The neuromuscular transmission fade (Wedensky inhibition) induced by L-arginine in neuromuscular preparations from rats

L-Arginine (4.7-18.8 mM) and 3-(4-morpholinyl)-sydonone imine hydrochloride (SIN-1; 1.15 mM) induced an increase in tetanic fade caused by indirect stimulation (180-200 Hz) of muscle. However, Wedensky inhibition, different from control, was not observed when the preparations treated with d-tubocurarine were directly stimulated by the same frequency. D-Arginine (9.4 mM) was ineffective in changing R values caused by indirect stimulation (180-200 Hz) of muscle. N-omega-Nitro-L-arginine (73 mM) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 mu M) did not produce any effect on Wedensky inhibition but did antagonize the tetanic fade induced by L-arginine (9.4 mM). The SIN-1 effect was antagonized by previous administration of ODQ (108 mu M), which alone did not produce any effects on R values. These results indicate that NO acting at the presynaptic level increases the Wedensky inhibition induced by high frequency of stimulation applied on motor nerves, and its effect may be produced through the cGMP-GC pathway. (C) 1999 Elsevier Science Inc. All rights reserved.