Quantal analysis of synaptic transmission in CA1 pyramidal cells of the rat hippocampus
Quantal analysis of synaptic transmission in CA1 pyramidal cells of the rat hippocampus
The hippocampal formation is an area of the limbic system involved in a number of brain functions including learning and memory. It is also involved in the pathogenesis of epilepsy. Using the recently developed recording technique of whole-cell patch-clamp in brain slices, the synaptic and cellular mechanisms of CA1 pyramidal neurons were investigated in rat hippocampal slices in vitro.
Two components to the excitatory postsynapti currents (EPSCs), evoked by afferent stimulation, were observed, a fast AMPA receptor-mediated event accounting for 90-95% of peak EPSC amplitude, and a small, slow NMDA receptor-mediated component. The local anaesthetic, N-(2,6-dimethyl-phenylcarbamoylmethyl)triethylammonium bromide (QX-314; 10-20mM), was found to block all voltage-gated Na+ conductances in CA1 cells when applied intracellularly, and blocked a conductance which exhibited characteristics of the anomalous rectifier IQ. EPSCs, however, were not blocked by intracellular QX-314. The space-clamp properties of CA1 cells were also investigated. The incomplete voltage control of EPSCs and voltage-gated Ca2+ currents indicated that CA1 pyramidal cells were poorly space-clamped. However, proximal areas of the cell were under better voltage control than the distal.
Excitatory synaptic transmission in area CA1 was investigated using quantal analysis. EPSCs were evoked by a minimal stimulation protocol with a `bridge' of axons sectioned in the stratum radiatum between the stimulating and recording sites. Precise positioning of a monopolar stimulating electrode enabled a small population of synapses to be selectively activated, and this was confirmed by input-output relationships. Data sets were analysed using Bayesian statistics and amplitude distributions were constructed. Initial studies indicated only a low number of data sets exhibiting regular fluctuations in EPSC amplitude. However, non-equivalent subsets of EPSCs were observed within the majority of data sets, which exhibited different rise times and quantal amplitudes. Data sets separated into subsets with `fast' and `slow' rise times, exhibited regular quantal fluctuations in EPSC amplitude, providing strong evidence for quantal transmission at these synapses.
University of Southampton
Isaac, John Timothy Roger
1993
Isaac, John Timothy Roger
Isaac, John Timothy Roger
(1993)
Quantal analysis of synaptic transmission in CA1 pyramidal cells of the rat hippocampus.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The hippocampal formation is an area of the limbic system involved in a number of brain functions including learning and memory. It is also involved in the pathogenesis of epilepsy. Using the recently developed recording technique of whole-cell patch-clamp in brain slices, the synaptic and cellular mechanisms of CA1 pyramidal neurons were investigated in rat hippocampal slices in vitro.
Two components to the excitatory postsynapti currents (EPSCs), evoked by afferent stimulation, were observed, a fast AMPA receptor-mediated event accounting for 90-95% of peak EPSC amplitude, and a small, slow NMDA receptor-mediated component. The local anaesthetic, N-(2,6-dimethyl-phenylcarbamoylmethyl)triethylammonium bromide (QX-314; 10-20mM), was found to block all voltage-gated Na+ conductances in CA1 cells when applied intracellularly, and blocked a conductance which exhibited characteristics of the anomalous rectifier IQ. EPSCs, however, were not blocked by intracellular QX-314. The space-clamp properties of CA1 cells were also investigated. The incomplete voltage control of EPSCs and voltage-gated Ca2+ currents indicated that CA1 pyramidal cells were poorly space-clamped. However, proximal areas of the cell were under better voltage control than the distal.
Excitatory synaptic transmission in area CA1 was investigated using quantal analysis. EPSCs were evoked by a minimal stimulation protocol with a `bridge' of axons sectioned in the stratum radiatum between the stimulating and recording sites. Precise positioning of a monopolar stimulating electrode enabled a small population of synapses to be selectively activated, and this was confirmed by input-output relationships. Data sets were analysed using Bayesian statistics and amplitude distributions were constructed. Initial studies indicated only a low number of data sets exhibiting regular fluctuations in EPSC amplitude. However, non-equivalent subsets of EPSCs were observed within the majority of data sets, which exhibited different rise times and quantal amplitudes. Data sets separated into subsets with `fast' and `slow' rise times, exhibited regular quantal fluctuations in EPSC amplitude, providing strong evidence for quantal transmission at these synapses.
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Published date: 1993
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Local EPrints ID: 462441
URI: http://eprints.soton.ac.uk/id/eprint/462441
PURE UUID: f3e12e04-655d-4675-a0d7-ddbf4185fa66
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Date deposited: 04 Jul 2022 19:08
Last modified: 04 Jul 2022 19:08
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Author:
John Timothy Roger Isaac
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