Novak C M, Smale L, Nunez A A
Department of Psychology, Michigan State University, East Lansing, Michigan 48824-1117, USA.
Am J Physiol Regul Integr Comp Physiol. 2000 May;278(5):R1267-74. doi: 10.1152/ajpregu.2000.278.5.R1267.
Most mammals show daily rhythms in sleep and wakefulness controlled by the primary circadian pacemaker, the suprachiasmatic nucleus (SCN). Regardless of whether a species is diurnal or nocturnal, neural activity in the SCN and expression of the immediate-early gene product Fos increases during the light phase of the cycle. This study investigated daily patterns of Fos expression in brain areas outside the SCN in the diurnal rodent Arvicanthis niloticus. We specifically focused on regions related to sleep and arousal in animals kept on a 12:12-h light-dark cycle and killed at 1 and 5 h after both lights-on and lights-off. The ventrolateral preoptic area (VLPO), which contained cells immunopositive for galanin, showed a rhythm in Fos expression with a peak at zeitgeber time (ZT) 17 (with lights-on at ZT 0). Fos expression in the paraventricular thalamic nucleus (PVT) increased during the morning (ZT 1) but not the evening activity peak of these animals. No rhythm in Fos expression was found in the centromedial thalamic nucleus (CMT), but Fos expression in the CMT and PVT was positively correlated. A rhythm in Fos expression in the ventral tuberomammillary nucleus (VTM) was 180 degrees out of phase with the rhythm in the VLPO. Furthermore, Fos production in histamine-immunoreactive neurons of the VTM cells increased at the light-dark transitions when A. niloticus show peaks of activity. The difference in the timing of the sleep-wake cycle in diurnal and nocturnal mammals may be due to changes in the daily pattern of activity in brain regions important in sleep and wakefulness such as the VLPO and the VTM.
大多数哺乳动物的睡眠和觉醒呈现出每日节律，受主要昼夜节律起搏器——视交叉上核（SCN）控制。无论物种是昼行性还是夜行性，在昼夜周期的光照阶段，SCN中的神经活动以及即刻早期基因产物Fos的表达都会增加。本研究调查了昼行性啮齿动物尼罗多棘鼠SCN以外脑区Fos表达的每日模式。我们特别关注了处于12:12小时明暗循环中的动物，在开灯和关灯后1小时及5小时处死，这些动物中与睡眠和觉醒相关的区域。腹外侧视前区（VLPO）含有甘丙肽免疫阳性细胞，Fos表达呈现节律性，在授时因子时间（ZT）17达到峰值（ZT 0时开灯）。这些动物的丘脑室旁核（PVT）中Fos表达在早晨（ZT 1）增加，但在傍晚活动高峰时没有增加。丘脑中央内侧核（CMT）中未发现Fos表达的节律，但CMT和PVT中的Fos表达呈正相关。腹侧结节乳头体核（VTM）中Fos表达的节律与VLPO中的节律相差180度。此外，当尼罗多棘鼠出现活动高峰时，VTM细胞中组胺免疫反应性神经元的Fos产生在明暗转换时增加。昼行性和夜行性哺乳动物睡眠-觉醒周期时间的差异可能是由于睡眠和觉醒中重要脑区（如VLPO和VTM）每日活动模式的变化所致。
