DEXAMETHASONE AND NITRIC-OXIDE SYNTHASE GENE-EXPRESSION IN BRAIN

Systemic administration of lipopolysaccharide (LPS), which causes endo toxemia and systemic inflammation, has been reported to induce express ion of the gene for type II inducible nitric oxide synthase (iNOS) in peripheral organs. This study was carried out to examine whether intra peritoneally injected LPS elicits the expression of iNOS messenger rib onucleic acid (mRNA) in the rat brain, We also investigated whether in traperitoneal treatment with dexamethasone (DEX) prevents this inducti on, To determine levels of iNOS mRNA, a quantitative reverse transcrip tion-polymerase chain reaction (RT-PCR) method was employed, Treatment with LPS induced the expression of iNOS mRNA in various brain regions , accounting for approximately 1 x 10(5) to 4 x 10(5) molecules per mu g of poly A(+)RNA, and these inductions were markedly suppressed by D EX, The results suggest that, during systemic inflammation, iNOS mRNA induction occurs in brain through a DEX-sensitive mechanism.