Kanematsu N, Honma S, Katsuno Y, Honma K
Department of Physiology, Hokkaido University School of Medicine, Sapporo, Japan.
Am J Physiol. 1994 Jun;266(6 Pt 2):R1849-55. doi: 10.1152/ajpregu.1994.266.6.R1849.
Melatonin in the extracellular space of the pineal gland was measured continuously for 4 consecutive days from single, freely moving rats by means of in vivo microdialysis. A robust circadian rhythm was observed in the pineal extracellular melatonin under both light-dark (LD) and continuous dark (DD) conditions, the patterns of which were almost identical for 4 days within individuals but varied substantially among individuals. The offset phase of melatonin rhythm was more stable than the onset phase. Light-induced phase shift of melatonin rhythm was measured in individual rats, which had been entrained to LD and subsequently released into DD. On the 1st day in DD, a 3-min light pulse of 200 lx was applied either at circadian time (CT) of 17 or 22 h (5 and 10 h after the dark onset, respectively). The light pulse rapidly suppressed the nocturnal melatonin level. The rate as well as the level of melatonin suppression was significantly greater by the pulse at CT22 than at CT17. A phase shift of the melatonin rhythm was calculated on the 2nd and 3rd days in DD. Significant phase delay shift was observed after the pulse at CT17 and advance shift after the pulse at CT22 of approximately 1 h in either case. Because the amount of phase shift was not different between the 2nd and 3rd days in DD, the phase shift of pineal melatonin rhythm by single light pulse seems to be completed immediately.
通过体内微透析技术，对单独自由活动的大鼠松果体胞外空间的褪黑素进行了连续4天的测量。在明暗（LD）和持续黑暗（DD）条件下，均观察到松果体胞外褪黑素存在强烈的昼夜节律。其模式在个体内4天几乎相同，但个体间差异很大。褪黑素节律的偏移期比起始期更稳定。在已适应LD并随后转入DD的个体大鼠中测量了褪黑素节律的光诱导相移。在DD的第1天，分别在昼夜时间（CT）17或22小时（分别在黑暗开始后5和10小时）施加200勒克斯的3分钟光脉冲。光脉冲迅速抑制夜间褪黑素水平。CT22时的脉冲对褪黑素的抑制速率和水平均显著高于CT17时的脉冲。在DD的第2天和第3天计算了褪黑素节律的相移。在CT17时的脉冲后观察到显著的相位延迟相移，在CT22时的脉冲后观察到提前相移，两种情况下均约为1小时。由于在DD的第2天和第3天之间相移量无差异，单次光脉冲引起的松果体褪黑素节律相移似乎立即完成。
