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Evidence suggests that endogenous opioid peptides (EOP) inhibit pulsatile luteinizing hormone (LH) secretion during both the luteal and follicular phases of the ovine estrous cycle. Further data from sheep and other species indicate that the hypothalamus is the primary site of action for this EOP inhibition. The purpose of the following experiments was to(More)
This study examined the role of two dopaminergic (DA) cell groups, the A-14 and A-15 DA groups, in the seasonal shift in the response of LH to estradiol negative feedback in ewes. Radiofrequency lesions were placed bilaterally, in the area of the A-15 or the ventromedial A-14 cell groups of ovariectomized ewes, while control animals underwent sham(More)
Norepinephrine (NE) and dopamine (DA) actively inhibit the release of LH in anestrous ewes. This can be detected as an increase in LH pulse frequency following i.v. injection of NE and DA antagonists. The objective of this study was to determine the sites of these inhibitory actions in the ovine hypothalamus by using local administrations of the NE(More)
It is now clear that estradiol acts in the brain to inhibit LH pulse amplitude in breeding season ewes, but the neural mechanisms underlying this action of estradiol have yet to be determined. In this study, we performed four experiments to examine the role of alpha-adrenergic neurons in the control of LH pulse amplitude in the ewe. In the first experiment,(More)
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