Studies of stress effects on the brain have traditionally focused on neurons, without considering the cerebral microcirculation. Here we report that stress impairs neurovascular coupling (NVC), the process that matches neuronal activity with increased local blood flow. A stressed phenotype was induced in male rats by administering a 7-d heterotypical stress paradigm. NVC was modeled by measuring parenchymal arteriole (PA) vasodilation in response to neuronal stimulation in amygdala brain slices. After stress, vasodilation of PAs to neuronal stimulation was greatly reduced, and dilation of isolated PAs to external K(+) was diminished, suggesting a defect in smooth muscle inwardly rectifying K(+) (KIR) channel function. Consistent with these observations, stress caused a reduction in PA KIR2.1 mRNA and smooth muscle KIR current density, and blocking KIR channels significantly inhibited NVC in control, but not in stressed, slices. Delivery of corticosterone for 7 d (without stressors) or RU486 (before stressors) mimicked and abrogated NVC impairment by stress, respectively. We conclude that stress causes a glucocorticoid-mediated decrease in functional KIR channels in amygdala PA myocytes. This renders arterioles less responsive to K(+) released from astrocytic endfeet during NVC, leading to impairment of this process. Because the fidelity of NVC is essential for neuronal health, the impairment characterized here may contribute to the pathophysiology of brain disorders with a stress component.
Keywords: chronic stress; limbic system; neurovascular unit; potassium channels.