Nitric oxide (NO)-synthase is present in diaphragm. phrenic nerve and vascular smooth muscle. It has been shown that the NO precursor L-arginine (L-Arg) at the presynaptic level increases the amplitude of muscular contraction (AMC) and induces tetanic fade when the muscle is indirectly stimulated at low and high frequencies. respectively. https://www.ngetikin.com/