Binding interaction of gamma aminobutyric acid A and B receptors in cell culture

We have examined the effects of 0.1 mM baclofen and pertussis toxin treatment on gamma aminobutyric acid A (GABAA) receptor binding in whole cells and in membrane of cells from cerebellar primary culture. Baclofen, a GABAB receptor ligand, caused a marked decrease in the bicuculline sensitive (GABAA) binding of [3H]muscimol on the whole cells, but failed to inhibit specific [3H]muscimol binding to cells pretreated with pertussis toxin. The effect of baclofen was only seen in whole cells and not in cell membranes. These findings suggest that activation of GABAB receptor reduces GABAA binding sites through a GTP binding protein.