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Intermittent long-wavelength red light increases the period of daily locomotor activity in mice.

Hofstetter JR, Hofstetter AR, Hughes AM, Mayeda AR - J Circadian Rhythms (2005)

Bottom Line: Blocking the light eliminated the effect.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Roudebush VA Medical Center, 1481 W. 10th St, Indianapolis, IN 46202, USA. jhofstet@iupui.edu

ABSTRACT

Background: 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.

Methods: 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.

Results: 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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus

Double-plotted actograms of C57BL/6 mice under DD, dim red LEDfb, and LEDs covered with black tape. Lighting conditions are shown to the right of each actogram. Arrows show onset of new lighting conditions.
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Figure 4: Double-plotted actograms of C57BL/6 mice under DD, dim red LEDfb, and LEDs covered with black tape. Lighting conditions are shown to the right of each actogram. Arrows show onset of new lighting conditions.

Mentions: Representative actograms of C57BL/6 mice under DD, dim red LEDfb, and LEDs coved with black tape are shown in Figure 4. The mean period of 12 mice in DD was 23.96 ± 0.03 h; under taped LEDs, it was 23.93 ± 0.03 h; and, under LEDfb, it was 24.07 ± 0.03 h. There was a significant effect of lighting condition by one-way ANOVA [F2,33 = 7.02, p = 0.0029]. A post-hoc Tukey's test showed a longer period under the uncovered LED than under the tape-covered LED (p < 0.01) or DD (p < 0.025), as summarized in Figure 5. Periods did not differ between DD and tape-covered LED.


Intermittent long-wavelength red light increases the period of daily locomotor activity in mice.

Hofstetter JR, Hofstetter AR, Hughes AM, Mayeda AR - J Circadian Rhythms (2005)

Double-plotted actograms of C57BL/6 mice under DD, dim red LEDfb, and LEDs covered with black tape. Lighting conditions are shown to the right of each actogram. Arrows show onset of new lighting conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1173135&req=5

Figure 4: Double-plotted actograms of C57BL/6 mice under DD, dim red LEDfb, and LEDs covered with black tape. Lighting conditions are shown to the right of each actogram. Arrows show onset of new lighting conditions.
Mentions: Representative actograms of C57BL/6 mice under DD, dim red LEDfb, and LEDs coved with black tape are shown in Figure 4. The mean period of 12 mice in DD was 23.96 ± 0.03 h; under taped LEDs, it was 23.93 ± 0.03 h; and, under LEDfb, it was 24.07 ± 0.03 h. There was a significant effect of lighting condition by one-way ANOVA [F2,33 = 7.02, p = 0.0029]. A post-hoc Tukey's test showed a longer period under the uncovered LED than under the tape-covered LED (p < 0.01) or DD (p < 0.025), as summarized in Figure 5. Periods did not differ between DD and tape-covered LED.

Bottom Line: Blocking the light eliminated the effect.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Roudebush VA Medical Center, 1481 W. 10th St, Indianapolis, IN 46202, USA. jhofstet@iupui.edu

ABSTRACT

Background: 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.

Methods: 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.

Results: 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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus