抄録
Master circadian clock of mammals locates in the suprachiasmatic nucleus (SCN) which is composed of multiple single cell oscillators. Neither the intra-SCN coupling mechanisms nor the output pathways to regulate behavioral rhythms are fully elucidated yet. By using a bioluminescent reporter of clock gene expression, we examined the mechanisms regulating photoperiodic behavioral response and extra-SCN oscillator underlies behavioral rhythms. Current hypothesis for photoperiodic clock assumes two oscillators, morning (M) and evening (E) ones, which change coupling intensity depending on the photoperiod. We compared behavioral rhythms with Per1 expression rhythms in cultured SCN from Per1-luc transgenic mice. Irrespective of photoperiods, Per1 peak in the anterior SCN was phase-locked to the activity onset, while that in the posterior, to the end of activity, suggesting the location of E and M oscillators, respectively. Furthermore, anterior SCN from mice in long-day exhibited bimodal Per1 peaks. These results suggest that three distinct oscillatory cell groups regulate photoperiodic responses of behavioral rhythms. We also examined the localization of extra-SCN circadian oscillator directly regulating behavioral rhythms by dissociating them from SCN rhythms with chronic methamphetamine (MAP) treatment. Various brain areas exhibited dissociated clock gene rhythms from SCN rhythms in situ, while limited areas continued to exhibit dissociated Per1-expression rhythms in culture. These areas are the candidate of peripheral oscillator for behavioral rhythms. [J Physiol Sci. 2007;57 Suppl:S63]
