Effects of Some Psychoactive Agents on Prolactin Secretion in Rats of Different Endocrine States

Abstract

Serum prolactin was determined by radioimmunoassay 4 hours after administration of several psychoactive drugs. Pimozide, an agent that blocks the dopamine-receptor interaction, and chlorpromazine, an agent that blocks both dopamine and norepinephrine-receptor interaction, stimulated prolactin secretion in male and intact and ovariectomized female rats. Reserpine and α-methyl-para-tyrosine also stimulated prolactin secretion. All drugs that stimulated prolactin secretion demonstrated a considerably greater ability to do so in intact female rats. Pretreatment for 10 days of ovariectomized rats with 50 ng of estradiol benzoate did not change baseline serum prolactin levels, but it greatly augmented the rise in serum prolactin observed after treatment with pimozide. Progesterone pretreatment of ovariectomized rats did not alter the amount of prolactin released after pimozide administration. This study demonstrates the importance of dopamine involvement in the inhibition of prolactin secretion, and it also shows that the reaction to psychoactive drugs can be modified by the endocrine status of the experimental subjects.

Key words

Psychoactive Drugs - Prolactin - Dopamine Neuroleptics - Prolactin Inhibiting Factor (PIF)