Rosenwasser A M
Department of Psychology, University of Maine, Orono 04469-5742, USA.
Physiol Behav. 1996 Aug;60(2):373-9.
Chronic treatment of rats with clonidine, an alpha-adrenoceptor agonist, alters the period and amplitude of free-running circadian activity rhythms, as well as the level of home cage locomotor activity. Agents that alter free-running period are presumed to act directly on the circadian pacemaker or on its input pathways. Because shortening of free-running period during clonidine treatment has been observed consistently under constant light but not under constant darkness, and because increasing light intensity itself lengthens free-running period, this agent may influence the circadian pacemaker by modulating light-evoked activity in the photic input pathway. The present study reexamined the possible dependence of clonidine-induced alterations of free-running circadian activity rhythms on lighting conditions. Similar effects were seen in both constant light and constant darkness, indicating that the effects of clonidine on the circadian pacemaker are not due to blockade of light-evoked activity in the photic input pathway. Instead, clonidine may act directly on the circadian pacemaker, or on other unspecified mechanisms influencing free-running period.
用α-肾上腺素能受体激动剂可乐定对大鼠进行长期治疗，会改变其自由活动的昼夜节律活动的周期和幅度，以及笼内自发活动水平。人们推测，改变自由活动周期的药物是直接作用于昼夜节律起搏器或其输入通路。由于在持续光照而非持续黑暗条件下，始终观察到可乐定治疗期间自由活动周期缩短，且由于增加光照强度本身会延长自由活动周期，因此这种药物可能通过调节光输入通路中的光诱发活动来影响昼夜节律起搏器。本研究重新审视了可乐定诱导的自由活动昼夜节律活动变化对光照条件的可能依赖性。在持续光照和持续黑暗条件下均观察到类似效应，这表明可乐定对昼夜节律起搏器的作用并非由于阻断了光输入通路中的光诱发活动。相反，可乐定可能直接作用于昼夜节律起搏器，或作用于影响自由活动周期的其他未明确机制。
