Response of isolated intracerebral arterioles to endothelins

The effects of endothelin-1, -2 and -3 (ET-1, -2, -3) on lumen diameter of intracerebral arterioles isolated from rat brain were examined. All three ETs produced concentration-dependent decreases in lumen diameter with EC50 values of 0.7, 1.5 and 58 mmol/l for ET-1, ET-2 and ET-3, respectively. The calcium channel antagonist, nicardipine, had no significant effect on ET-1-induced contractions except at a concentration of 1 mumol/l which attenuated the maximum response to ET-1, but had no effect on the EC50 value. The potent vasoconstrictor action of ET on intracerebral arterioles suggest an important role for this peptide in the regulation of the cerebral microvasculature.