Article date: 1990/12/1
PubMed ID: 2178232
Journal name: Neuroendocrinology (ISSN: 0028-3835)
The relationship between noradrenergic (NA) stimulatory and gamma-aminobutyric acid (GABA)-mediated inhibitory systems in the control of luteinizing hormone (LH) secretion was examined in ovariectomized rats. Stimulation of the GABAA receptor by an intraventricular (i.c.v.) administration of a GABAA agonist, muscimol, significantly attenuated the LH secretory response to the subsequent i.c.v. injection of NA in estrogen-primed rats. On the other hand, blockade of alpha-adrenergic receptors by phenoxybenzamine did not interfere with the stimulatory effect of an i.c.v. injection of a GABAA antagonist bicuculline. In a different series of experiments, ovariectomized animals had been treated with i.c.v. injections of 6-hydroxydopamine (6-OHDA) or its vehicle. An i.c.v. injection of muscimol or phentolamine significantly inhibited the estrogen-induced surge of LH secretion in vehicle-treated rats. Muscimol also inhibited the existing pulsatile LH secretion in vehicle-treated, estrogen-unprimed animals. In animals in which hypothalamic NA terminals were presumed to be destroyed by 6-OHDA, the inhibitory effect of phentolamine was significantly diminished while that of muscimol was unaltered. These results permit the following conclusions: (1) the central GABAergic system inhibits LH secretion via GABAA receptors; (2) this inhibitory GABA system operates without mediation by the NA system, and (3) the GABAergic non-NA-mediated system can affect physiological patterns of pituitary LH secretion in female rats.
Author List: Akema T, Chiba A, Kimura F
Publication Types: Journal Article
Substances mentioned in the article: Hydroxydopamines; Receptors, Adrenergic, alpha; Receptors, GABA-A; Phenoxybenzamine; Muscimol; Estradiol; gamma-Aminobutyric Acid; Oxidopamine; Luteinizing Hormone; Norepinephrine; Bicuculline;
Mesh terms: Animals; Bicuculline/pharmacology; Estradiol/pharmacology; Female; Hydroxydopamines/pharmacology; Luteinizing Hormone/secretion; Muscimol/pharmacology; Norepinephrine/pharmacology; Ovariectomy; Oxidopamine; Periodicity; Phenoxybenzamine/pharmacology; Rats; Rats, Inbred Strains; Receptors, Adrenergic, alpha/drug effects; Receptors, GABA-A/physiology; gamma-Aminobutyric Acid/physiology;