EDN1 and ischemia: As earlier demonstrated in cerebral arteries after subarachnoid hemorrhage, the biphasic ET-1 concentration-contraction curves of MCAs and ACA from rats with 15 minutes induced ischemia indicate the presence of two contractile ET receptor subtypes, ETB and ETA, where the first phase reflects contraction mediated by ETB receptors and the second phase is dominated by ETA-mediated contraction, whereas the sigmoidal curves seen in sham-operated rats reflects purely ETA-mediated contraction [10].