Abstract
Summary
1. Cervical probing of estrous rats resulted in an elevation of plasma prolactin 15 min later.
2. Plasma prolactin was not elevated on day 4 of pseudopregnancy and was actually lower on day 9 than in diestrous controls.
3. On day 4 of pseudopregnancy plasma LH levels were lower than those observed in the controls; where FSH levels were elevated on day 4 and 9.
4. Following castration on day 4 of pseudopregnancy, plasma FSH and LH levels both rose, but plasma LH rose to a higher value in the pseudopregnant castrates than in controls on the 5th day after spaying. Prolactin levels remained unchanged following spaying.
5. It is concluded that the discharge of prolactin which initiates pseudopregnancy in the rat is not maintained throughout pseudopregnancy and is associated with a suppression of LH and an augmentation of FSH release from the pituitary.
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