Vascular smooth muscle responses of mesenteric arteries and aorta in both genders of mice. Endothelium-independent relaxations of mesenteric arteries in response to SNP (an NO donor) in male (A) and female (B) mice, and those to NS-1619 (an opener of K_Ca channels) in male (C) and female (D) mice, are shown (n = 6 each). The relaxations to SNP were significantly enhanced in both genders of the three genotypes of NOS^−/− mice as compared with WT mice (A and B), whereas those to NS-1619 were unaltered (C and D). Endothelium-independent relaxations of the aorta in response to SNP in male (E) and female (F) mice, and those to NS-1619 in male (G) and female (H) mice are shown (n = 5 each). Those vasodilator responses of vascular smooth muscle were preserved in both genders of the three genotypes of NOS^−/− mice compared with WT mice. Data are shown as the mean ± SEM.