Correlation between regional and kinetic heterogeneities of beta-carboline/benzodiazepine receptor binding in rat...

Kinetic heterogeneity of [3H]methyl beta-carboline-3-carboxylate (CCM) binding was used to distinguish two populations of benzodiazepine binding sites in synaptic membranes of rat cerebral cortex. Curvilinear dissociation plots of CCM binding revealed major high affinity and minor lower affinity populations with slow and rapid dissociation rates, respectively. beta-Carbolines showed some selectivity to displace the higher affinity [3H]CCM binding. The selectivity decreased in the following order: CCM (inverse agonist), FG 7142 (partial inverse agonist), ZK 93426 (antagonist) and ZK 93423 (agonist). Regional selectivity of displacing potencies of these beta-carbolines on [3H]flunitrazepam binding in cerebellar versus hippocampal membranes decreased similarly.