Rusak B, Yu G D
Department of Biomedical Sciences, McMaster University, Hamilton, Ont., Canada.
Brain Res. 1993 Feb 5;602(2):200-4. doi: 10.1016/0006-8993(93)90683-e.
As a test of the origin of the melatonin-sensitivity rhythm recorded from SCN cells in brain slices from intact Syrian hamsters, hamsters were either pinealectomized to remove the influence of endogenous melatonin, or sham operated. Cells from sham-operated hamsters showed a trough in responsiveness during the projected night. Pinealectomy eliminated the daily rhythm of melatonin responsiveness, reduced the proportions of cells responding to melatonin, and raised response thresholds in those cells that did not meet the criterion for responsiveness. Pinealectomy also altered the firing-rate rhythm so that the morning peak in firing rate was not sustained and the nocturnal trough was attenuated, leading to a firing-rate rhythm with reduced amplitude compared to those recorded from sham-operated or intact animals. These results indicate a role for endogenous melatonin in regulating both melatonin sensitivity and the integrity of the SCN firing-rate rhythm, and they suggest why pinealectomy can disrupt circadian organization in some situations.
为了测试从完整叙利亚仓鼠脑切片的视交叉上核（SCN）细胞记录到的褪黑素敏感性节律的起源，仓鼠要么被摘除松果体以消除内源性褪黑素的影响，要么进行假手术。假手术仓鼠的细胞在预计的夜间反应性出现低谷。摘除松果体消除了褪黑素反应性的每日节律，降低了对褪黑素产生反应的细胞比例，并提高了那些不符合反应性标准的细胞的反应阈值。摘除松果体还改变了放电频率节律，使得早晨的放电频率峰值不再持续，夜间低谷减弱，导致与假手术或完整动物记录到的相比，放电频率节律的振幅降低。这些结果表明内源性褪黑素在调节褪黑素敏感性和SCN放电频率节律的完整性方面发挥作用，并且它们解释了为什么摘除松果体在某些情况下会破坏昼夜节律组织。
