Endothelin-B receptors in cerebral resistance arterioles and their functional significance after focal cerebral ischemia in cats

In the cerebral circulation, endothelin-A receptor activation mediates marked prolonged vasoconstriction whereas endothelin-B (ETB) receptor activation effects dilation. In contrast to some peripheral vascular beds, ETB receptor–induced vasoconstriction has not yet been demonstrated in brain vessels. In this study in chloralose-anesthetized cats, with perivascular microapplications of ETB selective agonist (BQ-3020) and antagonist (BQ-788), we investigated whether ETB receptor–mediated constriction could be uncovered in cortical arterioles in vivo. In addition, we examined whether normal dilator response to ETB receptor activation is preserved in postishemic cerebral arterioles. The first microapplication of the selective ETB receptor agonist BQ-3020 (1 μmol/L) onto a pial cortical arteriole elicited marked dilation (caliber increased by 26.3 ± 15.1% from preinjection baseline). A second application of BQ-3020 (10-minute interval) onto the same vessel failed to evoke any significant vasomotor response. Su...