Journal
JOURNAL OF BIOLOGICAL RHYTHMS
Volume 29, Issue 5, Pages 346-354Publisher
SAGE PUBLICATIONS INC
DOI: 10.1177/0748730414547111
Keywords
circadian; entrainment; masking; sleep; irradiance; duration; photic
Categories
Funding
- National Institute of Neurological Disorders and Stroke [NS061804]
Ask authors/readers for more resources
Brief exposure of mice to nocturnal light causes circadian rhythm phase shifts, simultaneously inducing locomotor suppression, a drop in body temperature, and associated sleep. The exact nature of the relationship between these light-induced responses is uncertain, although locomotor suppression and phase shift magnitudes are related to stimulus irradiance. Whether stimulus duration has similar effects is less clear. Here, the relationship between stimulus duration and response magnitude was evaluated further using 100 mu W/cm(2) white light-emitting diode pulses administered for 30, 300, 1200, or 3000 sec. The results show that, in general, shorter pulses yielded smaller responses and larger pulses yielded larger responses. However, the 300-sec pulse failed to augment locomotor suppression compared with the effect of a 30-sec pulse (44.7 +/- 4.8 vs 40.6 +/- 2.0 min) but simultaneously induced much larger phase shifts (1.28 +/- 0.20 vs 0.52 +/- 0.11 h). The larger phase shifts induced by the 300-sec stimulus did not differ from those induced by either the 1200- or 3000-sec pulses (1.43 +/- 0.10 and 1.30 +/- 0.17 h, respectively). The results demonstrate differential photic regulation of the two response types. Pulses ranging from 300 to 3000 sec produce equal phase shifts (present data); pulses ranging from 30 to 600 sec produce equal locomotor suppression levels. Greater suppression can occur additively in response to pulses of 1200 sec or more (present data), but this is not true for phase shifts. Nocturnal light appears to trigger a fixed duration event, locomotor suppression, or phase shift, with the latter followed by a light-refractory interval during which locomotor suppression can additively increase. The results also provide further support for the view that temporal integration of photic energy applies, at best, across a limited set of stimulus durations for both light-induced locomotor suppression/sleep and phase shift regulation.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available