Determination of the Characteristic of the GnRH Surge Generator by Multifarious Approaches

本研究在雌性大鼠上进行了一系列的实验，以确定促性腺激素释放激素（GnRH）峰发生器的特性，我们已经证明它是不同于GnRH脉冲发生器的神经机制，并获得了以下结果.为了确定视交叉上核（SCN）是否会驱动大鼠视前区（POA）GnRH的昼夜释放，我们在120 h内以2 h的间隔测定了视前区和SCN共培养物中GnRH、精氨酸加压素（AVP）和血管活性肠肽（VIP）的释放。在有雌激素存在的情况下，共培养物中GnRH的释放表现出显著的昼夜节律，但在没有雌激素的情况下则不然。GnRH的昼夜节律周期与AVP的昼夜节律周期相同，而与VIP的昼夜节律周期不同。此外，GnRh节律的峰期出现在与AVP节律的峰期相同的时间， ...更多信息 h文化，但并不总是一样的VIP节奏。实验结果表明，体外共培养可作为GnRH峰发生器的实验模型，SCN内AVP神经元介导POA内GnRH峰发生器的时钟信息.为探讨AVP V1受体拮抗剂是否影响LH的峰型分泌，我们将其注入发情前期大鼠的第三脑室，并于1100 ~ 2100 h测定血清LH浓度。注射AVP受体拮抗剂后1300 h，LH分泌明显减少，支持内源性AVP参与LH分泌高峰的假说.为了确定浪涌发生器是否涉及钠离子通道依赖的机制，我们在1300 h时在动情前期大鼠POA的两侧注射TTX，并以1 h的间隔测量血清LH浓度。与注射生理盐水的对照大鼠相比，注射TTX对LH分泌没有任何显著影响，表明GnRH浪涌发生器释放GnRH的机制与Na离子通道依赖性的不同。少

A series of multifarious experiments was performed in female rats to determine the characteristic of the gonadotropin-releasing hormone (GnRH) surge generator which had been evidenced, by us, to be the neural mechanism distinct from that the GnRH pulse generator and the following results were obtained.1. To determine whether the suprachiasmatic nucleus (SCN) will drive a circadian release of GnRH in the rat preoptic area (POA), we measured the release of GnRH, arginine-vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) in cocultures of the preoptic area and the SCN at 2-h intervals over a period of 120 h. The release of GnRH in cocultures exhibited a significant circadian rhythm in the presence of estrogen but not in the absence of estrogen. The period of GnRH circadian rhythm was the same as that of the AVP rhythm, and different from the VIP circadian rhythm in each coculture. Furthermore, the peak phase of the GnRh rhythm occurred at the time same as that of the AVP in eac … More h culture, but was not always the same as that of the VIP rhythm. The results demonstrated that these in vitro cocultures can be used as an experimental model for the GnRH surge generator and that AVP neurons in the SCN mediate the clock information to GnRH surge generator in the POA.2. To determine whether the AVP V1 receptor antagonist will affect the surge secretion of LH, we injected it into the third ventricle in the proestrous rat and measured serum concentrations of LH between 1100 and 2100 h. The injection of AVP receptor antagonist at 1300 h resulted in a significant decrease in LH secretion compared to saline-injected control rats, supporting evidence our hypothesis that endogenous AVP plays a role in the induction of the surge of LH secretion.3. To determine whether the surge generator involves the Na ion channel-dependent mechanism, we injected TTX into both sides of the POA at 1300 h in the proestrous rat and measured serum concentrations of LH at 1-h intervals. The injection of TTX did not induce any significant effect in LH secretion compared to saline-injected control rats, suggesting that the GnRH surge generator releases GnRH with mechanisms different from Na ion channels-dependent ones. Less