Effects of Reserpine and Serotonin on Milk Secretion and Mammary Growth in the Rat.

Abstract

1. In mature virgin rats, daily subcutaneous injections of 20 μg reserpine or .5 mg serotonin creatinine sulfate base/kg BW for 5 days, following daily injections of 10 μg estradiol for 10 days, initiated milk secretion in 14 out of 15 rats and induced growth of mammary lobuloalveolar tissue. When either drug was injected with estradiol for 10 days, mammary growth was greater than with estradiol alone, but there was little evidence of milk secretion. Injections of reserpine or serotonin alone for 21 days failed to elicit mammary growth or secretion. 2. In rats following litter removal on 4th day after parturition, milk secretion ceased and mammary glands showed pronounced involution 10 days later. Injections of 10 or 20 μg reserpine or .5 mg serotonin creatinine sulfate base for 10 days following litter removal, retarded mammary involution and maintained secretory function. 3. It is concluded that in estrogen-primed virgin rats or in post-partum rats after litter removal, reserpine and serotonin stimulate secretion of prolactin and perhaps other factors by the pituitary favorable to mammary growth and lactation.