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+description: "The microvascular inflow tract (MIT),\ncomprising the penetrating arterioles, precapillary sphincters, and first-order\ncapillaries, is the bottleneck for brain blood flow and energy supply. Exactly\nhow aging alters the structure and function of the MIT remains unclear. By in\nvivo 4-dimensional two-photon imaging, we reveal an age-dependent decrease in\nvaso-responsivity accompanied by a decrease in vessel density close to the\narterioles and loss of vascular mural cell processes, though the number of\nmural cell somas and their αSMA density were preserved. The age-related reduction\nin vascular reactivity was mostly pronounced at precapillary sphincters,\nhighlighting their crucial role in capillary blood flow regulation. Mathematical\nmodeling revealed impaired pressure and flow control in aged mice during\nvasoconstriction. Interventions that preserve dynamics of cerebral blood\nvessels may ameliorate age-related decreases in blood flow and prevent brain\nfrailty."
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