Effects of chlorpromazine on mammary glands of rats

¹ Department of Physiology and Pharmacology, Michigan State University, East Lansing, Michigan

The effects of chlorpromazine were determined on mammary growth and initiation of milk secretion in virgin rats, and on maintenance of mammary structure and secretion in postpartum rats after litter removal. When chlorpromazine was administered in doses of 5 or 15 mg/kg body weight for 5 days, only the higher dose was effective in inducing lobulo-alveolar growth and initiating milk secretion in rats initially primed with 10 µg estradiol daily for 10 days. The higher dose of chlorpromazine also maintained mammary lobulo-alveolar structure and secretion in post-partum rats for 10 days after litter removal. Chlorpromazine produced a significant increase in adrenal weight and decrease in thymus weight, indicating adrenal stimulation. In estrogen-primed rats neither prolactin nor ACTH alone could initiate mammary secretion; however they were effective when given in combination. The present data indicate that chlorpromazine promotes the secretion of both prolactin and ACTH. Hypophysectomy following estradiol treatment prevented chlorpromazine from initiating mammary secretion, showing that its effects are mediated through the anterior pituitary and not directly on the mammary gland.