BACKGROUND: Various local anesthetics have been shown to cause relaxation of isolated vascular rings contracted by phenylephrine. Recent studies reported that local anesthetics enhance nitric oxide (NO) production by human peripheral neutrophils. The author measured the effects of local anesthetics of nitrite production in LPS-treated rat aortic vascular smooth muscle cells and examined the effects of NW-nitro-L-arginine methyl ester (NAME) on vascular relaxant responses of lidocaine and bupivacaine in LPS-treated rat aortic rings. METHODS: Aortic ring preparations were obtained from LPS-treated (1.5 mg/kg, i. p. for 18hours) rat. Contractile responses of aorta to phenylephrine in dose-dependent administeration of lidocaine and bupivacaine (10(-6)M 10(-3)M) was examined. And also evaluated the effects of NAME (10(-6), 10(-5) and 10(-4)M) on relaxant responses of lidocaine and bupivacaine in LPS-treated rat aortic rings. From the cultured vascular smooth muscle cells, nitrite production of lidocaine and bupivacaine were measured by Griess reaction method. RESULTS: Lidocaine and bupivacaine enhanced the production of nitrite, the stable end product of nitric oxide, in cultured media of the vascular smooth muscle cells of the rat aorta but it didn't enhance significantly. NAME enhanced the contractile responses to lidocaine and bupivacaine in the LPS-treated rats significantly (p<0.05) but it didn't increase dose-dependently. CONCLUSION: These results show that lidocaine and bupivacaine increased NO production slightly in the LPS-treated rats and the vascular relaxant responses of local anesthetics were more enhanced because of NO production in LPS-treated rat.