Molecular mechanisms of development of circadian rhythm in relation to transcription factor of peptide synthesis.

哺乳动物的昼夜节律是由下丘脑视交叉上核（SCN）中的起搏点调节的。SCN含有多种多肽。精氨酸加压素（AVP）神经元是SCN向其他脑区输出昼夜节律信号的神经元之一。对于起搏器的转运机制，血管活性肠肽（VIP）、胃泌素释放肽（GRP）被认为是值得关注的。而这些肽对AVP释放的作用是相互的，即我们发现VIP增加AVP释放，而胃泌素释放肽减少AVP释放。光信息是导致这种夹带的最重要因素，它通过含谷氨酸的神经元传递给SCN。暗期SCN中谷氨酸含量虽较高，但呈暗脉冲型相反应曲线。光脉冲可引起SCN腹外侧区谷氨酸的增加，因此，我们正在利用生物传感器研究SCN释放谷氨酸的机制，这种生物传感器对谷氨酸是连续可测量的和特异的。GABA的释放呈昼夜节律，暗期高于明期。但GABA的功能尚不清楚。因此，我们使用切片培养系统来检测GABA对AVP释放的影响。GABA的直接作用不明显，蝇蕈醇（GABA α受体激动剂）增加AVP水平和荷包牡丹碱（GABAa拮抗剂）减少AVP释放，而GABAb受体激动剂和/或拮抗剂没有显示出显著的效果。在从转录因子肽分析起搏机制之前，我们正在筛选SCN特异性，发现许多来自SCN的mRNA在一天中以恒定的速率表达。然而，少数产品仅在CT 20-23出现。分析AP-1和cAMP水平与它们的关系。

Mammalian circadian rhythum is regulated by a pacemaker in the suprachiasmatic nuclei (SCN) of hypothalamus. The SCN containing variety of peptides. Arg-vasopressin (AVP) containing neuron is one of the output neuron of circadian signal from the SCN to the other brain area. For the entraining mechanism of pacemaker, vasoactive intestinal peptide (VIP), gastrin-releasing peptide are considered to be concerned. While the function of these peptides on the AVP release is reciprocal ; i.s.we found that the VIP increased AVP release, while gastrin-releasing peptide decreased AVP release. Photic information is the most important factor for the entrainment, which is conveyed to SCN by glutamate containing neuron. Although the glutamate is higher in SCN during the dark period, glutamate plays dark pulse type phase response curve. Light pulse induces increment of glutamate at the ventrolateral area of SCN.So, we are examining now the mechanism of glutamate release from the SCN using a biosensor, which is continuously measurable and specific to glutamate.Beside, almost all of the SCN neuron containing GABA for an inhibitory amino-acid. GABA release shows diurnal rhythm that is higher at dark period than in light period. However the function of GABA is not clear yet. Therefore, we examined the effect of GABA on the AVP release using a slice culture system. The direct effect of GABA is not obvious, but the muscimol (GABAa-receptor agonist) increased the AVP level and bicuculline (GABAa antagonist) decreased AVP release, while the GABAb receptor agonist and/or antagonist did not show a significant effect.In preceding to analyze the pacemaking mechanism from the transcription factor of peptides, we are screening a SCN-specific, mRNA using differential display PCR.Many mRNA from SCN found to be expressed at a constant rate throughout a day. However, a few products appeared only at CT 20-23. We are analyzing the relationship with AP-1 and cAMP levels with them.