Schwartz M D, Nunez A A, Smale L
Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA.
Neuroscience. 2004;127(1):13-23. doi: 10.1016/j.neuroscience.2004.04.049.
Diurnal and nocturnal species are profoundly different in terms of the temporal organization of daily rhythms in physiology and behavior. The neural bases for these divergent patterns are at present unknown. Here we examine functional differences in the suprachiasmatic nucleus (SCN) and one of its primary targets in a diurnal rodent, the unstriped Nile grass rat (Arvicanthis niloticus) and in a nocturnal one, the laboratory rat (Rattus norvegicus). Grass rats and laboratory rats were housed in a 12:12 light:dark cycle, and killed at six time points. cFos-immunoreactive rhythms in the SCN of grass rats and laboratory rats were similar to those reported previously, with peaks early in the light phase and troughs in the dark phase. However, cFos-immunoreactivity in the lower subparaventricular zone (LSPV) of grass rats rose sharply 5 h into the dark phase, and remained high through the first hour after light onset, whereas in laboratory rats it peaked 1 h after light onset and was low at all other sampling times. Daily cFos rhythms in both the SCN and the LSPV persisted in grass rats, but not in laboratory rats, after extended periods in constant darkness. In grass rats, the endogenous cFos rhythm in the LSPV, but not the SCN, was present both in calbindin-positive and in calbindin-negative cells. Cells that expressed cFos at night in the region of the LSPV in grass rats were clearly outside of the boundaries of the SCN as delineated by Nissl stain and immunoreactivity for vasopressin and vasoactive intestinal peptide. The LSPV of the grass rat, a region that receives substantial input from the SCN, displays a daily rhythm in cFos expression that differs from that of laboratory rats with respect to its rising phase, the duration of the peak and its dependence on a light/dark cycle. These characteristics may reflect the existence of mechanisms in the LSPV that enable it to modulate efferent SCN signals differently in diurnal and nocturnal species.
昼行性和夜行性物种在生理和行为的日常节律的时间组织方面存在深刻差异。目前尚不清楚这些不同模式的神经基础。在这里，我们研究了昼行性啮齿动物无条纹尼罗河草鼠（Arvicanthis niloticus）和夜行性啮齿动物实验室大鼠（Rattus norvegicus）的视交叉上核（SCN）及其主要靶标之一的功能差异。草鼠和实验室大鼠饲养在12:12的明暗循环中，并在六个时间点处死。草鼠和实验室大鼠SCN中cFos免疫反应性节律与先前报道的相似，在光照期早期达到峰值，在黑暗期达到谷值。然而，草鼠下丘脑室旁核下部（LSPV）的cFos免疫反应性在黑暗期开始5小时后急剧上升，并在光照开始后的第一个小时内保持高位，而在实验室大鼠中，它在光照开始后1小时达到峰值，在所有其他采样时间均较低。在持续黑暗中长时间饲养后，草鼠的SCN和LSPV中的每日cFos节律仍然存在，但实验室大鼠中则不存在。在草鼠中，LSPV中的内源性cFos节律，而非SCN中的，在钙结合蛋白阳性和阴性细胞中均存在。在草鼠LSPV区域夜间表达cFos的细胞明显位于由尼氏染色以及加压素和血管活性肠肽免疫反应性所界定的SCN边界之外。草鼠的LSPV接受来自SCN的大量输入，该区域在cFos表达上呈现出每日节律，在上升阶段、峰值持续时间及其对明暗循环的依赖性方面与实验室大鼠不同。这些特征可能反映了LSPV中存在一些机制，使其能够在昼行性和夜行性物种中以不同方式调节SCN传出信号。
