Participation of peroxynitrite in acetylcholine release induced by nitric oxide generators.

Peroxynitrite is a product produced by spontaneous reaction of nitric oxide (NO) with superoxide. Functional roles of peroxynitrite in the release of endogenous acetylcholine evoked by NO generators has been examined using primary-cultured cerebral cortical neurons. NO generators, such as sodium nitroprusside and S-nitroso-N-acetylpenicillamine, dose-dependently increased the release of acetylcholine (ACh); such increase of the release was significantly suppressed by hemoglobin which has the capacity to abolish biological effects of NO. Two types of superoxide scavengers, Cu2+, Zn2+ superoxide dismutase and ceruloplasmin, significantly reduced the NO-evoked ACh release. These results indicate that NO requires superoxide to evoke the release of ACh. Synthesized peroxynitrite evoked the release of ACh from cerebral cortical neurons in a dose-dependent manner. Thus, it is indicated that the NO-evoked ACh release is mediated, at least in part, by peroxynitrite produced by the reaction of NO with superoxide.