Effects of acetylcholine and nitric oxide on forearm blood flow at rest and after a single muscle contraction

acetylcholine and nitric oxide on forearm blood flow at rest and after a single muscle contraction. J. Appl. Physiol. 85(6): 2249–2254, 1998.—We tested the hypothesis that ACh or nitric oxide (NO) might be involved in the vasodilation that accompanies a single contraction of the forearm. Eight adults (3 women and 5 men) completed single 1-s-duration contrac-tions of the forearm to raise and lower a weight equivalent to,20 % maximal voluntary contraction through a distance of 5 cm. In a second protocol, each subject had a cuff, placed completely about the forearm, inflated to 120 mmHg for a 1-s period, then released as a simulation of the mechanical effect of muscle contraction. Three conditions were studied, always in this order: 1) control, with intra-arterial infusion of saline; 2) after muscarinic blockade with atropine; and 3) after NO synthase inhibition with NG-monomethyl-L-arginine (L-NMMA) plus atropine. Forearm blood flow (FBF), mea