Grosse J, Loudon A S, Hastings M H
Department of Anatomy, University of Cambridge, U.K.
Neuroscience. 1995 Mar;65(2):587-97. doi: 10.1016/0306-4522(94)00403-r.
The tau mutation shortens the free-running circadian period of the activity rhythm of the Syrian hamster from around 24 h in the wild-type, to 20 h in the homozygous mutant. The aim of this study was to examine the effects of light pulses on the activity rhythms and expression of c-fos in the suprachiasmatic nuclei of wild-type and mutant hamsters. This would make it possible to determine the relative durations of subjective day and night, and thereby characterize further the effect of the mutation upon the circadian cycle. Presentation of light pulses (15 min) to animals kept in dim red light for seven to 10 days induced phase-dependent shifts in the onset of activity. During subjective day (inactive phase) there was no effect of light upon the activity rhythm of either normal or mutant animals. Early in subjective night (i.e. after the start of the active phase), light pulses induced phase delays of approximately one circadian hour in both phenotypes. However, later in subjective night light pulses induced phase advances in activity rhythms. The magnitude of the advance phase shifts differed considerably between the two phenotypes, with the wild-types typically showing shifts of about one circadian hour, while the mutants showed much larger advances of up to 12 circadian hours. In both strains, advances were observed following light at circadian time 22 but not after light at circadian time 24. The relative duration of subjective night was therefore comparable in the mutants and wild-types i.e. around 11 circadian hours. In order to examine the light-induced expression of the immediate early gene c-fos at different circadian phases, animals received a second light pulse (15 min) or a control "dark pulse" at the same circadian time as they had received the first, but seven to 10 circadian days later. They were perfused 1 h after the start of the pulse and brains processed for the immunocytochemical detection of Fos, the protein product of c-fos. Animals receiving dark pulses showed minimal Fos immunoreactivity in the suprachiasmatic nucleus, regardless of the circadian time of presentation of the stimulus. During subjective day (circadian times 4-11), light induced very little Fos immunoreactivity. In contrast, light presented during subjective night (after circadian time 12) induced a dense pattern of Fos immunoreactivity in the ventrolateral, retino-recipient region of the suprachiasmatic nucleus of both wild-type and mutant animals.(ABSTRACT TRUNCATED AT 400 WORDS)
tau 突变使叙利亚仓鼠活动节律的自由运行昼夜周期从野生型的约24小时缩短至纯合突变体的20小时。本研究的目的是检测光脉冲对野生型和突变型仓鼠视交叉上核活动节律及c-fos表达的影响。这将有助于确定主观白天和黑夜的相对时长，从而进一步明确突变对昼夜节律周期的影响。对在暗红色暗光下饲养7至10天的动物给予15分钟的光脉冲，可诱导活动起始的相位依赖性偏移。在主观白天（非活动期），光对正常或突变动物的活动节律均无影响。在主观黑夜早期（即活动期开始后），光脉冲在两种表型中均诱导约一个昼夜小时的相位延迟。然而，在主观黑夜后期，光脉冲诱导活动节律的相位提前。两种表型的提前相移幅度差异很大，野生型通常显示约一个昼夜小时的相移，而突变体则显示高达12个昼夜小时的更大提前。在两个品系中，在昼夜时间22给予光后观察到提前，但在昼夜时间24给予光后未观察到。因此，突变体和野生型的主观黑夜相对时长相当，即约11个昼夜小时。为了检测不同昼夜相位下即时早期基因c-fos的光诱导表达，动物在与接受第一个光脉冲相同的昼夜时间，但在7至10个昼夜日后，接受第二个15分钟的光脉冲或对照“暗脉冲”。在脉冲开始1小时后对它们进行灌注，并对大脑进行处理，以免疫细胞化学方法检测c-fos的蛋白质产物Fos。接受暗脉冲的动物在视交叉上核中显示出最小的Fos免疫反应性，无论刺激呈现的昼夜时间如何。在主观白天（昼夜时间4至11），光诱导的Fos免疫反应性非常少。相反，在主观黑夜（昼夜时间12之后）给予光，在野生型和突变型动物视交叉上核的腹外侧、视网膜接受区域诱导出密集的Fos免疫反应性模式。（摘要截断于400字）
