Abstract
Summary
Lesions were located in the ME of ovariectomized rats to determine their effect on plasma levels of FSH, LH, and prolactin as determined by RIA. Initial levels of FSH and LH were elevated as a result of removal of steroid feedback from the ovaries. One week after placement of lesions plasma LH levels had fallen, 32-fold, to very low values. There was a lesser, 3-fold, fall in FSH, and a dramatic, 15-fold, rise in prolactin to levels nearly as high as those observed in lactating rats and in females in proestrus. In sham-operated controls, in which the electrodes were lowered into the hypothalamus stopping short of the ME, no significant changes were seen in the plasma levels of all three hormones. The results demonstrate that the release of LH and to a lesser extent FSH is decreased after removal of hypothalamic control, whereas the release of prolactin is greatly enhanced.
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