Differential effects of GABA on peripheral and central type benzodiazepine binding sites in brain.

The binding of the clinically inactive benzodiazepine [3H]RO-5-4864 to brain membranes was investigated. The peripheral type benzodiazepine binding site was demonstrated in brain with an apparent Kd of 1.6 nM and a Bmax of 20 fmol/mg protein. Monophasic Scatchard plots indicate a homogenous population of a high affinity sites. The major inhibitory transmitter GABA, has no effect on [3H]RO-5-4864 binding to extensively wash brain membranes. The peripheral type benzodiazepine binding site found in brain is therefore not modulated GABA.