Can the food-entrainable oscillator ameliorate the deleterious effect of circadian rhythm disruption in an animal model of social jet lag?

Abstract

Today’s society fosters circadian rhythm disruptions. In particular, individuals often experience “social jet lag” (SJL), resulting in differences between weekday and weekend sleep schedules, and disruption of their light-entrainable oscillator (LEO). The current study investigated the interaction between the LEO and the food-entrainable oscillator (FEO) by implementing a novel animal model of SJL, the “social jet lag manipulation” (SJM). Particularly, the impact of SJL on retention and acquisition of hippocampal-dependent and non-hippocampal-dependent tasks was investigated. During Experiment One, while receiving one (FEO access) or many (no FEO access) meals per day, rats were trained under a 12:12 light-dark cycle, then exposed to the SJM. SJM and Control rats retained the tasks equally, yet rats with FEO access retained hippocampal-dependent tasks better than rats without FEO access. During Experiment Two, while receiving one or many meals per day, rats were exposed to the SJM during hippocampal-dependent and non-hippocampal-dependent task training. SJM and Control rats acquired the tasks equally. However, rats with FEO access acquired the hippocampal-dependent task faster than rats without FEO access. While no detrimental impact of the SJM was apparent, actograms suggested that the SJM induced free-running activity. Previous shift work models have induced free-running activity, causing hippocampal-dependent learning and memory deficits. It is, therefore, possible that the hippocampal-dependent tasks used in the current study were not sensitive enough to display hippocampal deficits. Nonetheless, the current findings displaying the benefit of FEO access for learning and memory indicate the need to further investigate this oscillator and its potential benefits.