Aging is associated with reduced circadian (daily) rhythm amplitude in physiology and behavior, and decreased function of the prefrontal cortex (PFC). Similar effects are seen in younger mice experiencing circadian desynchrony (CD) caused by exposure to 20h light-dark cycles (T20). Given changes in PFC structure/function, underlying metabolic functioning of the PFC may also occur. We aimed to determine whether there are similarities in neurometabolism between Aged and CD mice. Using enzymatic amperometric biosensors, we recorded lactate concentration changes in the medial PFC in freely-behaving mice. Young mice displayed a circadian rhythm of lactate, which was severely blunted by CD, while Aging only changed the rhythm in constant conditions. We simultaneously probed the relationship between arousal state and PFC lactate rhythms, showing relationships between arousal state and lactate concentration, and documenting changes that occurred in CD and aging. Finally, using RT-qPCR, we found changes in genes related to metabolism and plasticity in both Aged and CD mice. Together, these data suggest both Aging and light cycle manipulation can disrupt mPFC neurometabolism.

Daily rhythms in lactate metabolism in the medial prefrontal cortex of mouse: Effects of light and aging