The circadian pacemaker generates similar circadian rhythms in the fractal structure of heart rate in humans and rats
The circadian pacemaker generates similar circadian rhythms in the fractal structure of heart rate in humans and rats
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DOI：
10.1093/cvr/cvn150
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发表时间：
2008-10-01
影响因子：
10.8
通讯作者：
Shea, Steven A.
中科院分区：
文献类型：
--
作者：
Hu, Kun;Scheer, Frank A. J. L.;Shea, Steven A.
人类不良心血管事件的发生具有昼夜模式，可能与日常行为模式或心血管变量的内源性昼夜节律有关。健康人在心跳波动中具有尺度不变/分形结构，表现出内源性昼夜节律和在心血管疾病中观察到的与心血管不良事件广泛高峰时间（上午10点左右）相对应的昼夜节律阶段的结构变化。为了探索休息/活动周期、内源性昼夜节律和心脏易感性之间的关系，我们测试了夜间活动的哺乳动物（Wistar大鼠）与白天活动的人类相比，心率的分形结构是否表现出相似的昼夜节律，以及在损伤大鼠的昼夜节律起搏器（视交叉上核，SCN）后，这种分形结构如何变化。方法和结果对8只完整的Wistar大鼠和6只scn损伤的Wistar大鼠在持续黑暗条件下10天的心率数据进行分析，结果表明：(1)与人类一样，大鼠在生理日（大鼠为非活动期，人类为活动期）表现出内源性的昼夜节律，表征心率的小时分形结构（P = 0.0005）；（ii） SCN损伤破坏了心率分形结构中的节律，系统地增加了标度指数（P = 0.01）。结论大鼠心率具有分形结构的昼夜节律，其时间模式与人类相似，尽管两者之间的休息/活动周期相反。SCN赋予这种内源性节律。此外，大鼠的SCN损伤会导致更大的缩放指数，就像人类心血管疾病一样。
Aims Adverse cardiovascular events in humans occur with a day/night pattern, presumably related to a daily pattern of behaviours or endogenous circadian rhythms in cardiovascular variables. Healthy humans possess a scale-invariant/fractal structure in heartbeat fluctuations that exhibits an endogenous circadian rhythm and changes towards the structure observed in cardiovascular disease at the circadian phase corresponding to the time of the broad peak of adverse cardiovascular events (at about 10 AM). To explore the relationship between the rest/activity cycle, endogenous circadian rhythmicity, and cardiac vulnerability, we tested whether the fractal structure of heart rate exhibits a similar circadian rhythm in a mammalian species that is nocturnally active (Wistar rats) compared with diurnally active humans, and how this fractal structure changes after lesioning the circadian pacemaker (suprachiasmatic nucleus, SCN) in rats.Methods and results Analysis of heart rate data collected over 10 days in eight intact and six SCN-lesioned Wistar rats during constant darkness revealed that: (i) as with humans, rats exhibit an endogenous circadian rhythm in the scaling exponent characterizing the hourly fractal structure of heart rate (P = 0.0005) with larger exponents during the biological day (inactive phase for rats; active phase for humans); (ii) SCN lesioning abolished the rhythm in the fractal structure of heart rate and systematically increased the scaling exponent (P = 0.01).Conclusion Rats possess a circadian rhythm of fractal structure of heart rate with a similar temporal pattern as previously observed in humans despite opposite rest/activity cycles between the two species. The SCN imparts this endogenous rhythm. Moreover, lesioning the SCN in rats results in a larger scaling exponent, as occurs with cardiovascular disease in humans.