We have found that nitric oxide(NO) contents are increased in skin acupoints associated with enhanced neuronal NO synthase(nNOS) protein level in rats.Our recent studies show that L-arginine-derived NO synthesis increases skin electric currents over acupoints in rats.Consistently

norepinephrine(NE) turnover rate is decreased in acupoints with high skin electric currents

and enhanced 3H-NE synthesis/release in acupoints/meridians is facilitated by presence of an exogenous NO donor and inhibited by an inhibitor of NO synthesis.We have developed an innovative method to collect and measure NO metabolites from acupoints and meridians on the skin surface in humans.NO contents are consistently increased over PC and BL acupoints in humans

and increased NO content is reduced by anti-bacteria on skin surface.We conclude that the nonenzymatic reduction of nitrate by bacteria is involved in chemical generation of NO on skin acupoints/meridians in addition to neuronal NOergic system.NO mediates noradrenergic function on skin sympathetic nerve activation

which contributes to low resistance characteristics of acupoints and meridians.