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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

The circadian period of both DBA/2 and C57BL/6 mice under DD (filled symbols) and dim red LEDfb (open symbols). Lines show the mean period for each group. Overall, mice had longer period under LEDfb than DD (p < 0.025), and C57BL/6 mice had longer periods than DBA/2 mice (p < 0.01).
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Figure 7: The circadian period of both DBA/2 and C57BL/6 mice under DD (filled symbols) and dim red LEDfb (open symbols). Lines show the mean period for each group. Overall, mice had longer period under LEDfb than DD (p < 0.025), and C57BL/6 mice had longer periods than DBA/2 mice (p < 0.01).

Mentions: Representative actograms of DBA/2 and C57BL/6 mice under DD and dim red LEDfb are shown in Figure 6. For C57BL/6 mice, the mean period under DD was 23.85 ± 0.07 h; the mean period under LEDfb was 24.00 ± 0.07 h. For DBA/2 mice, the mean period under DD was 23.46 ± 0.14 h; the mean period under LEDfb was 23.78 ± 0.08 h. A two-factor ANOVA testing for effect of strain and lighting condition (LEDfb compared to DD) showed a significant effect of both strain [F1,14 = 7.73, p = 0.0147] and lighting condition [F1,14 = 10.99, p = 0.0051] but no interaction. A post-hoc Tukey's test showed longer period with LEDfb compared to DD (p < 0.025). The C57BL/6 mice had different periods from the DBA/2 mice by post-hoc Tukey's test (p < 0.01). Figure 7 shows the effects of LEDfb on the circadian period of locomotor activity in the two strains of mice.


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)

The circadian period of both DBA/2 and C57BL/6 mice under DD (filled symbols) and dim red LEDfb (open symbols). Lines show the mean period for each group. Overall, mice had longer period under LEDfb than DD (p < 0.025), and C57BL/6 mice had longer periods than DBA/2 mice (p < 0.01).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: The circadian period of both DBA/2 and C57BL/6 mice under DD (filled symbols) and dim red LEDfb (open symbols). Lines show the mean period for each group. Overall, mice had longer period under LEDfb than DD (p < 0.025), and C57BL/6 mice had longer periods than DBA/2 mice (p < 0.01).
Mentions: Representative actograms of DBA/2 and C57BL/6 mice under DD and dim red LEDfb are shown in Figure 6. For C57BL/6 mice, the mean period under DD was 23.85 ± 0.07 h; the mean period under LEDfb was 24.00 ± 0.07 h. For DBA/2 mice, the mean period under DD was 23.46 ± 0.14 h; the mean period under LEDfb was 23.78 ± 0.08 h. A two-factor ANOVA testing for effect of strain and lighting condition (LEDfb compared to DD) showed a significant effect of both strain [F1,14 = 7.73, p = 0.0147] and lighting condition [F1,14 = 10.99, p = 0.0051] but no interaction. A post-hoc Tukey's test showed longer period with LEDfb compared to DD (p < 0.025). The C57BL/6 mice had different periods from the DBA/2 mice by post-hoc Tukey's test (p < 0.01). Figure 7 shows the effects of LEDfb on the circadian period of locomotor activity in the two strains of mice.

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