Induction and Maintenance of Mammary Growth and Lactation in Rats with Acetylcholine or Epinephrine.

Abstract

When virgin rats were injected subcutaneously for 10 days with 10 [mu]g estradiol daily, followed by twice-daily injections of 25 mg acetylcholine iodide/kg/body weight or 0.25 mg epinephrine in oil for 5 days, extensive lobule-alveolar growth and lactation occurred. Rats given estradiol or acetylcholine iodide alone showed little or no mammary growth, and no secretion. Weights of ovaries, uterus, adrenals and thymus glands were not changed by treatment with either neurohormone, nor was the estrous cycle disturbed in rats given acetylcholine iodide alone. When the litters of lactating rats were removed on the 4th day after parturition, and the mothers injected with acetylcholine iodide or epinephrine in oil for 10 days, mammary involution was retarded and secretion was maintained. Rats given saline during this period showed extensive disintegration of the mammary system and no secretion. These experiments suggest that the 2 neurohormones may induce release of prolactin and perhaps other factors from the pituitary favorable to mammary growth and lactation.