INFLUENCE OF THE ESTROUS-CYCLE AND ESTRADIOL ON THE BEHAVIORAL-EFFECTS OF AMPHETAMINE AND APOMORPHINE IN RATS

This experiment was designed to investigate the influence of hormonal status of the rat on the effects of two doses of an indirect-acting do pamine agonist (amphetamine 0.25 and 1.0 mg/kg, IP) and a direct-actin g dopamine agonist (apomorphine 62.5 and 250 mu g/kg, SC) on the acqui sition of conditioning avoidance responses (CARs) and the performance of some spontaneous behaviors. Active conditioned avoidance was improv ed by amphetamine in all the groups except in females at diestrus; apo morphine improved this response only in females at estrus and in ovari ectomized rats after estradiol replacement, but the avoidance response was deteriorated in males and females at diestrus and after ovariecto my without estradiol replacement. Both dopaminergic drugs had contrast ing effects on motor activity, number of rearings, and number of head shakes according to the hormonal status of the rat. Only the time spen t in grooming behavior decreased after the treatment with both dopamin e agonists in all of the five groups studied. These results provided b ehavioral evidence for the hypothesis that dopaminergic activity in th e CNS is affected distinctively by modifications in the sexual hormone status (gender, estrous cycle, ovariectomy, and estradiol replacement ). Relationships between ovarian hormones and dopaminergic system are discussed.