Fig. 3. Concentration-response curves to levcromakalim in the absence or in the presence of S(+) ketamine (10−4m) obtained in the rat thoracic aorta with or without endothelium. Data are shown as means ± SD and expressed as percent of maximal relaxation induced by papaverine (3 × 10−4m; 100%= 1,216 ± 278 mg [n = 5] and 1,072 ± 195 mg [n = 5], for control rings with endothelium and rings treated with S(+) ketamine [10−4m], 100%= 1,180 ± 155 mg [n = 6] and 1,083 ± 154 mg [n = 6], for control rings without endothelium and rings treated with S(+) ketamine [10−4m], respectively).