Benzodiazepine and gaba receptors are functionally related: further electrophysiological evidence in vivo

1. The effects of five benzodiazepines (Ro 21-3981, flurazepam, chlordiazepoxide, medazepam and clozapine) on GABA-mediated electrically-evoked cortical inhibition were tested. 2. These five drugs were chosen because their solubility in water allows their microiontophoresis and because their relative affinities for the benzodiazepine receptor in rat brain membranes have been measured. 3. When tested with equal iontophoretic doses in 11 different neurons, the degree of potentiation of electrically evoked cortical inhibition produced by these benzodiazepines correlated significantly (r = -0.60704; p less than 0.01; phi = 33) with the logarithm of the Ki values of these drugs for inhibiting specific 3H-diazepam binding to rat brain membranes. 4. When tested with iontophoretic doses which were directly proportional to their Ki values for inhibiting 3H-diazepam binding to rat brain membranes, these benzodiazepines produced very similar potentiations of electrically evoked cortical inhibition.