اثر L - آرژینین بر انتقال عصبی - عضلانی عضله دوبطنی گردنی جوجه

Background and Purpose: NO is a short-lived gas molecule generated by degradation of L-arg to citrulline and by the activation of enzyme NOS Ca2+/calmodulin-dependent. There are multiple NOS isoforms that strongly are expressed in skeletal muscle, suggesting the crucial role of NO in regulating muscular metabolism and function. In this study, the effect of L-arginine was examined at the neuromuscular junction of the chick biventer cervicis muscle. Materials and Methods: Biventer cervicis muscle preparations from chick’s age of 3 weeks were set up in the organ bath. The organ bath had a vessel with volume of about 70 ml it contained Tyrode solution aerated with oxygen and was kept at 37º C. NO levels was also measured in the chick biventer cervicis muscle homogenates, using spectrophotometer method for the direct detection of NO, nitrite and nitrate. Total nitrite (nitrite+nitrate) was measured by a spectrophotometer at 540 nm after the conversion of nitrate to nitrite by copperized cadmium granules. Results: L-Arginine at 500 µg/ml, decreased twitch response to electrical stimulation, and produced rightward shift of the dose-response curve for acetylcholine or carbachol. L-arginine at 1000 µg/ml produced a strong shift to the right of the dose-response curve for acetylcholine or carbachol with a reduction in efficacy. The inhibitory effect of L-arginine on the twitch response was blocked by caffeine (200 µg/ml). NO levels were found to be significantly increased in concentrations 500 and 1000 µg/ml of L-arginine in comparison with the control group (p < 0.001). Conclusion: These findings indicate a possible role of increased NO levels in the suppressive action of L-arginie on the twitch response. In addition, the results indicate that the post-junctional antagonistic action of L-arginine is probably the result of impaired sarcoplasmic reticulum (SR) Ca2+ release.