Direct demonstration of functional disconnection by anoxia of inhibitory interneurons from excitatory inputs in rat hippocampus

1995 ◽  
Vol 73 (1) ◽  
pp. 421-426 ◽  
Author(s):  
P. Congar ◽  
R. Khazipov ◽  
Y. Ben-Ari
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Reversal Potential ◽  
Pyramidal Cells ◽  
Stratum Radiatum ◽  
Patch Clamp Technique ◽  
Ca1 Region ◽  
Whole Cell Patch Clamp ◽  
Direct Demonstration ◽  
Outward Currents

1. We studied the effects of anoxia on excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs) evoked by electrical stimulation in the stratum radiatum in concomitantly recorded pyramidal cells and interneurons of the CA1 region of rat hippocampal slices. We used the blind whole cell patch-clamp technique, and anoxia was induced by switching perfusion of the slice from oxygenated artificial cerebral spinal fluid (ACSF) to ACSF saturated with 95% N2-5% CO2 for 4-6 min. 2. As in pyramidal neurons, anoxia induced in interneurons outward currents, during and shortly after the anoxic episode. Both currents were, however, significantly larger in interneurons than in pyramidal neurons. 3. EPSCs are more rapidly depressed by anoxia in interneurons than in simultaneously recorded pyramidal cells. 4. In pyramidal neurons, polysynaptic IPSCs (pIPSCs) evoked by conventional distant stimulation (> 1 mm) are more sensitive to anoxia then EPSCs. In contrast, in interneurons, anoxia blocks with a similar latency EPSCs and polysynaptic IPSCs. 5. To determine whether this block of pIPSCs in pyramidal cells is due to a shift in driving force or a change in conductance, we examined the current (I/V) relationships. The block by anoxia of pIPSCs is due to a reduction of IPSC conductance (> 98%) that occlude other events including the shift of IPSCs reversal potential (ECl).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Progesterone Withdrawal Reduces Paired-Pulse Inhibition in Rat Hippocampus: Dependence on GABAA Receptor α4 Subunit Upregulation

2003 ◽  
Vol 89 (1) ◽  
pp. 186-198 ◽  
Author(s):  
Fu-Chun Hsu ◽  
Sheryl S. Smith
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Extracellular Recording ◽  
Pyramidal Cells ◽  
Chronic Administration ◽  
Female Rats ◽  
Stratum Radiatum ◽  
Intraventricular Administration ◽  
Paired Pulse ◽  
Ca1 Region

Withdrawal from the endogenous steroid progesterone (P) after chronic administration increases anxiety and seizure susceptibility via declining levels of its potent GABA-modulatory metabolite 3α-OH-5α-pregnan-20-one (3α,5αTHP). This 3α,5α-THP withdrawal also results in a decreased decay time constant for GABA-gated current assessed using whole cell patch-clamp techniques on pyramidal cells acutely dissociated from CA1 hippocampus. The purpose of this study was to test the hypothesis that the decreases in total integrated GABA-gated current observed at the level of the isolated pyramidal cell would be manifested as a reduced GABA inhibition at the circuit level following hormone withdrawal. Toward this end, adult, female rats were administered P via subcutaneous capsule for 3 wk using a multiple withdrawal paradigm. We then evaluated paired-pulse inhibition (PPI) of pyramidal neurons in CA1 hippocampus using extracellular recording techniques in hippocampal slices from rats 24 h after removal of the capsule (P withdrawal, P Wd). The population spike (PS) was recorded at the stratum pyramidale following homosynaptic orthodromic stimulation in the nearby stratum radiatum. The threshold for eliciting a response was decreased after P Wd, and the mean PS amplitude was significantly increased compared with control values at this time. Paired pulses with 10-ms inter-pulse intervals were then applied across an intensity range from 2 to 20 times threshold. Evaluation of paired-pulse responses showed a significant 40–50% reduction in PPI for PS recorded in the hippocampal CA1 region after P Wd, suggesting an increase in circuit excitability. At this time, enhancement of PPI by the benzodiazepine lorazepam (LZM; 10 μM) was prevented, while pentobarbital (10 μM) potentiation of PPI was comparable to control levels of response. These data are consistent with upregulation of the α4 subunit of the GABAA receptor (GABAR) as we have previously shown. Moreover, the reduced PPI caused by P Wd was prevented by suppression of GABAR α4-subunit expression following intraventricular administration of specific antisense oligonucleotides (1 μg/h for 72 h). These results demonstrating a reduction in PPI following P Wd suggest that GABAergic-mediated recurrent or feed-forward inhibition occurring at the circuit level were decreased following P Wd in female rats, an effect at least partially attributable to alterations in the GABAR subunit gene expression.

Agent-selective Effects of Volatile Anesthetics on GABAAReceptor–mediated Synaptic Inhibition in Hippocampal Interneurons

2001 ◽  
Vol 94 (2) ◽  
pp. 340-347 ◽  
Author(s):  
Koichi Nishikawa ◽  
M. Bruce MacIver
Keyword(s):  
Gabaa Receptor ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Volatile Anesthetics ◽  
Stratum Radiatum ◽  
Synaptic Inhibition ◽  
Gamma Aminobutyric Acid ◽  
Ca1 Region ◽  
Whole Cell Patch Clamp ◽  
Cortical Regions

Background A relatively small number of inhibitory interneurons can control the excitability and synchronization of large numbers of pyramidal cells in hippocampus and other cortical regions. Thus, anesthetic modulation of interneurons could play an important role for the maintenance of anesthesia. The aim of this study was to compare effects produced by volatile anesthetics on inhibitory postsynaptic currents (IPSCs) of rat hippocampal interneurons. Methods Pharmacologically isolated gamma-aminobutyric acid type A (GABAA) receptor-mediated IPSCs were recorded with whole cell patch-clamp techniques in visually identified interneurons of rat hippocampal slices. Neurons located in the stratum radiatum-lacunosum moleculare of the CA1 region were studied. The effects of clinically relevant concentrations (1.0 rat minimum alveolar concentration) of halothane, enflurane, isoflurane, and sevoflurane were compared on kinetics of both stimulus-evoked and spontaneous GABAA receptor-mediated IPSCs in interneurons. Results Halothane (1.2 vol% approximately 0.35 mm), enflurane (2.2 vol% approximately 0.60 mm), isoflurane (1.4 vol% approximately 0.50 mm), and sevoflurane (2.7 vol% approximately 0.40 mm) preferentially depressed evoked IPSC amplitudes to 79.8 +/- 9.3% of control (n = 5), 38.2 +/- 8.6% (n = 6), 52.4 +/- 8.4% (n = 5), and 46.1 +/- 16.0% (n = 8), respectively. In addition, all anesthetics differentially prolonged the decay time constant of evoked IPSCs to 290.1 +/- 33.2% of control, 423.6 +/- 47.1, 277.0 +/- 32.2, and 529 +/- 48.5%, respectively. The frequencies of spontaneous IPSCs were increased by all anesthetics (twofold to threefold). Thus, the total negative charge transfer mediated by GABAA receptors between synaptically connected interneurons was enhanced by all anesthetics. Conclusions Volatile anesthetics differentially enhanced GABAA receptor-mediated synaptic inhibition in rat hippocampal interneurons, suggesting that hippocampal interneuron circuits are depressed by these anesthetics in an agent-specific manner.

Hippocampal inhibitory interneurons are functionally disconnected from excitatory inputs by anoxia

1993 ◽  
Vol 70 (6) ◽  
pp. 2251-2259 ◽  
Author(s):  
R. Khazipov ◽  
P. Bregestovski ◽  
Y. Ben-Ari
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Gabab Receptors ◽  
Stratum Radiatum ◽  
Gamma Aminobutyric Acid ◽  
Patch Clamp Recording ◽  
Synaptic Currents ◽  
Postsynaptic Currents ◽  
Whole Cell Patch Clamp

1. The effects of anoxia on inhibitory synaptic transmission were studied in hippocampal slices of 3- to 4-wk-old rats. CA1 pyramidal cells were examined by whole-cell patch-clamp recording. Synaptic currents were evoked by “distant” (> 0.5 mm) or “close” (< 0.5 mm) electrical stimulation in the stratum radiatum. 2. The excitatory postsynaptic currents (EPSCs) and inhibitory postsynaptic currents (IPSCs) evoked by distant stimulation were completely suppressed by brief anoxia (95% N2-5% CO2 for 4-6 min) and recovered upon reoxygenation. IPSCs were more sensitive to anoxia than EPSCs. EPSCs and IPSCs evoked by distant stimulation were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 20 microM) and D-2-amino-5-phosphonopentanoate (APV; 50 microM). This indicates that IPSCs were mediated via a polysynaptic pathway that involves glutamate receptors. 3. Synaptic currents evoked by close stimulation were only partly inhibited by anoxia. The bicuculline-sensitive gamma-aminobutyric acid-A (GABAA) receptor-mediated synaptic currents were particularly resistant to anoxia, suggesting that the GABAergic input to pyramidal neurons is not inhibited by anoxia. 4. At close stimulation in the stratum radiatum, monosynaptic IPSCs could be evoked in the presence of CNQX (20 microM) and APV (50 microM). The monosynaptic IPSCs had early bicuculline (15 microM) and late CGP 35348 (100 microM)-sensitive components confirming an involvement of GABAA and GABAB receptors (IPSCA and IPSCB components), respectively. 5. The monosynaptic IPSCA component evoked by close stimulation was not changed significantly during and after brief anoxia. Responses to pressure application of isoguvacine (GABAA agonist) were also not affected by anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of the Ca2+-Activated K+ Current sI AHP by aPhosphatase-Kinase Balance Under Basal Conditions inRat CA1 Pyramidal Neurons

1998 ◽  
Vol 79 (6) ◽  
pp. 3252-3256 ◽  
Author(s):  
Paola Pedarzani ◽  
Michael Krause ◽  
Trude Haug ◽  
Johan F. Storm ◽  
Walter Stühmer
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Phosphodiesterase Inhibitors ◽  
Gradual Decrease ◽  
Patch Clamp Technique ◽  
Hippocampal Pyramidal Neurons ◽  
Ca1 Pyramidal Neurons ◽  
Type Iv ◽  
Whole Cell Patch Clamp ◽  
Firing Properties

Pedarzani, Paola, Michael Krause, Trude Haug, Johan F. Storm, and Walter Stühmer. Modulation of the Ca2+-activated K+ current s I AHP by a phosphatase-kinase balance under basal conditions in rat CA1 pyramidal neurons. J. Neurophysiol. 79: 3252–3256, 1998. The slow Ca2+-activated K+ current, s I AHP, underlying spike frequency adaptation, was recorded with the whole cell patch-clamp technique in CA1 pyramidal neurons in rat hippocampal slices. Inhibitors of serine/threonine protein phosphatases (microcystin, calyculin A, cantharidic acid) caused a gradual decrease of s I AHP amplitude, suggesting the presence of a basal phosphorylation-dephosphorylation turnover regulating s I AHP. Because selective calcineurin (PP-2B) inhibitors did not affect the amplitude of s I AHP, protein phosphatase 1 (PP-1) or 2A (PP-2A) are most likely involved in the basal regulation of this current. The ATP analogue, ATP-γ-S, caused a gradual decrease in the s I AHP amplitude, supporting a role of protein phosphorylation in the basal modulation of s I AHP. When the protein kinase A (PKA) inhibitor adenosine-3′,5′-monophosphorothioate, Rp-isomer (Rp-cAMPS) was coapplied with the phosphatase inhibitor microcystin, it prevented the decrease in the s I AHP amplitude that was observed when microcystin alone was applied. Furthermore, inhibition of PKA by Rp-cAMPS led to an increase in the s I AHP amplitude. Finally, an adenylyl cyclase inhibitor (SQ22,536) and adenosine 3′,5′-cyclic monophosphate-specific type IV phosphodiesterase inhibitors (Ro 20–1724 and rolipram) led to an increase or a decrease in the s I AHP amplitude, respectively. These findings suggest that a balance between basally active PKA and a phosphatase (PP-1 or PP-2A) is responsible for the tonic modulation of s I AHP, resulting in a continuous modulation of excitability and firing properties of hippocampal pyramidal neurons.

scholarly journals Evidence of calcium-permeable AMPA receptors in dendritic spines of CA1 pyramidal neurons

2014 ◽  
Vol 112 (2) ◽  
pp. 263-275 ◽  
Author(s):  
Hayley A. Mattison ◽  
Ashish A. Bagal ◽  
Michael Mohammadi ◽  
Nisha S. Pulimood ◽  
Christian G. Reich ◽  
...  
Keyword(s):  
Dendritic Spines ◽  
Ampa Receptors ◽  
Pyramidal Neurons ◽  
Calcium Influx ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Stratum Radiatum ◽  
Acute Hippocampal Slices ◽  
Cultured Slices ◽  
Apical Dendrites

GluA2-lacking, calcium-permeable α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors (AMPARs) have unique properties, but their presence at excitatory synapses in pyramidal cells is controversial. We have tested certain predictions of the model that such receptors are present in CA1 cells and show here that the polyamine spermine, but not philanthotoxin, causes use-dependent inhibition of synaptically evoked excitatory responses in stratum radiatum, but not s. oriens, in cultured and acute hippocampal slices. Stimulation of single dendritic spines by photolytic release of caged glutamate induced an N-methyl-d-aspartate receptor-independent, use- and spermine-sensitive calcium influx only at apical spines in cultured slices. Bath application of glutamate also triggered a spermine-sensitive influx of cobalt into CA1 cell dendrites in s. radiatum. Responses of single apical, but not basal, spines to photostimulation displayed prominent paired-pulse facilitation (PPF) consistent with use-dependent relief of cytoplasmic polyamine block. Responses at apical dendrites were diminished, and PPF was increased, by spermine. Intracellular application of pep2m, which inhibits recycling of GluA2-containing AMPARs, reduced apical spine responses and increased PPF. We conclude that some calcium-permeable, polyamine-sensitive AMPARs, perhaps lacking GluA2 subunits, are present at synapses on apical dendrites of CA1 pyramidal cells, which may allow distinct forms of synaptic plasticity and computation at different sets of excitatory inputs.

Calcium Currents in Retrogradely Labeled Pyramidal Cells From Rat Sensorimotor Cortex

2000 ◽  
Vol 83 (4) ◽  
pp. 2349-2354 ◽  
Author(s):  
Ansalan Stewart ◽  
Robert C. Foehring
Keyword(s):  
Pyramidal Neurons ◽  
Pyramidal Cells ◽  
Cell Types ◽  
Calcium Currents ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Multiple Populations ◽  
Whole Cell Patch Clamp ◽  
The Mean ◽  
P Type

Our previous studies of calcium (Ca2+) currents in cortical pyramidal cells revealed that the percentage contribution of each Ca2+ current type to the whole cell Ca2+ current varies from cell to cell. The extent to which these currents are modulated by neurotransmitters is also variable. This study was directed at testing the hypothesis that a major source of this variability is recording from multiple populations of pyramidal cells. We used the whole cell patch-clamp technique to record from dissociated corticocortical, corticostriatal, and corticotectal projecting pyramidal cells. There were significant differences between the three pyramidal cell types in the mean percentage of L-, P-, and N-type Ca2+ currents. For both N- and P-type currents, the range of percentages expressed was small for corticostriatal and corticotectal cells as compared with cells which project to the corpus callosum or to the general population. The variance was significantly different between cell types for N- and P-type currents. These results suggest that an important source of the variability in the proportions of Ca2+ current types present in neocortical pyramidal neurons is recording from multiple populations of pyramidal cells.

Permeability of time-dependent K+ channel in guinea pig ventricular myocytes to Cs+, Na+, NH4+, and Rb+

1990 ◽  
Vol 259 (5) ◽  
pp. H1448-H1454 ◽  
Author(s):  
R. W. Hadley ◽  
J. R. Hume
Keyword(s):  
Guinea Pig ◽  
Ventricular Myocytes ◽  
Reversal Potential ◽  
Outward Current ◽  
Time Dependent ◽  
K Channel ◽  
Delayed Rectifier ◽  
Patch Clamp Technique ◽  
Whole Cell Patch Clamp ◽  
Outward Currents

Currents through time-dependent K+ channels (also referred to as IK or the delayed rectifier) were studied with the whole cell patch-clamp technique in isolated guinea pig ventricular myocytes. IK measurements were restricted to the examination of deactivation tail currents. Substitution of various monovalent cations for external K+ produced shifts of the reversal potential of IK. These shifts were used to calculate permeability ratios relative to K+. The permeability sequence for the IK channels was K+ = Rb+ greater than NH4+ = Cs+ greater than Na+. Time-dependent outward currents were also examined when the myocytes were dialyzed with Cs+ instead of K+. A sizeable time-dependent outward current, quite similar to that seen with K+ dialysis, was demonstrated. This current was primarily carried by intracellular Cs+, as the reversal potential of the current shifted 46 mV per 10-fold change of external Cs+ concentration. The significance of Cs+ permeation through IK channels is discussed with respect to the common use of Cs+ in isolating other currents.

Posttetanic Excitation Mediated by GABAA Receptors in Rat CA1 Pyramidal Neurons

1997 ◽  
Vol 77 (4) ◽  
pp. 2213-2218 ◽  
Author(s):  
Tomi Taira ◽  
Karri Lamsa ◽  
Kai Kaila
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Long Term Potentiation ◽  
Neuronal Firing ◽  
Stratum Radiatum ◽  
Tetanic Stimulation ◽  
Glutamate Antagonists ◽  
Ca1 Pyramidal Neurons ◽  
Spike Firing

Taira, Tomi, Karri Lamsa, and Kai Kaila. Posttetanic excitation mediated by GABAA receptors in rat CA1 pyramidal neurons. J.Neurophysiol. 77: 2213–2218, 1997. The contributions of γ-aminobutyric acid (GABA) receptors to posttetanic excitation of CA1 pyramidal neurons in rat hippocampal slices were studied using extracellular and intracellular recording techniques. Synaptic responses were evoked on tetanic stimulation (100–200 Hz, 40–100 pulses) applied in stratum radiatum close (300–600 μm) to the recording site. Under control conditions, tetanic stimulation resulted in a triphasic depolarization/hyperpolarization/sustained depolarization sequence in area CA1 pyramidal cells. The late depolarization usually gave rise to a prolonged (≤3 s) spike firing. The late depolarization and the associated spike firing were blocked both specifically and completely (within a time window of 3–6 min starting from picrotoxin application) by the GABAA receptor antagonist picrotoxin (PiTX, 100 μM). Paradoxically, at this early stage of PiTX application, overall neuronal firing was attenuated to a higher degree than what was achieved by ionotropic glutamate antagonists. Complete block of ionotropic glutamate receptors by the antagonists d-2-amino-5-phosphonopentoate (AP5, 80 μM), 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione (NBQX, 10 μM), and ketamine (50 μM) blocked the initial fast depolarization and suppressed the late one. Exposure to a permeable inhibitor of carbonic anhydrase, ethoxyzolamide (EZA, 50 μM) inhibited the late, apparently GABA-mediated depolarization. It is concluded that GABA can provide the main posttetanic excitatory drive in the adult hippocampus. The present results suggest that intense activation of GABAergic interneurons may accentuate the excitation of principal neurons and, hence, play an important facilitatory role in the induction of long-term potentiation (LTP) and epileptogenesis.

Pharmacology of a Slowly Inactivating Outward Current in Hippocampal CA3 Pyramidal Neurons

2006 ◽  
Vol 96 (3) ◽  
pp. 1116-1123 ◽  
Author(s):  
Riccardo Bianchi ◽  
Shih-Chieh Chuang ◽  
Robert K. S. Wong
Keyword(s):  
Time Course ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Reversal Potential ◽  
Outward Current ◽  
Pyramidal Cells ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Transient Outward Current ◽  
Activation Threshold

The pharmacology of a slowly inactivating outward current was examined using whole cell patch-clamp recordings in CA3 pyramidal cells of guinea pig hippocampal slices. The current had a low activation threshold (about −60 mV) and inactivated slowly (time constant of 3.4 ± 0.5 s at −50 mV) and completely at membrane voltages depolarized to −50 mV. The slowly inactivating outward current was mainly mediated by K+ with a reversal potential close to the equilibrium potential for K+. The slowly inactivating outward current had distinct pharmacological properties: its time course was not affected by extracellular Cs+ (1 mM) or 4-AP (1–5 mM)—broad spectrum inhibitors of K+ currents and of inactivating K+ currents, respectively. The presence of extracellular Mn2+ (0.5–1 mM), which suppresses several Ca2+-dependent K+ currents, also did not affect the slowly inactivating outward current. The current was partially suppressed by TEA (50 mM) and was blocked by intracellular Cs+ (134 mM). In addition, intracellular QX-314 (5 mM), a local anesthetic derivative, inhibited this current. The slowly inactivating outward current with its low activation threshold should be operational at the resting potential. Our results suggest that the transient outward current activated at subthreshold membrane potentials in hippocampal pyramidal cells consists of at least three components. In addition to the well-described A- and D-currents, the slowest decaying component reflects the time course of a distinct current, suppressible by QX-314.

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