Can voltammetry measure nitrogen monoxide (NO) and/or nitrites?

Recently, voltammetry with carbon fibre electrodes (CFE) has been implement ed for real time measurement of nitrogen monoxide (NO) indicating that it i s oxidised at the potential value of nitrites, approximately +700 mV. In co ntrast, here we show that modified CFE can monitor NO at oxidation potentia ls different than that of nitrites, i.e. +550 mV. Indeed, at +550 mV a sign ificant increase of amperometric current levels was obtained when NO but no t nitrites, were added to a phosphate buffer saline solution (PBS). Differe ntial pulse voltammetry (DPV) supports these findings as two oxidation peak s were obtained when examining air preserved NO; peak I at +550 mV and peak 2 at +700 mV, respectively. In contrast, only peak 2 was monitored when ni trites or a solution of NO oxidised in air was added to PBS. Biological sup port to these in vitro data comes from the observation that the relaxation of an adrenaline-contracted aortic ring produced via addition of NO is conc omitant with peak I at +550 mv. The relaxation is almost completed before t he appearance of peak 2 at +700 mV. Furthermore, in vivo experiments perfor med in the striatum. of rats show that the amperometric signal monitored at +550 mV is responsive to glutamatergic stimulation or inhibition of NO syn thase. (C) 2001 Elsevier Science B.V. All rights reserved.