Effects of desglycinamide9, (Arg8) vasopressin and vasopressin antiserum on the acquisition of intravenous cocaine self-administration in the rat.

The effect of the vasopressin neuropeptide desglycinamide9, (Arg8) vasopressin (DGAVP) on the acquisition of intravenous cocaine self-administration was studied. Rats were tested under conditions of reduced body weight in a continuous reinforcement operant procedure, during five daily 3 h sessions. Under these conditions, the rate of self-administration obtained with 0.125 and 0.25, but not 0.063 mg.ml-1 cocaine, exceeded the rate obtained with saline. Daily pretreatment with DGAVP (5 micrograms/rat, s.c.) decreased self-administration of 0.125 and 0.25 mg.ml-1 cocaine to the level obtained with saline, but had no effect on self-administration of 0.063 mg.ml-1 cocaine and saline. Using a similar procedure, it was shown that daily intracerebroventricular pretreatment with vasopressin antiserum significantly increased self-administration of 0.125 mg.ml-1 cocaine, without affecting self-administration of 0.063 and 0.25 mg.ml-1 cocaine and saline. The results support previous findings obtained with vasopressin neuropeptides in drug self-administration studies and suggest that DGAVP decreases the acquisition of cocaine self-administration by attenuating the reinforcing effects of cocaine and that endogenous vasopressin may be involved in the acquisition of cocaine self-administration.