Effects of TRIM on tension, intracellular calcium and nitrergic transmission in the rat anococcygeus muscle.
The effects of the putatively selective inhibitor of neuronal nitric oxide synthase (nNOS) 1-(2-trifluoromethylphenyl) imidazole (TRIM) were investigated on contractility, intracellular calcium and nitrergic relaxations in the rat anococcygeus muscle. TRIM (100-1000 microM) reduced the tension of rat anococcygeus muscles when contracted with guanethidine (10 microM) and clonidine (0.1 microM). Relaxations to TRIM persisted in the presence of the non-selective NOS inhibitor L-NAME (100 microM) and the inhibitor of soluble guanylate cyclase ODQ (1 microM). TRIM also reduced tension when muscles were contracted with phenylephrine (3 microM), noradrenaline (3 microM) or high K physiological salt solution (high KPSS; 60mM). Influx of calcium ([Ca(2+)](i)) in response to high KPSS was significantly reduced in the presence of TRIM (1mM). TRIM also inhibited the influx of (45)Ca(2+) induced by KPSS, but had no effect on the influx induced by phenylephrine (10 microM). TRIM (300 microM) had a modest, but significant, inhibitory effect on nitrergic relaxations that were evoked by electrical field stimulation (1-10 Hz, 15 V, 10s trains) in muscles contracted with guanethidine and clonidine. In contrast, L-NAME (1-100 microM) inhibited these nitrergic responses with an IC(50) of 9.31+/-0.87 microM (n=4). The results suggest that the smooth muscle relaxant effect of TRIM in the rat anococcygeus muscle may affect the entry of Ca(2+) possibly through voltage-operated calcium channels. Furthermore, the relatively modest effect of TRIM on nitrergic responses indicates that it is not a particularly reliable inhibitor of nNOS.
Che
Yan
Y
School of Medical Sciences, RMIT University, P.O. Box 71, Bundoora, Vic. 3083, Australia.
Potocnik
Simon
S
Ellis
Anthie
A
Li
Chun Guang
CG
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004558:Electric Stimulation; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D007093:Imidazoles; D010656:Phenylephrine; C098186:1-(2-trifluoromethylphenyl)imidazole; D009569:Nitric Oxide; D011189:Potassium Chloride; D002118:Calcium