Further Studies on Effects of Tranquilizing Drugs on Mammary Involution in the Rat.

Abstract

The action of several tranquilizing drugs was studied on the release of prolactin as judged primarily by effects on mammary involution. In rats, following weaning of litters on 4th day of lactation, administration of syrosingopine (50 [mu]g daily) for 9 days had much less effect than the same dose of reserpine on retardation of mammary involution, but was similar in effect at a higher dose level (100 [mu]g daily). Chlorpromazine (2.5 mg and 5 mg daily) also had a lesser retarding effect on mammary involution than reserpine. No noticeable effects on mammary involution were observed after administration of serotonin (250 [mu]g 3 X daily) or histamine (1 mg 3 X daily). Reserpine (100 /ig daily) had no effect on mammary involution in hypophysectomized animals. In adrenalectomized animals some involution-retarding effect of reserpine (100 [mu]g daily) was still apparent and was greatly enhanced by addition of 9a fluorocortisol. Reserpine, at higher dose level, depressed food consumption and body weight, and retarded return of normal cyclic function after weaning as did the higher dose of syrosingopine to a lesser degree. Marked effects on thymus and adrenal weights after reserpine administration indicated that ACTH secretion is stimulated by the drug, but neither syrosingopine nor chlorpromazine treatment resulted in any apparent stimulation of ACTH release. The significance of these findings in relation to a possible hypothalamic inhibition of prolactin release is discussed.