Earnest D J, Olschowka J A
University of Rochester School of Medicine, Department of Neurobiology and Anatomy, New York 14642.
J Biol Rhythms. 1993;8 Suppl:S65-71.
The primary objective of this research was to examine expression of the immediate-early gene c-fos within the suprachiasmatic nucleus (SCN) for evidence of circadian regulation by photic stimuli. In vivo and in vitro analyses demonstrate that photic signals have an inductive effect on c-fos expression in the SCN, but only at critical times when light is capable of phase-shifting circadian rhythms. This evidence for correlative relations between the effects of light signals in inducing c-fos gene expression in the SCN and modulating the circadian period of the SCN pacemaker suggests that immediate-early genes may be components of the signal transduction cascade by which light entrains circadian rhythms. In addition, dual-immunostaining methods were utilized to examine neurochemical identity of SCN cells that exhibit this circadian induction of c-fos expression in response to light. Within the ventrolateral SCN, the photic induction of Fos expression occurred in neurons expressing gastrin-releasing peptide (GRP), but not in those containing vasoactive intestinal polypeptide (VIP). This finding suggests that SCN neurons containing GRP may be involved in the transduction of photic signals mediating circadian entrainment.
本研究的主要目的是检测视交叉上核（SCN）中即早基因c-fos的表达情况，以寻找光刺激对昼夜节律调节作用的证据。体内和体外分析表明，光信号对SCN中c-fos的表达有诱导作用，但仅在光能够使昼夜节律发生相移的关键时间点才会出现这种作用。光信号在诱导SCN中c-fos基因表达以及调节SCN起搏器的昼夜周期方面的效应之间存在这种相关性证据，这表明即早基因可能是光调节昼夜节律的信号转导级联反应的组成部分。此外，采用双重免疫染色方法来检测SCN中对光产生这种昼夜节律性c-fos表达诱导作用的细胞的神经化学特性。在腹外侧SCN内，Fos表达的光诱导发生在表达胃泌素释放肽（GRP）的神经元中，而在含有血管活性肠肽（VIP）的神经元中则未出现。这一发现表明，含有GRP的SCN神经元可能参与介导昼夜节律性调节的光信号转导过程。
