Effects of adrenergic antagonists on LH surge in short-term ovariectomized-steroids-primed rats.
Characterization of adrenergic stimuli on luteinizing hormone (LH) release induced by ovarian steroids in short-term ovariectomized (OVX) rats was studied. Female Sprague-Dawley rats were OVX about 1000 h on the diestrous day 1. After ovariectomy, rats were immediately inserted estradiol-containing Silastic capsules s.c. and implanted atrial Silastic tubing for frequent blood samplings. All the rats received 2 mg of progesterone s.c. at 0930 h the next morning. At 1200 h, the rats received additional treatments: a saline vehicle, prazosin HC1 (an alpha 1-adrenergic antagonist), yohimbine HC1 (an alpha 2-adrenergic antagonist), or propranolol HC1 (a beta-adrenergic antagonist) s.c., respectively. Two different doses of individual adrenergic antagonists were used on an equimolar basis in order to show their effectiveness on steroids-induced LH secretion. Blood samples were collected before and 1, 3, and 5 hours after the treatments through indwelt tubings. LH surge induced by ovarian steroids was suppressed/delayed by prazosin and yohimbine, but potentiated by propranolol in a dose-dependent manner. Results suggested that the hypothalamic alpha 1-, alpha 2-, and beta-adrenoreceptors were involved in the control of LH surge in the short-term OVX-steroids-primed rats. Principally, the alpha 1- and alpha 2-adrenoreceptors played a facilitatory role, and the beta-adrenoreceptors played an inhibitory role in the regulation of LH surge induced by ovarian steroids.
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Department of Physiology, College of Medicine, National Taiwan University, Taipei, R.O.C.
D018674:Adrenergic Antagonists / Q000494:pharmacology*; D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007986:Luteinizing Hormone / Q000378:metabolism*; D010052:Ovariectomy; D011224:Prazosin / Q000494:pharmacology*; D011374:Progesterone / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D012636:Secretory Rate / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology*
D018674:Adrenergic Antagonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D004343:Drug Implants; D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; D011943:Receptors, Adrenergic, beta; D015016:Yohimbine; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D011433:Propranolol; D011224:Prazosin