Beck W, Wuttke W
J Endocrinol. 1977 Jul;74(1):67-74. doi: 10.1677/joe.0.0740067.
Increase of plasma prolactin in chronically ovariectomized rats by transplanting pituitary glands from male rats to the kidney capsule reduced pituitary LH output for 1 week. At the end of this time, despite the fact that prolactin remained high, plasma LH levels rose to reach the value seen in ovariectomized control rats. High plasma prolactin did not affect FSH concentrations. Treatment of ovariectomized rats with apomorphine, a dopamine-receptor stimulating drug, reduced pituitary LH release in a dose-dependent way at doses of 1, 2, 5 and 10 mg/kg body weight. Higher doses either had no effect or they stimulated pituitary LH release. Apomorphine did not reduce pituitary LH secretion in chronically hyperprolactinaemic rats at doses which significantly inhibited LH release in ovariectomized animals. Plasma FSH levels were not affected by apomorphine treatment. In both groups of animals the drug reduced plasma prolactin levels to basal values, indicating that the dopamine agonist inhibits pituitary prolactin release by direct action on the pituitary gland. These results suggest that dopamine inhibits pituitary LH release, probably by reducing hypothalamic LH-releasing hormone release. The mechanism by which chronically high prolactin levels cause apomorphine to be less effective in reducing pituitary LH release may be a desensitization of some dopamine-receptive mechanism which is inhibitory to LH release.
将雄性大鼠的垂体移植到去卵巢慢性化大鼠的肾包膜上，可使血浆催乳素增加，同时垂体促黄体生成素（LH）的分泌在1周内减少。在此时间段结束时，尽管催乳素仍处于高水平，但血浆LH水平上升至去卵巢对照大鼠的水平。高血浆催乳素水平并未影响促卵泡生成素（FSH）浓度。用阿扑吗啡（一种多巴胺受体激动剂）处理去卵巢大鼠，在剂量为1、2、5和10mg/kg体重时，可呈剂量依赖性地减少垂体LH释放。更高剂量则要么没有效果，要么刺激垂体LH释放。在慢性高催乳素血症大鼠中，阿扑吗啡在能显著抑制去卵巢动物LH释放的剂量下，并未减少垂体LH分泌。阿扑吗啡处理不影响血浆FSH水平。在两组动物中，该药物均将血浆催乳素水平降至基础值，表明多巴胺激动剂通过直接作用于垂体来抑制垂体催乳素释放。这些结果提示，多巴胺可能通过减少下丘脑促黄体生成素释放激素的释放来抑制垂体LH释放。慢性高催乳素水平导致阿扑吗啡在减少垂体LH释放方面效果降低的机制，可能是某些对LH释放起抑制作用的多巴胺受体机制发生了脱敏。
