Circadian characteristics of mice depleted with GPR7.

GPR7, now known as a receptor of neuropeptide B and neuropeptide W, is expressed in neurons of the suprachiasmatic nucleus (SCN), the mammalian circadian center. By the quantitative in situ hybridization, we demonstrated that GPR7 mRNA showed a significant circadian rhythm in the SCN showing a peak at early subjective night in both light-dark and constant dark. We characterized the circadian feature of GPR7-knockout mice, but the period length and the phase-dependent phase shift to light exposure were not disordered in GPR7-knockout mice. Moreover, the food-anticipatory behavior in restricted feeding schedule was observed in this gene-deleted mouse similar to wild-type. These results indicate that the role of GPR7 may be subtle or limited in relation to the circadian clock despite its robust expression in the SCN.