Increased late night response to light controls the circadian pacemaker in a nocturnal primate.
The mammalian endogenous circadian clock, the suprachiasmatic nuclei, receives environmental inputs, namely the light-dark cycle, through photopigments located in the eye and from melanopsin-expressing retinal ganglion cells. The authors investigated the influence of light wavelength and intensity on the synchronization of the rest-activity rhythm of the gray mouse lemur, a nocturnal Malagasy primate. Animals were tested at different irradiance levels (320, 45, 13, and 6 nmol x m(-2) x s(- 1)) under several light wavelengths (from 400 to 610 nm). Several parameters including circadian period, activity, and body temperature waveforms were used to assess synchronization to a 12:12 light-dark cycle in comparison to control treatments (12:12 white light or continuous darkness). Entrainment of the circadian rest-activity cycle increased with light intensity. It was more efficient for mid wavelengths relative to shorter or longer wavelengths but not coincident with melanopsin maximal sensitivity, suggesting other photoreceptors are likely involved in lemurs' photoentrainment. The authors obtained a novel synchronization pattern characterized by a clear synchronization to lights-on only without phasing to lights-off. Changes in photo-responsiveness at dusk and dawn highlight differential responses of evening and morning oscillators in the circadian clock.
Perret
Martine
M
UMR 7179 Centre National de la Recherche Scientifique, Muséum National d'Histoire Naturelle, Département d'Ecologie et Gestion de la Biodiversité, Brunoy, France. martine.perret@wanadoo.fr
Gomez
Doris
D
Barbosa
Alexandra
A
Aujard
Fabienne
F
Théry
Marc
M
D000204:Activity Cycles / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D001831:Body Temperature; D016565:Cheirogaleidae; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects*; D005260:Female; D008027:Light; D008297:Male; D009043:Motor Activity / Q000502:physiology / Q000528:radiation effects; D010775:Photic Stimulation; D017440:Photoperiod; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D017299:Rod Opsins; D000099210:Melanopsin
D017299:Rod Opsins; D000099210:Melanopsin