Abstract
Summary
Milk secretion in the six abdominal mammary glands of lactating rats was assessed after spinal cord transection at T-11 and after prolactin replacement, to further define the role of somatic sensory pathways in the suckling-induced release of prolactin. The six pectoral mammary glands were rendered nonfunctional by ligation of the main milk ducts on postpartum day 2. Somatic sensory denervation of the 6 abdominal mammary glands was accomplished on day 10–11. Each mother nursed 6 young. The growth of litters of cord-transected lactating rats was greatly reduced in comparison to that of sham-operated rats. Prolactin (17 IU) plus oxytocin (1 IU) 3 × daily resulted in significant improvement in litter growth and in food and water intake of the mothers in comparison with oxytocin-injected control rats, but was without detectable effect upon the loss in maternal body weight which follows spinal cord transection. Litter growth following prolactin treatment was less than that of sham-operated rats. Prolactin did not increase litter growth when the mothers were pair-fed to oxytocin-injected mothers. These data indicate that the spinal cord serves as a pathway for sensory impulses from the mammary gland to the CNS which are fundamental in the reflex release of prolactin from the adenohypophysis. The data also suggest that prolactin stimulates food intake in some manner with the additional food converted more readily into milk than into maternal tissue.
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