Relationship between cerebral energy metabolism in parietotemporal cortex and hippocampus and mental activity during aging in rats.

The present investigation demonstrates differences in both formation and utilization of the energy-rich compounds adenosine triphosphate ATP and creatine phosphate (CrP) in behaviorally well and poorly performing inbred male Wistar rats in parietotemporal cerebral cortex and hippocampus with aging from 1 to 2ys. Also, differences in learning and memory capacities (behavior) became obvious. By holeboard testing, good (GP) and poor performers (PP) have been discriminated. The pools of energy-rich phosphates as determined in parietotemporal cerebral cortex and in hippocampus under resting conditions were found to be reduced by nearly 10% for both creatine phosphate and the whole available energy pools in PP as compared to GP. Aging from 1 to 2y diminished the concentrations of energy-rich phosphates in the cerebral areas studied and in both GP and PP under resting conditions. Additionally, an age-related aggravation of the energy deficit became obvious between GP and PP. Repeated mental activation from 1y to 2y resulted in the maintenance of improvement as registered for the mean run time and the number of visited/revisited holes in GP. In contrast, PP deteriorated (mean run time), and could not maintain improvement (number of visited/revisited holes) over time. Repeated mental activation normalized the energy pool by increased formation of the energy-rich compounds ATP and CrP in both cerebral areas studied in GP and PP. However, differences became obvious between GP and PP. The energy-turnover in the latter group was found to be significantly reduced for both cerebral areas studied. GP could meet the enhanced energy demand of mental activation during aging by increasing formation and utilization of energy. PP could increase energy formation but were unable to sufficiently adapt energy utilization under the same conditions. This disturbance in energy metabolism may have impacts on energy-consuming processes in PP which may contribute to the markedly reduced cognitive reserve in PP. In human beings, PP approximately poorly educated people found to be prone to sporadic Alzheimer disease.