Role of Ca(2+)-dependent K+ channels in erythrocyte lysate-induced contraction of rabbit cerebral artery.

K+ channel openers may be useful in the treatment of cerebral vasospasm following subarachnoid hemorrhage. However, the role of Ca(2+)-dependent K+ channel (KCa) openers in cerebral vasospasm remain unclear. This study was undertaken to examine the role of KCa in hemolysate-induced contraction of rabbit cerebral and peripheral arteries: 1. Iberiotoxin (IBX), a selective KCa channel blocker, produced more pronounced contraction in basilar than in those of carotid or femoral arteries, indicating KCa channels are important regulating factors in cerebral arteries; 2. NS1619, a selective KCa channel opener, abolished the contraction of basilar artery to erythrocyte lysate, a causative agent for cerebral vasospasm; 3. In rabbit basilar artery, NS1619 relaxed the contractions to IBX, erythrocyte lysate and KCl (20 and 60 mM), indicating that NS1619, besides opening KCa channels, possesses other vasodilating actions. We conclude that KCa channels are important factors in the regulation of cerebral vascular tension and KCa channel opener NS1619 may have dual relaxant actions in cerebral arteries.