Light responsiveness of clock genes, Per1 and Per2, in the olfactory bulb of mice

► mRNAs of Per1, Per2 and Bmal1 in the Olfactory bulb (OB) showed significant circadian rhythms. ► Per1 and PER2 were mainly expressed in the mitral cell and granular cell layers of OB. ► Light responsiveness of Per1 and Per2 expression was different in the OB from that in the parietal cortex.