Effects of L-arginine on the diaphragm muscle twitches elicited at different frequencies of nerve stimulation

Brazilian Journal of Medical and Biological Research

R.n. Queiroz¹  Wilson Alves-do-prado² 

[1] ,Universidade Estadual de Maringá Departamento de Farmácia e Farmacologia

关键词: skeletal muscle;    nitric oxide;    L-arginine;    neuromuscular transmission;    tetanic fade;    S-nitroso-N-acetylpenicillamine;    superoxide dismutase;   

DOI  :  10.1590/S0100-879X2001000600020

来源: SciELO

【 摘 要 】

In rats, the nitric oxide (NO)-synthase pathway is present in skeletal muscle, vascular smooth muscle, and motor nerve terminals. Effects of NO were previously studied in rat neuromuscular preparations receiving low (0.2 Hz) or high (200 Hz) frequencies of stimulation. The latter frequency has always induced tetanic fade. However, in these previous studies we did not determine whether NO facilitates or impairs the neuromuscular transmission in preparations indirectly stimulated at frequencies which facilitate neuromuscular transmission. Thus, the present study was carried out to examine the effects of NO in rat neuromuscular preparations indirectly stimulated at 5 and 50 Hz. The amplitude of muscular contraction observed at the end (B) of a 10-s stimulation was taken as the ratio (R) of that obtained at the start (A) (R = B/A). S-nitroso-N-acetylpenicillamine (200 µM), superoxide dismutase (78 U/ml) and L-arginine (4.7 mM), but not D-arginine (4.7-9.4 mM), produced an increase in R (facilitation of neurotransmission) at 5 Hz. However, reduction in the R value (fade of transmission) was observed at 50 Hz. N G-nitro-L-arginine (8.0 mM) antagonized both the facilitatory and inhibitory effects of L-arginine (4.7 mM). The results suggest that NO may modulate the release of acetylcholine by motor nerve terminals.

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