The physiological and pharmacological properties of layer III entorhinal cortical neurones
The physiological and pharmacological properties of layer III entorhinal cortical neurones
In vitro electrophysiological techniques were used to study the intrinsic intracellular properties of the entorhinal layer III neurones and their synaptic properties following subicular stimulation. The neurones from which the data was recorded were pyramidal, as shown by dye fills and exhibited a variety of membrane properties. The neuronal population of layer III exhibited no distinctive types of neurones although a small proportion were singled out as having burst-like behaviour. Evoked synaptic responses following subicular stimulation were a mixture of either or both excitatory and inhibitory responses. Pharmacological investigation of the synaptic inputs showed that both non-NMDA and NMDA glutamate receptors are involved in excitatory responses, whilst GABAA receptors mediate the early inhibitory response. There was no `typical' synaptic response as the site of stimulation contained many fibres of passage. Evidence was collected which suggested that the subtypes of the glutamate receptors were localised at separate synapses, although dual receptor synapses were not ruled out. This preliminary study of the layer III neurones and the apparent importance of their projection to the CA1 pyramidal cells of the hippocampus, paves the way for elucidation of their role in a reverberating circuit causing seizure-like activity within the two anatomical structures. Such a circuit may be present in the kainic acid chronic model of epilepsy. This model produces a loss of hippocampal CA3 pyramidal cells and a time dependent, wide spread loss of interneurones. The present investigation also demonstrates that somatogstatin containing neurones are lost as a result of the kainic acid lesion. The CA1 pyramidal neurones support ictal-like behaviour in in vitro hippocampal slices but this activity may prove to be enhanced when the entorhinal cortex is incorporated into the slice, thus keeping the hippocampal/entorhinal circuit intact.
University of Southampton
1990
Bruce, Rosemary Claire
(1990)
The physiological and pharmacological properties of layer III entorhinal cortical neurones.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In vitro electrophysiological techniques were used to study the intrinsic intracellular properties of the entorhinal layer III neurones and their synaptic properties following subicular stimulation. The neurones from which the data was recorded were pyramidal, as shown by dye fills and exhibited a variety of membrane properties. The neuronal population of layer III exhibited no distinctive types of neurones although a small proportion were singled out as having burst-like behaviour. Evoked synaptic responses following subicular stimulation were a mixture of either or both excitatory and inhibitory responses. Pharmacological investigation of the synaptic inputs showed that both non-NMDA and NMDA glutamate receptors are involved in excitatory responses, whilst GABAA receptors mediate the early inhibitory response. There was no `typical' synaptic response as the site of stimulation contained many fibres of passage. Evidence was collected which suggested that the subtypes of the glutamate receptors were localised at separate synapses, although dual receptor synapses were not ruled out. This preliminary study of the layer III neurones and the apparent importance of their projection to the CA1 pyramidal cells of the hippocampus, paves the way for elucidation of their role in a reverberating circuit causing seizure-like activity within the two anatomical structures. Such a circuit may be present in the kainic acid chronic model of epilepsy. This model produces a loss of hippocampal CA3 pyramidal cells and a time dependent, wide spread loss of interneurones. The present investigation also demonstrates that somatogstatin containing neurones are lost as a result of the kainic acid lesion. The CA1 pyramidal neurones support ictal-like behaviour in in vitro hippocampal slices but this activity may prove to be enhanced when the entorhinal cortex is incorporated into the slice, thus keeping the hippocampal/entorhinal circuit intact.
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Published date: 1990
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Local EPrints ID: 462026
URI: http://eprints.soton.ac.uk/id/eprint/462026
PURE UUID: 9e772b44-1196-4f50-b763-5bf0cd44396b
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Date deposited: 04 Jul 2022 19:00
Last modified: 04 Jul 2022 19:00
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Author:
Rosemary Claire Bruce
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