Jurcovicová J, Le T, Krulich L
Institute for Experimental Endocrinology, Bratislava, Czechoslovakia.
Brain Res Bull. 1989 Dec;23(6):417-24. doi: 10.1016/0361-9230(89)90183-4.
Systemic (IV) administration of the alpha 2 receptor agonist clonidine is known to stimulate secretion of PRL and growth hormone (GH) suggesting a stimulatory role of the central alpha 2 receptors in the regulation of the two hormones. The present work confirms this notion for GH but indicates that the alpha 2 agonists stimulate PRL release by a peripheral action not involving central alpha 2 receptors. This conclusion is based on the following findings: 1) The minimum effective IV dose of clonidine or UK 14304 was four times larger for activation of PRL than GH secretion and had already manifest extracentral effects (elevation of arterial BP). 2) Subcutaneous injection of UK 14304 (220 micrograms/kg) elevated plasma GH but not PRL levels indicating that an effective activation of the central alpha 2 receptors does not stimulate PRL release. 3) Peripherally acting alpha 2 agonists (p-aminoclonidine, oxymetazoline) had no effect on GH secretion but stimulated PRL release in a manner identical with the effect of clonidine or UK 14304. 4) The peripherally acting alpha 2 antagonist DG-5128 blocked only the PRL secretory response to UK 14304 whereas the peripherally and centrally active yohimbine blocked the PRL and GH responses.
已知α2受体激动剂可乐定的全身（静脉）给药可刺激催乳素（PRL）和生长激素（GH）的分泌，这表明中枢α2受体在这两种激素的调节中起刺激作用。目前的研究证实了生长激素的这一观点，但表明α2激动剂通过不涉及中枢α2受体的外周作用刺激催乳素释放。这一结论基于以下发现：1）可乐定或UK 14304激活催乳素分泌的最小有效静脉剂量是激活生长激素分泌的四倍，并且已经表现出中枢外效应（动脉血压升高）。2）皮下注射UK 14304（220微克/千克）可提高血浆生长激素水平，但不提高催乳素水平，这表明中枢α2受体的有效激活不会刺激催乳素释放。3）外周作用的α2激动剂（对氨基可乐定、羟甲唑啉）对生长激素分泌无影响，但以与可乐定或UK 14304相同的方式刺激催乳素释放。4）外周作用的α2拮抗剂DG-5128仅阻断催乳素对UK 14304的分泌反应，而外周和中枢活性的育亨宾则阻断催乳素和生长激素的反应。
