Accession Number : ADA295056

Title :   Photoreceptors Regulating Circadian Behavior.

Descriptive Note : Final rept. 15 Mar 92-14 Mar 95,

Corporate Author : VIRGINIA UNIV CHARLOTTESVILLE

Personal Author(s) : Foster, Russell G.

PDF Url : ADA295056

Report Date : 14 MAR 1995

Pagination or Media Count : 14

Abstract : In mammals circadian responses to light are regulated by photoreceptors within the eye. Aged rd/rd mice (80-800 days) show unattenuated circadian responses to light but lack visual responses, while rodless transgenic mice (which lose rods earlier in development) show increased circadian responses to light. These data indicate that rod photoreceptors are not required for photoentrainment, but the early loss of rods may affect the development of the entrainment pathway. Aged rds/rds mice, lacking rod and cone outer segments, show circadian photo-sensitivities indistinguishable from +/+ animals. The circadian system of aged rd/rd mice shows spectral responses that are consistent with the involvement of the known mouse cone opsins (green cone-511 nm; UV cone-359 nm). Low levels of both the green and UV cone opsin mRNA remain with the eyes of aged rd/rd mice. The subcutaneous eyes of the blind mole rat are used to regulate circadian responses to light. Preliminary data suggest that these eyes contain a single opsin that most closely resembles a green cone opsin. Collectively these data suggests that photoentrainment in mammals is mediated by cones. However, if the residual cones mediate circadian responses to light then very few are needed to maintain sensitivity and they do not require an outer segment.

Descriptors :   *CIRCADIAN RHYTHMS, *PHOTORECEPTORS, ULTRAVIOLET RADIATION, MAMMALS, RATS, LIGHT, SPECTRA, RESIDUALS, RESPONSE, LOW LEVEL, ANIMALS, EXTERNAL, LOSSES, BEHAVIOR, VISION, EYE, RODS, MICE, CONICAL BODIES, GREEN(COLOR), ENTRAINMENT, SUBCUTANEOUS TISSUE.

Subject Categories : Anatomy and Physiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE