Mahoney M M, Nunez A A, Smale L
Department of Zoology, Michigan State University, East Lansing, MI 48824, USA.
Neuroscience. 2000;99(3):565-75. doi: 10.1016/s0306-4522(00)00212-8.
The suprachiasmatic nucleus is the site of the primary circadian pacemaker in mammals. The lower sub paraventricular zone that is dorsal to and receives input from the suprachiasmatic nucleus may also play a role in the regulation of circadian rhythms. Calbindin has been described in the suprachiasmatic nucleus of some mammals, and may be important in the control of endogenous rhythms. In the first study we characterized calbindin-expressing cells in the suprachiasmatic nucleus and lower sub-paraventricular zone of nocturnal and diurnal rodents. Specifically, Rattus norvegicus was compared to Arvicanthis niloticus, a primarily diurnal species within which some individuals exhibit nocturnal patterns of wheel running. Calbindin-immunoreactive cells were present in the suprachiasmatic nucleus of Arvicanthis and were most concentrated within its central region but were relatively sparse in the suprachiasmatic nucleus of Rattus. Calbindin-expressing cells were present in the lower sub-paraventricular zone of both species. In the second study we evaluated Fos expression within calbindin-immunoreactive cells in nocturnal Rattus and in Arvicanthis that were either diurnal or nocturnal with respect to wheel-running. All animals were kept on a 12:12 light/dark cycle and perfused at either 4h after lights-on or 4h after lights-off. In the suprachiasmatic nucleus in both species, Fos expression was elevated during the day relative to the night but less than 1% of calbindin cells contained Fos in Arvicanthis, compared with 13-17% in Rattus. In the lower sub-paraventricular zone of both species, 9-14% of calbindin cells expressed Fos, and this proportion did not change as a function of time. Among Arvicanthis, the number of calbindin expressing neurons in the lower sub-paraventricular zone was influenced by an interaction between the wheel running patterns (nocturnal vs diurnal) and time of day. Thus, the number of calbindin-positive cells within the suprachiasmatic nucleus differed in Arvicanthis and Rattus, whereas the number of calbindin-positive cells within the lower sub-paraventricular zone differed in nocturnal and diurnal Arvicanthis. Our examination of R. norvegicus and A. niloticus suggests potentially important relationships between calbindin-containing neurons and whether animals are nocturnal or diurnal. Specifically, rats had more Fos expression in calbindin containing cells in the suprachiasmatic nucleus than Arvicanthis. In contrast, Arvicanthis exhibiting diurnal and nocturnal patterns of wheel-running differed in the number of calbindin-containing cells in the lower sub-paraventricular zone, dorsal to the suprachiasmatic nucleus.
视交叉上核是哺乳动物主要昼夜节律起搏器的所在位置。位于视交叉上核背侧并接收其输入的下丘脑室旁核下部区域，可能在昼夜节律调节中也发挥作用。在一些哺乳动物的视交叉上核中已发现钙结合蛋白，它可能在控制内源性节律方面具有重要作用。在第一项研究中，我们对夜行性和昼行性啮齿动物视交叉上核及下丘脑室旁核下部区域中表达钙结合蛋白的细胞进行了特征描述。具体而言，将褐家鼠与尼罗多乳鼠进行了比较，尼罗多乳鼠是一种主要昼行的物种，其中一些个体表现出夜行性的转轮行为模式。钙结合蛋白免疫反应性细胞存在于尼罗多乳鼠的视交叉上核中，且最集中于其中心区域，但在褐家鼠的视交叉上核中相对较少。两种物种的下丘脑室旁核下部区域均存在表达钙结合蛋白的细胞。在第二项研究中，我们评估了夜行性褐家鼠以及在转轮行为方面为昼行或夜行的尼罗多乳鼠中，钙结合蛋白免疫反应性细胞内的Fos表达情况。所有动物均饲养在12:12的明暗循环环境中，并在开灯后4小时或关灯后4小时进行灌注。在两种物种的视交叉上核中，Fos表达在白天相对于夜晚有所升高，但尼罗多乳鼠中含有Fos的钙结合蛋白细胞不到1%，而褐家鼠中这一比例为13 - 17%。在两种物种的下丘脑室旁核下部区域，9 - 14%的钙结合蛋白细胞表达Fos，且这一比例不会随时间变化。在尼罗多乳鼠中，下丘脑室旁核下部区域中表达钙结合蛋白的神经元数量受转轮行为模式（夜行性与昼行性）和一天中的时间之间相互作用的影响。因此，尼罗多乳鼠和褐家鼠视交叉上核中钙结合蛋白阳性细胞的数量不同，而夜行性和昼行性尼罗多乳鼠下丘脑室旁核下部区域中钙结合蛋白阳性细胞的数量也不同。我们对褐家鼠和尼罗多乳鼠的研究表明，含钙结合蛋白的神经元与动物是夜行性还是昼行性之间可能存在重要关系。具体而言，褐家鼠视交叉上核中含钙结合蛋白的细胞中Fos表达比尼罗多乳鼠更多。相比之下，表现出昼行性和夜行性转轮行为模式的尼罗多乳鼠，在视交叉上核背侧的下丘脑室旁核下部区域中，含钙结合蛋白的细胞数量存在差异。
