Kalsbeek A, van Heerikhuize J J, Wortel J, Buijs R M
Netherlands Institute for Brain Research, Amsterdam.
J Biol Rhythms. 1998 Feb;13(1):18-29. doi: 10.1177/074873098128999880.
The authors have shown previously that vasopressin (VP) release from suprachiasmatic nucleus (SCN) efferents in rats is important for the timing of the circadian activity of the hypothalamo-pituitary-adrenal (HPA) axis, resulting in a circadian rise in corticosterone at dusk. When meals are supplied at a fixed time during the light period, however, this normal circadian activity of the HPA axis is strongly modified. Under such a restricted feeding regimen, a corticosterone peak appears just before the daily meal in addition to the circadian corticosterone peak at dusk. This feeding-associated rise in corticosterone is regarded as an SCN-independent circadian rhythm because it is sustained in SCN-lesioned animals. Despite these previous results, the authors investigated a putative involvement of SCN-derived VP in the control of the prefeeding corticosterone peak by measuring the intranuclear release of VP in the SCN and plasma corticosterone levels in rats in ad libitum feeding conditions as well as in animals that were obliged to feed during a 2-h period in the middle of the light period. Restricted daytime feeding caused clear changes in the daily release pattern of VP from SCN terminals. Both a delayed onset of the diurnal rise and a premature decline of the elevated daytime levels were observed, but the acrophase of the VP rhythm was not phase shifted. Concerning the circadian corticosterone peak, no phase shift of its acrophase was observed either. It is concluded that (1) restricted daytime feeding does affect SCN activity, (2) intranuclear release of VP within the SCN is an important mechanism to amplify and synchronize the circadian rhythms as dictated by the light/dark-entrained circadian pacemaker, and (3) VP release observed in animals on restricted feeding is completely compatible with the previously proposed inhibitory action of SCN-derived VP on the HPA axis.
作者先前已表明，大鼠视交叉上核（SCN）传出神经释放的血管加压素（VP）对于下丘脑 - 垂体 - 肾上腺（HPA）轴昼夜活动的定时很重要，导致黄昏时皮质酮出现昼夜性升高。然而，当在光照期固定时间供应食物时，HPA轴的这种正常昼夜活动会受到强烈改变。在这种限时进食方案下，除了黄昏时的昼夜皮质酮峰值外，在每日进食前还会出现一个皮质酮峰值。这种与进食相关的皮质酮升高被视为一种不依赖SCN的昼夜节律，因为它在SCN损伤的动物中仍然存在。尽管有这些先前的结果，作者通过测量自由进食条件下以及在光照期中间2小时内必须进食的动物的SCN内核内VP释放和血浆皮质酮水平，研究了SCN衍生的VP在控制进食前皮质酮峰值中的假定作用。白天限时进食导致SCN终末VP的每日释放模式发生明显变化。观察到昼夜升高的起始延迟以及白天升高水平的过早下降，但VP节律的峰相位没有发生相移。关于昼夜皮质酮峰值，其峰相位也未观察到相移。得出的结论是：（1）白天限时进食确实会影响SCN活动；（2）SCN内核内VP的释放是一种重要机制，可放大和同步由明暗节律起搏器决定的昼夜节律；（3）在限时进食动物中观察到的VP释放与先前提出的SCN衍生的VP对HPA轴的抑制作用完全一致。
