Schaap J, Bos N P, de Jeu M T, Geurtsen A M, Meijer J H, Pennartz C M
Dept. of Physiology, Leiden Universitair Medisch Centrum, The Netherlands.
Brain Res. 1999 Jan 2;815(1):154-66. doi: 10.1016/s0006-8993(98)01025-7.
The suprachiasmatic nucleus is commonly considered to contain the main pacemaker of behavioral and hormonal circadian rhythms. Using whole-cell patch-clamp recordings, the membrane properties of suprachiasmatic nucleus neurons were investigated in order to get more insight in membrane physiological mechanisms underlying the circadian rhythm in firing activity. Circadian rhythmicity could not be detected either in spontaneous firing rate or in other membrane properties when whole-cell measurements were made following an initial phase shortly after membrane rupture. However, this apparent lack of rhythmicity was not due to an unhealthy slice preparation or to seal formation, as a clear day/night difference in firing rate was found in cell-attached recordings. Furthermore, in a subsequent series of whole-cell recordings, membrane properties were assessed directly after membrane rupture, and in this series we did find a significant day/night difference in spontaneous firing rate, input resistance and frequency adaptation. As concerns the participation of different subpopulations of suprachiasmatic nucleus neurons expressing circadian rhythmicity, cluster I neurons exhibited strong rhythmicity, whereas no day/night differences were found in cluster II neurons. Vasopressin-containing cells form a subpopulation of cluster I neurons and showed a more pronounced circadian rhythmicity than the total population of cluster I neurons. In addition to their strong rhythm in spontaneous firing rate they also displayed a day/night difference in membrane potential.
视交叉上核通常被认为包含行为和激素昼夜节律的主要起搏器。为了更深入了解放电活动昼夜节律背后的膜生理机制，利用全细胞膜片钳记录技术研究了视交叉上核神经元的膜特性。当在膜破裂后不久的初始阶段进行全细胞测量时，无论是自发放电率还是其他膜特性都未检测到昼夜节律性。然而，这种明显的节律性缺乏并非由于切片制备不健康或封接形成问题，因为在细胞贴附式记录中发现了明显的昼夜放电率差异。此外，在随后的一系列全细胞记录中，在膜破裂后直接评估膜特性，在这个系列中我们确实发现自发放电率、输入电阻和频率适应性存在显著的昼夜差异。关于表达昼夜节律性的视交叉上核神经元不同亚群的参与情况，I 型神经元表现出强烈的节律性，而 II 型神经元未发现昼夜差异。含血管加压素的细胞构成 I 型神经元的一个亚群，并且比 I 型神经元的总体表现出更明显的昼夜节律性。除了自发放电率有强烈节律外，它们的膜电位也存在昼夜差异。
