Inhibitory effect of arcaine on nitric oxide synthase in the rat brain

Nitric oxide is synthesized by nitric oxide synthase (NOS) from L-Arg, which contains a guanidino group. Arcaine is the diguanidino compound and a derivative of Arg. This study was conducted to investigate the effects of arcaine on rat brain NOS activity, using nitrite and nitrate as indicators. Arcaine inhibited NOS activity in a linear mixed manner (K1 = 18.68 microM). Almost all previously reported NOS inhibitors were synthesized by substituting the guanidino nitrogen of Arg, but the guanidino nitrogens of arcaine were not substituted. Arcaine was also reported to be a competitive antagonist of the polyamine site on the N-methyl-D-aspartic acid (NMDA) receptor. Arcaine appears to be an excellent drug to investigate not only the chemical nature of NOS but also the functional and structural relationship between NOS and NMDA receptors.