Characteristics of [3H] propyl beta-carboline-3-carboxylate binding to benzodiazepine receptors in human brain.

Characterization of the binding of derivatives of beta-carboline-3-carboxylate, a putative endogenous ligand for benzodiazepine (BZ) receptors, has not previously been attempted in normal human brain. In the present study, we demonstrated saturable, high affinity binding of [3H] propyl beta-carboline-3-carboxylate [3H] PrCC) in normal human frontal cerebral cortex and cerebellum exhibiting pharmacological specificity similar to [3H] diazepam and [3H] flunitrazepam binding. The binding of [3H] PrCC is increased by chloride and GABA, but decreased by divalent cations, especially calcium. The profile of [3H] PrCC binding in human brain reflects specific interaction with BZ/ionophore/GABA receptor complexes.