The influence of L-NG-nitro-arginine on sympathetic nerve induced contraction and noradrenaline release in the rat isolated anococcygeus muscle.
1. The possibility of an interaction between the motor sympathetic and inhibitory non-adrenergic, non-cholinergic (NANC) nerves in the rat anococcygeus was investigated using L-NG-nitro-arginine (L-NOARG), an inhibitor of L-arginine: NO synthase. 2. L-NOARG (50 microM) increased contractions induced by field stimulation (20 s trains; 0.5-40 Hz); overall, the frequency-response curve was displaced six-fold to the left. D-NOARG (50 microM) was without effect. 3. The potentiation produced by L-NOARG was reversed by 200 microM L-, but not D-, arginine. 4. L-NOARG had no effect on contractions induced by exogenous noradrenaline (NA) or on field stimulation-induced overflow of tritium from muscles previously loaded with [3H]-NA. 5. It is concluded that the endogenous nitrate NANC transmitter does not influence release of NA from the sympathetic nerves and the potentiation of contractions induced by field stimulation in the presence of L-NOARG most probably results from removal of the opposing relaxing influence of concomitantly released NANC transmitter.
Biomedical Sciences Division, King's College London, UK.
S R
SR
Brave
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Bhat
A J
AJ
Hobbs
J F
JF
Tucker
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A
Gibson
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D019335:Nitroarginine; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000378:metabolism*
D019335:Nitroarginine; D001120:Arginine; D009638:Norepinephrine