Valdez et al. 2015, Invest Ophthalmol Vis Sci
PURPOSE: The vertebrate inner retina has a subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) that express the nonvisual photopigment melanopsin. The intrinsically photosensitive retinal ganglion cells send light information from the environment to the brain to control, among other parameters, the amount of energy entering the eyes through the pupillary light reflex (PLR). A daily variation in the PLR in both mice and humans has recently been shown, indicating circadian control of this response. In a previous work involving the sensitivity spectra for the PLR, we showed that blind chickens (GUCY1*) display the highest sensitivity to light of 480 nm. The aim of the present study was to evaluate the potential circadian control of PLR2 in blind birds under scotopic conditions.
METHODS: Circadian PLR was performed in GUCY1* with lights of different wavelengths (white or bue light of 475 nm) under scotopic conditions.
RESULTS: We found a significant daily variation in the PLRs of chickens exposed to white or blue ligth of 475nm, with increased sensitivity at circadian time 6 during the subjective day.
CONCLUSIONS: Our observations clearly point to circadian control of PLRs even in blindness, strongly indicating that both the entry of light into the eyes and its quality are differentially regulated durig the day in diurnal animals.
Authors: Valdez DJ, Nieto PS, Della Cosat NS, Schurrer C, Guido ME.