Hofstetter John R, Hofstetter Amelia R, Hughes Amanda M, Mayeda Aimee R
Roudebush VA Medical Center, 1481 W. 10th St, Indianapolis, IN 46202, USA.
J Circadian Rhythms. 2005 May 31;3:8. doi: 10.1186/1740-3391-3-8.
We observed that a dim, red light-emitting diode (LED) triggered by activity increased the circadian periods of lab mice compared to constant darkness. It is known that the circadian period of rats increases when vigorous wheel-running triggers full-spectrum lighting; however, spectral sensitivity of photoreceptors in mice suggests little or no response to red light. Thus, we decided to test the following hypotheses: dim red light illumination triggered by activity (LEDfb) increases the circadian period of mice compared to constant dark (DD); covering the LED prevents the effect on period; and DBA2/J mice have a different response to LEDfb than C57BL6/J mice.
The irradiance spectra of the LEDs were determined by spectrophotometer. Locomotor activity of C57BL/6J and DBA/2J mice was monitored by passive-infrared sensors and circadian period was calculated from the last 10 days under each light condition. For constant dark (DD), LEDs were switched off. For LED feedback (LEDfb), the red LED came on when the mouse was active and switched off seconds after activity stopped. For taped LED the red LED was switched on but covered with black tape. Single and multifactorial ANOVAs and post-hoc t-tests were done.
The circadian period of mice was longer under LEDfb than under DD. Blocking the light eliminated the effect. There was no difference in period change in response to LEDfb between C57BL/6 and DBA/2 mice.
An increase in mouse circadian period due to dim far-red light (1 lux at 652 nm) exposure was unexpected. Since blocking the light stopped the response, sound from the sensor's electronics was not the impetus of the response. The results suggest that red light as background illumination should be avoided, and indicator diodes on passive infrared motion sensors should be switched off.
我们观察到，与持续黑暗相比，由活动触发的昏暗红色发光二极管（LED）会延长实验室小鼠的昼夜节律周期。已知当剧烈的轮转运动触发全光谱照明时，大鼠的昼夜节律周期会延长；然而，小鼠光感受器的光谱敏感性表明其对红光几乎没有反应或无反应。因此，我们决定检验以下假设：与持续黑暗（DD）相比，由活动触发的昏暗红光照明（LEDfb）会延长小鼠的昼夜节律周期；遮挡LED可防止对周期产生影响；并且DBA2/J小鼠对LEDfb的反应与C57BL6/J小鼠不同。
通过分光光度计测定LED的辐照光谱。使用被动红外传感器监测C57BL/6J和DBA/2J小鼠的运动活动，并根据每种光照条件下的最后10天计算昼夜节律周期。对于持续黑暗（DD），关闭LED。对于LED反馈（LEDfb），当小鼠活动时红色LED亮起，活动停止后几秒关闭。对于用胶带粘贴的LED，红色LED开启但用黑色胶带覆盖。进行单因素和多因素方差分析以及事后t检验。
与DD相比，LEDfb条件下小鼠的昼夜节律周期更长。遮挡光线消除了这种影响。C57BL/6和DBA/2小鼠对LEDfb的周期变化没有差异。
由于暴露于昏暗远红光（652nm处1勒克斯）导致小鼠昼夜节律周期延长是出乎意料的。由于遮挡光线会停止反应，传感器电子设备发出的声音不是反应的推动力。结果表明应避免将红光用作背景照明，并且被动红外运动传感器上的指示灯二极管应关闭。
