On the brain endocoid for benzodiazepine recognition sites

Human and rat brain contain a neuropeptide with 105 amino acid residues which inhibits the binding of 3H-diazepam and other specific benzodiazepine recognition site ligands to crude brain synaptic membranes. DBI injected intracerebroventricularly in thirsty rats which are subjected to a conflict test (Corda et al., 1983), lowers the threshold for behavioral suppression by punishment. In this test DBI acts like an anxiogenic endocoid for the benzodiazepine recognition sites. The large abundance of lysine and arginine residues in the DBI molecule suggest that this polypeptide functions as a precursor of a putative endocoid which regulates anxiety levels. This endocoid acts as an agonist for the benzodiazepine recognition site. Because of the anxiogenic properties of this endocoid, it is proposed that anxiolytic benzodiazepine should be classified as an antagonist and beta-carboline as an agonist at the receptor level.