a. Example figure of the effect of 40 µM verapamil on high K+ and hypoxia-induced smooth muscle constriction. HPV consisted of a transient constriction (phase I) superimposed on a sustained constriction (phase II), and phase II was divided into IIa, IIb and IIc. b. Mean data showing effect of 10 µM verapamil, 40 µM verapamil, 50 µM SKF96365 and 50 µM 2-APB on hypoxic induced vasoconstriction in IPAs in term of percentage change in compare with corresponding parts in control group. *, P<0.05, **, P<0.001. For 10 µM verapamil (n = 4), high K+ response and phase I hypoxic constriction reduced to 13.7±1% and 63.3±5.9% respectively. For 40 µM verapamil (n = 6), high k response and phase I hypoxic constriction reduced to 6.1±1.6% and 54.4±4.3% respectively. SKF96365 (n = 3): high K+, phase I, phase II b and c has been reduced to 25.3±11.7%, 38.6±13%, 54.2±8.3% and 83.3±12.3% respectively. 2APB (n = 3), which has no effect on high K, reduce phase I, phase II b and c to 39.5±7.5%, 16.9±7% and 16.9±7% and 0 calcium solution (n = 3)reduced high k, phase I, phase II b and c to 5±7%, 35.1±10.4%, 58.6±7% and 42.1±0.7% of controls. All results normalized using max vasoconstriction induced by 80 mM high k in control group.