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Circadian rhythms of PERIOD1 expression in the dorsomedial hypothalamic nucleus in the absence of entrained food‐anticipatory activity rhythms in rats
Author(s) -
Verwey Michael,
Lam Germain Y. M.,
Amir Shimon
Publication year - 2009
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2009.06766.x
Subject(s) - rhythm , circadian rhythm , suprachiasmatic nucleus , zeitgeber , neuroscience , psychology , biology , communication , circadian clock , medicine
When food availability is restricted to a single time of day, circadian rhythms of behavior and physiology in rodents shift to anticipate the predictable time of food arrival. It has been hypothesized that certain food‐anticipatory rhythms are linked to the induction and entrainment of rhythms in clock gene expression in the dorsomedial hypothalamic nucleus (DMH), a putative food‐entrained circadian oscillator. To study this concept further, we made food availability unpredictable by presenting the meal at a random time each day (variable restricted feeding, VRF), either during the day, night or throughout the 24‐h cycle. Wheel running activity and the expression of the clock protein, Period1 (PER1), in the DMH and the suprachiasmatic nucleus (SCN) were assessed. Rats exhibited increased levels of activity during the portion of the day when food was randomly presented but, as expected, failed to entrain anticipatory wheel running activity to a single time of day. PER1 expression in the SCN was unchanged by VRF schedules. In the DMH, PER1 expression became rhythmic, peaking at opposite times of day in rats fed only during the day or during the night. In rats fed randomly throughout the entire 24‐h cycle, PER1 expression in the DMH remained arrhythmic, but was elevated. These results demonstrate that VRF schedules confined to the day or night can induce circadian rhythms of clock gene expression in the DMH. Such feeding schedules cannot entrain behavioral rhythms, thereby showing that food‐entrainment of behavior and circadian rhythms of clock gene expression in the DMH are dissociable.