Brain benzodiazepine receptors increase after chronic ethyl-β-carboline-3-carboxylate

Rats were treated with repeated intraventricular injections of ethyl-3-carboline-3-carboxylate (β-CCE) (10 ug/rat, twice daily for 8 days), 36 h after the last injection, the total number of H-diazepam binding sites was increased in the cerebral cortex, cerebellum and hippocampus by 63, 51 and 38%, respectively. On the other hand, there were no significant differences in the dissociation constants (K_D) between β-CCE and solvent treated rats. In contrast, chronic β-CCE administration failed to change the number of the apparent affinity of H-β-CCE binding sites in all the brain areas examined. The results suggest that β-CCE is an antagonist at the ³H- diazepam binding sites.