L-NG-nitro arginine p-nitroanilide (L-NAPNA) is anti-nociceptive in the mouse

L-NG-nitro arginine p-nitroanilide (L-NAPNA), L-NG nitro arginine methyl ester (L-NAME) and L-NG-monomethyl arginine (L-NMMA) inhibit rat cerebellar nitric oxide synthase (NOS) with IC50s of 1.4 +/- 0.1 microM, 0.81 +/- 0.16 microM and 5.1 +/- 0.07 microM respectively. L-NAPNA inhibits the late phase of formalin-induced hindpaw licking (ED50, 57.2 mg kg-1) and acetic acid induced abdominal constrictions (ED50, 25 mg kg-1) in the mouse. L-NAPNA is approximately 65 times less active than L-NAME as an inhibitor of endothelium-dependent relaxation in the rabbit aorta and about 10 fold less potent as a vasopressor in the anaesthetized mouse. LNAPNA shows some degree of selectivity for the central NOS isoform and may be of clinical interest for the treatment of pain.