Abstract
Summary
A rubber collar was placed around the neck of rats on day 1 or 12 of pregnancy to restrain the animal from self-licking its mammary glands. Content of mammary gland DNA and RNA in rats sacrificed on day 12 was not statistically different between collared and control groups. However, nucleic acid contents of mammary glands of rats collared from days 1 to 20 and days 12 to 20 and autopsied on day 20 of pregnancy were significantly less (p < .05) than the controls. Body, uteri, placenta, and fetus weights and fetus numbers were not altered by collaring. Adrenal weights were increased as a result of the treatment however (p < .05). It is postulated that direct stimulation by self-licking enhances the action of endocrines for optimal mammary growth in rats.
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