Irahara M, Tamura T, Matuzaki T, Saito S, Yasui T, Yamano S, Kamada M, Aono T
Department of Obstetrics and Gynecology, University of Tokushima School of Medicine, Tokushima, Japan.
Biochem Biophys Res Commun. 2001 Feb 16;281(1):232-6. doi: 10.1006/bbrc.2001.4328.
Orexins, the novel hypothalamic neuropeptides that stimulate feeding behavior, have been shown to suppress the pulsatile secretion of LH in ovariectomized rats. However, the mechanism of this action is still not clear. We examined the effect of naloxone, a specific opioid antagonist, on the suppression of the pulsatile secretion of LH by orexins to determine whether beta-endorphin is involved in this suppressive effect. We administered orexins intracerebroventricularly and injected naloxone intravenously in ovariectomized rats, and we measured the serum LH concentration to analyze the pulsatile secretion. Administration of orexin-A significantly reduced the mean LH concentration and the pulse frequency, but coadministration of naloxone significantly restored the mean LH concentration and the pulse frequency. Administration of orexin-B also significantly reduced the mean LH concentration and the pulse frequency, and coadministration of naloxone did not restore them. These results indicate that orexin-A, but not orexin-B, suppresses GnRH secretion via beta-endorphin.
食欲肽是一种新型下丘脑神经肽，可刺激摄食行为，已被证明能抑制去卵巢大鼠促黄体生成素（LH）的脉冲式分泌。然而，这种作用的机制仍不清楚。我们研究了特异性阿片受体拮抗剂纳洛酮对食欲肽抑制LH脉冲式分泌的影响，以确定β-内啡肽是否参与了这种抑制作用。我们对去卵巢大鼠进行脑室内注射食欲肽并静脉注射纳洛酮，然后测量血清LH浓度以分析脉冲式分泌情况。注射食欲肽A显著降低了LH平均浓度和脉冲频率，但同时注射纳洛酮可显著恢复LH平均浓度和脉冲频率。注射食欲肽B也显著降低了LH平均浓度和脉冲频率，而同时注射纳洛酮并未使其恢复。这些结果表明，食欲肽A通过β-内啡肽抑制促性腺激素释放激素（GnRH）分泌，而食欲肽B则不然。
