Circadian sleep and feeding patterns in the rat: possible dependence on lipogenesis and lipolysis

Sleep and feeding patterns were continuously recorded in rats under intravenous saline (control) and alternating insulin-epinephrine (experimental) infusions. The infusion of insulin (lipogenetic hormone) during the normally light period (0800-1600) replaced by epinephrine (lipolytic hormone) during the normally lipogenetic dark period (1600-0800) resulted in a complete inversion of the normal circadian distribution of sleep and feeding patterns and also of their correlation. Insulin infusion resulted in low blood glucose and glycerol levels whereas epinephrine increased these physiological parameters. Different control conditions showed that the fluctuations of sleep and feeding were dependent on the rate of utilization of the circulating metabolites at the cellular level. These results together with previous data suggest that the relation between sleep and feeding and their concomitant circadian fluctuation are possibly modulated by a common factor, namely the metabolic rate that is influenced by the lipogenesis/lipolysis rate.