Abstract
Summary
The effect of intravenous infusion of stalk-median extracts (SME) on serum prolactin levels was studied in male rats 24 hr after complete forebrain removal. Brain removal was used to produce pituitary islands (PI) and insure the absence of endogenous hypothalamic inhibitory factors. Twenty-four hours after forebrain removal, prolactin levels showed a twofold increase above “nonstress” levels in intact animals. In ether-anesthetized intact male rats, infusion of the hypothalamic extract (5 SME equivalents) markedly decreased prolactin levels. In contrast, prolactin levels were not significantly reduced in PI preparations 40 min following initiation of infusion. The results suggest that the decreased blood levels of prolactin observed after administration of hypothalamic extract to intact animals may reflect the release of endogenous prolactin release inhibitory hormone (PRIH), evoked by the extract, and not a direct inhibitory effect on pituitary prolactin secretion.
We express our appreciation to Laurel Patterson and Jacqueline Skaggs for their excellent technical and secretarial assistance.
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