Grosse J, Velickovic A, Davis F C
Department of Biology, Northeastern University, Boston, Massachusetts 02115, USA.
Am J Physiol. 1996 Mar;270(3 Pt 2):R533-40. doi: 10.1152/ajpregu.1996.270.3.R533.
The circadian rhythms of fetal and neonatal rodents are entrained by their mother. This entrainment is dependent upon the maternal suprachiasmatic nucleus (SCN), but the mechanism of entrainment is unknown. Administration of the pineal hormone melatonin to pregnant, SCN-lesioned female Syrian hamsters entrains the activity rhythms of their hamster pups. The aim of this study was to determine whether melatonin injected directly in neonatal Syrian hamsters is able to entrain circadian rhythms and, if so, for how long this effect persists during development. Injection of melatonin in two groups of hamster pups at opposite phases on postnatal days 1-5 entrained the onset of activity rhythms on the day of weaning to two phases 10.67 h apart. Melatonin injection did not entrain activity rhythms to opposite phases on either postnatal days 6-10 or 21-25. Vehicle injection did not entrain animals to opposite phases at any of the ages studied. These results demonstrate that melatonin is able to act directly on the neonate to cause entrainment and that this effect disappears after postnatal day 6.
胎儿和新生啮齿动物的昼夜节律受其母亲的调节。这种调节依赖于母体的视交叉上核（SCN），但调节机制尚不清楚。给怀孕的、SCN损伤的雌性叙利亚仓鼠注射松果体激素褪黑素，可调节其幼崽的活动节律。本研究的目的是确定直接注射到新生叙利亚仓鼠体内的褪黑素是否能够调节昼夜节律，如果可以，这种作用在发育过程中持续多长时间。在出生后第1 - 5天的两个相反阶段给两组仓鼠幼崽注射褪黑素，使断奶当天的活动节律开始时间调整为相隔10.67小时的两个阶段。在出生后第6 - 10天或21 - 25天，注射褪黑素均未使活动节律调整到相反阶段。在任何研究的年龄段，注射赋形剂均未使动物的活动节律调整到相反阶段。这些结果表明，褪黑素能够直接作用于新生儿以引起节律调整，且这种作用在出生后第6天之后消失。
