Lactation in Rat Mammary Glands After Spinal Cord Section

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Abstract
The essentiality of the nervous component of suckling in the maintenance of lactation was tested in the rat. The milk ducts of the 6 pectoral mammary glands were ligated on postpartum day 2. After 1 to 2 days the 6 young nursed only the 6 pelvic mammary glands. On postpartum day 9 or 10 the pelvic glands were deprived of somatic sensory innervation by pithing the spinal cord caudal to T-13 and removing it by suction. Suckling young were able to retard the loss of body weight, or maintain or increase body weight during the following 5 days though suckling only the pelvic glands. Injections of oxytocin into the mothers 3 times daily did not result in significant improvement in litter growth. Litter growth was reduced in both groups in comparison with control groups. The pelvic mammary glands at autopsy were large and well vascularized, in contrast with the small and relatively avascular involuted pectoral glands. These data indicate that some milk synthesis can occur in the absence of somatic sensory innervation of rat mammary glands. Lactation, however, is greatly diminished, demonstrating that an intact spinal cord is essential to normal lactation, probably as an afferent pathway involved in the reflex release of hypophysial hormones. (Endocrinology74: 548, 1964)