Effects of bicuculline on central inhibition

Abstract

The effects of the specific gamma aminobutyric acid (GABA) antagonist bicuculline were investigated on direct, presynaptic and reticular inhibition and cerebellar disfacilitation of the segmental monosynaptic action potentials of decerebrate cats. Bicuculline markedly suppressed presynaptic inhibition of the quadriceps, posterior bicepssemitendinosus and gastrocnemius-soleus monosynaptic action potentials but had no effect on direct inhibition of these same potentials. Reticular inhibition of the quadriceps potentials was unaltered with bicuculline, but reticular inhibition of the posterior biceps-semitendinosus potentials was significantly suppressed. Cerebellar disfacilitation of both the quadriceps and posterior biceps-semitendinosus potentials was also blocked with bicuculline. The present study supports earlier propositions that GABA may be involved in presynaptic inhibition and cerebellar disfacilitation of the segmental potentials and suggests that reticular inhibition of the posterior biceps-semitendinosus monosynaptic action potentials may also be mediated by GABA.