ESTIMATED DURATION OF THE SPONTANEOUS ACTIVATION WHICH CAUSES RELEASE OF OVULATING HORMONE FROM THE RAT HYPOPHYSIS1
- 1 January 1953
- journal article
- other
- Published by The Endocrine Society in Endocrinology
- Vol. 52 (1) , 83-92
- https://doi.org/10.1210/endo-52-1-83
Abstract
Introduction NEUROGENIC activation of the rabbit adenohypophysis causing discharge of ovulating hormone is now considered to be accomplished within about one minute after coitus (Sawyer, Markee et al., 1947, 1949). Actual discharge into the bloodstream of hormone sufficient for ovulation requires approximately one hour in that species (Fee and Parkes, 1929). Whereas, in spontaneously ovulating animals, discharge of the hormone was long thought to be invoked by direct action of ovarian steroids on the hypophysis, there is now strong evidence that this effect is mediated by the hypothalamus (Sawyer, Everett and Markee, 1949; Everett and Sawyer, 1949). Activation of the hypophysis in cyclic rats occurs within a restricted period of time during the day of proestrus (Everett, Sawyer and Markee, 1949). In our colony this critical period is between 2 and 4 p.m. for the great majority of animals (4-day cycle), about 9 to 11 hours before ovulation.Keywords
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