Circadian and ultradian activity rhythms in male long‐evans rats: Relationship to feeding

Abstract

Abstract Rats exhibit ultradian as well as circadian rhythms in activity. Short‐term activity rhythms appear to result from bouts of feeding‐related behavior interspersed with periods of quiescence. We examined the relationship of activity to feeding in 12 male Long‐Evans derived rats during ad lib and restricted feeding (RF) conditions to determine the effect of RF on both circadian and ultradian activity rhythms. By the end of 20 days of RF all animals exhibited an ultradian periodicity of approximately 12 hours. A twenty‐four hour rhythm in feeding persisted, apparently due to the rats adapting to the diurnal feeding period. General findings were that RF resulted in anticipatory activity prior to feeding and that short‐term activity fluctuations and investigations of the food bin continued during RF even though overall nocturnal activity decreased. The results suggest that male rats of this strain exhibit ultradian activity rhythms that appear to be strongly related to feeding.