The behavioral syndrome induced by adreno corticotropic hormone in rats is prevented by Ca++ channel blockade.

The most typical signs (stretchings, yawnings, penile erections, excessive grooming) of the behavioral syndrome induced in rats by the intracerebroventricular administration of ACTH- (1-24) (4 micrograms/rat) were dose-dependently antagonized by the intraperitoneal injection of the selective Ca++ channel inhibitor, nicardipine (dose range: 0.1-1 mg/kg). These data suggest that the influx of Ca++ into target neurons is a step of key importance for the occurrence of ACTH-induced behavioral signs, and that Ca++ may play the role of second intracellular messenger for the behavioral effects of melanocortins.