l-aspartate (NMA), or combined 5-HT/NMA, and was monitored via hindlimb flexor (peroneal) and extensor (tibial) electroneurograms (ENGs) or ventral root recordings. In some experiments, synchronous patterns were produced by the addition of inhibitory amino acid (IAA) receptor antagonists. Selective application of 5-HT to cervical and thoracic cord regions induced rhythmic activity in these segments but failed to evoke hindlimb ENG discharge. Exposure of the isolated lumbar region to 5-HT produced tonic activity only. Application of 5-HT to the whole cord produced locomotor-like activity in hindlimb ENGs that persisted after midsagittal section of the spinal cord from the conus to the thoracolumbar junction. In other experiments, transverse hemisection of the rostral lumbar cord during whole cord exposure to 5-HT abolished rhythmic activity in ipsilateral hindlimb ENGs, suggesting that under these conditions rhythmic activity on one side of the lumbar cord was insufficient to maintain rhythmic activity on the contralateral side. Selective application of NMA or ACh to cervical and/or thoracic cord regions evoked rhythmic activity in these supralumbar segments, as well as rhythmic, but non-locomotor-like, activity in the lumbar region. In contrast to the effect of 5-HT, both NMA and ACh evoked rhythmic activity when applied solely to the lumbar region, and the side-to-side alternation produced by whole cord ACh application was uncoupled by midsagittal lesions of the lumbar region. In the presence of IAA antagonists, the side-to-side coupling of bilaterally synchronous rhythms was maintained despite extensive midsagittal lesions leaving all but one or two segments of either cervical, thoracic, or lumbar cord bilaterally intact, and rhythmic activity could be maintained even in single isolated hemisegments. The effects of 5-HT/NMA were similar to those observed with the use of 5-HT alone, although 5-HT/NMA induced rhythmic activity in hindlimb ENGs when applied selectively to supralumbar regions. The results suggest that 1) a 5-HT-sensitive oscillatory network, capable of producing a locomotor-like pattern of activity, is distributed throughout the supralumbar region of the spinal cord and mediates descending rhythmic drive to lumbar motor centers; 2) NMA- and ACh-sensitive rhythmogenic elements are distributed throughout the spinal cord, including the lumbar region; and 3) the spinal cord contains an extensive propriospinal network of reciprocal inhibitory and excitatory connections characterized by redundantly organized side-to-side projections.

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Bregman, Barbara S. "Development of serotonin immunoreactivity in the rat spinal cord and its plasticity after neonatal spinal cord lesions." Developmental Brain Research 34, no. 2 (August 1987): 245–63. http://dx.doi.org/10.1016/0165-3806(87)90213-6.

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Gabbay, H., I. Delvolvé, and A. Lev-Tov. "Pattern Generation in Caudal-Lumbar and Sacrococcygeal Segments of the Neonatal Rat Spinal Cord." Journal of Neurophysiology 88, no. 2 (August 1, 2002): 732–39. http://dx.doi.org/10.1152/jn.2002.88.2.732.

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The rhythmogenic capacity of the tail-innervating segments (L4-Co3) of the spinal cord was studied in isolated spinal cord and tail–spinal cord preparations of neonatal rats. Bath-applied serotonin/ N-methyl-d-aspartate (NMDA) failed to produce a robust sacrococcygeal rhythmicity following midlumbar transection of the spinal cord. By contrast, a regular alternating left–right rhythm could be induced in the sacrococcygeal segments by application of noradrenaline (NA) or NA and NMDA before and after midlumbar transection of the cord. This rhythm was accelerated with the concentration of NMDA and was blocked by α1 or α2 adrenoceptor antagonists. The efferent bursts induced by NA/NMDA were accompanied by rhythmic tail movements produced by alternating activation of the left and right tail muscles and by coactivation of flexors, extensors, and abductors on a given side of the tail. This coactivation implies that reciprocal inhibitory pathways were not activated during the rhythm. Lesion experiments revealed that the rhythmogenic circuitry is distributed along all or most of the sacrococcygeal segments. The NA/NMDA-induced rhythm persisted in the isolated sacrococcygeal (S1-Co3), sacral (S1-S4), coccygeal (Co1-Co3), and smaller isolated regions of the sacrococcygeal cord. The rhythm also could be maintained in longitudinally split sacrococcygeal hemicords in which flexor, extensor, and abductor motoneurons are coactivated. This finding indicates that neither left/right nor flexor/extensor inhibitory interactions are required for rhythmogenesis in the sacrococcygeal cord. A slow rhythm lacking the alternating left–right pattern was induced by NA/NMDA in tail-innervating caudal lumbar segments of isolated L4-Co3 preparations. This rhythm was independent of the concurrent sacrococcygeal rhythm and the activity pattern of the tail musculature and it does not seem to contribute to rhythmic tail movements under these conditions. Comparative studies of the rhythm produced in the isolated caudal lumbar, sacrococcygeal cord, and caudal thoracic–rostral lumbar segments revealed that the S1-Co3 rhythm was faster than the L4-L6 pattern and slower than the T6-L3 rhythm. It is suggested that the caudal lumbar and sacrococcygeal segments of the cord are normally driven by the faster rostral lumbar central pattern generators. The relevance of the findings described above to pattern generation in the mammalian spinal cord is discussed.

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Hsieh, Cheng-Ta, Yih-Jing Lee, Xiaoli Dai, Norma Ojeda, Hyun Lee, Lu-Tai Tien, and Lir-Wan Fan. "Systemic Lipopolysaccharide-Induced Pain Sensitivity and Spinal Inflammation Were Reduced by Minocycline in Neonatal Rats." International Journal of Molecular Sciences 19, no. 10 (September 27, 2018): 2947. http://dx.doi.org/10.3390/ijms19102947.

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In this study, we investigated the effects of minocycline, a putative suppressor of microglial activation, on systemic lipopolysaccharide (LPS)-induced spinal cord inflammation, allodynia, and hyperalgesia in neonatal rats. Intraperitoneal (i.p.) injection of LPS (2 mg/kg) or sterile saline was performed in postnatal day 5 (P5) rat pups and minocycline (45 mg/kg) or vehicle (phosphate buffer saline; PBS) was administered (i.p.) 5 min after LPS injection. The von Frey filament and tail-flick tests were performed to determine mechanical allodynia (a painful sensation caused by innocuous stimuli, e.g., light touch) and thermal hyperalgesia (a condition of altered perception of temperature), respectively, and spinal cord inflammation was examined 24 h after the administration of drugs. Systemic LPS administration resulted in a reduction of tactile threshold in the von Frey filament tests and pain response latency in the tail-flick test of neonatal rats. The levels of microglia and astrocyte activation, pro-inflammatory cytokine interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), and prostaglandin E2 (PGE2) in the spinal cord of neonatal rats were increased 24 h after the administration of LPS. Treatment with minocycline significantly attenuated LPS-induced allodynia, hyperalgesia, the increase in spinal cord microglia, and astrocyte activation, and elevated levels of IL-1β, COX-2, and PGE2 in neonatal rats. These results suggest that minocycline provides protection against neonatal systemic LPS exposure-induced enhanced pain sensitivity (allodynia and hyperalgesia), and that the protective effects may be associated with its ability to attenuate LPS-induced microglia activation, and the levels of IL-1β, COX-2, and PGE2 in the spinal cord of neonatal rats.

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Dourado, Michelle, and Peter B. Sargent. "Properties of Nicotinic Receptors Underlying Renshaw Cell Excitation by α-Motor Neurons in Neonatal Rat Spinal Cord." Journal of Neurophysiology 87, no. 6 (June 1, 2002): 3117–25. http://dx.doi.org/10.1152/jn.2002.87.6.3117.

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We used anatomical and physiological approaches to characterize nicotinic receptors (AChRs) on Renshaw cells of the neonatal rat spinal cord. Confocal imaging of Renshaw cells, identified by their characteristic pattern of gephyrin immunoreactivity, revealed that these neurons are immuno-positive for the α4 and β2 AChR subunits but not for the α7 subunit. We used whole cell recording in spinal cord slices to characterize synaptic transmission from α-motor neurons to Renshaw cells, which could be identified pharmacologically by the sensitivity of transmission to d-tubocurarine. α-Motor neuron-to-Renshaw cell synapses were blocked by 10 μM dihydro-β-erythroidine (dHβE), but not 50 nM methyllycaconitine (MLA), a selective α7 antagonist. These findings support a role for α4β2-like AChRs, but not α7 AChRs, in rapid excitatory transmission between α-motor neurons and Renshaw cells in rat spinal cord.

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Takahashi, T. "Membrane currents in visually identified motoneurones of neonatal rat spinal cord." Journal of Physiology 423, no. 1 (April 1, 1990): 27–46. http://dx.doi.org/10.1113/jphysiol.1990.sp018009.

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Sakuma, Masafumi, Koichi Yoshioka, Mitsuhiko Yanagisawa, Yuko Onishi, and Masanori Otsuka. "Tachykinins induce a release of acetylcholine from neonatal rat spinal cord." Japanese Journal of Pharmacology 52 (1990): 143. http://dx.doi.org/10.1016/s0021-5198(19)55256-8.

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Mouveroux, J. M. P., E. A. J. F. Lakke, and E. Marani. "Intrinsic Properties Inhibit Axonal Outgrowth from Neonatal Rat Spinal Cord Explant." Archives of Physiology and Biochemistry 110, no. 3 (January 2002): 177–85. http://dx.doi.org/10.1076/apab.110.3.177.8292.

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Bryz-Gornia, Walter F., and Dennis J. Stelzner. "Ascending tract neurons survive spinal cord transection in the neonatal rat." Experimental Neurology 93, no. 1 (July 1986): 195–210. http://dx.doi.org/10.1016/0014-4886(86)90159-7.

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Kendig, Joan J., Maarit K. T. Savola, Scott J. Woodley, and Mervyn Maze. "α2-Adrenoceptors inhibit a nociceptive response in neonatal rat spinal cord." European Journal of Pharmacology 192, no. 2 (January 1991): 293–300. http://dx.doi.org/10.1016/0014-2999(91)90055-u.

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Li, Yu-Qing, and C. Shun Wong. "Radiation-Induced Apoptosis in the Neonatal and Adult Rat Spinal Cord." Radiation Research 154, no. 3 (September 2000): 268–76. http://dx.doi.org/10.1667/0033-7587(2000)154[0268:riaitn]2.0.co;2.

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Sanders, Robert D., Jing Xu, Yi Shu, Antonio Fidalgo, Daqing Ma, and Mervyn Maze. "General Anesthetics Induce Apoptotic Neurodegeneration in the Neonatal Rat Spinal Cord." Anesthesia & Analgesia 106, no. 6 (June 2008): 1708–11. http://dx.doi.org/10.1213/ane.0b013e3181733fdb.

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Bos, Rémi, and Laurent Vinay. "Glucose is an adequate energy substrate for the depolarizing action of GABA and glycine in the neonatal rat spinal cord in vitro." Journal of Neurophysiology 107, no. 11 (June 1, 2012): 3107–15. http://dx.doi.org/10.1152/jn.00571.2011.

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In vitro studies have repeatedly demonstrated that the neurotransmitters γ-aminobutyric acid (GABA) and glycine depolarize immature neurons in many areas of the CNS, including the spinal cord. This widely accepted phenomenon was recently challenged by experiments showing that the depolarizing action of GABA on neonatal hippocampus and neocortex in vitro was prevented by adding energy substrates (ES), such as the ketone body metabolite dl-β-hydroxybutyric acid (DL-BHB), lactate, or pyruvate to the artificial cerebrospinal fluid (ACSF). It was suggested that GABA-induced depolarizations in vitro might be an artifact due to inadequate energy supply when glucose is the sole energy source, consistent with the energy metabolism of neonatal rat brain being largely dependent on ESs other than glucose. Here we examined the effects of these ESs (DL-BHB, lactate, pyruvate) on inhibitory postsynaptic potentials (IPSPs) recorded from neonatal rat lumbar spinal cord motoneurons (MNs), in vitro. We report that supplementing the ACSF with physiologic concentrations of DL-BHB, lactate, or pyruvate does not alter the reversal potential of IPSPs ( EIPSP). Only high concentrations of pyruvate hyperpolarized EIPSP. In addition, the depolarizing action of GABA on primary afferent terminals was not affected by supplementing the ACSF with ES at physiologic concentrations. We conclude that depolarizing IPSPs in immature MNs and the primary afferent depolarizations are not caused by inadequate energy supply. Glucose at its standard concentration appears to be an adequate ES for the neonatal spinal cord in vitro.

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Ecob-Prince, M. S., M. Jenkison, G. S. Butler-Browne, and R. G. Whalen. "Neonatal and adult myosin heavy chain isoforms in a nerve-muscle culture system." Journal of Cell Biology 103, no. 3 (September 1, 1986): 995–1005. http://dx.doi.org/10.1083/jcb.103.3.995.

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When adult mouse muscle fibers are co-cultured with embryonic mouse spinal cord, the muscle regenerates to form myotubes that develop cross-striations and contractions. We have investigated the myosin heavy chain (MHC) isoforms present in these cultures using polyclonal antibodies to the neonatal, adult fast, and slow MHC isoforms of rat (all of which were shown to react specifically with the analogous mouse isoforms) in an immunocytochemical assay. The adult fast MHC was absent in newly formed myotubes but was found at later times, although it was absent when the myotubes myotubes were cultured without spinal cord tissue. When nerve-induced muscle contractions were blocked by the continuous presence of alpha-bungarotoxin, there was no decrease in the proportion of fibers that contained adult fast MHC. Neonatal and slow MHC were found at all times in culture, even in the absence of the spinal cord, and so their expression was not thought to be nerve-dependent. Thus, in this culture system, the expression of adult fast MHC required the presence of the spinal cord, but was probably not dependent upon nerve-induced contractile activity in the muscle fibers.

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Blivis, D., G. Z. Mentis, M. J. O'Donovan, and A. Lev-Tov. "Differential Effects of Opioids on Sacrocaudal Afferent Pathways and Central Pattern Generators in the Neonatal Rat Spinal Cord." Journal of Neurophysiology 97, no. 4 (April 2007): 2875–86. http://dx.doi.org/10.1152/jn.01313.2006.

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The effects of opioids on sacrocaudal afferent (SCA) pathways and the pattern-generating circuitry of the thoracolumbar and sacrocaudal segments of the spinal cord were studied in isolated spinal cord and brain stem-spinal cord preparations of the neonatal rat. The locomotor and tail moving rhythm produced by activation of nociceptive and nonnociceptive sacrocaudal afferents was completely blocked by specific application of the μ-opioid receptor agonist [d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin acetate salt (DAMGO) to the sacrocaudal but not the thoracolumbar segments of the spinal cord. The rhythmic activity could be restored after addition of the opioid receptor antagonist naloxone to the experimental chamber. The opioid block of the SCA-induced rhythm is not due to impaired rhythmogenic capacity of the spinal cord because a robust rhythmic activity could be initiated in the thoracolumbar and sacrocaudal segments in the presence of DAMGO, either by stimulation of the ventromedial medulla or by bath application of N-methyl-d-aspartate/serotonin. We suggest that the opioid block of the SCA-induced rhythm involves suppression of synaptic transmission through sacrocaudal interneurons interposed between SCA and the pattern-generating circuitry. The expression of μ opioid receptors in several groups of dorsal, intermediate and ventral horn interneurons in the sacrocaudal segments of the cord, documented in this study, provides an anatomical basis for this suggestion.

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Jean-Xavier, Céline, Jean-François Pflieger, Sylvie Liabeuf, and Laurent Vinay. "Inhibitory Postsynaptic Potentials in Lumbar Motoneurons Remain Depolarizing After Neonatal Spinal Cord Transection in the Rat." Journal of Neurophysiology 96, no. 5 (November 2006): 2274–81. http://dx.doi.org/10.1152/jn.00328.2006.

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GABA and glycine are excitatory in the immature spinal cord and become inhibitory during development. The shift from depolarizing to hyperpolarizing inhibitory postsynaptic potentials (IPSPs) occurs during the perinatal period in the rat, a time window during which the projections from the brain stem reach the lumbar enlargement. In this study, we investigated the effects of suppressing influences of the brain on lumbar motoneurons during this critical period for the negative shift of the reversal potential of IPSPs ( EIPSP). The spinal cord was transected at the thoracic level on the day of birth [postnatal day 0 (P0)]. EIPSP, at P4–P7, was significantly more depolarized in cord-transected than in cord-intact animals ( EIPSP above and below resting potential, respectively). EIPSP at P4–P7 in cord-transected animals was close to EIPSP at P0–P2. K-Cl cotransporter KCC2 immunohistochemistry revealed a developmental increase of staining in the area of lumbar motoneurons between P0 and P7 in cord-intact animals; this increase was not observed after spinal cord transection. The motoneurons recorded from cord-transected animals were less sensitive to the experimental manipulations aimed at testing the functionality of the KCC2 system, which is sensitive to [K+]o and blocked by bumetanide. Although bumetanide significantly depolarized EIPSP, the shift was less pronounced than in cord-intact animals. In addition, a reduction of [K+]o affected EIPSP significantly only in cord-intact animals. Therefore influences from the brain stem may play an essential role in the maturation of inhibitory synaptic transmission, possibly by upregulating KCC2 and its functionality.

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Klein, David A., Angelica Patino, and Matthew C. Tresch. "Flexibility of Motor Pattern Generation Across Stimulation Conditions by the Neonatal Rat Spinal Cord." Journal of Neurophysiology 103, no. 3 (March 2010): 1580–90. http://dx.doi.org/10.1152/jn.00961.2009.

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Previous studies have demonstrated that “locomotor-like” rhythmic patterns can be evoked in the isolated neonatal rat spinal cord by several means, including pharmacological neuromodulation and electrical stimulation of various pathways. Recent studies have used stimulation of afferent pathways to evoke rhythmic patterns, relying on synaptic activation of interneuronal systems rather than global imposition of neuromodulatory state by pharmacological agents. We use the in vitro neonatal rat spinal cord with attached hindlimb to examine the muscle activation patterns evoked by stimulation of these different pathways and evaluate whether stimulation of these pathways all evoke the same patterns. We find that the patterns evoked by bath application of serotonin (5-HT) and N-methyl-d-aspartic acid (NMDA) consisted of alternation between hip flexors and extensors and similar alternation was observed in the patterns evoked by electrical stimulation of the cauda equina (CE) or contralateral fifth lumbar (L5) dorsal nerve root. In contrast, the knee extensor/hip flexor rectus femoris (RF) and knee flexor/hip extensor semitendinosus (ST) were activated differentially across stimulation conditions. In 5-HT/NMDA patterns, RF was active in late flexion and ST in late extension. In CE patterns, these two muscles switched places with RF typically active in late extension and ST active in flexion. In L5 patterns, ST was activated in extension and RF was silent or weakly active during flexion. There were also systematic differences in the consistency of rhythms evoked by each stimulation method: patterns evoked by electrical stimulation of CE or L5 were less consistently modulated with the rhythm when compared with 5-HT/NMDA-evoked patterns. All differences were preserved following deafferentation, demonstrating that they reflect intrinsic properties of spinal systems. These results highlight the intrinsic flexibility of motor pattern generation by spinal motor circuitry which is present from birth and provides important information to many studies examining spinal pattern generating networks.

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MacLean, Jason N., and Brian J. Schmidt. "Voltage-Sensitivity of Motoneuron NMDA Receptor Channels Is Modulated by Serotonin in the Neonatal Rat Spinal Cord." Journal of Neurophysiology 86, no. 3 (September 1, 2001): 1131–38. http://dx.doi.org/10.1152/jn.2001.86.3.1131.

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Both N-methyl-d-aspartate (NMDA) and serotonin (5-HT) receptors contribute to the generation of rhythmic motor patterns in the rat spinal cord. Co-application of these chemicals is more effective at producing locomotor-like activity than either neurochemical alone. In addition, NMDA application to rat spinal motoneurons, synaptically isolated in tetrodotoxin, induces nonlinear membrane behavior that results in voltage oscillations which can be blocked by 5-HT antagonists. However, the mechanisms underlying NMDA and 5-HT receptor interactions pertinent to motor rhythm production remain to be determined. In the present study, an in vitro neonatal rat spinal cord preparation was used to examine whether NMDA receptor-mediated nonlinear membrane voltage is modulated by 5-HT. Whole-cell recordings of spinal motoneurons demonstrated that 5-HT shifts the region of NMDA receptor-dependent negative slope conductance (RNSC) of the current-voltage relationship to more hyperpolarized potentials and enhances whole-cell inward current. The influence of 5-HT on the RNSC was similar to the effect on the RNSC of decreasing the extracellular Mg2+concentration. The results suggest that 5-HT may modulate this form of membrane voltage nonlinearity by regulating Mg2+ blockade of the NMDA ionophore.

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Bremner, L., M. Fitzgerald, and M. Baccei. "Functional GABAA-Receptor–Mediated Inhibition in the Neonatal Dorsal Horn." Journal of Neurophysiology 95, no. 6 (June 2006): 3893–97. http://dx.doi.org/10.1152/jn.00123.2006.

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Neonatal nociceptive circuits and dorsal horn cells are characterized by an apparent lack of inhibitory control: receptive fields are large and thresholds low in the first weeks of life. It has been suggested that this may reflect immature GABAA-receptor (GABAAR) signaling whereby an early developmental shift in transmembrane anion gradient is followed by a longer period of low Cl− extrusion capacity. To investigate whether functional GABAAR-mediated inhibition does indeed undergo postnatal regulation at the level of dorsal horn circuits, we applied the selective GABAAR antagonist gabazine to the spinal cord in anesthetized rat pups [postnatal day (P) 3 or 21] while recording spike activity in single lumbar dorsal horn cells in vivo. At both ages, blockade of GABAAR activity resulted in enlarged hind paw receptive field areas and increased activity evoked by low- and high-intensity cutaneous stimulation, revealing comparable inhibition of dorsal horn cell firing by spinal GABAARs at P3 and P21. This inhibition did not require descending pathways to the spinal cord because perforated patch-clamp recordings of deep dorsal horn neurons in P3 spinal cord slices also showed an increase in evoked spike activity after application of gabazine. We conclude that spinal GABAergic inhibitory transmission onto single dorsal horn cells “in vivo” is functional at P3 and that low Cl− extrusion capacity does not restrict GABAergic function over the normal range of evoked sensory activity. The excitability of neonatal spinal sensory circuits could reflect immaturity in other intrinsic or descending inhibitory networks rather than weak spinal GABAergic inhibition.

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Miura, Akira, Masahito Kawatani, Isao Araki, and William C. de Groat. "Electrophysiological properties of lumbosacral preganglionic neurons in the neonatal rat spinal cord." Brain Research 872, no. 1-2 (July 2000): 54–63. http://dx.doi.org/10.1016/s0006-8993(00)02448-3.

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Ma, R. C., and N. J. Dun. "Norepinephrine depolarizes lateral horn cells of neonatal rat spinal cord in vitro." Neuroscience Letters 60, no. 2 (September 1985): 163–68. http://dx.doi.org/10.1016/0304-3940(85)90238-1.

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Tarasiuk, Ariel, Lisa Gibbs, and Joan J. Kendig. "Descending inhibition in neonatal rat spinal cord: Actions of pentobarbital and morphine." Brain Research Bulletin 41, no. 1 (January 1996): 39–45. http://dx.doi.org/10.1016/0361-9230(96)00168-2.

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Feng, J., and J. J. Kendig. "Synergistic interactions between midazolam and alfentanil in isolated neonatal rat spinal cord." British Journal of Anaesthesia 77, no. 3 (September 1996): 375–80. http://dx.doi.org/10.1093/bja/77.3.375.

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Kremer, E., and A. Lev-Tov. "GABA-independent dorsal root afferent depolarization in the neonatal rat spinal cord." Neuroscience Letters 237 (November 1997): S30. http://dx.doi.org/10.1016/s0304-3940(97)90120-8.

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Newberry, N. R., and G. P. Connolly. "Muscarinic pharmacology of the spinal cord of the neonatal rat in vitro." Neuropharmacology 28, no. 2 (February 1989): 149–52. http://dx.doi.org/10.1016/0028-3908(89)90051-8.

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Kao, T., J. S. Shumsky, M. Murray, and K. A. Moxon. "Exercise Induces Cortical Plasticity after Neonatal Spinal Cord Injury in the Rat." Journal of Neuroscience 29, no. 23 (June 10, 2009): 7549–57. http://dx.doi.org/10.1523/jneurosci.2474-08.2009.

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Savola, Maarit K. T., and Juha-Matti Savola. "α2A/D-Adrenoceptor subtype predominates also in the neonatal rat spinal cord." Developmental Brain Research 94, no. 1 (June 1996): 106–8. http://dx.doi.org/10.1016/0165-3806(96)00060-0.

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43

Oz, Murat, Keun-Hang Yang, Toni S. Shippenberg, Leo P. Renaud, and Michael J. O'Donovan. "Cholecystokinin B-Type Receptors Mediate a G-Protein-Dependent Depolarizing Action of Sulphated Cholecystokinin Ocatapeptide (CCK-8s) on Rodent Neonatal Spinal Ventral Horn Neurons." Journal of Neurophysiology 98, no. 3 (September 2007): 1108–14. http://dx.doi.org/10.1152/jn.00148.2007.

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Reports of cholecystokinin (CCK) binding and expression of CCK receptors in neonatal rodent spinal cord suggest that CCK may influence neuronal excitability. In patch-clamp recordings from 19/21 ventral horn motoneurons in neonatal (PN 5–12 days) rat spinal cord slices, we noted a slowly rising and prolonged membrane depolarization induced by bath-applied sulfated CCK octapeptide (CCK-8s; 1 μM), blockable by the CCKB receptor antagonist L-365,260 (1 μM). Responses to nonsulfated CCK-8 or CCK-4 were significantly weaker. Under voltage clamp ( VH −65 mV), 22/24 motoneurons displayed a CCK-8s-induced tetrodotoxin-resistant inward current [peak: −136 ± 28 pA] with a similar time course, mediated via reduction in a potassium conductance. In 29/31 unidentified neurons, CCK-8s induced a significantly smaller inward current (peak: −42.8 ± 5.6 pA), and I-V plots revealed either membrane conductance decrease with net inward current reversal at 101.3 ± 4.4 mV ( n = 16), membrane conductance increase with net current reversing at 36.1 ± 3.8 mV ( n = 4), or parallel shift ( n = 9). Intracellular GTP-γ-S significantly prolonged the effect of CCK-8s ( n = 6), whereas GDP-β-S significantly reduced the CCK-8s response ( n = 6). Peak inward currents were significantly reduced after 5-min perfusion with N-ethylmaleimide. In isolated neonatal mouse spinal cord preparations, CCK-8s (30–300 nM) increased the amplitude and discharge of spontaneous depolarizations recorded from lumbosacral ventral roots. These observations imply functional postsynaptic G-protein-coupled CCKB receptors are prevalent in neonatal rodent spinal cord.

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Chu, Ya-Chun, Kwok-Hon Chan, Mei-Yung Tsou, Su-Man Lin, Ying-Chou Hsieh, and Yuan-Xiang Tao. "Mechanical Pain Hypersensitivity after Incisional Surgery Is Enhanced in Rats Subjected to Neonatal Peripheral Inflammation." Anesthesiology 106, no. 6 (June 1, 2007): 1204–12. http://dx.doi.org/10.1097/01.anes.0000267604.40258.d1.

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Background Neonatal pain and inflammation may lead to a long-term effect on nociceptive processing in adults. The current study examined the characteristics of postoperative incisional pain behaviors in adult rats that were subjected to neonatal peripheral inflammation. Methods Rat pups received a subcutaneous injection of saline or carrageenan into the plantar surface of the left hind paw at postnatal day 1. Naive pups were used as the control. Paw withdrawal thresholds to punctuate mechanical stimuli were examined at postnatal days 35, 42, and 49. After rats received a plantar incision on the left or right hind paw at postnatal day 50, paw withdrawal thresholds were measured at 4 h, 1 day, 2 days, 3 days, 5 days, and 7 days after incision. In addition, spinal cord Fos expression was detected at 2 h after incision. Finally, the effects of intrathecal N-methyl-D-aspartate receptor antagonists DL-2-amino-5-phosphonovaleric acid and dizocilpine and the nitric oxide synthase inhibitor L-N-nitro-arginine methylester on incisional pain were examined at 4 h after incision. Results Although the rats subjected to neonatal peripheral carrageenan injection developed mechanical hypoalgesia in bilateral hind paws at baseline, they displayed increased spinal cord Fos expression at 2 h and exaggerated mechanical pain hypersensitivity at 4 h (but not at other time points) after plantar incision. Intrathecal DL-2-amino-5-phosphonovaleric acid, dizocilpine, and L-N-nitro-arginine methylester significantly attenuated incision-induced mechanical pain hypersensitivity at 4 h after incision in the neonatally carrageenan-treated rats, but not in the naive or neonatally saline-treated rats. Conclusions The authors' results suggest that early inflammatory insults during the neonatal period could produce excessive incision-associated mechanical pain hypersensitivity in adult rats. Spinal cord N-methyl-D-aspartate receptors and downstream nitric oxide signaling might contribute to this abnormal pain hypersensitivity, although the mechanisms underlying the long-term effect of neonatal inflammation are still unclear.

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Smith, D. O., C. Franke, J. L. Rosenheimer, F. Zufall, and H. Hatt. "Glutamate-activated channels in adult rat ventral spinal cord cells." Journal of Neurophysiology 66, no. 2 (August 1, 1991): 369–78. http://dx.doi.org/10.1152/jn.1991.66.2.369.

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1. Currents in response to rapid application of glutamate and its agonists were studied in cells dissociated from the ventral spinal cord of adult rats. 2. Glutamate activated an inward current that desensitized in less than 15 ms. 3. Responses to quisqualate and to DL-alpha-amino-3-hydroxy-5-methyl-isoxeazolepropionic acid (AMPA) also desensitized with time constants ranging from 7 to 18 ms in whole cell configuration and from 3.4 to 4.3 ms in outside-out configuration. Desensitization rate was independent of membrane potential. Single-channel conductance was 12 pS. 4. Currents in response to N-methyl-D-aspartate activation also desensitized; the time constants ranged from 15 to 50 ms. Single-channel conductance was 23 pS. 5. Kainate responses did not desensitize appreciably. Single-channel conductance was 17 pS. 6. These data obtained from adult cells are similar to values reported for cultured embryonic and neonatal neurons, indicating minimal postnatal changes in these aspects of glutamate receptors.

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Ikeda, Y., C. Fry, F. Hayashi, D. Stolz, D. Griffiths, and A. Kanai. "Role of gap junctions in spontaneous activity of the rat bladder." American Journal of Physiology-Renal Physiology 293, no. 4 (October 2007): F1018—F1025. http://dx.doi.org/10.1152/ajprenal.00183.2007.

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Increased gap junction expression in lamina propria myofibroblasts and urothelial cells may be involved in detrusor overactivity, leading to incontinence. Immunohistochemistry was used to compare connexin (Cx) 26, 43, and 45 expression in the bladders of neonatal, adult, and spinal cord-transected rats, while optical imaging was used to map the spread of spontaneous activity and the effects of gap junction blockade. Female adult Sprague-Dawley rats were deeply anesthetized, a laminectomy was performed, and the spinal cord was transected (T8/T9). After 14 days, their bladders and those of age-matched adults (4 mo old) and neonates (7–21 day old) were excised and studied immunohistochemically using frozen sections or optically using whole bladders stained with voltage- and Ca2+-sensitive dyes. The expression of Cx26 was localized to the urothelium, Cx43 to the lamina propria myofibroblasts, and Cx45 to the detrusor smooth muscle. While the expression of Cx45 was comparable in all bladders, the expression of Cx43 and Cx26 was increased in neonate and transected animals. In the bladders of adults, spontaneous activity was initiated at multiple sites, resulting in a lack of coordination. Alternatively, in neonate and transected animals spontaneous activity was initiated at a focal site near the dome and spread in a coordinated fashion throughout the bladder. Gap junction blockade (18β-glycyrrhetinic acid, 1 μM) abolished this coordinated activity but had no effect on the uncoordinated activity in adult bladders. These data suggest that coordinated spontaneous activity requires gap junction upregulation in urothelial cells and lamina propria myofibroblasts.

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Shu, Liang, Jingjing Su, Lingyan Jing, Ying Huang, Yu Di, Lichao Peng, and Jianren Liu. "Reduced Renshaw Recurrent Inhibition after Neonatal Sciatic Nerve Crush in Rats." Neural Plasticity 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/786985.

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Renshaw recurrent inhibition (RI) plays an important gated role in spinal motion circuit. Peripheral nerve injury is a common disease in clinic. Our current research was designed to investigate the change of the recurrent inhibitory function in the spinal cord after the peripheral nerve crush injury in neonatal rat. Sciatic nerve crush was performed on 5-day-old rat puppies and the recurrent inhibition between lateral gastrocnemius-soleus (LG-S) and medial gastrocnemius (MG) motor pools was assessed by conditioning monosynaptic reflexes (MSR) elicited from the sectioned dorsal roots and recorded either from the LG-S and MG nerves by antidromic stimulation of the synergist muscle nerve. Our results demonstrated that the MSR recorded from both LG-S or MG nerves had larger amplitude and longer latency after neonatal sciatic nerve crush. The RI in both LG-S and MG motoneuron pools was significantly reduced to virtual loss (15–20% of the normal RI size) even after a long recovery period upto 30 weeks after nerve crush. Further, the degree of the RI reduction after tibial nerve crush was much less than that after sciatic nerve crush indicatig that the neuron-muscle disconnection time is vital to the recovery of the spinal neuronal circuit function during reinnervation. In addition, sciatic nerve crush injury did not cause any spinal motor neuron loss but severally damaged peripheral muscle structure and function. In conclusion, our results suggest that peripheral nerve injury during neonatal early development period would cause a more sever spinal cord inhibitory circuit damage, particularly to the Renshaw recurrent inhibition pathway, which might be the target of neuroregeneration therapy.

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Qtsuka, M., K. Yoshioka, M. Yanagisawa, H. Suzuki, F. Y. Zhao, J. Z. Guo, R. Hosoki, and T. Kurihara. "Use of NK1 receptor antagonists in the exploration of physiological functions of substance P and neurokinin A." Canadian Journal of Physiology and Pharmacology 73, no. 7 (July 1, 1995): 903–7. http://dx.doi.org/10.1139/y95-124.

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Tachykinin NK1 receptor antagonists were used to explore the physiological functions of substance P (SP) and neurokinin A (NKA). Pharmacological profiles of three NK1 receptor antagonists, GR71251, GR82334, and RP 67580, were examined in the isolated spinal cord preparation of the neonatal rat. These tachykinin receptor antagonists exhibited considerable specificities and antagonized the actions of both SP and NKA to induce the depolarization of ventral roots. Electrical stimulation of the saphenous nerve with C-fiber strength evoked a depolarization lasting about 30 s of the ipsilateral L3 ventral root. This response, which is referred to as saphenous-nerve-evoked slow ventral root potential (VRP), was depressed by these NK1 receptor antagonists. In contrast, the saphenous-nerve-evoked slow VRP was potentiated by application of a mixture of peptidase inhibitors, including thiorphan, actinonin, and captopril in the presence of naloxone, but not after further addition of GR71251. Likewise, in the isolated coeliac ganglion of the guinea pig, electrical stimulation of the mesenteric nerves evoked in some ganglionic cells slow excitatory postsynaptic potentials (EPSPs), which were depressed by GR71251 and potentiated by peptidase inhibitors. These results further support the notion that SP and NKA serve as neurotransmitters producing slow EPSPs in the neonatal rat spinal cord and guinea pig prevertebral ganglia.Key words: substance P, neurokinin A, neurotransmitter, tachykinin antagonist, spinal cord.

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Kolaj, Miloslav, and Leo P. Renaud. "Vasopressin-Induced Currents in Rat Neonatal Spinal Lateral Horn Neurons Are G-Protein Mediated and Involve Two Conductances." Journal of Neurophysiology 80, no. 4 (October 1, 1998): 1900–1910. http://dx.doi.org/10.1152/jn.1998.80.4.1900.

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Kolaj, Miloslav and Leo P. Renaud. Vasopressin-induced currents in rat neonatal spinal lateral horn neurons are G-protein mediated and involve two conductances . J. Neurophysiol. 80: 1900–1910, 1998. Arginine vasopressin (AVP) receptors are expressed early in the developing spinal cord. To characterize AVP-induced conductances in lower thoracic sympathetic preganglionic (SPN) and other lateral horn neurons, we used patch-clamp recording techniques in neonatal (11–21 days) rat spinal cord slices. Most (90%) of 273 neurons, including all 68 SPNs, responded to AVP with membrane depolarization and/or a V1 receptor-mediated, dose-dependent (0.01–1.0 μM) and tetrodotoxin (TTX)-resistant inward current. A role for G-proteins was indicated by persistence of this inward current after intracellular dialysis with GTP-γ-S or GMP-PNP, its marked reduction with GDP-β-S, and significant reduction, but not abolition, after preincubation with pertussis toxin or in the presence of N-ethylmaleimide. Analysis of individual current-voltage ( I- V) relationships in 57 cells indicated the presence of two different membrane conductances. In 21 cells, net AVP-induced currents reversed around −103 mV, reflecting reduction in one or more barium-sensitive potassium conductances; in 12 cells, net AVP-induced current reversed around −40 mV and was not significantly sensitive to several potassium channel blockers including barium, tetraethylammonium chloride (TEA), 4-aminopyridine (4AP), cesium, or glibenclamide, suggesting increase in a nonselective cationic conductance that was separate from I h; in 24 cells where I- V lines shifted in parallel, AVP-induced inward currents were significantly greater and probably involved both conductances. These data indicate that SPNs and a majority of unidentified neonatal lateral horn neurons possess functional G-protein–coupled V1-type vasopressin receptors. The wide distribution of AVP receptors in neonatal spinal lateral column cells suggests a role that may extend beyond involvement in regulation of autonomic nervous system function.

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Diener, Pamela S., and Barbara S. Bregman. "Fetal Spinal Cord Transplants Support Growth of Supraspinal and Segmental Projections after Cervical Spinal Cord Hemisection in the Neonatal Rat." Journal of Neuroscience 18, no. 2 (January 15, 1998): 779–93. http://dx.doi.org/10.1523/jneurosci.18-02-00779.1998.

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Journal articles on the topic 'Neonatal rat spinal cord'

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