放线菌酮和纳洛酮影响甾体避孕药对大鼠垂体的GnRH激发效应

以动情前期大鼠垂体对ＧｎＲＨ的激发效应为模型，观察不同构型的甾体避孕药－抗孕５３和１８甲基炔诺酮（ＬＮＧ）对大鼠垂体功能的反应。电刺激视前区（ＰＯＡ）显示抗孕－５３组ＬＨ峰高于对照组（Ｐ＜０．０５），而ＬＮＧ组则显著低于对照组（Ｐ＜０．０１），表明抗孕－５３的增强效应和ＬＮＧ的抑制效应的关键部位在垂体前叶。若对经避孕药处理后的动情前期大鼠作静脉注射蛋白抑制剂放线菌酮（Ｃｙｃｌｏｈｅｘｉｍｉｄｅ）１００μｇ／１００ｇｂ．ｗ．，则抗孕－５３＋Ｃｙｃｌｏｈｅｘｉｍｉｄｅ组或Ｃｙｃｌｏｈｅｘｉｍｉｄｅ组均低于对照组（Ｐ＜０．０１），但抗孕－５３＋Ｃｙｃｌｏｘｉｍｉｄｅ组仍高于Ｃｙｃｌｏｈｅｘｉｍｉｄｅ组（Ｐ＜０．０５）。Ｃｙｃｌｏｈｅｘｉｍｉｄｅ组和ＬＮＧ＋Ｃｙｃｌｏｈｅｘｉｍｉｄｅ组相比前者比后者稍有下降，但无显著性差异。若对ＬＮＧ处理后的大鼠静脉注射纳洛酮（０．２５ｍｇ／１００ｇｂ．Ｗ）结果显示纳洛酮可解除ＬＮＧ的抑制效应。以上结果表明在一定剂量下抗孕－５３引起的增强垂体激发效应，可能不完全是增加ＧｎＲＨ分泌量，而主要是通过加强蛋白的合成来完成。ＬＮＧ的抑制垂体激发反应不是抑制ＧｎＲＨ的分泌而是通过垂体与阿片肽?

Cycloheximide and Naloxone Affect the GnRH-Pituitary Priming Effect induced by Steroidal Contraceptives in Rat

The model for priming effect of GnRH in proestrous rat has been used for this study.The results showed that stimulation of POA could induce more LH release in#53(Anordrin) treatedgroup than in control group(P<0.05),but significantly inhibit LH release to much lower level inLNG (Levonorgestrel) group than that in control group.It is obvious that the key position foraugmentation or inhibition of LH release by these two drugs is in the anterior pituitary. Intravenous injection of cycloheximide 100μg/100g b. w. to rats pre-treated with steroidal contraceptives,the LH release in # 53+cycloheximide group or cycloheximide group showed lower thanthat in control group (P<0.01),but the # 53+ cycloheximide group had relatively more LH release than that in cycloheximide group(P<0.05).As comparing the cycloheximide group withLNG+cycloheximide group,the former would gain more LH release,but there was no statisticalsignificance.In case of intravenous injection of naloxone 0.25mg/100g b.w.)to the rats pretreated with LNG,the result showed that naloxone could reverse the inhibitory effect of LNG.From the result mentioned above the augmentation of LH release under the certain dosage of # 53treatment is not due to the increase output of GnRH, but mainly through the enhancement of protein synthesis.For LNG action,it does not influence the pathway of protein synthesis but interferes the opioid receptor related route.