Absence of nitric oxide synthase in rat oligodendrocytes: a light and electron microscopic study

The existence of nitric oxide synthase (NOS) in oligodendroglial cells is still a matter of debate. Therefore, by using immunocytochemistry, NADPH-diaphorase (NADPH-d) histochemistry and in-situ hybridization, NOS was analysed in oligodendroglial cells of rat brain tissue and in tissue cultures. Independent of the method utilized, NOS was found to be absent in oligodendrocytes. An exception was the presence of NADPH-d activity in some oligodendroglial cells when the electron microscopic BSPT-technique was used. However, this activity is probably not related to NOS. The absence of NO-producing capacity in these cells may explain their high vulnerability to radical-mediated toxicity.