title: Age affects photoentrainment in a nocturnal primate.
abstract: The endogenous circadian clock is entrained by external cues, mainly the light-dark cycle received by photopigments located in the retina. The authors investigated (1) the effect of aging on the synchronization of the rest-activity rhythm and (2) the physiological basis of light photoreception in the gray mouse lemur, a nocturnal Malagasy primate. Old individuals were tested at different irradiance levels under 3 different light wavelengths previously shown to trigger maximal response in young adults. Investigators analyzed animal activity and temperature waveforms and used 2 reference treatments, strong white light and continuous darkness. The investigation revealed manifold effects of aging picturing a general loss of responsiveness to light and age-related changes in activity and temperature. In addition, the investigation shows that photoentrainment is a continuous process. Short wavelengths (430 nm) are more efficient than longer wavelengths (470-540 nm) at low light levels at dawn and across all light levels at dusk. This suggests an implication of S-cones, differential at dawn and dusk. This results, surprising for several reasons, calls for further investigation. The study brings an interesting contribution to the understanding of the physiological processes underlying synchronization to light.
authors.affiliation: UMR 7179 CNRS (National Centre for Scientific Research), MNHN (National Museum of Natural History), Department of Ecology and Biodiversity Management, Brunoy, France.
authors.forename: Doris
authors.initials: D
authors.lastname: Gomez
authors.forename: Alexandra
authors.initials: A
authors.lastname: Barbosa
authors.forename: Marc
authors.initials: M
authors.lastname: Théry
authors.forename: Fabienne
authors.initials: F
authors.lastname: Aujard
authors.forename: Martine
authors.initials: M
authors.lastname: Perret
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001831:Body Temperature / Q000502:physiology / Q000528:radiation effects; D002940:Circadian Rhythm / Q000502:physiology / Q000528:radiation effects*; D005260:Female; D007900:Lemur / Q000502:physiology*; D008027:Light; D008270:Madagascar; D009043:Motor Activity / Q000502:physiology / Q000528:radiation effects; D017440:Photoperiod; D013997:Time Factors