Morphine suppresses the proestrous surge of GnrH in pituitary portal plasma of rats.
Morphine suppresses the proestrous surge of GnrH in pituitary portal plasma of rats.
复制标题
吗啡抑制大鼠垂体门静脉血浆中 GnrH 的发情前激增。
作者：
M. Ching
用2种剂量的硫酸吗啡(MS)(5~8和40 mg/kgbw)或纳洛酮(NH)(10 mg/kgbw)联合大剂量硫酸吗啡(MS)急性给药，并与未处理的发情期(PE)和发情间期(DE)对照组动物比较。在门静脉采血前通过静脉穿刺法测定血浆中的促黄体生成素和卵泡刺激素。两种剂量的MS均能显著降低黄体生成素和卵泡刺激素的PE峰，但NH能逆转MS的作用，使循环中的促性腺激素恢复到PE水平。然而，只有高剂量MS处理的PE大鼠门脉血浆中GnRH浓度显著降低。这表明促性腺激素浓度的降低不仅仅是由于下丘脑GnRH分泌的减少，还可能涉及其他机制(S)。然而，在给予大剂量MS的大鼠中，垂体促性腺激素分泌的严重减少在很大程度上是由于下丘脑GnRH释放的相应减少，因为NH使GnRH和LH/FSH血浆浓度恢复到PE水平。
Virgin proestrous rats were acutely treated with 2 doses of morphine sulfate (MS) (5-8 and 40 mg/kg BW) or naloxone HCl (NH) (10 mg/kg BW) co-administered with the high dose of MS, and the pituitary portal plasma concentrations of gonadotropin releasing hormone (GnRH) were compared with those of untreated proestrous (PE) and diestrous (DE) control animals. LH and FSH were measured in systemic plasma obtained by venipuncture just prior to the collection of portal blood. Both doses of MS severely diminished the PE surges of LH and FSH, but NH reversed the effect of MS and restored the circulating gonadotropins to PE levels. However, only PE rats treated with the high dose of MS exhibited significantly reduced GnRH concentrations in portal plasma. This suggests that the reduction of gonadotropin concentrations is not due merely to reduced GnRH secretion by the hypothalamus but may involve other mechanism(s) as well. However, in rats given the high dose of MS the severe reduction in pituitary gonadotropin secretion is attributable in large part to the corresponding decrease in hypothalamic GnRH release, since NH restored the GnRH and LH/FSH plasma concentrations to PE levels.