Hofman M A, Swaab D F
Netherlands Institute for Brain Research, Graduate School of Neurosciences, Amsterdam.
J Biol Rhythms. 1993 Winter;8(4):283-95. doi: 10.1177/074873049300800402.
The mammalian suprachiasmatic nucleus (SCN) is considered to be a critical component of a neural system implicated in the temporal organization of a wide variety of biological processes. Since the environmental light-dark cycle is the main zeitgeber for many of these rhythms, photic information may have a synchronizing effect on the endogenous clock in the SCN by inducing periodic changes in the activity of certain groups of neurons. The present study was conducted to investigate whether the daily light-dark cycle as well as seasonal variations in photoperiod would affect the vasopressin cell population of the human SCN. To that end, the brains of 30 young human subjects (ranging in age from 6 to 47 years) were investigated. We found that the subdivision of the human SCN that contains vasopressin-producing neurons fluctuated significantly over the 24-hr period. The volume of the vasopressin cell population was, on average, 1.4 times as large during the daytime (1000-1800 hr) as during the nighttime (2200-0600 hr), and contained 1.8 times as many vasopressin-immunoreactive neurons. Peak values in both vasopressin volume and vasopressin cell number were observed in the early morning (0600-1000 hr). In general, the SCN contained fewer vasopressin-immunoreactive neurons during the night than during any other period of the natural light-dark cycle. In addition to the diurnal cycle of the SCN, a marked seasonal rhythm was observed. The volume of the vasopressin cell population was, on average, 2.4 times as large in the autumn as in the summer, and contained 3 times as many vasopressin-immunoreactive neurons. In general, the annual cycle of the human SCN showed a nonsinusoidal pattern with a maximum in early autumn, a lower plateau in winter, and a deep trough in late spring and early summer. In contrast with the periodic fluctuations in the number of vasopressin-immunoreactive neurons in the SCN, no significant diurnal or seasonal variations could be detected in the numerical cell density or cell nuclear diameter of vasopressin neurons. In conclusion, the findings indicate that the synthesizing activity of the vasopressin neurons of the human SCN exhibits a diurnal as well as a seasonal rhythm, and that the temporal organization of these processes becomes disturbed later in life.
哺乳动物的视交叉上核（SCN）被认为是一个神经系统的关键组成部分，该系统与多种生物过程的时间组织有关。由于环境光暗周期是许多这些节律的主要授时因子，光信息可能通过诱导某些神经元群活动的周期性变化，对SCN中的内源性时钟产生同步作用。本研究旨在调查每日光暗周期以及光周期的季节性变化是否会影响人类SCN中的加压素细胞群。为此，对30名年轻人类受试者（年龄在6至47岁之间）的大脑进行了研究。我们发现，人类SCN中含有产生加压素神经元的细分区域在24小时内有显著波动。加压素细胞群的体积在白天（1000 - 1800时）平均是夜间（2200 - 0600时）的1.4倍，且含有加压素免疫反应性神经元的数量是夜间的1.8倍。加压素体积和加压素细胞数量的峰值出现在清晨（0600 - 1000时）。一般来说，SCN中加压素免疫反应性神经元在夜间比自然光暗周期的任何其他时间段都少。除了SCN的昼夜节律外，还观察到明显的季节性节律。加压素细胞群的体积在秋季平均是夏季的2.4倍，且含有加压素免疫反应性神经元的数量是夏季的3倍。一般来说，人类SCN的年度周期呈现出非正弦模式，在初秋达到最大值，冬季处于较低平台期，在晚春和初夏出现深谷。与SCN中加压素免疫反应性神经元数量的周期性波动相反，在加压素神经元的细胞数密度或细胞核直径方面未检测到显著的昼夜或季节性变化。总之，研究结果表明，人类SCN中加压素神经元的合成活动呈现出昼夜节律以及季节性节律，并且这些过程的时间组织在生命后期会受到干扰。
