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Studies by others have shown that parenteral administration of antiestrogens blocks the positive feedback effect of estrogen on the luteinizing hormone (LH) surge mechanism. Since all estrogen-accumulating cells could be affected by this treatment, it is difficult to identify the site(s) at which this steroid acts to affect LH surges. In the present study(More)
Progesterone (P) amplifies and advances gonadotropin surges when administered to estradiol (E2)-treated ovariectomized rats. While daily rhythmic LH surges continue to occur in E2-treated rats, they are extinguished in E2- and P (E2P)-treated animals 24 h after P treatment. We examined whether this negative feedback effect on P affect catecholamine activity(More)
Previous studies by others suggest that mid- and hindbrain noradrenergic projections to the hypothalamus may be stimulatory or inhibitory to luteinizing hormone releasing hormone (LHRH) release depending upon the steroid environment of the rat. In the present study we reevaluated the effects of electrical stimulation of the locus coeruleus (LC) in(More)