Restricted-feeding-induced anticipatory activity rhythm is associated witha phase-shift of the expression of mPer1 and mPer2 mRNA in the cerebral cortex and hippocampus but not in the suprachiasmatic nucleus of mice

Daily restricted feeding (RF) can produce food-entrainable oscillations in both intact and suprachiasmatic nucleus (SCN)-lesioned animals. Thus, there are two circadian rhythms, one of which is SCN-dependent and the other SCN -independent. Recently, it has been established that several mouse clock ge nes, such as mPer1, mPer2 and mPer3 are expressed in the SCN and other brai n tissues. Although the role of mPer genes expressed in the SCN has recentl y been evaluated in the SCN-dependent rhythm, their function in the SCN-ind ependent rhythm is still poorly understood. In order to understand the role of these genes in SCN-independent rhythm, we examined the expression patte rn of mPer1 and mPer2 mRNA in each brain area of mice under RF. Mice were a llowed access to food for 4 h during either the daytime under a light-dark cycle or the subjective daytime under constant dark. After 6 days of schedu led RF, the night-time or subjective night-time peak of mPer mRNA changed t o a daytime peak in the cerebral cortex and hippocampus, with moderate expr ession in the striatum, pyriform cortex and paraventricular nucleus, and no expression in the SCN. The daytime peak in the cerebral cortex returned to a night-time peak after the release of RF to a free-feeding schedule. Alth ough the basal rhythm of mPer expression disappeared in SCN-lesioned mice, RF produced mPer mRNA rhythm in the cerebral cortex of these mice. The pres ent results provide evidence of an association between food-entrainable osc illations and the expression of mPer1 and mPer2 in the cerebral cortex and hippocampus.