Abstract
Summary
By the fifth week of restricting water intake at 1100 to a 15-min period per day, estrous cycle lengths had shifted in most animals (31/40) from 4 to 5 days with the 5-day cycles usually consisting of 3 days of diestrus. In the 5-day cycling rats, plasma corticosterone peaked at 1100 and also at 1900 hr, the proestrous surge in plasma LH was not significantly changed, although the variation in individual animals was greater and the prolactin surge was prolonged. Similar prolonged cycles followed water restriction at 1800 hr with animals returning to regular 4-day cycles when given water ad libitum. These results suggest that the alteration of the normal corticosteroid rhythm and/or changes in prolactin secretion may account, in part at least, for the changes noted in cycle length after restricting the water intake.
The authors thank Miss Katherine Bangs, Mr. Mike Profit, and Mrs. Frances Smith for valuable technical and secretarial assistance, and Mr. Bob McAlister for drawing the figures. We would also like to express our thanks to Dr. Anna Taylor and Berilyn Branch for their assistance in the Fluoro-metric determinations.
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