Fig. 5. ( A ) Effect of acetylcholine (ACh; 10−6m), alone and in combination with ketamine, on extracellular Ca2+-induced increases in tension in endothelium-denuded pulmonary vein strips. ( B ) Effect of acetylcholine, alone and in combination with ketamine, on extracellular Ca2+-induced increases in intracellular Ca2+concentration ([Ca2+]i) in endothelium-denuded pulmonary vein strips. ( C ) Effect of acetylcholine, alone and in combination with ketamine, on the pulmonary vein [Ca2+]i–tension relation. Acetylcholine increased tension ( P = 0.004), had no effect on [Ca2+]i( P = 0.836), and caused a leftward shift ( P = 0.004) in the [Ca2+]i–tension relation. Ketamine attenuated ( P = 0.034) the acetylcholine-induced increases in tension, had no effect on [Ca2+]i( P = 0.836), and caused a rightward shift ( P = 0.038) in the [Ca2+]i–tension relation in acetylcholine-pretreated pulmonary vein strips. n = 6.