Abstract
Hormonal changes occur in female mammals as a consequence of stimuli derived from mating. In rats, a rise in the plasma concentration of LH occurs within 5–10 min after coitus, and a slight rise in the FSH content of the pituitary is seen 1 hr after copulation 1 . Pituitary LTH falls within 30 min after cervical stimulation 2 , whereas plasma progesterone rises 24 hr after mating 3 .
Despite the potentially mammotropic effects of these hormones 4 , no changes in rat mammary tissue in the period shortly following mating have been reported. The present study was undertaken to investigate the effects of various levels of copulatory activity on mammary secretion in female rats during the first 5 days following coitus.
Materials and Methods. Adult virgin Sprague-Dawley rats (at least 90 and less than 150 days old) were purchased from Berkeley Pacific Laboratories, Berkeley, California. The females were housed in individual cages, and the colony was maintained on a reversed light-dark cycle, in a windowless room, with the temperature averaging 78°F. The photoperiod was 12 hr on and 12 hr off; the midpoint of the light segment was at 3 p.m.
There were four groups of females: (i) no copulatory stimulation; (ii) low stimulation — females received three or fewer intromissions; (iii) medium stimulation—females received 4–20 intromissions; (iv) high stimulation—females received more than 40 intromissions. Females in groups 2, 3. and 4 all received sperm and showed a vaginal plug 5 .
One to 5 days after mating, the females were sacrificed. All the mammary glands from each animal were fixed in 15% formalin and stained as wholemounts with hematoxylin. Pieces of tissue adjacent to the nipple of the no. 2 thoracic glands were taken from the wholemounts for preparation of paraffin sections which were stained with hematoxylin and eosin.
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