Voltage-clamp study on GABA response desensitization in single pyramidal cells dissociated from the hippocampus of adult guinea pigs.

Acutely dissociated pyramidal cells prepared from the hippocampus of adult guinea pigs were used for the present study. The characteristic dual response of pyramidal cells to GABA as demonstrated in the in vivo and slice preparations was retained in the dissociated cells. The results show that the fading of the GABA hyperpolarizing response during prolonged GABA application cannot be accounted for by the development of an opposing depolarizing response, nor can it be explained by changes in the intracellular ionic composition during GABA action. The data strongly suggest that GABA receptors mediating the hyperpolarizing response exhibit desensitization and the time course of the GABA response is significantly controlled by this property of the receptors.