Circadian pattern, light responsiveness and localization of rPer1 and rPer2 gene expression in the rat retina

Circadian expression, light-responsiveness and localization of clock genes, rPer1 and rPer2, were examined in the rat retina under constant darkness. A significant circadian variation was detected in rPer2 transcript levels w ith a peak at ZT14, but not in the rPer1. A light pulse given after constan t darkness of 3 days increased both rPer1 and rPer2 expression phase-depend ently, while rPer1 was induced at more times than rPer2. A major site of th ese gene expression within the retina was the inner nuclear layer. These fi ndings indicate that rPer1 and rPeR2 genes play different roles in the gene ration and regulation of circadian rhythms in the retina from those in the suprachiasmatic nucleus. NeuroReport 12:471-475 (C) 2001 Lippincott William s & Wilkins.