Inhibition of GABA release from slices prepared from several brain regions of rats at various times following a convulsion

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Abstract
A method is described for the measurement of the K+‐evoked release of endogenous γ‐aminobutyric acid (GABA) from slices of rat cortex, hippocampus and striatum. In tissue prepared 30 min following an electroconvulsive shock, K+‐evoked GABA release (above basal release) was inhibited by 45% in cortex, 50% in hippocampus and 75% in striatum. A similar inhibition of release was observed with slices prepared from rats in which a convulsion had been induced by flurothyl. There was no change in spontaneous (basal) release following either procedure. An inhibition of K+‐evoked endogenous GABA release was also seen in tissue prepared 4 min postictally but not 2 h after the seizure. No difference was observed in the release of [3H]‐GABA from preloaded cortical slices prepared from rats given a single electroconvulsive shock. It is proposed that a convulsion results in an inhibition of GABA release and that this inhibition may in turn inhibit GABA synthesis as described in the preceding paper. It is also proposed that changes in the endogenous releasable pool of GABA may not be detected by preloading slices with [3H]‐GABA.