Effect of K+ channels on the contraction of aortic rings. (A) The contraction of aortic rings with 10-5 M PE before and after pre-incubation with 4-AP, 3 mM, KV channel blocker; TEA 1 mM, BKCa channel blocker and GLYB, 1 μM, KATP channel blocker respectively for 30 min. (B) The percent change in relaxation ((tension PE - tension Ach)/tension PE) to 10-4 M ACh after 10-5 M PE before and after pre-incubation with three K+ channel blockers respectively. Data presented as mean ± S.E.M. and expressed as percentage of baseline tension. * P < 0.01 vs. contraction value of corresponding group before pre-incubation of K+ channel blocker, n = 8-10 rings from 5-6 rats.