CNS benzodiazepine receptors: physiological studies and putative endogenous ligands.

The recent demonstration of benzodiazepine receptors in the mammalian CNS has provided new information on the mechanism of action of this important class of drugs. In addition, the presence of these receptors has prompted studies on their physiological significance, including attempts at isolating an endogenous ligand. The isolation of a number of substances from bovine brain that competitively inhibit (3H)-diazepam binding to synaptosomal membrane suggests the presence of an endogenous ligand. Two of these substances have been identified as the purines inosine and hypoxanthine. Pharmacological studies of these purines suggest that they may have diazepam-like effect in vivo. The possibility that the brain may contain its own benzodiazepine-like compound is currently being studied.