The effect of endothelin receptor A antagonism on basilar artery endothelium-dependent relaxation after ischemic stroke

Aims: Endothelin (ET) receptor A antagonism decreases neuronal damage in experimental models of stroke. Since large arteries like basilar artery contribute significantly to total cerebrovascular resistance and are major determinants of microvascular pressure, dysregulation of basilar artery function may worsen stroke injury. ET-1 is involved in the regulation of basilar constriction. However, whether stroke influences vasoreactivity of basilar artery and to what extent ET-1 contributes to basilar vascular dysfunction after stroke remained unknown. The goal of this study was to test the hypothesis that ET-1 impairs basilar artery vasorelaxation after ischemia/reperfusion (I/R) injury via activation of ET_A receptor. Main methods: Male Wistar rats were subjected to 3 h middle cerebral artery occlusion (MCAO) and 21 h reperfusion. One group received ET_A receptor antagonist atrasentan (5 mg/kg, i.p.) at reperfusion. At 24 h, basilar arteries were isolated from control non-stroked, stroked and stroked + atrasentan-treated animals for vascular reactivity measurements using pressurized arteriograph. Key findings: Acetylcholine (Ach)-induced maximum relaxation (R_max) was decreased in stroked animals as compared to non-stroked group and ET_A antagonism partially restored it. There was also a trend for decreased EC ₅₀ value for the antagonist treatment group indicating improved Ach sensitivity. Significance: These findings suggest that I/R not only affects vessels distal to the occlusion but also impairs relaxation of proximal large vessels. ET-1-mediated basilar artery dysfunction may contribute to neurovascular damage after stroke and early restoration of vascular function by ET receptor antagonism after I/R injury may offer a therapeutic strategy.