Flemmer D D, Dilsaver S C, Peck J A
Department of Psychiatry, University of Texas School of Medicine, Houston 77225.
Pharmacol Biochem Behav. 1991 Jan;38(1):227-30. doi: 10.1016/0091-3057(91)90617-b.
Bright artificial light is used to treat patients with major depression with a seasonal component ("Winter Depression"). Hyperactivity of muscarinic cholinergic systems is implicated in the pathophysiology of depression. Continual exposure to bright light for 7 days or during discrete portions of the photoperiod blunts the thermic response to a muscarinic agonist (oxotremorine) in the rat. Exposure to either 24 hours per day of bright light (in contrast to periods of circumscribed exposure) or darkness would tend to produce free-running. Observers have suggested that the reduced responsiveness to oxotremorine may result from the induction of free-running (the "free-running hypothesis"). The "free-running hypothesis" leads to the prediction that rats exposed to constant darkness will exhibit a reduction in thermic responsiveness to oxotremorine. The authors hypothesized that constant exposure to darkness would, contrary to the "free-running hypothesis," enhance the thermic response to oxotremorine. Rats (n = 12) exposed to constant darkness for 7 days exhibited super-sensitivity to oxotremorine 5 days after return to standard light/dark cycle in the vivarium. This argues against the hypothesis that the induction of free-running enhances sensitivity to the thermic effects of oxotremorine.
明亮的人造光被用于治疗伴有季节性因素的重度抑郁症患者（“冬季抑郁症”）。毒蕈碱胆碱能系统功能亢进与抑郁症的病理生理学有关。持续7天或在光周期的特定时间段内持续暴露于明亮光线下，会减弱大鼠对毒蕈碱激动剂（氧化震颤素）的热反应。每天暴露于24小时明亮光线下（与有限暴露期相比）或黑暗中会倾向于产生自由运行。观察家认为，对氧化震颤素反应性降低可能是由于自由运行的诱导（“自由运行假说”）。“自由运行假说”导致这样的预测，即暴露于持续黑暗中的大鼠对氧化震颤素的热反应性会降低。作者假设，与“自由运行假说”相反，持续暴露于黑暗中会增强对氧化震颤素的热反应。暴露于持续黑暗中7天的大鼠（n = 12）在返回饲养室的标准明暗循环5天后，对氧化震颤素表现出超敏感性。这与自由运行的诱导会增强对氧化震颤素热效应敏感性的假说相悖。
