scholarly journals Action potential counting at giant mossy fiber terminals gates information transfer in the hippocampus

2017 ◽  
Author(s):  
Simon Chamberland ◽  
Yulia Timofeeva ◽  
Alesya Evstratova ◽  
Kirill Volynski ◽  
Katalin Tóth
Keyword(s):  
Information Transfer ◽  
Pyramidal Neurons ◽  
Mossy Fiber ◽  
Mossy Fibers ◽  
Pyramidal Cells ◽  
Short Term ◽  
Ca3 Pyramidal Neurons ◽  
Presynaptic Calcium ◽  
Ca3 Pyramidal Cells ◽  
The Brain

AbstractHippocampal mossy fibers have long been recognized as conditional detonators owing to prominent short-term facilitation, but the patterns of activity required to fire postsynaptic CA3 pyramidal neurons remain poorly understood. We show that mossy fibers count the number of spikes to transmit information to CA3 pyramidal cells through a distinctive interplay between presynaptic calcium dynamics, buffering and vesicle replenishment. This identifies a previously unexplored information coding mechanism in the brain.

scholarly journals Presynaptic NMDA receptors facilitate short-term plasticity and BDNF release at hippocampal mossy fiber synapses

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Pablo J Lituma ◽  
Hyung-Bae Kwon ◽  
Karina Alviña ◽  
Rafael Luján ◽  
Pablo E Castillo
Keyword(s):  
Nmda Receptors ◽  
Information Transfer ◽  
Mossy Fiber ◽  
Pyramidal Cells ◽  
Synaptic Function ◽  
Fine Tuning ◽  
Short Term ◽  
Dentate Granule Cell ◽  
Presynaptic Calcium ◽  
Presynaptic Nmda Receptors

Neurotransmitter release is a highly controlled process by which synapses can critically regulate information transfer within neural circuits. While presynaptic receptors –typically activated by neurotransmitters and modulated by neuromodulators– provide a powerful way of fine-tuning synaptic function, their contribution to activity-dependent changes in transmitter release remains poorly understood. Here, we report that presynaptic NMDA receptors (preNMDARs) at mossy fiber boutons in the rodent hippocampus can be activated by physiologically relevant patterns of activity and selectively enhance short-term synaptic plasticity at mossy fiber inputs onto CA3 pyramidal cells and mossy cells, but not onto inhibitory interneurons. Moreover, preNMDARs facilitate brain-derived neurotrophic factor (BDNF) release and contribute to presynaptic calcium rise. Taken together, our results indicate that by increasing presynaptic calcium, preNMDARs fine tune mossy fiber neurotransmission and can control information transfer during dentate granule cell burst activity that normally occur in vivo.

scholarly journals Presynaptic NMDA receptors facilitate short-term plasticity and BDNF release at hippocampal mossy fiber synapses

2021 ◽  
Author(s):  
Pablo J. Lituma ◽  
Hyung-Bae Kwon ◽  
Rafael Lujan ◽  
Pablo E. Castillo
Keyword(s):  
Nmda Receptors ◽  
Information Transfer ◽  
Mossy Fiber ◽  
Pyramidal Cells ◽  
Synaptic Function ◽  
Fine Tuning ◽  
Short Term ◽  
Dentate Granule Cell ◽  
Presynaptic Calcium ◽  
Presynaptic Nmda Receptors

AbstractNeurotransmitter release is a highly controlled process by which synapses can critically regulate information transfer within neural circuits. While presynaptic receptors –typically activated by neurotransmitters and modulated by neuromodulators– provide a powerful way of fine tuning synaptic function, their contribution to activity-dependent changes in transmitter release remains poorly understood. Here, we report that presynaptic NMDA receptors (preNMDARs) at hippocampal mossy fiber boutons can be activated by physiologically relevant patterns of activity and selectively enhance short-term synaptic plasticity at mossy fiber inputs onto CA3 pyramidal cells and mossy cells, but not onto inhibitory interneurons. Moreover, preNMDARs facilitate brain-derived neurotrophic factor (BDNF) release and contribute to presynaptic calcium rise. Taken together, our results indicate that preNMDARs, by increasing presynaptic calcium, fine tune mossy fiber neurotransmission and can control information transfer during dentate granule cell burst activity that normally occur in vivo.

Effect of tolbutamide on tetraethylammonium-induced postsynaptic zinc signals at hippocampal mossy fiber-CA3 synapses

2017 ◽  
Vol 95 (9) ◽  
pp. 1058-1063 ◽  
Author(s):  
Fatima C. Bastos ◽  
Vanessa N. Corceiro ◽  
Sandra A. Lopes ◽  
José G. de Almeida ◽  
Carlos M. Matias ◽  
...  
Keyword(s):  
Mossy Fiber ◽  
Mossy Fibers ◽  
Pyramidal Cells ◽  
Long Term Potentiation ◽  
Chemical Stimulation ◽  
Term Potentiation ◽  
Voltage Dependent ◽  
Zinc Release ◽  
Ca3 Pyramidal Cells

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.

Calcium Signaling at Single Mossy Fiber Presynaptic Terminals in the Rat Hippocampus

2002 ◽  
Vol 87 (2) ◽  
pp. 1132-1137 ◽  
Author(s):  
Yong Liang ◽  
Li-Lian Yuan ◽  
Daniel Johnston ◽  
Richard Gray
Keyword(s):  
Pyramidal Neurons ◽  
Mossy Fiber ◽  
Imaging Techniques ◽  
Cyclopiazonic Acid ◽  
Mossy Fibers ◽  
Ruthenium Red ◽  
Experimental Conditions ◽  
Intracellular Ca ◽  
Ca3 Pyramidal Neurons ◽  
Calcium Green

We investigated internal Ca2+ release at mossy fiber synapses on CA3 pyramidal neurons (mossy fiber terminals, MFTs) in the hippocampus. Presynaptic Ca2+ influx was induced by giving a brief train of 20 stimuli at 100 Hz to the mossy fiber pathway. Using Ca2+ imaging techniques, we recorded the Ca2+ response as Δ F/ F,which increased rapidly with stimulation, but was often accompanied by a delayed peak that occurred after the train. The rise in presynaptic [Ca2+] could be completely blocked by application of 400 μM Cd2+. Furthermore, the evoked Ca2+ signals were reduced by group II mGluR agonists. Under the same experimental conditions, we investigated the effects of several agents on MFTs that disrupt regulation of intracellular Ca2+ stores resulting in depletion of internal Ca2+. We found that ryanodine, cyclopiazonic acid, thapsigargin, and ruthenium red all decreased both the early and the delayed increase in the Ca2+signals. We applied d,l-2-amino-5-phosphonovaleric acid (d,l-APV; 50 μM) and 6,7-Dinitroquinoxaline-2,3-dione (DNQX; 20 μM) to exclude the action of N-methyl-d-aspartate (NMDA) and non-NMDA receptors. Experiments with alternative lower affinity indicators for Ca2+ (fura-2FF and calcium green-2) and the transient K+ channel blocker, 4-aminopyridine were performed to control for the possible saturation of fura-2. Taken together, these results strongly support the hypothesis that the recorded terminals were from the mossy fibers of the dentate gyrus and suggest that a portion of the presynaptic Ca2+signal in response to brief trains of stimuli is due to release of Ca2+ from internal stores.

scholarly journals Recruitment of an inhibitory hippocampal network after bursting in a single granule cell

2007 ◽  
Vol 104 (18) ◽  
pp. 7640-7645 ◽  
Author(s):  
Masahiro Mori ◽  
Beat H. Gähwiler ◽  
Urs Gerber
Keyword(s):  
Pyramidal Cell ◽  
Granule Cell ◽  
Mossy Fiber ◽  
Mossy Fibers ◽  
Pyramidal Cells ◽  
Network Activity ◽  
Inhibitory Input ◽  
Inhibitory Interneurons ◽  
Failure Rates ◽  
Ca3 Pyramidal Cells

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.

Permanent Reduction of Seizure Threshold in Post-Ischemic CA3 Pyramidal Neurons

2000 ◽  
Vol 83 (4) ◽  
pp. 2040-2046 ◽  
Author(s):  
Patrice Congar ◽  
Jean-Luc Gaïarsa ◽  
Théodora Popovici ◽  
Yezekiel Ben-Ari ◽  
Valérie Crépel
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Input Resistance ◽  
Seizure Threshold ◽  
Resting Membrane Potential ◽  
Epileptic Syndromes ◽  
Ca3 Pyramidal Neurons ◽  
Ca3 Pyramidal Cells ◽  
Firing Properties

The effects of ischemia were examined on CA3 pyramidal neurons recorded in hippocampal slices 2–4 mo after a global forebrain insult. With intracellular recordings, CA3 post-ischemic neurons had a more depolarized resting membrane potential but no change of the input resistance, spike threshold and amplitude, fast and slow afterhyperpolarization (AHP) or ADP, and firing properties in response to depolarizing pulses. With both field and whole-cell recordings, synaptic responses were similar in control and post-ischemic neurons. Although there were no spontaneous network-driven discharges, the post-ischemic synaptic network had a smaller threshold to generate evoked and spontaneous synchronized burst discharges. Thus lower concentrations of convulsive agents (kainate, high K+) triggered all-or-none network-driven synaptic events in post-ischemic neurons more readily than in control ones. Also, paired-pulse protocol generates, in post-ischemics but not controls, synchronized field burst discharges when interpulse intervals ranged from 60 to 100 ms. In conclusion, 2–4 mo after the insult, the post-ischemic CA3 pyramidal cells are permanently depolarized and have a reduced threshold to generate synchronized bursts. This may explain some neuropathological and behavioral consequences of ischemia as epileptic syndromes observed several months to several years after the ischemic insult.

scholarly journals Action potential counting at giant mossy fiber terminals gates information transfer in the hippocampus

2018 ◽  
Vol 115 (28) ◽  
pp. 7434-7439 ◽  
Author(s):  
Simon Chamberland ◽  
Yulia Timofeeva ◽  
Alesya Evstratova ◽  
Kirill Volynski ◽  
Katalin Tóth
Keyword(s):  
Action Potential ◽  
Granule Cell ◽  
Pyramidal Neurons ◽  
Mossy Fiber ◽  
Glutamate Release ◽  
Mossy Fibers ◽  
Action Potential Firing ◽  
Potential Firing ◽  
Ca3 Pyramidal Neurons ◽  
Calbindin D

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.

Neonatal irradiation prevents the formation of hippocampal mossy fibers and the epileptic action of kainate on rat CA3 pyramidal neurons

1994 ◽  
Vol 71 (1) ◽  
pp. 204-215 ◽  
Author(s):  
J. L. Gaiarsa ◽  
L. Zagrean ◽  
Y. Ben-Ari
Keyword(s):  
Pyramidal Neurons ◽  
Gamma Ray ◽  
Mossy Fiber ◽  
Epileptiform Activity ◽  
Hippocampal Slices ◽  
Reversal Potential ◽  
Mossy Fibers ◽  
Bath Application ◽  
Gamma Ray Irradiation ◽  
Ca3 Pyramidal Neurons

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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