Barbiturate-induced expression of neuronal nitric oxide synthase in the rat cerebellum.

Neuronal nitric oxide synthase (nNOS) is known to share some structural and functional similarities with the cytochrome P450 mixed function oxidase system. Unlike P450, it does not require a second enzyme, reductase, to transfer electrons. This characteristic is similar to P450(BM-3) of Bacillus megaterium. P450(BM-3) and certain mammalian subfamilies of P450, such as P4502B, are known to be induced by phenobarbital (PB), and these P450s share a consensus sequence called the Barbie box. Because of the similarities nNOS shares with P450(BM-3) and other mammalian P450s, we have examined whether nNOS also responds to PB treatment. We have used semi-quantitative PCR, Western blot analysis, a functional assay, and immunohistochemistry in order to answer this question. These data show a threefold increase in nNOS mRNA expression, more modest nNOS protein and activity induction, and no discernible changes in localization of nNOS within the cerebellum following PB treatment.