Effect of Aging on Daily Rhythms of Lactate Metabolism in the Medial Prefrontal Cortex of Male Mice

•Lactate and EEG/EMG recordings were taken in the prefrontal cortex of Control (7 months) and Aged (20 months) male mice.•Aged mice spent less time awake and more time in NREM sleep than their younger counterparts.•Extracellular lactate was rhythmic, but the Aged peak was phase advanced, and was reduced in amplitude in constant dark.•The relationship between sleep state and lactate was modified by Aging and by exposure to constant conditions.•The daily expression of several genes related to lactate production and metabolite transport was modified in Aged mice.