Page T L
Department of Biology, Vanderbilt University, Nashville, TN 37235, USA.
J Biol Rhythms. 2000 Apr;15(2):155-62. doi: 10.1177/074873040001500209.
The free-running period expressed by circadian clocks in constant environmental conditions is history dependent, and one effect of entrainment of circadian clocks by light cycles is to cause long-lasting changes in the free-running period that are termed aftereffects. It has been suggested that aftereffects are a consequence of the particular phase relationships among constituent oscillators of the circadian system that are established by the entrainment. In a test of this hypothesis, it is shown that aftereffects of entrainment of the free-running rhythm of nerve impulse activity from the eye of Bulla gouldiana are completely unaffected by treatment with 12-, 24-, or 48-h pulses of the translation inhibitor cycloheximide or with 24-h pulses of the transcription inhibitor DRB (5,6-dichlorobenzimidazole riboside). These treatments reset the phase of circadian oscillators generally and those in the eye of B. gouldiana specifically. The absence of any effect of the treatments indicates that aftereffects are independent of oscillator phase. These results suggest that history-dependent changes in period result from a novel, long-lasting, and previously unrecognized mechanism of action of light on the circadian pacemaking system. Furthermore, the data indicate that aftereffects can persist in the absence of translation, transcription, or the continued cycling of the circadian system.
在恒定环境条件下，生物钟所表现出的自由运行周期依赖于历史，而光周期对生物钟的一种影响是导致自由运行周期发生持久变化，这种变化被称为后效应。有人提出，后效应是由夹带所建立的昼夜节律系统组成振荡器之间特定相位关系所导致的结果。在对这一假设的测试中，研究表明，来自沟纹泡螺眼睛的神经冲动活动自由运行节律的夹带后效应，完全不受翻译抑制剂环己酰亚胺12小时、24小时或48小时脉冲处理，或转录抑制剂DRB（5,6 - 二氯苯并咪唑核糖苷）24小时脉冲处理的影响。这些处理通常会重置生物钟振荡器的相位，特别是沟纹泡螺眼睛中的振荡器相位。处理没有产生任何影响，这表明后效应与振荡器相位无关。这些结果表明，周期中依赖历史的变化源于光对昼夜节律起搏系统一种新的、持久的且以前未被认识的作用机制。此外，数据表明，在后效应在没有翻译、转录或昼夜节律系统持续循环的情况下仍可存在。
