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.

Fiberoptic System for Recording Dendritic Calcium Signals in Layer 5 Neocortical Pyramidal Cells in Freely Moving Rats

2007 ◽  
Vol 98 (3) ◽  
pp. 1791-1805 ◽  
Author(s):  
Masanori Murayama ◽  
Enrique Pérez-Garci ◽  
Hans-Rudolf Lüscher ◽  
Matthew E. Larkum
Keyword(s):  
Pyramidal Neurons ◽  
Calcium Influx ◽  
Signal To Noise Ratio ◽  
Pyramidal Cells ◽  
Cellular Mechanisms ◽  
Novel Approach ◽  
Specific Loading ◽  
Apical Dendrites

Calcium influx into the dendritic tufts of layer 5 neocortical pyramidal neurons modifies a number of important cellular mechanisms. It can trigger local synaptic plasticity and switch the firing properties from regular to burst firing. Due to methodological limitations, our knowledge about Ca2+ spikes in the dendritic tuft stems mostly from in vitro experiments. However, it has been speculated that regenerative Ca2+ events in the distal dendrites correlate with distinct behavioral states. Therefore it would be most desirable to be able to record these Ca2+ events in vivo, preferably in the behaving animal. Here, we present a novel approach for recording Ca2+ signals in the dendrites of populations of layer 5 pyramidal neurons in vivo, which ensures that all recorded fluorescence changes are due to intracellular Ca2+ signals in the apical dendrites. The method has two main features: 1) bolus loading of layer 5 with a membrane-permeant Ca2+ dye resulting in specific loading of pyramidal cell dendrites in the upper layers and 2) a fiberoptic cable attached to a gradient index lens and a prism reflecting light horizontally at 90° to the angle of the apical dendrites. We demonstrate that the in vivo signal-to-noise ratio recorded with this relatively inexpensive and easy-to-implement fiberoptic-based device is comparable to conventional camera-based imaging systems used in vitro. In addition, the device is flexible and lightweight and can be used for recording Ca2+ signals in the distal dendritic tuft of freely behaving animals.

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.

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)

scholarly journals Hypoosmolar dose-dependent swelling occurs in both pyramidal neurons and astrocytes in acute hippocampal slices

2017 ◽  
Author(s):  
Thomas R. Murphy ◽  
David Davila ◽  
Nicholas Cuvelier ◽  
Leslie R. Young ◽  
Kelli Lauderdale ◽  
...  
Keyword(s):  
Ampa Receptors ◽  
Extracellular Space ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Water Channel ◽  
Pyramidal Cells ◽  
Volume Changes ◽  
Osmotic Swelling ◽  
Neuronal Swelling

AbstractNormal nervous system function is critically dependent on the balance of water and ions in the extracellular space. Pathological reduction in brain interstitial osmolarity results in osmotically-driven flux of water into cells, causing cellular edema which reduces the extracellular space and increases neuronal excitability and risk of seizures. Astrocytes are widely considered to be particularly susceptible to cellular edema due to selective expression of the water channel aquaporin-4 (AQP4). The apparent resistance of pyramidal neurons to osmotic swelling has been attributed to lack of functional water channels. In this study we report rapid volume changes in CA1 pyramidal cells in hypoosmolar ACSF (hACSF) that are equivalent to volume changes in astrocytes across a variety of conditions. Astrocyte and neuronal swelling was significant within 1 minute of exposure to 17 or 40% hACSF, was rapidly reversible upon return to normosmolar ACSF, and repeatable upon re-exposure to hACSF. Neuronal swelling was not an artifact of patch clamp, occurred deep in tissue, was similar at physiological vs. room temperature, and occurred in both juvenile and adult hippocampal slices. Neuronal swelling was neither inhibited by TTX, nor by antagonists of NMDA or AMPA receptors, suggesting that it was not occurring as a result of excitotoxicity. Surprisingly, genetic deletion of AQP4 did not inhibit, but rather augmented, astrocyte swelling in severe hypoosmolar conditions. Taken together, our results indicate that neurons are not osmoresistant as previously reported, and that osmotic swelling is driven by an AQP4-independent mechanism.

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.

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)

Two-Photon Microscopy of Single Molecules

2000 ◽  
Vol 6 (S2) ◽  
pp. 804-805
Author(s):  
R. Yuste ◽  
A. Majewska ◽  
K. Holthoff ◽  
K. Holthoff
Keyword(s):  
Dendritic Spines ◽  
Pyramidal Neurons ◽  
Calcium Influx ◽  
Pyramidal Cells ◽  
Scattering Media ◽  
Decay Kinetics ◽  
Two Photon ◽  
Photon Excitation ◽  
Cortical Pyramidal Neurons ◽  
Two Photon Excitation

Two-photon excitation has enabled investigators to image living cells in highly scattering media like the central nervous system (1). We have used a custom-built two-photon microscope to image dendritic spines from living cortical pyramidal neurons. Pyramidal cells form the majority of the neuron in the mammalian cortex and they receive practically all their synaptic contacts through dendritic spines. Dendritic spines are small (<1 μm diameter) appendages that have been practically inaccessible to physiological measurements until the application of two-photon excitation to their study (2). We have concentrated in two questions:A- Calcium compartmentalization of spines: Mechanisms of calcium decay kinetics.Dendritic spines can compartmentalize calcium (2). Although the mechanisms of calcium influx into spines have been explored (3), it is unknown what determines the calcium decay kinetics in spines. We investigate calcium dynamics in spines from rat CA1 pyramidal neurons in slices.

Endogenous Zinc Inhibits GABAA Receptors in a Hippocampal Pathway

2004 ◽  
Vol 91 (2) ◽  
pp. 1091-1096 ◽  
Author(s):  
Arnaud Ruiz ◽  
Matthew C. Walker ◽  
Ruth Fabian-Fine ◽  
Dimitri M. Kullmann
Keyword(s):  
Pyramidal Neurons ◽  
Granule Cells ◽  
Mossy Fiber ◽  
Hippocampal Slices ◽  
Mossy Fibers ◽  
Gaba Release ◽  
Stratum Radiatum ◽  
Highly Sensitive ◽  
Acute Hippocampal Slices ◽  
First Time

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.

Group I mGluRs Increase Excitability of Hippocampal CA1 Pyramidal Neurons by a PLC-Independent Mechanism

2002 ◽  
Vol 88 (1) ◽  
pp. 107-116 ◽  
Author(s):  
David R. Ireland ◽  
Wickliffe C. Abraham
Keyword(s):  
Metabotropic Glutamate Receptors ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Receptor Subtypes ◽  
Ca1 Pyramidal Neurons ◽  
Group I ◽  
Hippocampal Ca1 ◽  
Group I Mglurs ◽  
Induced Changes

Previous studies have implicated phospholipase C (PLC)-linked Group I metabotropic glutamate receptors (mGluRs) in regulating the excitability of hippocampal CA1 pyramidal neurons. We used intracellular recordings from rat hippocampal slices and specific antagonists to examine in more detail the mGluR receptor subtypes and signal transduction mechanisms underlying this effect. Application of the Group I mGluR agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) suppressed slow- and medium-duration afterhyperpolarizations (s- and mAHP) and caused a consequent increase in cell excitability as well as a depolarization of the membrane and an increase in input resistance. Interestingly, with the exception of the suppression of the mAHP, these effects were persistent, and in the case of the sAHP lasting for more than 1 h of drug washout. Preincubation with the specific mGluR5 antagonist, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), reduced but did not completely prevent the effects of DHPG. However, preincubation with both MPEP and the mGluR1 antagonist LY367385 completely prevented the DHPG-induced changes. These results demonstrate that the DHPG-induced changes are mediated partly by mGluR5 and partly by mGluR1. Because Group I mGluRs are linked to PLC via G-protein activation, we also investigated pathways downstream of PLC activation, using chelerythrine and cyclopiazonic acid to block protein kinase C (PKC) and inositol 1,4,5-trisphosphate-(IP3)-activated Ca2+ stores, respectively. Neither inhibitor affected the DHPG-induced suppression of the sAHP or the increase in excitability nor did an inhibitor of PLC itself, U-73122. Taken together, these results argue that in CA1 pyramidal cells in the adult rat, DHPG activates mGluRs of both the mGluR5 and mGluR1 subtypes, causing a long-lasting suppression of the sAHP and a consequent persistent increase in excitability via a PLC-, PKC-, and IP3-independent transduction pathway.

Relationships Between Intracellular Calcium and Afterhyperpolarizations in Neocortical Pyramidal Neurons

2004 ◽  
Vol 91 (1) ◽  
pp. 324-335 ◽  
Author(s):  
H. J. Abel ◽  
J.C.F. Lee ◽  
J. C. Callaway ◽  
R. C. Foehring
Keyword(s):  
Intracellular Calcium ◽  
Linear Relationship ◽  
Pyramidal Neurons ◽  
Pyramidal Cells ◽  
Firing Frequency ◽  
Discharge Activity ◽  
Apical Dendrites ◽  
Neocortical Pyramidal Neurons

We examined the effects of recent discharge activity on [Ca2+]i in neocortical pyramidal cells. Our data confirm and extend the observation that there is a linear relationship between plateau [Ca2+]i and firing frequency in soma and proximal apical dendrites. The rise in [Ca2+] activates K+ channels underlying the afterhyperpolarization (AHP), which consists of 2 Ca2+-dependent components: the medium AHP (mAHP) and the slow AHP (sAHP). The mAHP is blocked by apamin, indicating involvement of SK-type Ca2+-dependent K+ channels. The identity of the apamin-insensitive sAHP channel is unknown. We compared the sAHP and the mAHP with regard to: 1) number and frequency of spikes versus AHP amplitude; 2) number and frequency of spikes versus [Ca2+]i; 3) IAHP versus [Ca2+]i. Our data suggest that sAHP channels require an elevation of [Ca2+]i in the cytoplasm, rather than at the membrane, consistent with a role for a cytoplasmic intermediate between Ca2+ and the K+ channels. The mAHP channels appear to respond to a restricted Ca2+ domain.

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