Bicuculline-pentobarbital interactions on [35S]TBPS binding in various brain areas.

The effect of in vitro addition of pentobarbital to brain membrane preparations from cerebellum and cortex of C57B1 mice was examined in the presence and absence of the specific GABAA receptor "antagonist" bicuculline. In the cortex pentobarbital produced a biphasic effect (stimulation followed by inhibition) on [35S]TBPS binding, whereas only inhibition of [35S]TBPS binding was observed in the cerebellum. When bicuculline was added to assay mixtures, the stimulatory action of pentobarbital was markedly enhanced in the cortex. In the cerebellum the presence of bicuculline uncovered a biphasic effect of pentobarbital on [35S]TBPS binding, that is lower doses of pentobarbital increased, while higher doses decreased [35S]TBPS to the membrane receptors from the cerebellum.