The neural mechanisms underlying the food-associated rhythms in mice

Abstract

Clock gene expression rhythm in the dorsomedial hypothalamic nucleus (DMH) correlates well with food-anticipatory activity (FAA) rhythm. As acute feeding (AF) after fasting is an important first step to establish FAA rhythm, we examined the involvement of the DMH in both AF and FAA processes. AF elicited NMDA receptor-dependent expression of mPer1 and/or mPer2 mRNAs drastically in the DMH and weakly in the arcuate nucleus (ARC), the nucleus of solitary tract (NTS) and area postrema (AP). DMH lesions did not affect AF-induced mPer mRNA expression in the ARC, NTS and AP. Daily restricted feeding (RF) for 4 hrs caused a rapid phase shift and increased amplitude of mPer1 and mPer2 mRNA and mPER2 protein expression rhythms, not only in the DMH, but also in the ARC and cerebral cortex. DMH lesioning resulted in an overall decrease in activity level; however, it failed to abolish FAA rhythms under light-dark and constant darkness conditions. Furthermore, RF-induced daily rhythm of mPer2 mRNA in ARC and cortex was unaffected in DMH-lesioned mice. Although clock gene expression in the DMH is susceptible to AF, it is not necessary for the performance of AF and FAA rhythms. Thus, the present results suggest that multiple areas distributed throughout the brain, including the DMH, may be involved in the establishment of the FAA rhythm. [J Physiol Sci. 2008;58 Suppl:S91]