Abstract
The influence of the nursing stimulus upon thyroid gland secretion was tested in the lactating rat during mid-lactation. Milk removal from the 6 pectoral mammary glands was prevented in all rats by galactophore ligation on postpartum day 2. Injection of 1.5 μg/100 g/day L-thyroxin was less effective in blocking thyroidal 131I release in lactating rats than in nonlactating rats. The effectiveness of the injected thyroxin in the lactating rat increased within 24 hr after the young were removed. In another experiment, a significant increase in plasma PB131I resulted from 6 hr of normal nursing of the pelvic mammary glands. No increase in plasma PB131I occurred following 6 hr of nursing of pelvic mammary glands from which milk removal was prevented by ligation of the galactophores. When the pelvic mammary glands were deprived of somatic sensory innervation by spinal cord transection and the contained milk was removed by nursing young with the aid of oxytocin injections to the mothers, the PB13lI level after 6...
Published Version
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