scholarly journals An In Vitro Model of Hippocampal Sharp Waves: Regional Initiation and Intracellular Correlates

2005 ◽  
Vol 94 (1) ◽  
pp. 741-753 ◽  
Author(s):  
Chiping Wu ◽  
Marjan Nassiri Asl ◽  
Jesse Gillis ◽  
Frances K. Skinner ◽  
Liang Zhang
Keyword(s):  
Dentate Gyrus ◽  
Large Amplitude ◽  
Pyramidal Neurons ◽  
Slow Wave Sleep ◽  
Hippocampal Slices ◽  
Field Potentials ◽  
Sharp Wave ◽  
Sharp Waves ◽  
Hippocampal Circuitry

During slow wave sleep and consummatory behaviors, electroencephalographic recordings from the rodent hippocampus reveal large amplitude potentials called sharp waves. The sharp waves originate from the CA3 circuitry and their generation is correlated with coherent discharges of CA3 pyramidal neurons and dependent on activities mediated by AMPA glutamate receptors. To model sharp waves in a relatively large hippocampal circuitry in vitro, we developed thick (1 mm) mouse hippocampal slices by separating the dentate gyrus from the CA2/CA1 areas while keeping the functional dentate gyrus-CA3-CA1 connections. We found that large amplitude (0.3–3 mV) sharp wave-like field potentials occurred spontaneously in the thick slices without extra ionic or pharmacological manipulation and they resemble closely electroencephalographic sharp waves with respect to waveform, regional initiation, pharmacological manipulations, and intracellular correlates. Through measuring tissue O2, K+, and synaptic and single cell activities, we verified that the sharp wave-like potentials are not a consequence of anoxia, nonspecific elevation of extracellular K+ and dissection-related tissue damage. Our data suggest that a subtle but crucial increase in the CA3 glutamatergic activity effectively recruits a population of neurons thus responsible for the generation of the sharp wave-like spontaneous field potentials in isolated hippocampal circuitry.

Selective Modulation of Tonic and Phasic Inhibitions in Dentate Gyrus Granule Cells

2002 ◽  
Vol 87 (5) ◽  
pp. 2624-2628 ◽  
Author(s):  
Zoltan Nusser ◽  
Istvan Mody
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Hippocampal Slices ◽  
Tonic Inhibition ◽  
Adult Rats ◽  
Adult Rat ◽  
Phasic Inhibition ◽  
The Mean

In some nerve cells, activation of GABAA receptors by GABA results in phasic and tonic conductances. Transient activation of synaptic receptors generates phasic inhibition, whereas tonic inhibition originates from GABA acting on extrasynaptic receptors, like in cerebellar granule cells, where it is thought to result from the activation of extrasynaptic GABAA receptors with a specific subunit composition (α6βxδ). Here we show that in adult rat hippocampal slices, extracellular GABA levels are sufficiently high to generate a powerful tonic inhibition in δ subunit–expressing dentate gyrus granule cells. In these cells, the mean tonic current is approximately four times larger than that produced by spontaneous synaptic currents occurring at a frequency of ∼10 Hz. Antagonizing the GABA transporter GAT-1 with NO-711 (2.5 μM) selectively enhanced tonic inhibition by 330% without affecting the phasic component. In contrast, by prolonging the decay of inhibitory postsynaptic currents (IPSCs), the benzodiazepine agonist zolpidem (0.5 μM) augmented phasic inhibition by 66%, while leaving the mean tonic conductance unchanged. These results demonstrate that a tonic GABAA receptor–mediated conductance can be recorded from dentate gyrus granule cells of adult rats in in vitro slice preparations. Furthermore, we have identified distinct pharmacological tools to selectively modify tonic and phasic inhibitions, allowing future studies to investigate their specific roles in neuronal function.

Ethanol Alters the Frequency, Amplitude, and Decay Kinetics of Sr2+-Supported, Asynchronous NMDAR mEPSCs in Rat Hippocampal Slices

2004 ◽  
Vol 91 (6) ◽  
pp. 2568-2577 ◽  
Author(s):  
Adam W. Hendricson ◽  
John R. Sibbald ◽  
Richard A. Morrisett
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Mean Amplitude ◽  
Long Term Potentiation ◽  
Exponential Fitting ◽  
Decay Kinetics ◽  
Current Decay ◽  
Event Frequency

To discriminate between pre- and postsynaptic effects of ethanol on N-methyl-d-aspartate receptor (NMDAR) signaling in hippocampus, we adapted the technique of Sr2+ substitution to the hippocampal blind slice patch-clamp preparation. Hippocampal slices were isolated from 12- to 20-day-old rats that were killed in accordance with University of Texas Institutional Animal Care and Use Committee guidelines. NMDAR miniature excitatory postsynaptic currents (mEPSCs) were evoked from CA1 pyramidal neurons in the presence of Sr2+ (4 mM), causing the synchronous EPSC observed in the presence of Ca2+ to be supplanted by asynchronous mEPSCs. Amplitudes typically ranged from 5 to 40 pA and responded to the NMDAR antagonist (DL)-APV (50 μM), with a statistically significant reduction in mean amplitude. Ethanol (25, 50, and 75 mM) exerted dose-dependent effects on mEPSC amplitude and frequency. Peak amplitude inhibition was observed at 75 mM ethanol. Notably, ethanol significantly decreased event frequency at 50 and 75 mM ethanol. Ethanol (75 mM) also significantly increased the paired-pulse ratio of NMDAR EPSCs. Cumulative comparisons of decay time constants derived from single-exponential fitting of mEPSCs revealed significantly accelerated current decay kinetics in the presence of 75 mM ethanol. Taken together, these reductions in miniature event frequency and amplitude, concurrent with an increased rate of decay, suggest that the acute effects of ethanol on NMDAR signaling at hippocampal synapses are multifocal in nature. This finding of pre- and postsynaptic effects of ethanol on NMDAR signal strength in a brain region central to cognition is wholly consistent with previous reports of ethanol inhibition of NMDAR–long-term potentiation in vitro and with the profound cognitive deficits associated with binge-level intoxication in vivo.

scholarly journals Examinations of Bilateral Epileptiform Activities in Hippocampal Slices Obtained From Young Mice

2021 ◽  
Vol 14 ◽  
Author(s):  
Haiyu Liu ◽  
Peter L. Carlen ◽  
Liang Zhang
Keyword(s):  
Room Temperature ◽  
Hippocampal Slices ◽  
Field Potentials ◽  
Hippocampal Commissure ◽  
Extracellular Recordings ◽  
Adult Mice ◽  
Unilateral Stimulation ◽  
Dorsal Hippocampal ◽  
Young Mice

Bilateral interconnections through the hippocampal commissure play important roles in synchronizing or spreading hippocampal seizure activities. Intact hippocampi or bilateral hippocampal slices have been isolated from neonatal or immature rats (6–7 or 12–21 days old, respectively) and the mechanisms underlying the bilateral synchrony of hippocampal epileptiform activities have been investigated. However, the feasibility of examining bilateral epileptiform activities of more developed hippocampal circuitry in vitro remains to be explored. For this, we prepared bilateral hippocampal slices from C57 black mice, a strain commonly used in neuroscience and for genetic/molecular modifications. Young mice (21–24-day-old) were used in most experiments. A 600-μm-thick slice was obtained from each mouse by horizontal vibratome sectioning. Bilateral dorsal hippocampal and connecting dorsal hippocampal commissure (DHC) tissues were preserved in the slice and extrahippocampal tissues were removed. Slices were recorded in a submerged chamber mainly at a room temperature (21–22°C). Bilateral CA3 areas were monitored by extracellular recordings, and unilateral electrical stimulation was used to elicit CA3 synaptic field potentials. The unilateral stimulation could elicit population spikes in the contralateral CA3 area. These contralateral spikes were attenuated by inhibiting synaptic transmission with cobalt-containing medium and were abolished when a cut was made at the DHC. Self-sustained and bilaterally correlated epileptiform potentials were observed following application of 4-aminopyradine and became independent after the DHC cut. Bilateral hippocampal activities were detectable in some slices of adult mice and/or at 35–36°C, but with smaller amplitudes and variable waveforms compared to those observed from slices of young mice and at the room temperature. Together, these observations suggested that examining bilateral epileptiform activities in hippocampal slices of young mice is feasible. The weaknesses and limitations of this preparation and our experimentation are discussed.

scholarly journals Methods for recording and imaging spreading depolarizations and seizure-like events in mouse hippocampal slices

2021 ◽  
Author(s):  
Yi-Ling Lu ◽  
Helen E Scharfman
Keyword(s):  
Dentate Gyrus ◽  
Optical Imaging ◽  
Hippocampal Slices ◽  
Brain Regions ◽  
Electrophysiological Recordings ◽  
Artificial Cerebrospinal Fluid ◽  
Vitro Model ◽  
Acute Hippocampal Slices ◽  
Molecular Layers

Spreading depolarization (SD) is a sudden and synchronized depolarization of principal cells followed by depression of activity, which slowly propagates across brain regions like cortex or hippocampus. SD is considered to be mechanistically relevant to migraine, epilepsy, and traumatic brain injury. Interestingly, research into SD typically uses SD triggered immediately after a focal stimulus. Here we optimize an in vitro experimental model allowing us to record SD without focal stimulation. This method uses electrophysiological recordings and intrinsic optical imaging in slices. The method is also relatively easy and inexpensive. Acute hippocampal slices from mice or rats were prepared and used for extracellular and whole-cell recordings. Recordings were made in a submerged-style chamber with flow of artificial cerebrospinal fluid (aCSF) above and below the slices. Flow was fast (> 5ml/min), and temperature was 32°C. As soon as slices were placed in the chamber, aCSF containing 0 mM Mg2+ and 5 mM K+ (0 Mg2+/5 K+ aCSF) was used. Two major types of activity were observed: SD and seizure-like events (SLEs). Both occurred after many minutes of recording. Although both mouse and rat slices showed SLEs, only mouse slices developed SD and did so in the first hour of 0 Mg2+/5 K+ aCSF exposure. Intrinsic optical imaging showed that most SDs initiated in CA3 and could propagate into CA1 and dentate gyrus. In dentate gyrus, SD propagated in two separate waves: (1) into the hilus and (2) into granule cell and molecular layers simultaneously. This in vitro model can be used to better understand the mechanisms and relationship between SD and SLEs. It could also be useful in preclinical drug screening.

scholarly journals In vitro hippocampal uptake of tritiated serotonin (3H-5HT): A morphological, biochemical, and pharmacological approach to specificity.

1980 ◽  
Vol 28 (7) ◽  
pp. 636-644 ◽  
Author(s):  
E C Azmitia ◽  
W F Marovitz
Keyword(s):  
Dentate Gyrus ◽  
Linear Regression Analysis ◽  
Hippocampal Slices ◽  
Stratum Radiatum ◽  
Ammon's Horn ◽  
Uptake Mechanism ◽  
Cingulum Bundle ◽  
Specific Uptake ◽  
Ammon’S Horn

The in vitro uptake of tritiated serotonin (3H-5HT) into hippocampal slices was measured in Ringer's solution (37 degrees C) containing pargyline, ascorbic acid, and dextrose. The specific uptake of 3H-5HT rose asymptotically as the 3H-5HT molarity was increased from 5 x 10(-10) to 1.5 x 10(-6) M. Linear regression analysis gave a Km value for the specific uptake of 1.4 x 10(-7) M. The nonspecific binding (NSB) was the amount of 3H-5HT retained by the slices following incubation in a medium with a very large excess of unlabeled 5-HT added to dilute the specific uptake of 3H-5HT. This NSB increased with increasing molarity of 3H-5HT, and was linearly related to 3H-5HT concentrations between 5 x 10(-9) and 1.5 x 10(-6) M. The ratio of specific uptake to NSB was highest at 5 x 10(-8) M (2.75) and lowest at 1.5 x 10(-6) M of 3H-5HT (0.54). Competition studies with noradrenaline, desipramine (a noradrenergic uptake blocker), fluoxetine (a 5-HT uptake blocker), and tryptophan confirmed the specificity of the 3H-5HT uptake mechanism. Radioautographic studies of in vitro incubated hippocampal slices showed silver grain aggregates at 3H-5HT specific uptake sites. Addition of an excess of unlabeled 5-HT to the slices, or the use of hippocampi from 5,7-dihydroxytryptamine intracerebral microinjected rats (5 microgram/400 nl into the fornix-fimbria and the cingulum bundle, 6 day survival) caused a dramatic decrease in these aggregates. The distribution of hippocampal 5-HT axons and terminals, inferred from the pattern of silver grain aggregates, is more widespread than previously described. 5-HT varicosities were clearly seen in all layers of Ammon's horn, dentate gyrus, and the subicular cortex. Innervation routes were seen to the stratum radiatum and stratum lacunosum from stratum oriens in Ammon's horn, and to the polymorphic layer of the dentate gyrus from the subicular cortex and from the fimbria. Semiquantitation of the occurrence of silver grain aggregates was done in the various hippocampal regions. The highest density in Ammon's horn was 119.5 boutons/10,000 micron2, in the dentate gyrus it was 67.4 boutons/10,000 micron2, and in the subicular cortex it was 79.2 boutons/10,000 micron2. These results are consistent with previous quantitative results.

scholarly journals Enhanced Neuronal Damage After Ischemic Insults in Mice Lacking Kir6.2-Containing ATP-Sensitive K+ Channels

2006 ◽  
Vol 95 (4) ◽  
pp. 2590-2601 ◽  
Author(s):  
Hong-Shuo Sun ◽  
Zhong-Ping Feng ◽  
Takashi Miki ◽  
Susumu Seino ◽  
Robert J. French
Keyword(s):  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Neuronal Damage ◽  
Focal Cerebral Ischemia ◽  
Hippocampal Slices ◽  
Immunocytochemical Staining ◽  
Sulfonylurea Receptor ◽  
Ca1 Pyramidal Neurons

Adenosine triphosphate (ATP)–sensitive potassium (KATP) channels, incorporating Kir6.x and sulfonylurea receptor subunits, are weak inward rectifiers that are thought to play a role in neuronal protection from ischemic insults. However, the involvement of Kir6.2-containing KATP channel in hippocampus and neocortex has not been tested directly. To delineate the physiological roles of Kir6.2 channels in the CNS, we used knockout (KO) mice that do not express Kir6.2. Immunocytochemical staining demonstrated that Kir6.2 protein was expressed robustly in hippocampal neurons of the wild-type (WT) mice and absent in the KO. To examine neuronal sensitivity to metabolic stress in vitro, and to ischemia in vivo, we 1) exposed hippocampal slices to transient oxygen and glucose deprivation (OGD) and 2) produced focal cerebral ischemia by middle cerebral artery occlusion (MCAO). Both slice and whole animal studies showed that neurons from the KO mice were severely damaged after anoxia or ischemia, whereas few injured neurons were observed in the WT, suggesting that Kir6.2 channels are necessary to protect neurons from ischemic insults. Membrane potential recordings from the WT CA1 pyramidal neurons showed a biphasic response to OGD; a brief hyperpolarization was followed by a small depolarization during OGD, with complete recovery within 30 min after returning to normoxic conditions. By contrast, CA1 pyramidal neurons from the KO mice were irreversibly depolarized by OGD exposure, without any preceding hyperpolarization. These data suggest that expression of Kir6.2 channels prevents prolonged depolarization of neurons resulting from acute hypoxic or ischemic insults, and thus protects these central neurons from the injury.

Burst characteristics of dentate gyrus granule cells: evidence for endogenous and nonsynaptic properties

1996 ◽  
Vol 75 (1) ◽  
pp. 124-132 ◽  
Author(s):  
E. Pan ◽  
J. L. Stringer
Keyword(s):  
Dentate Gyrus ◽  
Action Potentials ◽  
Granule Cells ◽  
Epileptiform Activity ◽  
Hippocampal Slices ◽  
Current Injection ◽  
Single Action ◽  
Epileptiform Discharges

1. Hippocampal slices bathed in 8 mM potassium and 0-added calcium exhibited spontaneous epileptiform activity in the dentate gyrus. Extracellular recording revealed recurrent prolonged bursts of population spikes and an associated negative DC shift. These episodes were very similar to the in vivo phenomenon termed maximal dentate activation (MDA). Therefore this in vitro activity will be referred to as MDA-like activity or events. 2. During the MDA-like activity, the individual granule cells exhibited a sustained depolarization that matched the duration of the negative extracellular DC shift. At the beginning of the MDA-like activity, there was a burst of action potentials. After the burst, most granule cells either continued to fire action potentials regularly or in bursts. Some cells exhibited this initial burst of activity and then a dramatic reduction in firing rate. This reduction in rate was followed by a gradual increase in the amplitude and frequency of the epileptiform activity recorded during the remainder of the MDA-like event. 3. Before and between MDA-like events, spontaneous cellular activity consisted of single action potentials and bursts of action potentials on a depolarizing envelope. In addition, depolarizing potentials, up to 13 mV, were recorded. There were no extracellular field potentials associated with these intracellularly recorded potentials. 4. In the 8 mM potassium, 0-added calcium test solution, the membrane potential threshold for burst production was significantly lower than in normal potassium and calcium medium. 5. The effect of depolarizing and hyperpolarizing current injections on the amplitude and frequency of the epileptiform activity was tested. Current injection had no effect on the frequency of the epileptiform activity recorded during the MDA-like events. However, the frequency of the cellular bursts between MDA-like events was very sensitive to current injection. Depolarizing current increased the frequency, and hyperpolarizing current decreased the frequency of the spontaneous activity. 6. This study has shown that in 8 mM potassium and 0-added calcium the granule cells of the dentate gyrus are capable of generating spontaneous bursts that appear to be mediated by endogenous mechanisms. In addition, synchronized epileptiform discharges were recorded from the granule cells at regular intervals that appear were recorded from the granule cells at regular intervals that appear to be mediated by exogenous nonsynaptic mechanisms.

scholarly journals GABA–glutamate supramammillary neurons control theta and gamma oscillations in the dentate gyrus during paradoxical (REM) sleep

2020 ◽  
Vol 225 (9) ◽  
pp. 2643-2668 ◽  
Author(s):  
Francesca Billwiller ◽  
Laura Castillo ◽  
Heba Elseedy ◽  
Anton Ivanovich Ivanov ◽  
Jennyfer Scapula ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Rem Sleep ◽  
Slow Wave Sleep ◽  
Granule Cells ◽  
Structural Connectivity ◽  
Gamma Oscillations ◽  
Network Activity ◽  
Projection Neurons ◽  
Gamma Power

AbstractSeveral studies suggest that neurons from the lateral region of the SuM (SuML) innervating the dorsal dentate gyrus (DG) display a dual GABAergic and glutamatergic transmission and are specifically activated during paradoxical (REM) sleep (PS). The objective of the present study is to characterize the anatomical, neurochemical and electrophysiological properties of the SuML-DG projection neurons and to determine how they control DG oscillations and neuronal activation during PS and other vigilance states. For this purpose, we combine structural connectivity techniques using neurotropic viral vectors (rabies virus, AAV), neurochemical anatomy (immunohistochemistry, in situ hybridization) and imaging (light, electron and confocal microscopy) with in vitro (patch clamp) and in vivo (LFP, EEG) optogenetic and electrophysiological recordings performed in transgenic VGLUT2-cre male mice. At the cellular level, we show that the SuML-DG neurons co-release GABA and glutamate on dentate granule cells and increase the activity of a subset of DG granule cells. At the network level, we show that activation of the SuML-DG pathway increases theta power and frequency during PS as well as gamma power during PS and waking in the DG. At the behavioral level, we show that the activation of this pathway does not change animal behavior during PS, induces awakening during slow wave sleep and increases motor activity during waking. These results suggest that the SuML-DG pathway is capable of supporting the increase of theta and gamma power in the DG observed during PS and plays an important modulatory role of DG network activity during this state.

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