Dihydroergotoxine modulation of the GABAA receptor-associated Cl- ionophore in mouse brain.

Dihydroergotoxine non-competitively displaced the binding of t-[3H]butylbicycloorthobenzoate ([3H]TBOB) to crude synaptosomal membranes from the mouse brain (cerebrum minus cortex), and gamma-aminobutyric acid (GABA) (10 microM) enhanced the displacement potency of dihydroergotoxine in a bicuculline-sensitive manner. The same ergot compound prolonged pentobarbital-induced sleeping in mice and diminished the convulsive potency of picrotoxin in the same animal species. The results are indicative of the positive coupling between GABA and dihydroergotoxine.