[abstract] EFFECTS OF HIGH HELIUM PRESSURE ON THE ACTION OF EXCITATORY AMINO ACIDS IN RAT HIPPOCAMPAL SLICES.

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[abstract] EFFECTS OF HIGH HELIUM PRESSURE ON THE ACTION OF EXCITATORY AMINO ACIDS IN RAT HIPPOCAMPAL SLICES.

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Title: [abstract] EFFECTS OF HIGH HELIUM PRESSURE ON THE ACTION OF EXCITATORY AMINO ACIDS IN RAT HIPPOCAMPAL SLICES.
Author: Fagni, L; Zinebi, F; Hugon, M
Abstract: High helium pressure increases the intrinsic. excitability of hippocampal CAl pyramidal cells, but decreases the efficiency of excitatory synaptic transmission on these cells. The present study was undertaken to examine the neurochemical bases of these changes. Experiments were performed on hippocampal slices. Bipolar stimulating electrodes were used to activate the Schaffer-commissural afferents and the alveus. Micropipettes were positioned in the stratum radiatum to record the population EPSP and in the stratum pyramidale to record the population spike and the antidromic field potential. The maximal decrease induced by the tested amino acids on the amplitude of either the population EPSP or the antidromic potential was taken as an index of the drug effect. High helium pressure (80 bar) did nO,t significantly modify the effects of L-glutamate (1 mM), quisqualate (0.005 mM) and L-aspartate (1 mM).Given that these amino acids are supposed to bind to the synaptic receptors of the tested pathway, our findings suggest that the reduced efficiency of synaptic transmission did not result from lesser sensitivity of t~ese receptors. On the other hand, high pressure potentiated the effect of NMDA (0.01 mM), a ligand of extrasynaptic receptors of CAl pyramidal cells. Moreover, the ratio between the amplitudes of population spike and population EPSP increased under pressure. This change indicates a hyperexcitability of these cells. Antagonists (2-APV and 2-APH 0.03 mM) of NMDA receptors significantly reduced this change. Given the well known involvement of NMDA receptors in the regulation of CAl pyramidal cell excitability, these results suggest that endogenous NMDA related mechanisms may underlay the pressure-induced intrinsic hyperexcitability of these cells.
Description: Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting held May 26-30, 1987. The Hyatt Regency Hotel, Baltimore, Maryland (http://www.uhms.org)
URI: http://archive.rubicon-foundation.org/5537
Date: 1987

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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