Pharmacological evidence of catecholaminergic involvement in the behavioral effects of luteinizing hormone releasing hormone in rats.

The influence of L-DOPA on the behavioral effects of LHRH was studied in male rats. Subcutaneous administration of LHRH (100 micrograms/kg) caused a significant disruption in the acquisition of a conditioned avoidance response (CAR) and a significant increase in head shaking behavior (HSB). Pretreatment with this hormone antagonized the stimulatory action of amphetamine (1 mg/kg, IP) in acquisition of CARs, spontaneous motor activity (SMA) and rearing behavior (RB). L-DOPA (100 mg/kg, IP), administered after LHRH, stimulated SMA, RB and HSB. In addition L-DOPA antagonized the effect of LHRH on acquisition of CARs and counteracted the antagonism between LHRH and amphetamine in acquisition of CARs and SMA. These findings indicate that LHRH could exert its behavioral effects through an inhibitory action upon brain catecholamine synthesis. The suppression of CARs may be the response to DA antagonism and the interaction with amphetamine could be mediated by an inhibition of both DA and NE activities. The possibility of an interaction between LHRH and central serotonin mechanisms is also discussed.