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

A comprehensive spectral analysis of the vibrational components of the myogenic, neurogenic, and endothelial components of microvascular tone was performed and the dynamics of oxygen transport in the cerebral cortex of rats aged 4, 18, and 23 months was evaluated using the method of laser Doppler flowmetry and tissue optical oximetry. Regional differences in age-related changes in the regulatory mechanisms of microcirculation and the effectiveness of tissue oxygen extraction have been identified. It was found that at the age of 18 months, microcirculatory changes are observed in the frontal and parietal cortex and manifest themselves as a decrease in sympathetic regulation of microcirculation, a decrease in precapillary myogenic resistance, vasodilation, and an increase in the contribution of the capillary link to microcirculation. In the parietal cortex, these changes contribute to the activation of tissue oxidative metabolism and increased oxygen consumption from the flowing blood. With further aging, microvascular endothelial dysfunction develops and the contribution of the endothelial component to the overall perfusion level of all cortical regions 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 link to microcirculation in the occipital region and the development of stagnant processes in the venous region of the microcirculatory bed of the parietal cortex, reducing the effectiveness of tissue oxygen extraction from the blood.