Neural basis for generating gonadotropin-releasing hormone surge

本研究通过培养嗅板，探讨体外GnRH峰发生器模型的实用性。我们发现，该模型是有用的，因为阻断cAMP的产生显着调谐释放的GnRH在体内一样。在GT 1 -1细胞中，细胞外记录的电活动有时与Ca ~（2+）振荡有关。这一结果表明，GTI-1细胞可用作脉冲发生器的体外模型。接下来，我们研究了产生GnRH分泌激增的多巴胺能神经元的可能作用。GluR 1-C-tail是GluR 1（AMPA受体的亚基）的显性负突变体，在神经可塑性过程中与GluR 1竞争突触传递。GluR 1-C-tail在雌性大鼠的POA中使用慢病毒表达。注射GluR 1-C尾对成年大鼠LH分泌高峰无影响。当在21天进行注射时，通过检查阴道开口，青春期的开始显著延迟。之后，通过阴道涂片检查动情周期，发现注射GIuR 1-C-尾的大鼠表现出不规则的动情周期。注射GluR 1-C-tail的成年大鼠在21天的促黄体生成素（LH）分泌的激增显着减弱，与对照组相比。结果表明，GluR 1介导的可塑性发生在青春期的时候，是重要的，以维持LH分泌激增的成年人。我们现在正在研究的运输GluR 1在GnRH神经元的全细胞电压钳记录。关于CREB在浪涌发生器中的作用，我们目前正在研究mCREB（显性阴性）或cCREB（组成型活性）对LH分泌浪涌的影响。

The present study investigated the utility of model for in vitro GnRH surge generator by culturing the olfactory placode. We found that model was useful since blockade of cAMP production markedly attunated release of GnRH as did in vivo. In GT1-1 cells, the electrical activity examined by extracellular recording was sometimes related to Ca2+ oscillations. This result suggests that GTI-1 cells are useful as in vitro model for pulse generator. Next, we examined the possible role for glutamatergic neurons generating the surge of GnRH secretion. GluR1-C-tail, a dominant negative mutant of GluR1 (subunit of AMPA receptors), has been shown to act by competing with GluR1 for synaptic delivery during neural plasticity. GluR1-C-tail was expressed in the POA of female rats using lentivirus. Injection with GluR1-C-tail in adult rats had no effect on the surge of LH secretion. When the injection was done at 21-day, the onset of puberty was significantly delayed, by checking viginal opening. After that, the estrous cyclicity was checked by viginal smear and found that the rat injected with GIuR1-C-tail exhibited an irregular estrous cycle. The surge of luteinizing hormone (LH) secretion in the adult rat injected with GluR1-C-tail at 21-day was significantly attenuated, compared to the control rat. The result suggests that GluR1 -mediated plasticity occurs at the time of puberty and is important to maintain surge of LH secretion in adults. We are now examining the trafficking of GluR1 in GnRH neurons by a whole-cell voltage clamp recording. With regard to the role of CREB in the surge generator, we are currently examining the effects of mCREB (dominant negative) or cCREB (constitutively active) on the surge of LH secretion.