Effects of barbiturates on responses evoked by excitatory amino acids in slices of rat olfactory cortex

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A study has been made of the effects of ranges of concentrations of phenobarbitone, pentobarbitone and thiopentone on responses evoked by γ-aminobutyric acid (GABA), l-glutamate, l-aspartate, N- methyl- D- aspartate , kainate and quisqualate in slices of olfactory cortex of the rat. All three barbiturates affected GABA-evoked depolarizations similarly in that responses were potentiated by small doses but markedly inhibited at greater concentrations. Responses to l-aspartate and l-glutamate were little affected except at the largest dose of phenobarbitone tested (10 mM). The responses evoked by the selective agonists of excitatory amino acid receptors were inhibited by the barbiturates, the relative sensitivities being quisqualate ⩾ N- methyl- D-aspartate ⩾ kainate with phenobarbitone, quisqualate ⩾ kainate > N- methyl- D-aspartate with pentobarbitone and quisqualate > kainate = N- methyl- D-aspartate with thiopentone. The possible significance of these findings is discussed.