Circadian expression of clock gene in the optic tectum of Japanese quail

The physiological activity of avian optic tectum (TeO) is known to be regulated by the circadian system. In a previous study, we found clock gene expression in the TeO of Japanese quail. Here we report rhythmic expression of the Per2 gene in the stratum griseum et fibrosum (SGF) of the TeO under a light-dark (LD) cycle, constant darkness (DD), and constant light (LL) conditions. However, light pulse did not affect Per2 expression in the TeO. These results suggest that light stimulus and melatonin rhythm are not essential for rhythmic expression of Per2 in the avian TeO in spite of the localization of melatonin receptors and retinal input.