Beaulé C, Amir S
Center for Studies in Behavioral Neurobiology, Concordia University, 1455 De Maisonneuve Boulevard West, Montreal, Québec, Canada.
Brain Res. 1999 Mar 6;821(1):95-100. doi: 10.1016/s0006-8993(99)01073-2.
Immediate-early genes (IEGs) are transiently expressed within the rodent circadian system in response to nocturnal light. The two most studied light-induced IEGs within this system are Fos and Jun-B. Molecular expression of these two genes within the hypothalamic suprachiasmatic nucleus (SCN) correlates with light-induced behavioral phase shifts. Previous studies of the role of Fos and Jun-B in circadian clock resetting have used light stimuli that induce strong phase shifts. However, the relationship of Fos and Jun-B expression in the SCN and light-induced phase shifts in an entrainment context is undocumented in rats. In this study, male rats for which the free running period was determined were entrained to a 0.5 h:23.5 h LD cycle. On the fifteenth day of stable entrainment, the entraining light pulse was reduced to 10 min. Animals were killed 50 min later and brains were processed for IEG immunocytochemistry. Strong Fos induction was observed in the SCN and the intergeniculate leaflet (IGL). Strong Jun-B immunoreactivity was observed only in the SCN whereas Jun-B labeling in the IGL was weak. Significant correlations were obtained between the magnitude of light-induced IEGs in the SCN and the magnitude of the daily phase shift required for stable entrainment to the 0.5 h:23.5 h LD cycle. Further, a significant correlation was observed between the number of Fos and Jun-B immunoreactive cells in the SCN and IGL. These data suggest that the magnitude of Fos and Jun-B induction within the SCN is related to the magnitude of the daily phase shift required for stable entrainment.
即刻早期基因（IEGs）在啮齿动物的昼夜节律系统中会因夜间光照而短暂表达。该系统中研究最多的两种光诱导即刻早期基因是Fos和Jun-B。这两种基因在下丘脑视交叉上核（SCN）中的分子表达与光诱导的行为相位偏移相关。先前关于Fos和Jun-B在昼夜节律重置中作用的研究使用的是能诱导强烈相位偏移的光刺激。然而，在大鼠中，SCN中Fos和Jun-B的表达与在同步化环境下光诱导的相位偏移之间的关系尚无文献记载。在本研究中，确定了自由运行周期的雄性大鼠被同步到0.5小时：23.5小时的明暗周期。在稳定同步化的第15天，同步化光脉冲缩短至10分钟。50分钟后处死动物，对大脑进行即刻早期基因免疫细胞化学处理。在SCN和膝间小叶（IGL）中观察到强烈的Fos诱导。仅在SCN中观察到强烈的Jun-B免疫反应性，而IGL中的Jun-B标记较弱。SCN中光诱导即刻早期基因的幅度与稳定同步到0.5小时：23.5小时明暗周期所需的每日相位偏移幅度之间存在显著相关性。此外，在SCN和IGL中Fos和Jun-B免疫反应性细胞的数量之间观察到显著相关性。这些数据表明，SCN内Fos和Jun-B诱导的幅度与稳定同步所需的每日相位偏移幅度有关。
