Inner retinal circadian clocks and non-visual photoreceptors: novel players in the circadian system.

GUIDO M. E.; GARBARINO-PICO EDUARDO; CONTÍN MARÍA A; VALDEZ DIEGO J; NIETO PAULA S; VERRA DANIELA M; ACOSTA RODRÍGUEZ V. A.; DE ZAVALÍA NURIA; ROSENSTEIN RUTH E

PROGRESS IN NEUROBIOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2010 vol. 92 p. 484 - 504

0301-0082

Inner retinal circadian clocks and non-visual photoreceptors: novel players in the circadian system.Daily and annual changes in ambient illumination serve as specific stimuli that associate light with time and regulate the physiology of the organism through the eye. The eye acts as a dual sense organ linking light and vision, and detecting light that provides specific stimuli for nonclassical photoreceptors located in the inner retina. These photoreceptors convey information to the master circadian pacemaker, the hypothalamic suprachiasmatic nuclei (SCN). Responsible for sensing the light that regulates several non-visual functions (i.e. behavior, pupil reflex, sleep, and pineal melatonin production), the retina plays a key role in the temporal symphony orchestra playing the musical score of life: it is intrinsically rhythmic in its physiological and metabolicactivities. We discuss here recent evidence in support of the hypothesis that retinal oscillatorsdistributed over different cell populations may act as clocks, inducing changes in the visual andcircadian system according to the time of the day. Significant progress has recently been made inidentifying photoreceptors/photopigments localized in retinal ganglion cells (RGCs) that setcircadian rhythms and modulate non-visual functions. Autonomous retinal and brain oscillatorscould have a more complex organization than previously recognized, involving a network of “RGC clock/SCN clock cross-talkE. The convergence of oscillatory and photoreceptive capacities of retinal cells could deeply impact on the circadian system, which in turn may be severely impaired in different retinal pathologies. The aim of this review is to discuss the state of the art on inner retinal cell involvement in the light and temporal regulation of health and disease.