Increase in plasma ACTH after dopaminergic stimulation in rats

The effects of a dopaminergic agonist, apomorphine, and a dopaminergic antagonist, haloperidol, on plasma ACTH, and corticosterone levels were evaluated in adult male rats. Subcutaneous administration of apomorphine in the dose range of 50-500 micrograms X kg-1 significantly increased plasma corticosterone levels. Acute treatment with apomorphine (250 micrograms X kg-1) resulted in an elevation of plasma ACTH concentration, peak values being reached 15 min after the injection. The apomorphine-induced rise in plasma ACTH levels was completely inhibited by pretreatment with haloperidol (1 mg X kg-1). A stimulatory role for dopamine receptors in the control of pituitary ACTH release in the rat is suggested.