Humlová M, Illnerová H
Institute of Physiology, Czechoslovak Academy of Sciences, Prague.
J Pineal Res. 1992 Nov;13(4):151-7. doi: 10.1111/j.1600-079x.1992.tb00070.x.
Entraining effect of melatonin on the circadian rhythm in rat pineal N-acetyltransferase (NAT) activity was studied under various photoperiods. Melatonin administration prior to dark onset for 5 successive days phase-advanced the evening NAT rise under the light:dark (LD) cycle of either LD 10:14 or LD 8:16, but not under LD 12:12. It is assumed that under the latter regime, the end of a light period exhibited a phase-delaying effect on the NAT rise. The light exposure appeared to be a stronger Zeitgeber than melatonin itself. Data show that melatonin applied in the late light period advances the evening NAT rise under a short photoperiod only; under a longer photoperiod, the phase-advancing effect of melatonin may conflict with a phase-delaying effect of the end of a light period, and the effect of light exposure overrides that of melatonin.
在不同光周期条件下，研究了褪黑素对大鼠松果体N - 乙酰基转移酶（NAT）活性昼夜节律的同步作用。在黑暗开始前连续5天给予褪黑素，在10:14或8:16的光照:黑暗（LD）周期下，可使傍晚NAT活性升高提前出现相位变化，但在12:12的LD周期下则无此现象。据推测，在后一种光照周期条件下，光照期结束对NAT活性升高表现出相位延迟作用。光照似乎是比褪黑素本身更强的授时因子。数据表明，仅在短光周期条件下，在光照后期应用褪黑素可使傍晚NAT活性升高提前出现相位变化；在较长光周期条件下，褪黑素的相位提前作用可能与光照期结束的相位延迟作用相冲突，且光照的作用超过了褪黑素的作用。
