Nocturnal time restricted feeding increases motivation for food reward and improve mood related behaviors under environmental enrichment

Food is a strong non-photic synchronizer of circadian rhythms. In nocturnal animals, time restricted feeding during the night (nTRF), as compared to ad libitum (AL) access to food, improves several behavioral and cognitive processes. In addition, enrichment of the housing cage can also prompt well-being and improve mood related behaviors. The reward system shows a prominent rhythm in the activity of dopaminergic efferents from the nucleus accumbens to the ventral tegmental area. We previously demonstrated that motivation behavior for food reward shows a circadian rhythm, which is disrupted under constant light and chronic jet lag conditions. In this work, we ask whether motivation levels under an enriched environment (EE, vs. unenriched, UE) interact with a nocturnal time restricted feeding protocol (nTRF), taking the hypothesis that the reward system can be entrained by nTRF. Motivation levels were increased both by EE and nTRF. In addition, depressive-like behavior measured by sucrose preference and tail suspension tests was modulated by this interaction, being higher under UE-AL conditions. These results suggest that nTRF is a modulatory circadian input for the reward system and can be proposed as a chronotherapy for treating mood related disorders.