Grattan D R, Park S K, Selmanoff M
Department of Physiology, School of Medicine, University of Maryland, Baltimore 21201-1559, USA.
Am J Physiol. 1995 Apr;268(4 Pt 1):E685-92. doi: 10.1152/ajpendo.1995.268.4.E685.
Using push-pull perfusion to measure concentrations of gonadotropin-releasing hormone (GnRH) in the extracellular fluid of the anterior pituitary gland of the male rat, we have measured GnRH release at specific times before and after castration and in response to acute administration of N-methyl-D-aspartate (NMDA). After castration (7 days), mean GnRH levels were substantially increased (4.3-fold) compared with intact controls (0.94 +/- 0.16 vs. 0.22 +/- 0.08 pg/10 min, respectively, P < 0.05) due to an increase in both the frequency and amplitude of GnRH pulses. Testosterone partially reduced GnRH release (0.62 +/- 0.10 pg/10 min). NMDA induced a rapid increase in plasma luteinizing hormone (LH) in both intact and castrated rats and increased GnRH concentrations in the perfusion samples (P < 0.05). There was no change in LH release induced by two doses of injected GnRH (5 and 25 ng/100 g body wt) 2 days after castration, but by 6 days after castration the response to both doses was significantly increased. These results demonstrate that GnRH release in the male rat is acutely increased by NMDA and is chronically increased after orchidectomy. Increased pituitary sensitivity to GnRH also contributes to the hypersecretion of LH after castration, particularly at longer times after removal of testosterone negative feedback.
我们采用推挽式灌流法来测定雄性大鼠垂体前叶细胞外液中促性腺激素释放激素（GnRH）的浓度，以此来测量阉割前后特定时间以及注射N-甲基-D-天冬氨酸（NMDA）后GnRH的释放情况。阉割后（7天），GnRH的平均水平相较于完整对照组大幅升高（4.3倍）（分别为0.94±0.16与0.22±0.08 pg/10分钟，P<0.05），这是由于GnRH脉冲的频率和幅度均有所增加。睾酮可部分降低GnRH的释放（0.62±0.10 pg/10分钟）。NMDA可使完整和阉割大鼠的血浆促黄体生成素（LH）迅速升高，并使灌流样本中的GnRH浓度增加（P<0.05）。阉割2天后，注射两剂GnRH（5和25 ng/100 g体重）所诱导的LH释放没有变化，但阉割6天后，对这两剂GnRH的反应均显著增强。这些结果表明，NMDA可使雄性大鼠的GnRH释放急性增加，而睾丸切除术后则会慢性增加。垂体对GnRH敏感性的增加也导致阉割后LH的分泌过多，尤其是在去除睾酮负反馈后的较长时间内。
