scholarly journals EPSPs of dentate gyrus granule cells during epileptiform bursts of dentate hilar "mossy" cells and area CA3 pyramidal cells in disinhibited rat hippocampal slices

1994 ◽  
Vol 14 (10) ◽  
pp. 6041-6057 ◽  
Author(s):  
HE Scharfman
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Mossy Cells ◽  
Ca3 Pyramidal Cells ◽  
Area Ca3

Evidence from simultaneous intracellular recordings in rat hippocampal slices that area CA3 pyramidal cells innervate dentate hilar mossy cells

1994 ◽  
Vol 72 (5) ◽  
pp. 2167-2180 ◽  
Author(s):  
H. E. Scharfman
Keyword(s):  
Pyramidal Cell ◽  
Action Potentials ◽  
Granule Cells ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Probability Of Failure ◽  
Mossy Cells ◽  
Mossy Cell ◽  
Ca3 Pyramidal Cells ◽  
Area Ca3

1. Simultaneous intracellular recordings of area CA3 pyramidal cells and dentate hilar “mossy” cells were made in rat hippocampal slices to test the hypothesis that area CA3 pyramidal cells excite mossy cells monosynaptically. Mossy cells and pyramidal cells were differentiated by location and electrophysiological characteristics. When cells were impaled near the border of area CA3 and the hilus, their identity was confirmed morphologically after injection of the marker Neurobiotin. 2. Evidence for monosynaptic excitation of a mossy cell by a pyramidal cell was obtained in 7 of 481 (1.4%) paired recordings. In these cases, a pyramidal cell action potential was followed immediately by a 0.40 to 6.75 (mean, 2.26) mV depolarization in the simultaneously recorded mossy cell (mossy cell membrane potentials, -60 to -70 mV). Given that pyramidal cells used an excitatory amino acid as a neurotransmitter (Cotman and Nadler 1987; Ottersen and Storm-Mathisen 1987) and recordings were made in the presence of the GABAA receptor antagonist bicuculline (25 microM), it is likely that the depolarizations were unitary excitatory postsynaptic potentials (EPSPs). 3. Unitary EPSPs of mossy cells were prone to apparent “failure.” The probability of failure was extremely high (up to 0.72; mean = 0.48) if the effects of all presynaptic action potentials were examined, including action potentials triggered inadvertently during other spontaneous EPSPs of the mossy cell. Probability of failure was relatively low (as low as 0; mean = 0.24) if action potentials that occurred during spontaneous activity of the mossy cell were excluded. These data suggest that unitary EPSPs produced by pyramidal cells are strongly affected by concurrent synaptic inputs to the mossy cell. 4. Unitary EPSPs were not clearly affected by manipulation of the mossy cell's membrane potential. This is consistent with the recent report that area CA3 pyramidal cells innervate distal dendrites of mossy cells (Kunkel et al. 1993). Such a distal location also may contribute to the high incidence of apparent failures. 5. Characteristics of unitary EPSPs generated by pyramidal cells were compared with the properties of the unitary EPSPs produced by granule cells. In two slices, pyramidal cell and granule cell inputs to the same mossy cell were compared. In other slices, inputs to different mossy cells were compared. In all experiments, unitary EPSPs produced by granule cells were larger in amplitude but similar in time course to unitary EPSPs produced by pyramidal cells. Probability of failure was lower and paired-pulse facilitation more common among EPSPs triggered by granule cells.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Dentate Gyrus Mossy Cells Share a Role in Pattern Separation with Dentate Granule Cells and Proximal CA3 Pyramidal Cells

2019 ◽  
Vol 39 (48) ◽  
pp. 9570-9584 ◽  
Author(s):  
Douglas GoodSmith ◽  
Heekyung Lee ◽  
Joshua P. Neunuebel ◽  
Hongjun Song ◽  
James J. Knierim
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Pyramidal Cells ◽  
Pattern Separation ◽  
Dentate Granule Cells ◽  
Mossy Cells ◽  
Ca3 Pyramidal Cells

scholarly journals Does a Unique Type of CA3 Pyramidal Cell in Primates Bypass the Dentate Gate?

2005 ◽  
Vol 94 (1) ◽  
pp. 896-900 ◽  
Author(s):  
Paul S. Buckmaster
Keyword(s):  
Dentate Gyrus ◽  
Entorhinal Cortex ◽  
Synaptic Input ◽  
Granule Cells ◽  
Molecular Layer ◽  
Pyramidal Cells ◽  
Dendritic Morphology ◽  
Dentate Granule Cells ◽  
Excitatory Synaptic Input ◽  
Ca3 Pyramidal Cells

The predominant excitatory synaptic input to the hippocampus arises from entorhinal cortical axons that synapse with dentate granule cells, which in turn synapse with CA3 pyramidal cells.Thus two highly excitable brain areas—the entorhinal cortex and the CA3 field—are separated by dentate granule cells, which have been proposed to function as a gate or filter. However, unlike rats, primates have “dentate” CA3 pyramidal cells with an apical dendrite that extends into the molecular layer of the dentate gyrus, where they could receive strong, monosynaptic, excitatory synaptic input from the entorhinal cortex. To test this possibility, the dentate gyrus molecular layer was stimulated while intracellular recordings were obtained from CA3 pyramidal cells in hippocampal slices from neurologically normal macaque monkeys. Stimulus intensity of the outer molecular layer of the dentate gyrus was standardized by the threshold intensity for evoking a dentate gyrus field potential population spike. Recorded proximal CA3 pyramidal cells were labeled with biocytin, processed with diaminobenzidine for visualization, and classified according to their dendritic morphology. In response to stimulation of the dentate gyrus molecular layer, action potential thresholds were similar in proximal CA3 pyramidal cells with different dendritic morphologies. These findings do not support the hypothesis that dentate CA3 pyramidal cells receive stronger synaptic input from the entorhinal cortex than do other proximal CA3 pyramidal cells.

Characteristics of local excitatory circuits studied with glutamate microapplication in the CA3 area of rat hippocampal slices

1988 ◽  
Vol 59 (1) ◽  
pp. 90-109 ◽  
Author(s):  
E. P. Christian ◽  
F. E. Dudek
Keyword(s):  
Granule Cells ◽  
Mossy Fiber ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Firing Frequency ◽  
Block Transmission ◽  
Inhibitory Circuits ◽  
Axon Terminals ◽  
Stratum Pyramidale ◽  
Ca3 Pyramidal Cells

1. Local neuronal circuits in CA3 of hippocampal slices were studied by recording excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) intracellularly during glutamate microapplication in CA3. Control experiments validated this approach by providing evidence that glutamate microdrops stimulated neurons but not axons-of-passage or axon terminals in CA3. 2. Glutamate microdrops (10-20 mM, 10-20 microns diam) increased the firing frequency of extracellularly recorded dentate granule cells for 5–10 s when applied to their somata but not when applied to their mossy fiber axons and terminals in the hilus and in CA3. 3. Glutamate microapplications to granule cell somata, but not to mossy fiber axons, also increased the frequency of intracellularly recorded EPSPs in CA3 pyramidal cells for 5-10 s. This provided a second line of evidence that glutamate did not cause firing in mossy fiber axons synapsing in CA3. 4. In slices where the CA3 region was surgically separated from the dentate gyrus and CA2, glutamate microdrops placed in the CA3 stratum pyramidale within 400 microns of intracellularly recorded pyramidal cells increased the frequency of EPSPs and IPSPs. Tetrodotoxin (1 microgram/ml) blocked these increases in PSP frequency, indicating that they did not result from glutamate-induced depolarization and associated transmitter release from presynaptic terminals. Increases in PSP frequency were interpreted to reflect glutamate activations of CA3 neurons with local synaptic connections to recorded cells. 5. Low concentrations of picrotoxin (PTX, 5-10 microM) blocked glutamate-induced increases in IPSP frequency and often revealed increases in EPSP frequency where they were not previously observed. This suggests that recurrent inhibitory circuits normally mask or block transmission through recurrent excitatory pathways in CA3. 6. In five experiments following PTX treatment (7.5–10 microM), large and prolonged (up to 2 min) increases in EPSP frequency were observed in CA3 pyramidal cells to glutamate microapplications in CA3. Rhythmic epileptiform bursts eventually occurred in two of these cases, suggesting that the protracted increases in EPSP frequency represent a form of reverberating excitation during a transition from normal to epileptic states. 7. Sixteen CA3 pyramidal cells were recorded in PTX (5-10 microM) during glutamate microapplications at 200 and 400 microns on each side of the recording site. The most consistent glutamate-induced increases in EPSP frequency occurred to microapplications 200 microns from recording sites on the hilar side.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Excitatory effects of dentate gyrus mossy cells and their ability to influence granule cell firing: an optogenetic study in adult mouse hippocampal slices

2020 ◽  
Author(s):  
Hannah L. Bernstein ◽  
Yi-Ling Lu ◽  
Justin J. Botterill ◽  
Áine M. Duffy ◽  
John J. LaFrancois ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Molecular Layer ◽  
Hippocampal Slices ◽  
Gabaergic Neurons ◽  
Excitatory Effect ◽  
Experimental Conditions ◽  
Mossy Cells ◽  
Direct Excitation ◽  
Cell Firing

ABSTRACTGlutamatergic dentate gyrus (DG) mossy cells (MCs) innervate the primary cell type, granule cells (GCs), and GABAergic neurons which inhibit GCs. Prior studies suggest that the net effect of MCs is mainly to inhibit GCs, leading one to question why direct excitation of GCs is often missed. We hypothesized that MCs do have excitatory effects, but each GC is only excited weakly, at least under most experimental conditions. To address this hypothesis, MC axons were stimulated optogenetically in slices. A brief optogenetic stimulus to MC axons in the inner molecular layer (IML) led to a short-latency field EPSP (fEPSP) in the IML, suggesting there was a direct excitatory effect on GCs. Population spikes were negligible however, consistent with weak excitation. FEPSPs reflected AMPA/NMDA receptor-mediated EPSPs in GCs. EPSPs reached threshold after GC depolarization or facilitating NMDA receptors. GABAA and GABAB receptor-mediated IPSPs often followed EPSPs. At the network level, an optogenetic stimulus led to a brief, small facilitation of the PP-evoked population spike followed by a longer, greater inhibition. These data are consistent with rapid and selective GC firing by MCs (MC → GC) and disynaptic inhibition (MC → GABAergic neuron → GC). Notably, optogenetic excitation was evoked for both dorsal and ventral MCs, ipsilateral and contralateral MC axons, and two Cre lines. Together the results suggest a way to reconcile past studies and provide new insight into the balance of excitation and inhibition of GCs by MCs.SIGNIFICANCE STATEMENTMossy cells (MCs) of the dentate gyrus (DG) are glutamatergic and innervate granule cells (GCs). The net effect of MCs has been debated because MCs also innervate GABAergic neurons which inhibit GCs. The results shown here suggest that MCs excite numerous GCs, but excitation is weak at GC resting potentials, and requires specific conditions to trigger GC APs. The results are consistent with a GC network that is designed for selective activation.

Spontaneous and stimulation-induced synchronized burst afterdischarges in the isolated CA1 of kainate-treated rats

1996 ◽  
Vol 76 (4) ◽  
pp. 2231-2239 ◽  
Author(s):  
C. L. Meier ◽  
F. E. Dudek
Keyword(s):  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Stratum Radiatum ◽  
Maximal Response ◽  
Gamma Aminobutyric Acid ◽  
Population Spikes ◽  
Ca3 Pyramidal Cells ◽  
Ca1 Area ◽  
Hilar Neurons ◽  
Area Ca3

1. Kainate treatment preferentially kills dentate hilar neurons and CA3 pyramidal cells and ultimately leads to a chronic epileptic state. Bicuculline-induced epileptiform bursts were studied to test the hypothesis that multiple kainate injections and consequent status epilepticus would lead-after weeks to months of recovery-to prolonged synchronous afterdischarges in the isolated CA1 area of rat hippocampal slices, as would be expected if new recurrent excitatory circuits had formed. 2. Synaptic responses evoked in CA1 pyramidal cells of rats injected subcutaneously with kainate (10 hourly injections, 5 mg/kg each) 24-316 days before the slice experiment were compared with responses in slices from untreated and saline-injected controls. The maximal response to stratum radiatum stimulation in normal solution consisted of two to eight population spikes. 3. When gamma-aminobutyric acid-A receptor-mediated inhibition was reduced with bicuculline, synchronized burst afterdischarges after the initial stimulation-evoked burst, similar to the type of activity described in area CA3 under conditions where inhibition is impaired, occurred in 23% of slices. 4. The prolonged synchronized burst afterdischarges in the isolated CA1 area of kainate-treated rats were associated with large excitatory postsynaptic potentials (EPSPs). These prolonged bursts were not graded with the stimulus intensity; rather, they were triggered in an all-or-none manner, even though there was some variability across bursts. The bursts of population spikes also were correlated with subthreshold EPSPs. 5. Slices that had synchronized burst afterdischarges had significantly more damage in area CA3 than slices without afterdischarges. 6. The data indicate that kainate-induced damage in CA3 can lead to prolonged synchronous afterdischarges, even after CA1 is surgically isolated from the CA3 area. Because the repetitive bursts during the prolonged and synchronous afterdischarges were associated with large EPSPs, these data suggest that kainate-induced damage to CA3 and subsequent degeneration of synaptic terminals in the CA1 area causes the formation of new recurrent excitatory circuits that could be involved in the development of chronic epilepsy.

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