Daily restricted feeding rescues a rhythm of period2 expression in the arrhythmic suprachiasmatic nucleus

Second only to light, daily restricted feeding schedules can entrain circadian rhythms in mammals [Neurosci Biobehav Rev 4 (1980) 119; J Biol Rhythms 17 (2002) 284]. Contrary to light, however, such feeding schedules have been found not to affect the master circadian clock in the suprachiasmatic nucleus (SCN) [Genes Dev 14 (2000) 2950; Eur J Neurosci 13 (2001) 1190]. Here, we show that in rats that are arrhythmic as a consequence of prolonged housing in constant light, a daily restricted feeding schedule not only restores behavioral rhythmicity, as previously shown [Physiol Behav 53 (1993) 509], but in addition, induces a rhythm of the clock protein, Period2 in the SCN. These findings challenge the idea that the SCN is invulnerable to feeding schedules and call for a reevaluation of the role of the SCN clock in the circadian effects of such schedules.