In pig tracheal smooth muscle, the isometric tension responses to electrical field stimulation (EFS) were studied after raising the tone with carbamylcholine chloride (carbachol). EFS induced frequency-dependent relaxations that were nonadrenergic, noncholinergic (NANC) in nature. Addition of N(G)-nitro-L-arginine (L-NOArg), an inhibitor of nitric oxide (NO) synthesis from L-arginine, resulted in concentration-dependent inhibition of the relaxation response to EFS. Pretreatment of the tissues with L-arginine (1 mM) prevented the inhibitory effect of L-NOArg on the EFS- induced relaxations at the frequencies studied. However, in the presence of D-arginine, EFS-induced relaxations were inhibited by L-NOArg. L-Arginine, D- arginine, and L-NOArg had no significant effects on basal tone of the muscle. In the presence of L-NOArg, vasoactive intestinal polypeptide (3 x 10-7 M), the nicotinic agonist dimethylphenyl piperazinium bromide (100 μM), and isoproterenol (1 μM) relaxed carbachol-induced tone. The concentration- dependent selective inhibition of neural relaxation by L-NOArg and its reversal by L-arginine in a stereospecific manner are consistent with NO- mediated NANC relaxation of pig tracheal smooth muscle.
|Original language||English (US)|
|Journal||American Journal of Physiology - Lung Cellular and Molecular Physiology|
|Issue number||4 6-4|
|State||Published - 1992|
- electrical field stimulation
- isometric tension