The neuronal nitric oxide synthase (nNOS) is predominantly expressed in nervous tissues and subject to complex transcriptional controls. To determine the effect of acetylation on nNOS expression, human neuroblastoma SK-N-SH cells were treated with trichostatin A (TSA), a histone deacetylase inhibitor. As a consequence, total and exon 1f-specific nNOS mRNA, nNOS protein and nNOS-derived nitric oxide production were increased. Immunoprecipitation and western blot showed both nuclear factor-kappaB (NF-kappaB) subunits p65 and p50 were acetylated in the presence of TSA. The enhancement of the p65 and p50 acetylation was in accordance with their increased binding affinities to the NF-kappaB responsive element, which was identified at position -893 to -884 of the nNOS exon 1f promoter. Luciferase assays revealed that TSA up-regulated the transcriptional activity of the nNOS 1f promoter through NF-kappaB-mediated transactivation. Taken together, we demonstrate that acetylation plays a crucial role in nNOS expression and suggest that acetylation of NF-kappaB p65 and p50 subunits by TSA treatment may augment their DNA-binding affinities, thereby activating the nNOS exon 1f promoter. It may be one of the mechanisms by which acetylation modulates nNOS expression and nitric oxide output in SK-N-SH cells and may be the molecular basis for certain neurological disorders.