Akema T, Chiba A, Kimura F
Department of Physiology, St. Marianna University School of Medicine, Kawasaki, Japan.
Neuroendocrinology. 1990 Dec;52(6):566-72. doi: 10.1159/000125645.
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.
在去卵巢大鼠中研究了去甲肾上腺素能（NA）刺激系统与γ-氨基丁酸（GABA）介导的抑制系统在促黄体生成素（LH）分泌控制中的关系。在雌激素预处理的大鼠中，脑室内（i.c.v.）注射GABAA激动剂蝇蕈醇刺激GABAA受体，可显著减弱随后i.c.v.注射NA时LH的分泌反应。另一方面，用苯氧苄胺阻断α-肾上腺素能受体并不干扰i.c.v.注射GABAA拮抗剂荷包牡丹碱的刺激作用。在另一系列实验中，对去卵巢动物进行i.c.v.注射6-羟基多巴胺（6-OHDA）或其溶剂处理。i.c.v.注射蝇蕈醇或酚妥拉明可显著抑制溶剂处理大鼠中雌激素诱导的LH分泌高峰。蝇蕈醇还抑制了溶剂处理、未用雌激素预处理动物中现有的LH脉冲式分泌。在推测下丘脑NA终末被6-OHDA破坏的动物中，酚妥拉明的抑制作用显著减弱，而蝇蕈醇的抑制作用未改变。这些结果可得出以下结论：（1）中枢GABA能系统通过GABAA受体抑制LH分泌；（2）这种抑制性GABA系统在没有NA系统介导的情况下发挥作用；（3）GABA能非NA介导系统可影响雌性大鼠垂体LH分泌的生理模式。
