Mechanisms of circadian rhythm analyzed from transcription factor of mRNA in suprachiasmatic nucleus

视交叉上核（SCN）中含有arg -加压素（AVP）的神经元是昼夜节律信息向大脑其他部分输出的途径之一。在恒定昏暗光照下，AVP含量呈自由跑动的规律，其峰期在主观日前期发育。在动物个体中比较AVP肽水平及其编码mRNA是有用的。在本研究中，我们采用反转录PCR （PT-PCR）分析AVP mRNA水平。我们利用特异引物的PT-PCR方法检测了同一只大鼠两孔SCN中AVP mRNA的表达水平。研究了光或暗反应对SCN AVP mRNA的影响。AVP肽对光的反应比暗的反应更有效。而AVP mRNA在过渡到新的光照条件后没有明显的变化。PCR产物强度的昼夜变化模式与Northern blot分析结果相似。这些昼夜变化在持续的昏暗光线下自由运行，直到第21天。我们发现SCN（含旁细胞AVP的神经元）和视上核（大细胞）对GABA和皮质酮/地塞米松的不同反应。视网膜的光刺激诱导SCN中c-fos的发育。C-fos的发育与昼夜节律的相位响应等指标相关。这些结果表明，AVP肽的节律不仅受到合成的控制，还受到其他系统的控制。我们有理由推测，AVP编码基因可能在5′启动子区上游含有IEG（c-fos）结合位点。虽然，AVP编码DNA没有从视上核或其他脑区获得的基因组测序的AP-1结合位点。我们正在寻找编码源自SCN的AVP mRNA的特定基因组。

Arg-vasopressin (AVP) containing neurons in the suprachiasmatic nucleus (SCN) is one of the output paths of circadian information to other parts of the brain. The AVP contents show a free-running rhythm under the constant dim light, whose acrophase is developing during the early period of subjective day. It is useful to compare the AVP peptide levels with its coding mRNA in individual animals. In the present study, we analyzed the AVP mRNA levels by reverse transcription PCR (PT-PCR). We could detect the AVP mRNA levels extracted from two punches of SCN in one rat by using PT-PCR with specific primers. Effects of light or dark response to the SCN AVP mRNA were examined. The light responses to AVP peptide were more effective than to the dark. While, the AVP mRNA did not show an obvious change after transition to new lighting regime. The patterns of day-night variations in PCR product-intensity are similar with that analyzed by Northern blot. These day-night variations free-run until 21st day under the constant dim light. We find the differential responses in SCN (parvocellular AVP containing neuron) and supraoptic nucleus (magnocellular) against to GABA and corticosterone/dexamethasone. Photic stimulation from retina induces c-fos development in SCN. C-fos development couples with the phase responses and other indexes of circadian rhythm. These results suggest that the AVP peptide rhythm be checked not only by the control of synthesis, but also by the other systems. It is reasonable to speculate that the AVP coding gene might containing IEG(c-fos) binding site at the upstream of 5' promoter area. Although, the AVP coding DNA has no AP-1 binding site that was sequenced from the genome obtained from supraoptic nucleus or other brain area. We are searching the specific genome, which code AVP mRNA originating from the SCN.