NO production during neuronal cell death can be directly assessed by a chemical reaction in vivo.

The role of nitric oxide (NO) as a putative mediator of neuronal death can be understood best if NO is detected directly. For this purpose, we developed a new sensitive method that for the first time directly captures released NO during neurodegeneration in vivo and at the cellular site of its generation. The non-fluorescent substance 1,2-diaminoanthraquinone (DAA) was injected into the eyes of rats whose optic nerve was injured to induce retrograde degeneration of the ganglion cells. The reaction product of DAA with NO is a triazole with red fluorescence. The two major NO producing cell populations in the retina are capillary endothelial cells and microglial cells. The methodology of NO assessment is convenient and applicable to numerous living systems both in vivo and in vitro.