It?s time to be motivated: circadian modulation of motivation for food rewards

ACOSTA J.; GOLOMBEK D.A.; AGOSTINO P.V.

Córdoba

Congreso; XXXIII Congreso Anual de la Sociedad Argentina de Investigación en Neurociencia; 2018

Organisms exposed to daily environmental cycles display diurnal rhythms in physiology, metabolism and behavior. These rhythms are generated and sustained by cell-autonomous circadian clocks, which help organisms anticipate predictable changes in the environment. They continue to operate in constant environmental conditions (i.e., free-run) with a period of about 24 hours. In mammals, the circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and is mainly synchronized by the light-dark (LD) cycle. Synchrony or temporal coordination of circadian oscillators between central and peripheral tissues, and alignment with the external environment, is important for maintaining organism homeostasis. On the other hand, eating behavior is driven by the need to maintain energy homeostasis, which is critical for survival. Food is the most potent natural reward conserved across species. Homeostatic and hedonic mechanisms may interact to regulate food intake, and palatable food has higher hedonic value than bland food and promotes greater activation within reward areas of the brain. Evidence suggests that the reward circuitry in the brain (limbic system) may be under modulation of the circadian system.In this work, we present evidence that motivation for food reward (normal pellets) varies dramatically with the LD cycle in young (4-months old) and old-aged (over 1.5 years old) C57BL/6 mice. We also assayed motivation under constant dark (DD) conditions, and mice shown an endogenous rhythmicity of the motivational behavior. Finally, the effect of the circadian clock on motivation was also studied by using a palatable reward (chocolate) under a protocol without food restriction.