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Electrophysiological and pharmacological studies on mammalian cerebral slices

Electrophysiological and pharmacological studies on mammalian cerebral slices
Electrophysiological and pharmacological studies on mammalian cerebral slices

This work describes the development of use of in vitro 800μm thick brain slice preparation from adult rats, as a model for studying the electrical activity and the pharmacology of the mammalian cerebral cortex. The cerebral slices were shown to be electrically viable with optimum field potential amplitudes recorded at 30.5-32^oC. Stimulation of the corpus callosum both ipsilaterally and contralaterally to the recording sites produced cortical field potentials detectable in both hemispheres. A comparative study of laminar recording showed that the positive phase of the biphasic (positive-negative) field potential recorded at 0.2mm below the pial surface to callosal stimulation, was reversed to a deep negative potential at 0.4mm below the surface. The conduction velocity of the cortical afferents obtained by ipsilateral and contralateral stimulation of the corpus callosum was 0.246m/sec and 0.177m/sec respectively. Stimulation of the cerebral cortex elicited a slow negative potential of the stimulating electrode. A period of inhibition evoked in the cortex by callosal stimulation lasting about 1.3 sec was also demonstrated. Evoked spikes were recorded from single cerebral neurones following stimulation of the corpus callosum. The latency of both the evoked field potential and the evoked spikes of single neurones was found to be voltage dependent. Pharmacological investigations were performed on the cerebral cortex slice. Drugs were applied by bath perfusion. GABA, at successive concentrations increased the peak amplitude of the field potential but shortened its duration. GABA (2 x 10^-3M) inhibited the evoked activity of single neurones, whereas glycine (3 x 10^-3M) had no effect on this activity. Picrotoxin and bicuculline potentiated the evoked field potentials at low concentrations (10^-9 -5 x 10^-8M), while strychnine had little effect at 10^-5M. Bicuculline (10^-5M) was shown to reverse the effect of GABA on the evoked cortical activity. Extracellular recordings were obtained from spontaneously firing cerebral neurones, the activity of which was analysed using the interspike interval histogram programme. Five cell types were identified in layers II - V which were subsequently shown to have different pharmacological profiles to GABA. (D72317/87)

University of Southampton
Ibrahim, Nagi Ali Ahmed
Ibrahim, Nagi Ali Ahmed

Ibrahim, Nagi Ali Ahmed (1986) Electrophysiological and pharmacological studies on mammalian cerebral slices. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

This work describes the development of use of in vitro 800μm thick brain slice preparation from adult rats, as a model for studying the electrical activity and the pharmacology of the mammalian cerebral cortex. The cerebral slices were shown to be electrically viable with optimum field potential amplitudes recorded at 30.5-32^oC. Stimulation of the corpus callosum both ipsilaterally and contralaterally to the recording sites produced cortical field potentials detectable in both hemispheres. A comparative study of laminar recording showed that the positive phase of the biphasic (positive-negative) field potential recorded at 0.2mm below the pial surface to callosal stimulation, was reversed to a deep negative potential at 0.4mm below the surface. The conduction velocity of the cortical afferents obtained by ipsilateral and contralateral stimulation of the corpus callosum was 0.246m/sec and 0.177m/sec respectively. Stimulation of the cerebral cortex elicited a slow negative potential of the stimulating electrode. A period of inhibition evoked in the cortex by callosal stimulation lasting about 1.3 sec was also demonstrated. Evoked spikes were recorded from single cerebral neurones following stimulation of the corpus callosum. The latency of both the evoked field potential and the evoked spikes of single neurones was found to be voltage dependent. Pharmacological investigations were performed on the cerebral cortex slice. Drugs were applied by bath perfusion. GABA, at successive concentrations increased the peak amplitude of the field potential but shortened its duration. GABA (2 x 10^-3M) inhibited the evoked activity of single neurones, whereas glycine (3 x 10^-3M) had no effect on this activity. Picrotoxin and bicuculline potentiated the evoked field potentials at low concentrations (10^-9 -5 x 10^-8M), while strychnine had little effect at 10^-5M. Bicuculline (10^-5M) was shown to reverse the effect of GABA on the evoked cortical activity. Extracellular recordings were obtained from spontaneously firing cerebral neurones, the activity of which was analysed using the interspike interval histogram programme. Five cell types were identified in layers II - V which were subsequently shown to have different pharmacological profiles to GABA. (D72317/87)

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Published date: 1986

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Local EPrints ID: 460731
URI: http://eprints.soton.ac.uk/id/eprint/460731
PURE UUID: 78da65cb-40c7-48e1-82bf-93e4ed4e6bc2

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Date deposited: 04 Jul 2022 18:28
Last modified: 04 Jul 2022 18:28

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Author: Nagi Ali Ahmed Ibrahim

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