Proconflict effect of ACTH1-24: interaction with benzodiazepines

The intracerebroventricular injection of ACTH1-24 (0.1-10 micrograms) produced a dose-dependent decrease of punished licking periods in the conflict test in rats. The same treatment failed to modify unpunished behavior. A similar effect was produced by alpha-MSH (0.25-5 micrograms), whereas ACTH4-10 and ACTH11-24 were ineffective in doses up to 10 micrograms. The proconflict effect of ACTH1-24 was completely antagonized by diazepam (1.5 mg/kg IP) and partially by the benzodiazepine receptor antagonist Ro 15-1788 (5 mg/kg IP). The results are in line with a possible "anxiogenic" action of ACTH1-24.