Comprehensive Assessment of the Functional State of the Cerebral Cortex Microcirculatory Bed at Different Stages of Aging

Using Doppler flowmetry and tissue optical oximetry, a comprehensive spectral analysis of the oscillatory components of the myogenic, neurogenic and endothelial components of microvascular tone and an assessment of the oxygen transport dynamics in the cerebral cortex of rats at the age of 4, 18 and 23 months were performed. Regional differences of age-dependent changes in the regulatory mechanisms of microcirculation and the efficiency of tissue oxygen extraction were revealed. It was found that at the age of 18 months, microcirculatory changes are observed in the frontal and parietal cortical areas and are manifested as a decrease in sympathetic regulation of microcirculation, a decrease in precapillary myogenic resistance, vasodilation and an increase in the contribution of the capillary unit to microcirculation. In the parietal cortical area, these changes contribute to the activation of tissue oxidative metabolism and to an increase in oxygen consumption. With further aging, microvascular endothelial dysfunction develops and the contribution of the endothelial component to the total perfusion level of all cortical areas decreases. These disorders in 23-month-old rats are accompanied by an increase in the contribution of sympathetic regulation of microcirculation in the frontal cortex, a decrease in the contribution of the capillary unit to the microcirculation in the occipital area, and the development of stagnant processes in the venous area of the microcirculatory bed of the parietal cortex, reducing the efficiency of tissue oxygen extraction from the blood.