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1
Hendricks, William D., Gary L. Westbrook, and Eric Schnell. "Early detonation by sprouted mossy fibers enables aberrant dentate network activity." Proceedings of the National Academy of Sciences 116, no. 22 (May 13, 2019): 10994–99. http://dx.doi.org/10.1073/pnas.1821227116.
Повний текст джерелаАнотація:
In temporal lobe epilepsy, sprouting of hippocampal mossy fiber axons onto dentate granule cell dendrites creates a recurrent excitatory network. However, unlike mossy fibers projecting to CA3, sprouted mossy fiber synapses depress upon repetitive activation. Thus, despite their proximal location, relatively large presynaptic terminals, and ability to excite target neurons, the impact of sprouted mossy fiber synapses on hippocampal hyperexcitability is unclear. We find that despite their short-term depression, single episodes of sprouted mossy fiber activation in hippocampal slices initiated bursts of recurrent polysynaptic excitation. Consistent with a contribution to network hyperexcitability, optogenetic activation of sprouted mossy fibers reliably triggered action potential firing in postsynaptic dentate granule cells after single light pulses. This pattern resulted in a shift in network recruitment dynamics to an “early detonation” mode and an increased probability of release compared with mossy fiber synapses in CA3. A lack of tonic adenosine-mediated inhibition contributed to the higher probability of glutamate release, thus facilitating reverberant circuit activity.
2
Otsu, Yo, Eiichi Maru, Hisayuki Ohata, Ichiro Takashima, Riichi Kajiwara, and Toshio Iijima. "Optical Recording Study of Granule Cell Activities in the Hippocampal Dentate Gyrus of Kainate-Treated Rats." Journal of Neurophysiology 83, no. 4 (April 1, 2000): 2421–30. http://dx.doi.org/10.1152/jn.2000.83.4.2421.
Повний текст джерелаАнотація:
In the epileptic hippocampus, newly sprouted mossy fibers are considered to form recurrent excitatory connections to granule cells in the dentate gyrus and thereby increase seizure susceptibility. To study the effects of mossy fiber sprouting on neural activity in individual lamellae of the dentate gyrus, we used high-speed optical recording to record signals from voltage-sensitive dye in hippocampal slices prepared from kainate-treated epileptic rats (KA rats). In 14 of 24 slices from KA rats, hilar stimulation evoked a large depolarization in almost the entire molecular layer in which granule cell apical dendrites are located. The signals were identified as postsynaptic responses because of their dependence on extracellular Ca2+. The depolarization amplitude was largest in the inner molecular layer (the target area of sprouted mossy fibers) and declined with increasing distance from the granule cell layer. In the inner molecular layer, a good correlation was obtained between depolarization size and the density of mossy fiber terminals detected by Timm staining methods. Blockade of GABAergic inhibition by bicuculline enlarged the depolarization in granule cell dendrites. Our data indicate that mossy fiber sprouting results in a large and prolonged synaptic depolarization in an extensive dendritic area and that the enhanced GABAergic inhibition partly masks the synaptic depolarization. However, despite the large dendritic excitation induced by the sprouted mossy fibers, seizurelike activity of granule cells was never observed, even when GABAergic inhibition was blocked. Therefore, mossy fiber sprouting may not play a critical role in epileptogenesis.
3
Frotscher, M., E. Soriano, and U. Misgeld. "Divergence of hippocampal mossy fibers." Synapse 16, no. 2 (February 1994): 148–60. http://dx.doi.org/10.1002/syn.890160208.
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4
Williams, Brent L., Mady Hornig, Kavitha Yaddanapudi, and W. Ian Lipkin. "Hippocampal Poly(ADP-Ribose) Polymerase 1 and Caspase 3 Activation in Neonatal Bornavirus Infection." Journal of Virology 82, no. 4 (December 5, 2007): 1748–58. http://dx.doi.org/10.1128/jvi.02014-07.
Повний текст джерелаАнотація:
ABSTRACT Infection of neonatal rats with Borna disease virus results in a characteristic behavioral syndrome and apoptosis of subsets of neurons in the hippocampus, cerebellum, and cortex (neonatal Borna disease [NBD]). In the NBD rat hippocampus, dentate gyrus granule cells progressively degenerate. Apoptotic loss of granule cells in NBD is associated with accumulation of zinc in degenerating neurons and reduced zinc in granule cell mossy fibers. Excess zinc can trigger poly(ADP-ribose) polymerase 1 (PARP-1) activation, and PARP-1 activation can mediate neuronal death. Here, we evaluate hippocampal PARP-1 mRNA and protein expression levels, activation, and cleavage, as well as apoptosis-inducing factor (AIF) nuclear translocation and executioner caspase 3 activation, in NBD rats. PARP-1 mRNA and protein levels were increased in NBD hippocampi. PARP-1 expression and activity were increased in granule cell neurons and glia with enhanced ribosylation of proteins, including PARP-1 itself. In contrast, levels of poly(ADP-ribose) glycohydrolase mRNA were decreased in NBD hippocampi. PARP-1 cleavage and AIF expression were also increased in astrocytes in NBD hippocampi. Levels of activated caspase 3 protein were increased in NBD hippocampi and localized to nuclei, mossy fibers, and dendrites of granule cell neurons. These results implicate aberrant zinc homeostasis, PARP-1, and caspase 3 activation as contributing factors in hippocampal neurodegeneration in NBD.
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Okazaki, Maxine M., Péter Molnár, and J. Victor Nadler. "Recurrent Mossy Fiber Pathway in Rat Dentate Gyrus: Synaptic Currents Evoked in Presence and Absence of Seizure-Induced Growth." Journal of Neurophysiology 81, no. 4 (April 1, 1999): 1645–60. http://dx.doi.org/10.1152/jn.1999.81.4.1645.
Повний текст джерелаАнотація:
Recurrent mossy fiber pathway in rat dentate gyrus: synaptic currents evoked in presence and absence of seizure-induced growth. A common feature of temporal lobe epilepsy and of animal models of epilepsy is the growth of hippocampal mossy fibers into the dentate molecular layer, where at least some of them innervate granule cells. Because the mossy fibers are axons of granule cells, the recurrent mossy fiber pathway provides monosynaptic excitatory feedback to these neurons that could facilitate seizure discharge. We used the pilocarpine model of temporal lobe epilepsy to study the synaptic responses evoked by activating this pathway. Whole cell patch-clamp recording demonstrated that antidromic stimulation of the mossy fibers evoked an excitatory postsynaptic current (EPSC) in ∼74% of granule cells from rats that had survived >10 wk after pilocarpine-induced status epilepticus. Recurrent mossy fiber growth was demonstrated with the Timm stain in all instances. In contrast, antidromic stimulation of the mossy fibers evoked an EPSC in only 5% of granule cells studied 4–6 days after status epilepticus, before recurrent mossy fiber growth became detectable. Notably, antidromic mossy fiber stimulation also evoked an EPSC in many granule cells from control rats. Clusters of mossy fiber-like Timm staining normally were present in the inner third of the dentate molecular layer at the level of the hippocampal formation from which slices were prepared, and several considerations suggested that the recorded EPSCs depended mainly on activation of recurrent mossy fibers rather than associational fibers. In both status epilepticus and control groups, the antidromically evoked EPSC was glutamatergic and involved the activation of both AMPA/kainate and N-methyl-d-aspartate (NMDA) receptors. EPSCs recorded in granule cells from rats with recurrent mossy fiber growth differed in three respects from those recorded in control granule cells: they were much more frequently evoked, a number of them were unusually large, and the NMDA component of the response was generally much more prominent. In contrast to the antidromically evoked EPSC, the EPSC evoked by stimulation of the perforant path appeared to be unaffected by a prior episode of status epilepticus. These results support the hypothesis that recurrent mossy fiber growth and synapse formation increases the excitatory drive to dentate granule cells and thus facilitates repetitive synchronous discharge. Activation of NMDA receptors in the recurrent pathway may contribute to seizure propagation under depolarizing conditions. Mossy fiber-granule cell synapses also are present in normal rats, where they may contribute to repetitive granule cell discharge in regions of the dentate gyrus where their numbers are significant.
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Kress, Geraldine J., Margaret J. Dowling, Julian P. Meeks, and Steven Mennerick. "High Threshold, Proximal Initiation, and Slow Conduction Velocity of Action Potentials in Dentate Granule Neuron Mossy Fibers." Journal of Neurophysiology 100, no. 1 (July 2008): 281–91. http://dx.doi.org/10.1152/jn.90295.2008.
Повний текст джерелаАнотація:
Dentate granule neurons give rise to some of the smallest unmyelinated fibers in the mammalian CNS, the hippocampal mossy fibers. These neurons are also key regulators of physiological and pathophysiological information flow through the hippocampus. We took a comparative approach to studying mossy fiber action potential initiation and propagation in hippocampal slices from juvenile rats. Dentate granule neurons exhibited axonal action potential initiation significantly more proximal than CA3 pyramidal neurons. This conclusion was suggested by phase plot analysis of somatic action potentials and by local tetrodotoxin application to the axon and somatodendritic compartments. This conclusion was also verified by immunostaining for voltage-gated sodium channel alpha subunits and by direct dual soma/axonal recordings. Dentate neurons exhibited a significantly higher action potential threshold and slower axonal conduction velocity than CA3 neurons. We conclude that while the electrotonically proximal axon location of action potential initiation allows granule neurons to sensitively detect and integrate synaptic inputs, the neurons are sluggish to initiate and propagate an action potential.
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Ruiz, Arnaud, Ruth Fabian-Fine, Ricardo Scott, Matthew C. Walker, Dmitri A. Rusakov, and Dimitri M. Kullmann. "GABAA Receptors at Hippocampal Mossy Fibers." Neuron 39, no. 6 (September 2003): 961–73. http://dx.doi.org/10.1016/s0896-6273(03)00559-2.
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Pan, Enhui, Zirun Zhao, and James O. McNamara. "LTD at mossy fiber synapses onto stratum lucidum interneurons requires TrkB and retrograde endocannabinoid signaling." Journal of Neurophysiology 121, no. 2 (February 1, 2019): 609–19. http://dx.doi.org/10.1152/jn.00669.2018.
Повний текст джерелаАнотація:
Hippocampal mossy fiber axons simultaneously activate CA3 pyramidal cells and stratum lucidum interneurons (SLINs), the latter providing feedforward inhibition to control CA3 pyramidal cell excitability. Filopodial extensions of giant boutons of mossy fibers provide excitatory synaptic input to the SLIN. These filopodia undergo extraordinary structural plasticity causally linked to execution of memory tasks, leading us to seek the mechanisms by which activity regulates these synapses. High-frequency stimulation of the mossy fibers induces long-term depression (LTD) of their calcium-permeable AMPA receptor synapses with SLINs; previous work localized the site of induction to be postsynaptic and the site of expression to be presynaptic. Yet, the underlying signaling events and the identity of the retrograde signal are incompletely understood. We used whole cell recordings of SLINs in hippocampal slices from wild-type and mutant mice to explore the mechanisms. Genetic and pharmacologic perturbations revealed a requirement for both the receptor tyrosine kinase TrkB and its agonist, brain-derived neurotrophic factor (BDNF), for induction of LTD. Inclusion of inhibitors of Trk receptor kinase and PLC in the patch pipette prevented LTD. Endocannabinoid receptor antagonists and genetic deletion of the CB1 receptor prevented LTD. We propose a model whereby release of BDNF from mossy fiber filopodia activates TrkB and PLCγ1 signaling postsynaptically within SLINs, triggering synthesis and release of an endocannabinoid that serves as a retrograde signal, culminating in reduced glutamate release. Insights into the signaling pathways by which activity modifies function of these synapses will facilitate an understanding of their contribution to the local circuit and behavioral consequences of hippocampal granule cell activity. NEW & NOTEWORTHY We investigated signaling mechanisms underlying plasticity of the hippocampal mossy fiber filopodial synapse with interneurons in stratum lucidum. High-frequency stimulation of the mossy fibers induces long-term depression of this synapse. Our findings are consistent with a model in which brain-derived neurotrophic factor released from filopodia activates TrkB of a stratum lucidum interneuron; the ensuing activation of PLCγ1 induces synthesis of an endocannabinoid, which provides a retrograde signal leading to reduced release of glutamate presynaptically.
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Sekino, Yuko, Kunihiko Obata, Manabu Tanifuji, Makoto Mizuno, and Jin Murayama. "Delayed Signal Propagation via CA2 in Rat Hippocampal Slices Revealed by Optical Recording." Journal of Neurophysiology 78, no. 3 (September 1, 1997): 1662–68. http://dx.doi.org/10.1152/jn.1997.78.3.1662.
Повний текст джерелаАнотація:
Sekino, Yuko, Kunihiko Obata, Manabu Tanifuji, Makoto Mizuno, and Jin Murayama. Delayed signal propagation via CA2 in rat hippocampal slices revealed by optical recording. J. Neurophysiol. 78: 1662–1668, 1997. Signal propagation from mossy fibers to CA1 neurons was investigated in rat hippocampal slices by a combination of electrical and optical recordings. The slices were prepared by oblique sectioning of the middle part of the hippocampus to preserve fiber connections. The mossy fibers were stimulated to induce population spikes (PSs) and excitatory postsynaptic potentials in the middle part of the CA1 region. Latencies of maximal PSs in CA1 varied widely among slices; they ranged from 7 to 13.5 ms, with two maxima at 9 and 11.5 ms. The fastest PSs probably are evoked by the Schaffer collaterals that connect the CA3 and CA1 regions in the well-known trisynaptic circuit. However, the slower PSs suggest the existence of additional delayed inputs. To determine the source of the delayed input, slices were stained with a voltage-sensitive dye, RH482, and the optical signals relevant to membrane potential changes were detected by a high-resolution optical imaging system. Optical recording of responses to mossy fiber stimulation indicated two distinct types of signal propagation from CA3 to CA1. In preparations evincing the fast type of propagation, signals spread to CA1 within 7.2 ms after the mossy fiber stimulation. During such propagation, activity flowed directly from CA3 to the stratum radiatum of CA1. Other preparations illustrated slow signal propagation, in which optical signals were generated in CA2 before spreading to CA1. During such slow signal transmission, activity persisted in CA2 and its surrounding area for 3 ms before propagating to the strata radiatum and oriens in CA1. In such cases, CA1 activity was detected within 10.8 ms of mossy fiber stimulation. In some slices, a mixture of the fast and slow propagation patterns was observed, indicating that these two transmission modes can coexist. Our data reveal that CA2 neurons can transmit delayed excitatory signals to CA1 neurons. We therefore conclude that consideration of electrical signal propagation through the hippocampus should include flow through the CA2 region in addition to the traditional dentate gyrus–CA3–CA1 trisynaptic circuit.
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Scharfman, Helen E. "Does the Development of a GABAergic Phenotype by Hippocampal Dentate Gyrus Granule Cells Contribute to Epileptogenesis?" Epilepsy Currents 2, no. 2 (March 2002): 63. http://dx.doi.org/10.1111/j.1535-7597.2002.00023.x.
Повний текст джерелаАнотація:
Monosynaptic GABAergic Signaling from Dentate to CA3 with a Pharmacological and Physiological Profile Typical of Mossy Fiber Synapses Walker MC, Ruiz A, Kullmann DM Neuron 2001;29:703–715 Mossy fibers are the sole excitatory projection from dentate gyrus granule cells to the hippocampus, where they release glutamate, dynorphin, and zinc. In addition, mossy fiber terminals show intense immunoreactivity for the inhibitory neurotransmitter GABA. Fast inhibitory transmission at mossy fiber synapses, however, has not previously been reported. Here, we show that electrical or chemical stimuli that recruit dentate granule cells elicit monosynaptic GABA(A) receptor-mediated synaptic signals in CA3 pyramidal neurons. These inhibitory signals satisfy the criteria that distinguish mossy fiber-CA3 synapses: high sensitivity to metabotropic glutamate receptor agonists, facilitation during repetitive stimulation, and NMDA receptor-independent long-term potentiation. GABAergic transmission from the dentate gyrus to CA3 has major implications not only for information flow into the hippocampus but also for developmental and pathological processes involving the hippocampus. Seizures Induce Simultaneous GABAergic and Glutamatergic Transmission in the Dentate Gyrus-CA3 System Gutierrez R J Neurophysiol 2000;84:3088–3090 Monosynaptic and polysynaptic responses of CA3 pyramidal cells (PC) to stimulation of the dentate gyrus (DG) are normally blocked by glutamate receptor antagonists (GluRAs). However, after kindled seizures, GluRAs block the monosynaptic excitatory postsynaptic potential (EPSP) and isolate a monosynaptic inhibitory postsynaptic potential (IPSP), suggesting that mossy fibers release GABA. However, kindling epilepsy induces neuronal sprouting, which can underlie this fast inhibitory response. To explore this possibility, the synaptic responses of PC to DG stimulation were analyzed in kindled epileptic rats, with and without seizures, and in nonepileptic rats, immediately after a single pentylenetetrazol (PTZ)-induced seizure, in which sprouting is unlikely to have occurred. Excitatory and inhibitory synaptic responses of PC to DG stimulation were blocked by GluRAs in control cells and in cells from kindled nonseizing rats, confirming that inhibitory potentials are disynaptically mediated. However, a fast IPSP could be evoked in kindled epileptic rats and in nonepileptic rats after a single PTZ-induced seizure. The same response was induced after rekindling the epileptic nonseizing rats. This IPSP has an onset latency that parallels that of the control EPSP and is not altered under low Ca(2+) medium or halothane perfusion. In addition, it was reversibly depressed by L(+)-2-amino-4-phosphonobutyric acid (L-AP4), which is known to inhibit transmitter release from mossy fibers. These results demonstrate that seizures, and not the synaptic rearrangement due to an underlying epileptic state, induce the emergence of fast inhibition in the DG-CA3 system, and suggest that the mossy fibers underlie this plastic change. Kindling Induces Transient Fast Inhibition in the Dentate Gyrus-CA3 Projection Gutierrez R, Heinemann U Eur J Neurosci 2001;13:1371–1379 The granule cells of the dentate gyrus (DG) send a strong glutamatergic projection, the mossy fibre tract, toward the hippocampal CA3 field, where it excites pyramidal cells and neighbouring inhibitory interneurons. Despite their excitatory nature, granule cells contain small amounts of GAD (glutamate decarboxylase), the main synthetic enzyme for the inhibitory transmitter GABA. Chronic temporal lobe epilepsy results in transient upregulation of GAD and GABA in granule cells, giving rise to the speculation that following overexcitation, mossy fibres exert an inhibitory effect by release of GABA. We therefore stimulated the DG and recorded synaptic potentials from CA3 pyramidal cells in brain slices from kindled and control rats. In both preparations, DG stimulation caused excitatory postsynaptic potential (EPSP)/inhibitory postsynaptic potential (IPSP) sequences. These potentials could be completely blocked by glutamate receptor antagonists in control rats, while in the kindled rats, a bicuculline-sensitive fast IPSP remained, with an onset latency similar to that of the control EPSP. Interestingly, this IPSP disappeared 1 month after the last seizure. When synaptic responses were evoked by high-frequency stimulation, EPSPs in normal rats readily summate to evoke action potentials. In slices from kindled rats, a summation of IPSPs overrides that of the EPSPs and reduces the probability of evoking action potentials. Our data show for the first time that kindling induces functionally relevant activity-dependent expression of fast inhibition onto pyramidal cells, coming from the DG, that can limit CA3 excitation in a frequency-dependent manner. Vesicular GABA Transporter mRNA Expression in the Dentate Gyrus and in Mossy Fiber Synaptosomes Lamas M, Gomez-Lira G, Gutierrez R Brain Res Mol Brain Res 2001;93:209–214 In the normal granule cells of the dentate gyrus, glutamate and both gamma-aminobutyric acid (GABA) and glutamic acid decarboxylase (GAD) coexist. GAD expression is increased after seizures, and simultaneous glutamatergic and GABAergic neurotransmission from the mossy fibers to CA3 appears, supporting the hypothesis that GABA can be released from the mossy fibers. To sustain GABAergic neurotransmission, the amino acids for the presence and regulation of expression of the vesicular GABA transporter (VGAT) mRNA in the dentate gyrus and in mossy fiber synaptosomes of control and kindled rats. We found trace amounts of VGAT mRNA in the dentate gyrus and mossy fiber synaptosomes of control rats. In the dentate gyrus of kindled rats with several seizures and of control rats subject to one acute seizure, no changes were apparent either 1 or 24 h after the seizures. However, repetitive synaptic or antidromic activation of the granule cells in slices of control rats in vitro induces an activity-dependent enhancement of VGAT mRNA expression in the dentate. Surprisingly, in the mossy fiber synaptosomes of seizing rats, the levels of VGAT mRNA were significantly higher than in controls. These data show that the granule cells and their mossy fibers, besides containing machinery for the synthesis of GABA, also contain the elements that support its vesiculation. This further supports the notion that local synaptic molecular changes enable mossy fibers to release GABA in response to enhanced excitability.
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Ruiz, Arnaud, Matthew C. Walker, Ruth Fabian-Fine, and Dimitri M. Kullmann. "Endogenous Zinc Inhibits GABAA Receptors in a Hippocampal Pathway." Journal of Neurophysiology 91, no. 2 (February 2004): 1091–96. http://dx.doi.org/10.1152/jn.00755.2003.
Повний текст джерелаАнотація:
Depending on their subunit composition, GABAA receptors can be highly sensitive to Zn2+. Although a pathological role for Zn2+-mediated inhibition of GABAA receptors has been postulated, no direct evidence exists that endogenous Zn2+ can modulate GABAergic signaling in the brain. A possible explanation is that Zn2+ is mainly localized to a subset of glutamatergic synapses. Hippocampal mossy fibers are unusual in that they are glutamatergic but have also been reported to contain GABA and Zn2+. Here, we show, using combined Timm's method and post-embedding immunogold, that the same mossy fiber varicosities can contain both GABA and Zn2+. Chelating Zn2+ with either calcium-saturated EDTA or N,N,N′ ,N′-tetrakis (2-pyridylmethyl)ethylenediamine had no effect on stratum-radiatum-evoked inhibitory postsynaptic currents (IPSCs), but enhanced IPSCs evoked by stimuli designed to recruit dentate granule cells. We also show that IPSCs recorded in CA3 pyramidal neurons in acute hippocampal slices are depressed by exogenous Zn2+. This depression was of similar amplitude whether the IPSCs were evoked by stimulation in s. radiatum (to recruit local interneurons) or in the s. granulosum of the dentate gyrus (to recruit mossy fibers). These results show for the first time that GABAergic IPSCs can be modulated by endogenous Zn2+ and are consistent with GABA release at Zn2+-containing mossy fiber synapses.
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Kubota, Hisahiko, Henrik Alle, Heinrich Betz, and Jörg R. P. Geiger. "Presynaptic glycine receptors on hippocampal mossy fibers." Biochemical and Biophysical Research Communications 393, no. 4 (March 2010): 587–91. http://dx.doi.org/10.1016/j.bbrc.2010.02.019.
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Hu, Bingren, Chunli Liu, Helen Bramlett, Thomas J. Sick, Ofelia F. Alonso, Shaoyi Chen, and W. Dalton Dietrich. "Changes in TrkB–ERK1/2–CREB/Elk-1 Pathways in Hippocampal Mossy Fiber Organization after Traumatic Brain Injury." Journal of Cerebral Blood Flow & Metabolism 24, no. 8 (August 2004): 934–43. http://dx.doi.org/10.1097/01.wcb.0000125888.56462.a1.
Повний текст джерелаАнотація:
Traumatic brain injury (TBI) leads to mossy fiber reorganization, which is considered to be a causative factor in the development of temporal lobe epilepsy. However, the underlying mechanism is not fully understood. Emerging evidence suggests that TrkB–ERK1/2–CREB/Elk-1 pathways are highly related to synaptic plasticity. This study used the rat fluid-percussion injury model to investigate activation of TrkB–ERK1/2–CREB/Elk-1 signaling pathways after TBI. Rats were subjected to 2.0-atm parasagittal TBI followed by 30 minutes, 4 hours, 24 hours, and 72 hours of recovery. After TBI, striking activation of TrkB–ERK1/2–CREB/Elk-1 signaling pathways in mossy fiber organization were observed with confocal microscopy and Western blot analysis. ERK1/2 was highly phosphorylated predominantly in hippocampal mossy fibers, whereas TrkB was phosphorylated both in the mossy fibers and the dentate gyrus region at 30 minutes and 4 hours of recovery after TBI. CREB was also activated at 30 minutes, peaked at 24 hours of recovery, and returned to the control level at 72 hours of recovery in dentate gyrus granule cells. Elk-1 phosphorylation was seen in CA3 neurons at 4 hours after TBI. The results suggest that the signaling pathways of TrkB–ERK1/2–CREB/Elk-1 are highly activated in mossy fiber organization, which may contribute to mossy fiber reorganization seen after TBI.
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Quach, Tam, Nathalie Auvergnon, Rajesh Khanna, Marie-Françoise Belin, Papachan Kolattukudy, Jérome Honnorat, and Anne-Marie Duchemin. "Opposing Morphogenetic Defects on Dendrites and Mossy Fibers of Dentate Granular Neurons in CRMP3-Deficient Mice." Brain Sciences 8, no. 11 (November 3, 2018): 196. http://dx.doi.org/10.3390/brainsci8110196.
Повний текст джерелаАнотація:
Collapsin response mediator proteins (CRMPs) are highly expressed in the brain during early postnatal development and continue to be present in specific regions into adulthood, especially in areas with extensive neuronal plasticity including the hippocampus. They are found in the axons and dendrites of neurons wherein they contribute to specific signaling mechanisms involved in the regulation of axonal and dendritic development/maintenance. We previously identified CRMP3’s role on the morphology of hippocampal CA1 pyramidal dendrites and hippocampus-dependent functions. Our focus here was to further analyze its role in the dentate gyrus where it is highly expressed during development and in adults. On the basis of our new findings, it appears that CRMP3 has critical roles both in axonal and dendritic morphogenesis of dentate granular neurons. In CRMP3-deficient mice, the dendrites become dystrophic while the infrapyramidal bundle of the mossy fiber shows aberrant extension into the stratum oriens of CA3. This axonal misguided projection of granular neurons suggests that the mossy fiber-CA3 synaptic transmission, important for the evoked propagation of the activity of the hippocampal trisynaptic circuitry, may be altered, whereas the dystrophic dendrites may impair the dynamic interactions with the entorhinal cortex, both expected to affect hippocampal function.
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Koyama, Ryuta. "Development of functional networks by hippocampal mossy fibers." Neuroscience Research 58 (January 2007): S14. http://dx.doi.org/10.1016/j.neures.2007.06.077.
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Alle, H., A. Roth, and J. R. P. Geiger. "Energy-Efficient Action Potentials in Hippocampal Mossy Fibers." Science 325, no. 5946 (September 10, 2009): 1405–8. http://dx.doi.org/10.1126/science.1174331.
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Chandy, Joby, Joseph P. Pierce, and Teresa A. Milner. "Rat hippocampal mossy fibers contain cholecystokinin-like immunoreactivity." Anatomical Record 243, no. 4 (December 1995): 519–23. http://dx.doi.org/10.1002/ar.1092430415.
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Mori, Masahiro, Beat H. Gähwiler, and Urs Gerber. "Recruitment of an inhibitory hippocampal network after bursting in a single granule cell." Proceedings of the National Academy of Sciences 104, no. 18 (April 16, 2007): 7640–45. http://dx.doi.org/10.1073/pnas.0702164104.
Повний текст джерелаАнотація:
The hippocampal CA3 area, an associational network implicated in memory function, receives monosynaptic excitatory as well as disynaptic inhibitory input through the mossy-fiber axons of the dentate granule cells. Synapses made by mossy fibers exhibit low release probability, resulting in high failure rates at resting discharge frequencies of 0.1 Hz. In recordings from functionally connected pairs of neurons, burst firing of a granule cell increased the probability of glutamate release onto both CA3 pyramidal cells and inhibitory interneurons, such that subsequent low-frequency stimulation evoked biphasic excitatory/inhibitory responses in a CA3 pyramidal cell, an effect lasting for minutes. Analysis of the unitary connections in the circuit revealed that granule cell bursting caused powerful activation of an inhibitory network, thereby transiently suppressing excitatory input to CA3 pyramidal cells. This phenomenon reflects the high incidence of spike-to-spike transmission at granule cell to interneuron synapses, the numerically much greater targeting by mossy fibers of inhibitory interneurons versus principal cells, and the extensively divergent output of interneurons targeting CA3 pyramidal cells. Thus, mossy-fiber input to CA3 pyramidal cells appears to function in three distinct modes: a resting mode, in which synaptic transmission is ineffectual because of high failure rates; a bursting mode, in which excitation predominates; and a postbursting mode, in which inhibitory input to the CA3 pyramidal cells is greatly enhanced. A mechanism allowing the transient recruitment of inhibitory input may be important for controlling network activity in the highly interconnected CA3 pyramidal cell region.
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Bausch, Suzanne B., and James O. McNamara. "Contributions of Mossy Fiber and CA1 Pyramidal Cell Sprouting to Dentate Granule Cell Hyperexcitability in Kainic Acid–Treated Hippocampal Slice Cultures." Journal of Neurophysiology 92, no. 6 (December 2004): 3582–95. http://dx.doi.org/10.1152/jn.01028.2003.
Повний текст джерелаАнотація:
Axonal sprouting like that of the mossy fibers is commonly associated with temporal lobe epilepsy, but its significance remains uncertain. To investigate the functional consequences of sprouting of mossy fibers and alternative pathways, kainic acid (KA) was used to induce robust mossy fiber sprouting in hippocampal slice cultures. Physiological comparisons documented many similarities in granule cell responses between KA- and vehicle-treated cultures, including: seizures, epileptiform bursts, and spontaneous excitatoty postsynaptic currents (sEPSCs) >600pA. GABAergic control and contribution of glutamatergic synaptic transmission were similar. Analyses of neurobiotin-filled CA1 pyramidal cells revealed robust axonal sprouting in both vehicle- and KA-treated cultures, which was significantly greater in KA-treated cultures. Hilar stimulation evoked an antidromic population spike followed by variable numbers of postsynaptic potentials (PSPs) and population spikes in both vehicle- and KA-treated cultures. Despite robust mossy fiber sprouting, knife cuts separating CA1 from dentate gyrus virtually abolished EPSPs evoked by hilar stimulation in KA-treated but not vehicle-treated cultures, suggesting a pivotal role of functional afferents from CA1 to dentate gyrus in KA-treated cultures. Together, these findings demonstrate striking hyperexcitability of dentate granule cells in long-term hippocampal slice cultures after treatment with either vehicle or KA. The contribution to hilar-evoked hyperexcitability of granule cells by the unexpected axonal projection from CA1 to dentate in KA-treated cultures reinforces the idea that axonal sprouting may contribute to pathologic hyperexcitability of granule cells.
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Bastos, Fatima C., Vanessa N. Corceiro, Sandra A. Lopes, José G. de Almeida, Carlos M. Matias, Jose C. Dionisio, Paulo J. Mendes, Fernando D. S. Sampaio dos Aidos, Rosa M. Quinta-Ferreira, and M. Emilia Quinta-Ferreira. "Effect of tolbutamide on tetraethylammonium-induced postsynaptic zinc signals at hippocampal mossy fiber-CA3 synapses." Canadian Journal of Physiology and Pharmacology 95, no. 9 (September 2017): 1058–63. http://dx.doi.org/10.1139/cjpp-2016-0379.
Повний текст джерелаАнотація:
The application of tetraethylammonium (TEA), a blocker of voltage-dependent potassium channels, can induce long-term potentiation (LTP) in the synaptic systems CA3–CA1 and mossy fiber-CA3 pyramidal cells of the hippocampus. In the mossy fibers, the depolarization evoked by extracellular TEA induces a large amount of glutamate and also of zinc release. It is considered that zinc has a neuromodulatory role at the mossy fiber synapses, which can, at least in part, be due to the activation of presynaptic ATP-dependent potassium (KATP) channels. The aim of this work was to study properties of TEA-induced zinc signals, detected at the mossy fiber region, using the permeant form of the zinc indicator Newport Green. The application of TEA caused a depression of those signals that was partially blocked by the KATP channel inhibitor tolbutamide. After the removal of TEA, the signals usually increased to a level above baseline. These results are in agreement with the idea that intense zinc release during strong synaptic events triggers a negative feedback action. The zinc depression, caused by the LTP-evoking chemical stimulation, turns into potentiation after TEA washout, suggesting the existence of a correspondence between the observed zinc potentiation and TEA-evoked mossy fiber LTP.
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Kapur, Ajay, Mark F. Yeckel, Richard Gray, and Daniel Johnston. "L-Type Calcium Channels Are Required for One Form of Hippocampal Mossy Fiber LTP." Journal of Neurophysiology 79, no. 4 (April 1, 1998): 2181–90. http://dx.doi.org/10.1152/jn.1998.79.4.2181.
Повний текст джерелаАнотація:
Kapur, Ajay, Mark F. Yeckel, Richard Gray, and Daniel Johnston. L-type calcium channels are required for one form of hippocampal mossy fiber LTP. J. Neurophysiol. 79: 2181–2190, 1998. The requirement of postsynaptic calcium influx via L-type channels for the induction of long-term potentiation (LTP) of mossy fiber input to CA3 pyramidal neurons was tested for two different patterns of stimulation. Two types of LTP-inducing stimuli were used based on the suggestion that one of them, brief high-frequency stimulation (B-HFS), induces LTP postsynaptically, whereas the other pattern, long high-frequency stimulation (L-HFS), induces mossy fiber LTP presynaptically. To test whether or not calcium influx into CA3 pyramidal neurons is necessary for LTP induced by either pattern of stimulation, nimodipine, a L-type calcium channel antagonist, was added during stimulation. In these experiments nimodipine blocked the induction of mossy fiber LTP when B-HFS was given [34 ± 5% (mean ± SE) increase in control versus 7 ± 4% in nimodipine, P < 0.003]; in contrast, nimodipine did not block the induction of LTP with L-HFS (107 ± 10% in control vs. 80 ± 9% in nimodipine, P > 0.05). Administration of nimodipine after the induction of LTP had no effect on the expression of LTP. In addition, B- and L-HFS delivered directly to commissural/associational fibers in stratum radiatum failed to induce a N-methyl-d-aspartate-independent form of LTP, obviating the possibility that the presumed mossy fiber LTP resulted from potentiation of other synapses. Nimodipine had no effect on calcium transients recorded from mossy fiber presynaptic terminals evoked with the B-HFS paradigm but reduced postsynaptic calcium transients. Our results support the hypothesis that induction of mossy fiber LTP by B-HFS is mediated postsynaptically and requires entry of calcium through L-type channels into CA3 neurons.
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Santhakumar, Vijayalakshmi, Ildiko Aradi, and Ivan Soltesz. "Role of Mossy Fiber Sprouting and Mossy Cell Loss in Hyperexcitability: A Network Model of the Dentate Gyrus Incorporating Cell Types and Axonal Topography." Journal of Neurophysiology 93, no. 1 (January 2005): 437–53. http://dx.doi.org/10.1152/jn.00777.2004.
Повний текст джерелаАнотація:
Mossy cell loss and mossy fiber sprouting are two characteristic consequences of repeated seizures and head trauma. However, their precise contributions to the hyperexcitable state are not well understood. Because it is difficult, and frequently impossible, to independently examine using experimental techniques whether it is the loss of mossy cells or the sprouting of mossy fibers that leads to dentate hyperexcitability, we built a biophysically realistic and anatomically representative computational model of the dentate gyrus to examine this question. The 527-cell model, containing granule, mossy, basket, and hilar cells with axonal projections to the perforant-path termination zone, showed that even weak mossy fiber sprouting (10–15% of the strong sprouting observed in the pilocarpine model of epilepsy) resulted in the spread of seizure-like activity to the adjacent model hippocampal laminae after focal stimulation of the perforant path. The simulations also indicated that the spatially restricted, lamellar distribution of the sprouted mossy fiber contacts reported in in vivo studies was an important factor in sustaining seizure-like activity in the network. In contrast to the robust hyperexcitability-inducing effects of mossy fiber sprouting, removal of mossy cells resulted in decreased granule cell responses to perforant-path activation in agreement with recent experimental data. These results indicate the crucial role of mossy fiber sprouting even in situations where there is only relatively weak mossy fiber sprouting as is the case after moderate concussive experimental head injury.
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Gaiarsa, J. L., L. Zagrean, and Y. Ben-Ari. "Neonatal irradiation prevents the formation of hippocampal mossy fibers and the epileptic action of kainate on rat CA3 pyramidal neurons." Journal of Neurophysiology 71, no. 1 (January 1, 1994): 204–15. http://dx.doi.org/10.1152/jn.1994.71.1.204.
Повний текст джерелаАнотація:
1. The effects of unilateral gamma-ray irradiation at birth on the properties of adult CA3 pyramidal neurons have been studied in hippocampal slices. 2. Neonatal gamma-ray irradiation reduced by 80% the number of granule cells and prevented the formation of mossy fiber synapses without reducing the number of CA3 pyramidal cells. The destruction of the mossy fibers was also confirmed with extracellular recordings. 3. Excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) evoked by stimulation of the stratum radiatum had similar properties in nonirradiated and irradiated hippocampi: the EPSP reversed polarity near 0 mV, was reduced in amplitude by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10 microM) and D(-)-2-amino-5-phosphonovalerate (APV, 50 microM); the fast and slow IPSPs reversed at -75 and -100 mV, were blocked by bicuculline (10 microM), and reduced by phaclofen (0.5 mM), respectively. 4. Bath application of kainate (300–500 nM) evoked epileptiform activity in 81.5% of nonirradiated hippocampal CA3 regions and only in 29% of the irradiated CA3 regions. In contrast, bath application of high potassium (7 mM) and bicuculline (10 microM) generated spontaneous and evoked epileptiform activity in both nonirradiated and irradiated CA3 regions. 5. In nonirradiated and irradiated CA3 regions, kainate (200–300 nM) reduced the amplitude of the fast and slow IPSPs, reduced spike accommodation, and increased the duration of the action potential generated by a depolarizing pulse. 6. The postsynaptic responses of CA3 neurons to bath application of glutamatergic agonists were similar in nonirradiated and irradiated hippocampi in terms of amplitude, reversal potential, and pharmacology. 7. It is concluded that the most conspicuous effect of neonatal gamma-ray irradiation is to prevent the epileptic action of kainate. We propose that kainate generates epileptiform activity in the intact CA3 region by activating high-affinity binding sites located on the mossy fiber terminals.
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Henze, Darrell A., Nathaniel N. Urban, and German Barrionuevo. "Origin of the Apparent Asynchronous Activity of Hippocampal Mossy Fibers." Journal of Neurophysiology 78, no. 1 (July 1, 1997): 24–30. http://dx.doi.org/10.1152/jn.1997.78.1.24.
Повний текст джерелаАнотація:
Henze, Darrell A., Nathaniel N. Urban, and German Barrionuevo. Origin of the apparent asynchronous activity of hippocampal mossy fibers. J. Neurophysiol. 78: 24–30, 1997. Fiber volleys (FVs) from the stratum lucidum of rat hippocampal area CA3 were recorded extracellularly from in vitro slices in the presence of 10 mM kynurenic acid. In agreement with previous work, bulk stimulation of the dentate gyrus (DG) near the hilar border leads to an asynchronous FV. Transection of the stratum lucidum between the DG stimulation site and the CA3 recording site reduced or eliminated the early components of the asynchronous FV, indicating that they are of mossy fiber (MF) origin. In contrast, moving the stimulating electrode away from the hilus toward the hippocampal fissure reduced or eliminated the late components of the FV. Subsequently, we found that bulk stimulation on the DG/hilar border induces an antidromic population spike in CA3 pyramidal cells. Finally, the MFs and associational collaterals have differentconduction velocities (0.51 and 0.37 m/s, respectively; temperature =33°C). From these data, we conclude that the late components of the asynchronous FV are due to antidromic activation of CA3 collaterals that have been shown to be present in the DG and hilus. A corollary of these findings is that bulk stimulation on the DG/hilar border can lead to at least two different monosynaptic inputs to CA3 pyramidal cells: the MFs and the antidromically activated associational collaterals. We suggest that when MF synaptic responses are being evoked with the use of bulk stimulation, stimulating electrodes should be placed in the outer molecular layer of the DG to prevent the activation of hilar-projecting associational collaterals. This procedure should be added to the previously proposed criteria for preventing polysynaptic contamination of the intracellularly recorded evoked MF synaptic response.
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Frotscher, Michael, Peter Jonas, and Robert S. Sloviter. "Synapses formed by normal and abnormal hippocampal mossy fibers." Cell and Tissue Research 326, no. 2 (July 4, 2006): 361–67. http://dx.doi.org/10.1007/s00441-006-0269-2.
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Quinta-Ferreira, M. E., C. M. Matias, M. Arif, and J. C. Dionísio. "Measurement of presynaptic zinc changes in hippocampal mossy fibers." Brain Research 1026, no. 1 (November 2004): 1–10. http://dx.doi.org/10.1016/j.brainres.2004.07.054.
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Simmons, Michele L., Gregory W. Terman та Charles Chavkin. "Spontaneous Excitatory Currents and κ-Opioid Receptor Inhibition in Dentate Gyrus Are Increased in the Rat Pilocarpine Model of Temporal Lobe Epilepsy". Journal of Neurophysiology 78, № 4 (1 жовтня 1997): 1860–68. http://dx.doi.org/10.1152/jn.1997.78.4.1860.
Повний текст джерелаАнотація:
Simmons, Michele L., Gregory W. Terman, and Charles Chavkin. Spontaneous excitatory currents and κ-opioid receptor inhibition in dentate gyrus are increased in the rat pilocarpine model of temporal lobe epilepsy. J. Neurophysiol. 78: 1860–1868, 1997. Temporal lobe epilepsy is associated with a characteristic pattern of synaptic reorganization in the hippocampal formation, consisting of neuronal loss and aberrant growth of mossy fiber collaterals into the dentate gyrus inner molecular layer. We have used the rat pilocarpine model of temporal lobe epilepsy to study the functional consequences of mossy fiber sprouting on excitatory activity and κ-opioid receptor-mediated inhibition. Using the whole cell voltage-clamp technique, we found that abnormal excitatory activity was evident in granule cells of the dentate gyrus from pilocarpine-treated rats. The frequency of spontaneous excitatory postsynaptic currents (EPSCs) was increased greatly in cells from tissue in which significant mossy fiber sprouting had developed. In the presence of bicuculline, giant spontaneous EPSCs, with large amplitudes and long durations, were seen only in association with mossy fiber sprouting. Giant EPSCs also could be evoked by low-intensity stimulation of the perforant path. Mossy fibers release not only excitatory amino acids, but also opioid peptides. κ-Opioid receptor-mediated inhibition in normal Sprague-Dawley rats was seen only in hippocampal sections from the ventral pole. In pilocarpine-treated rats, however, kappa receptor-mediated effects were seen in both ventral and more dorsal sections. Thus in this model of temporal lobe epilepsy, several types of abnormal excitatory activity were observed, thereby supporting the idea that mossy fiber sprouting leads to recurrent excitatory connections. At the same time, inhibition of excitatory activity by κ-opioid receptors was increased, perhaps representing an endogenous anticonvulsant mechanism.
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Hardison, Jeremy L., Maxine M. Okazaki, and J. Victor Nadler. "Modest Increase in Extracellular Potassium Unmasks Effect of Recurrent Mossy Fiber Growth." Journal of Neurophysiology 84, no. 5 (November 1, 2000): 2380–89. http://dx.doi.org/10.1152/jn.2000.84.5.2380.
Повний текст джерелаАнотація:
The recurrent mossy fiber pathway of the dentate gyrus expands dramatically in many persons with temporal lobe epilepsy. The new connections among granule cells provide a novel mechanism of synchronization that could enhance the participation of these cells in seizures. Despite the presence of robust recurrent mossy fiber growth, orthodromic or antidromic activation of granule cells usually does not evoke repetitive discharge. This study tested the ability of modestly elevated [K+]o, reduced GABAA receptor-mediated inhibition and frequency facilitation to unmask the effect of recurrent excitation. Transverse slices of the caudal hippocampal formation were prepared from pilocarpine-treated rats that either had or had not developed status epilepticus with subsequent recurrent mossy fiber growth. During superfusion with standard medium (3.5 mM K+), antidromic stimulation of the mossy fibers evoked epileptiform activity in 14% of slices with recurrent mossy fiber growth. This value increased to ∼50% when [K+]o was raised to either 4.75 or 6 mM. Addition of bicuculline (3 or 30 μM) to the superfusion medium did not enhance the probability of evoking epileptiform activity but did increase the magnitude of epileptiform discharge if such activity was already present. (2S,2′R,3′R)-2-(2′,3′-dicarboxycyclopropyl)glycine (1 μM), which selectively activates type II metabotropic glutamate receptors present on mossy fiber terminals, strongly depressed epileptiform responses. This result implies a critical role for the recurrent mossy fiber pathway. No enhancement of the epileptiform discharge occurred during repetitive antidromic stimulation at frequencies of 0.2, 1, or 10 Hz. In fact, antidromically evoked epileptiform activity became progressively attenuated during a 10-Hz train. Antidromic stimulation of the mossy fibers never evoked epileptiform activity in slices from control rats under any condition tested. These results indicate that even modest changes in [K+]o dramatically affect granule cell epileptiform activity supported by the recurrent mossy fiber pathway. A small increase in [K+]o reduces the amount of recurrent mossy fiber growth required to synchronize granule cell discharge. Block of GABAA receptor-mediated inhibition is less efficacious and frequency facilitation may not be a significant factor.
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Mazarati, Andrey. "ATP-dependent Potassium Channels: A Converging Target for Endogenous Anticonvulsant Factors." Epilepsy Currents 5, no. 4 (July 2005): 139–41. http://dx.doi.org/10.1111/j.1535-7511.2005.00048.x.
Повний текст джерелаАнотація:
Zinc Inhibits Glutamate Release via Activation of Presynaptic K Channels and Reduces Ischaemic Damage in Rat Hippocampus Bancila V, Nikonenko I, Dunant Y, Bloc A J Neurochem 2004;90:1243–1250 Purpose Zinc is concentrated in certain CNS excitatory tracts, especially in hippocampal mossy fibers, where it has been suggested to modulate synaptic transmission and plasticity. Methods By using rat mossy fiber synaptosomes depolarized by 4-aminopyridine, we show here that low zinc concentrations restore the membrane potential and reduce glutamate release. Both effects arose from activation of ATP-sensitive potassium channels (KATP), because they were mimicked by the KATP-opener diazoxide and antagonized by the KATP-blocker tolbutamide. By using recombinant channels expressed in COS-7 cells, we confirmed that micromolar zinc did activate KATP of the type found in hippocampus. We tested the hypothesis that this action of zinc could be beneficial during an ischemic challenge by using organotypic hippocampal slice cultures. Results When zinc was applied at micromolar concentrations during a brief anoxic–hypoglycemic episode, it significantly attenuated the ensuing neuronal death, whereas chelation of endogenous zinc markedly aggravated cell damage. Protective effect of zinc was mediated through KATP, as was shown by using the opener diazoxide and the blocker tolbutamide. Conclusions Thus, by activating presynaptic KATP channels, zinc protects neurons from hyperexcitation, excessive transmitter release, and exitotoxicity, and may thus act as an endogenous neuroprotector in conditions such as epilepsy or stroke.
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Scharfman, Helen E. "Hyperexcitability in Combined Entorhinal/Hippocampal Slices of Adult Rat After Exposure to Brain-Derived Neurotrophic Factor." Journal of Neurophysiology 78, no. 2 (August 1, 1997): 1082–95. http://dx.doi.org/10.1152/jn.1997.78.2.1082.
Повний текст джерелаАнотація:
Scharfman, Helen E. Hyperexcitability in combined entorhinal/hippocampal slices of adult rat after exposure to brain-derived neurotrophic factor. J. Neurophysiol. 78: 1082–1095, 1997. Effects of brain-derived neurotrophic factor (BDNF) in area CA3, the dentate gyrus, and medial entorhinal cortex were examined electrophysiologically by bath application of BDNF in slices containing the hippocampus and entorhinal cortex. Bath application of 25–100 ng/ml BDNF for 30–90 min increased responses to single afferent stimuli in selective pathways in the majority of slices. In area CA3, responses to mossy fiber stimulation increased in 73% of slices and entorhinal cortex responses to white matter stimulation increased in 64% of slices. After exposure to BDNF, these areas also demonstrated evidence of hyperexcitability, because responses to repetitive stimulation (1-Hz paired pulses for several s) produced multiple population spikes in response to mossy fiber stimulation in CA3 or multiple field potentials in response to white matter stimulation in the entorhinal cortex. Repetitive field potentials persisted after repetitive stimulation ended and usually were followed by spreading depression. Enhancement of responses to single stimuli and hyperexcitability were never evoked in untreated slices or after bath application of boiled BDNF or cytochrome C. The tyrosine kinase antagonist K252a (2 μM) blocked the effects of BDNF. In area CA3, both the potentiation of responses to single stimuli and hyperexcitability showed afferent specificity, because responses to mossy fiber stimulation were affected but responses to fimbria or Schaffer collateral stimulation were not. In addition, regional specificity was demonstrated in that the dentate gyrus was much less affected. The effects of BDNF in area CA3 were similar to those produced by bath application of low doses of kainic acid, which is thought to modulate glutamate release from mossy fiber terminals by a presynaptic action. These results suggest that BDNF has acute effects on excitability in different areas of the hippocampal-entorhinal circuit. These effects appear to be greatest in areas that are highly immunoreactive for BDNF, such as the mossy fibers and the entorhinal cortex. Although the present experiments do not elucidate mechanism(s) definitively, the afferent specificity, similarity to the effects of kainic acid, and block by K252a are consistent with previous hypotheses that BDNF affects acute excitability by a presynaptic action on trkB receptors that modulate excitatory amino acid transmission. However, we cannot rule out actions on inhibitory synapses or postsynaptic processes.
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Alle, H. "Combined Analog and Action Potential Coding in Hippocampal Mossy Fibers." Science 311, no. 5765 (March 3, 2006): 1290–93. http://dx.doi.org/10.1126/science.1119055.
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Kobayashi, Katsunori. "Regulation of neural circuit and behavior by hippocampal mossy fibers." Neuroscience Research 58 (January 2007): S13. http://dx.doi.org/10.1016/j.neures.2007.06.076.
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Chamberland, Simon, Yulia Timofeeva, Alesya Evstratova, Kirill Volynski, and Katalin Tóth. "Action potential counting at giant mossy fiber terminals gates information transfer in the hippocampus." Proceedings of the National Academy of Sciences 115, no. 28 (June 26, 2018): 7434–39. http://dx.doi.org/10.1073/pnas.1720659115.
Повний текст джерелаАнотація:
Neuronal communication relies on action potential discharge, with the frequency and the temporal precision of action potentials encoding information. Hippocampal mossy fibers have long been recognized as conditional detonators owing to prominent short-term facilitation of glutamate release displayed during granule cell burst firing. However, the spiking patterns required to trigger action potential firing in CA3 pyramidal neurons remain poorly understood. Here, we show that glutamate release from mossy fiber terminals triggers action potential firing of the target CA3 pyramidal neurons independently of the average granule cell burst frequency, a phenomenon we term action potential counting. We find that action potential counting in mossy fibers gates glutamate release over a broad physiological range of frequencies and action potential numbers. Using rapid Ca2+ imaging we also show that the magnitude of evoked Ca2+ influx stays constant during action potential trains and that accumulated residual Ca2+ is gradually extruded on a time scale of several hundred milliseconds. Using experimentally constrained 3D model of presynaptic Ca2+ influx, buffering, and diffusion, and a Monte Carlo model of Ca2+-activated vesicle fusion, we argue that action potential counting at mossy fiber boutons can be explained by a unique interplay between Ca2+ dynamics and buffering at release sites. This is largely determined by the differential contribution of major endogenous Ca2+ buffers calbindin-D28K and calmodulin and by the loose coupling between presynaptic voltage-gated Ca2+ channels and release sensors and the relatively slow Ca2+ extrusion rate. Taken together, our results identify a previously unexplored information-coding mechanism in the brain.
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Tamura, Makoto, Ryuta Koyama, Yuji Ikegaya, Norio Matsuki, and Maki K. Yamada. "K252a, an inhibitor of Trk, disturbs pathfinding of hippocampal mossy fibers." NeuroReport 17, no. 5 (April 2006): 481–86. http://dx.doi.org/10.1097/01.wnr.0000208997.23448.ea.
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Vivar, Carmen, Roger D. Traub, and Rafael Gutiérrez. "Mixed electrical-chemical transmission between hippocampal mossy fibers and pyramidal cells." European Journal of Neuroscience 35, no. 1 (December 13, 2011): 76–82. http://dx.doi.org/10.1111/j.1460-9568.2011.07930.x.
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Represa, A., E. Tremblay, and Y. Ben-Ari. "Kainate binding sites in the hippocampal mossy fibers: Localization and plasticity." Neuroscience 20, no. 3 (March 1987): 739–48. http://dx.doi.org/10.1016/0306-4522(87)90237-5.
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Nguyen, Loan B., Thomas N. Ricciardi, and Alfred T. malouf. "Reinnervation of stratum lucidum by hippocampal mossy fibers is developmentally regulated." Developmental Brain Research 95, no. 2 (September 1996): 184–93. http://dx.doi.org/10.1016/0165-3806(96)00090-9.
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Stritt, Christine, and Bernd Knöll. "Serum Response Factor Regulates Hippocampal Lamination and Dendrite Development and Is Connected with Reelin Signaling." Molecular and Cellular Biology 30, no. 7 (February 1, 2010): 1828–37. http://dx.doi.org/10.1128/mcb.01434-09.
Повний текст джерелаАнотація:
ABSTRACT During brain development, neurons and their nerve fibers are often segregated in specific layers. The hippocampus is a well-suited model system to study lamination in health and aberrant cell/fiber lamination associated with neurological disorders. SRF (serum response factor), a transcription factor, regulates synaptic-activity-induced immediate-early gene (IEG) induction and cytoskeleton-based neuronal motility. Using early postnatal conditional SRF ablation, we uncovered distorted hippocampal lamination, including malpositioning of granule cell neurons and disruption of layer-restricted termination of commissural-associational and mossy fiber axons. Besides axons, dendrite branching and spine morphogenesis in Srf mutants were impaired, offering a first morphological basis for SRF's reported role in learning and memory. Srf mutants resemble mice lacking components of the reelin signaling cascade, a fundamental signaling entity in brain lamination. Our data indicate that reelin signaling and SRF-mediated gene transcription might be connected: reelin induces IEG and cytoskeletal genes in an SRF-dependent manner. Further, reelin-induced neurite motility is blocked in Srf mutants and constitutively active SRF rescues impaired neurite extension in reeler mouse mutants in vitro. In sum, data provided in this report show that SRF contributes to hippocampal layer and nerve fiber organization and point at a link between Srf gene transcription and reelin signaling.
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Benardo, Larry S. "Insights into the Cellular Basis of Posttraumatic Epilepsy." Epilepsy Currents 2, no. 2 (March 2002): 59. http://dx.doi.org/10.1111/j.1535-7597.2002.00021.x.
Повний текст джерелаАнотація:
Physiological and Structural Evidence for Hippocampal Involvement in Persistent Seizure Susceptibility after Traumatic Brain Injury Golarai G, Greenwood AC, Feeney DM, Connor JA J Neurosci 2001;21:8523–8537 Epilepsy is a common outcome of traumatic brain injury (TBI), but the mechanisms of posttraumatic epileptogenesis are poorly understood. One clue is the occurrence of selective hippocampal cell death after fluid-percussion TBI in rats, consistent with the reported reduction of hippocampal volume bilaterally in humans after TBI and resembling hippocampal sclerosis, a hallmark of temporal-lobe epilepsy. Other features of temporal-lobe epilepsy, such as long-term seizure susceptibility, persistent hyperexcitability in the dentate gyrus (DG), and mossy fiber synaptic reorganization, however, have not been examined after TBI. To determine whether TBI induces these changes, we used a well studied model of TBI by weight drop on somatosensory cortex in adult rats. First, we confirmed an early and selective cell loss in the hilus of the DG and area CA3 of hippocampus, ipsilateral to the impact. Second, we found persistently enhanced susceptibility to pentylenetetrazole-induced convulsions 15 weeks after TBI. Third, by applying GABAA antagonists during field-potential and optical recordings in hippocampal slices 3 and 15 weeks after TBI, we unmasked a persistent, abnormal APV-sensitive hyperexcitability that was bilateral and localized to the granule cell and molecular layers of the DG. Finally, using Timm histo-chemistry, we detected progressive sprouting of mossy fibers into the inner molecular layers of the DG bilaterally 2–27 weeks after TBI. These findings are consistent with the development of posttraumatic epilepsy in an animal model of impact head injury, showing a striking similarity to the enduring behavioral, functional, and structural alterations associated with temporal-lobe epilepsy. Long-Term Hyperexcitability in the Hippocampus After Experimental Head Trauma Santhakumar V, Ratzliff AD, Jeng J, Toth Z, Soltesz I Ann Neurol 2001;50:708–717 Head injury is a causative factor in the development of temporal lobe epilepsy. However, whether a single episode of concussive head trauma causes a persistent increase in neuronal excitability in the limbic system has not been unequivocally determined. This study used the rodent fluid percussion injury (FPI) model, in combination with electrophysiological and histochemical techniques, to investigate the early (1 week) and long-term (1 month or longer) changes in the hippocampus after head trauma. Low-frequency, single-shock stimulation of the perforant path revealed an early granule cell hyperexcitability in head-injured animals that returned to control levels by 1 month. However, there was a persistent decrease in threshold to induction of seizure-like electrical activity in response to high-frequency tetanic stimulation in the hippocampus after head injury. Timm staining revealed both early- and long-term mossy fiber sprouting at low to moderate levels in the dentate gyrus of animals that experienced FPI. There was a long-lasting increase in the frequency of spontaneous inhibitory postsynaptic currents in dentate granule cells after FPI, and ionotropic glutamate receptor antagonists selectively decreased the spontaneous inhibitory postsynaptic current frequency in the head-injured animals. These results demonstrate that a single episode of experimental closed head trauma induces long-lasting alterations in the hippocampus. These persistent structural and functional alterations in inhibitory and excitatory circuits are likely to influence the development of hyperexcitable foci in posttraumatic limbic circuits.
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Segev, Amir, Masaya Yanagi, Daniel Scott, Sarah A. Southcott, Jacob M. Lister, Chunfeng Tan, Wei Li, Shari G. Birnbaum, Saïd Kourrich, and Carol A. Tamminga. "Reduced GluN1 in mouse dentate gyrus is associated with CA3 hyperactivity and psychosis-like behaviors." Molecular Psychiatry 25, no. 11 (July 23, 2018): 2832–43. http://dx.doi.org/10.1038/s41380-018-0124-3.
Повний текст джерелаАнотація:
Abstract Recent findings from in vivo-imaging and human post-mortem tissue studies in schizophrenic psychosis (SzP), have demonstrated functional and molecular changes in hippocampal subfields that can be associated with hippocampal hyperexcitability. In this study, we used a subfield-specific GluN1 knockout mouse with a disease-like molecular perturbation expressed only in hippocampal dentate gyrus (DG) and assessed its association with hippocampal physiology and psychosis-like behaviors. First, we used whole-cell patch-clamp recordings to measure the physiological changes in hippocampal subfields and cFos immunohistochemistry to examine cellular excitability. DG-GluN1 KO mice show CA3 cellular hyperactivity, detected using two approaches: (1) increased excitatory glutamate transmission at mossy fibers (MF)-CA3 synapses, and (2) an increased number of cFos-activated pyramidal neurons in CA3, an outcome that appears to project downstream to CA1 and basolateral amygdala (BLA). Furthermore, we examined psychosis-like behaviors and pathological memory processing; these show an increase in fear conditioning (FC), a reduction in prepulse inhibition (PPI) in the KO animal, along with a deterioration in memory accuracy with Morris Water Maze (MWM) and reduced social memory (SM). Moreover, with DREADD vectors, we demonstrate a remarkably similar behavioral profile when we induce CA3 hyperactivity. These hippocampal subfield changes could provide the basis for the observed increase in human hippocampal activity in SzP, based on the shared DG-specific GluN1 reduction. With further characterization, these animal model systems may serve as targets to test psychosis mechanisms related to hippocampus and assess potential hippocampus-directed treatments.
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Smith, Mark A., Li-Xin Zhang, W. Ernest Lyons, and Laura A. Mamounas. "Anterograde transport of endogenous brain-derived neurotrophic factor in hippocampal mossy fibers." NeuroReport 8, no. 8 (May 1997): 1829–34. http://dx.doi.org/10.1097/00001756-199705260-00008.
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Villanueva-Castillo, Cindy, Carolina Tecuatl, Gabriel Herrera-López, and Emilio J. Galván. "Aging-related impairments of hippocampal mossy fibers synapses on CA3 pyramidal cells." Neurobiology of Aging 49 (January 2017): 119–37. http://dx.doi.org/10.1016/j.neurobiolaging.2016.09.010.
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Zhang, Binbin, Minqin Ren, Fwu-Shan Sheu, Frank Watt, and Aryeh Routtenberg. "Quantitative analysis of zinc in rat hippocampal mossy fibers by nuclear microscopy." Neuroscience Research 74, no. 1 (September 2012): 17–24. http://dx.doi.org/10.1016/j.neures.2012.06.004.
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Koyama, Ryuta, Maki K. Yamada, Nobuyoshi Nishiyama, Norio Matsuki, and Yuji Ikegaya. "Developmental switch in axon guidance modes of hippocampal mossy fibers in vitro." Developmental Biology 267, no. 1 (March 2004): 29–42. http://dx.doi.org/10.1016/j.ydbio.2003.11.008.
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Aniksztejn, L., G. Charton, and Y. Ben-Ari. "Selective release of endogenous zinc from the hippocampal mossy fibers in situ." Brain Research 404, no. 1-2 (February 1987): 58–64. http://dx.doi.org/10.1016/0006-8993(87)91355-2.
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Freeman, Linnea R., and Ann-Charlotte E. Granholm. "Vascular Changes in Rat Hippocampus following a High Saturated Fat and Cholesterol Diet." Journal of Cerebral Blood Flow & Metabolism 32, no. 4 (November 23, 2011): 643–53. http://dx.doi.org/10.1038/jcbfm.2011.168.
Повний текст джерелаАнотація:
The long-term effects of a diet rich in saturated fat and cholesterol on the hippocampus were evaluated in this study. It has previously been shown that this type of diet is detrimental to health, particularly affecting peripheral organs such as the heart and liver. However, effects on the brain have not been fully evaluated. This study focused on the hippocampus, a brain region instrumental for learning and memory and vulnerable to ischemic damage. Reduced blood—brain barrier (BBB) integrity and increased microgliosis were observed in the hippocampus of rats fed a high-saturated-fat and cholesterol (HFHC) diet for 6 months. Interestingly, an increase in hippocampal protein levels of occludin, a tight junction protein, was found in HFHC-treated rats as well. Further investigation revealed decreased expression of the occludin protein in blood vessels and increased expression in the dentate gyrus hilar neurons and mossy fibers of the hippocampal cornus ammonis 3 in HFHC-treated rats. Our results show alterations in BBB integrity and expression of tight junction proteins after long-term exposure to HFHC diet in rats. These findings may suggest a biologic mechanism for previously observed behavioral deficits occurring in rats fed this diet.
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Dudek, F. Edward. "Neuropeptide Y May be an Endogenous Anticonvulsant in Hippocampus." Epilepsy Currents 2, no. 1 (January 2002): 25. http://dx.doi.org/10.1111/j.1535-7597.2002.00009.x.
Повний текст джерелаАнотація:
Plasticity of Y1 and Y2 Receptors and Neuropeptide Y Fibers in Patients with Temporal Lobe Epilepsy Furtinger S, Pirker S, Czech T, Baumgartner C, Ransmayr G, Sperk G J Neurosci 2001;21:5804–5812 Marked expression of neuropeptide Y (NPY) and its Y2 receptors in hippocampal mossy fibers has been reported in animal models of epilepsy. Because NPY can suppress glutamate release by activating presynaptic Y2 receptors, these changes have been proposed as an endogenous protective mechanism. Therefore, we investigated whether similar changes in the NPY system may also take place in human epilepsy. We investigated Y1 and Y2 receptor binding and NPY immunoreactivity in hippocampal specimens that were obtained at surgery from patients with temporal lobe epilepsy and in autopsy controls. Significant increases in Y2 receptor binding (by 43–48%) were observed in the dentate hilus, sectors CA1 to CA3, and subiculum of specimens with, but not in those without, hippocampal sclerosis. On the other hand, Y1 receptor binding was significantly reduced (by 62%) in the dentate molecular layer of sclerotic specimens. In the same patients, the total lengths of NPY immunoreactive (NPY-IR) fibers were markedly increased (by 115–958%) in the dentate molecular layer and hilus, in the stratum lucidum of CA3, and throughout sectors CA1 to CA3 and the subiculum, as compared with autopsies. In nonsclerotic specimens, increases in lengths of NPY-IR fibers were more moderate and statistically not significant. NPY mRNA was increased threefold in hilar interneurons of sclerotic and nonsclerotic specimens. It is suggested that abundant sprouting of NPY fibers, concomitant upregulation of Y2 receptors, and downregulation of Y1 receptors in the hippocampus of patients with Ammon's horn sclerosis may be endogenous anticonvulsant mechanisms.
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Ramos-Languren, L. E., and M. L. Escobar. "Plasticity and metaplasticity of adult rat hippocampal mossy fibers induced by neurotrophin-3." European Journal of Neuroscience 37, no. 8 (February 7, 2013): 1248–59. http://dx.doi.org/10.1111/ejn.12141.
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Ikegaya, Yuji, Nobuyoshi Nishiyama, and Norio Matsuki. "Hyperexcitability causes excessive and ectopic synaptogenesis of the hippocampal mossy fibers in vitro." Japanese Journal of Pharmacology 79 (1999): 232. http://dx.doi.org/10.1016/s0021-5198(19)34942-x.
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Takeda, Atsushi, Kohei Yamada, Akira Minami, Tetsuo Nagano, and Naoto Oku. "Enhanced excitability of hippocampal mossy fibers and CA3 neurons under dietary zinc deficiency." Epilepsy Research 63, no. 2-3 (February 2005): 77–84. http://dx.doi.org/10.1016/j.eplepsyres.2004.11.002.
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