Abstract
(1) Entrainment signals to suprachiasmatic (SCN)-independent circadian oscillations. Daily restricted feeding (RF) or methamphetamine (MAP) injection produces anticipatory locomotor activity rhythm and entrains peripheral molecular oscillator. As orexins are neuropeptides that coordinate sleep/wakefulness and motivated behaviors such as food seeking, we tested the involvement of orexin neruons on induction of food anticipatory activity (FAA) rhythm by RF. RF shifted the peak of Fos expression of the orexin neurons from the night to daytime. Genetic ablation of orexin neurons in mice severely reduced acquisition of FAA by RF and MAP-induced oscillation. These results suggest that activity of orexin neuron in the LHA contributes the promotion and maintenance of FAA and MAP-induced oscillation. (2) Out put signals from the SCN to peripheral clock systems. We investigated whether injection of adrenaline/noradrenaline or sympathetic nerve stimulation could induce mPer gene expression in the mouse liver. Acute administration of adrenaline or noradrenaline increased mPer1 expression in the liver. Electrical stimulation of the sympathetic nerves or adrenaline injection caused an elevation of bioluminescence in the liver area of transgenic mice carrying mPer1 promoter-luciferase. Daily injection of adrenaline, administered at a fixed time for 6 days, recovered oscillations of mPer2 and mBmal1 gene expression in the liver of SCN-lesioned mice on day 7. Thus, activation of the sympathetic nerves through noradrenaline and/or adrenaline release was a factor controlling the peripheral clock. [Jpn J Physiol 54 Suppl:S6 (2004)]
