Temporal changes in the expression of TNF-α, IL1-β and iNOS mRNAs in the rat hippocampus after LPS injection. The expression of mRNA coding for the proinflammatory cytokines TNF-α and IL1-β and for the enzyme iNOS was quantified at different times post-injection (from 3 hours to 7 days) in samples from hippocampi injected with 5 μg of LPS. Data are presented as the mean ± SD relative to saline-injected animals. Data were obtained from triplicate assays. In the insert is shown a representative western blot for the iNOS enzyme in samples from the same animals used for gene expression. *P <0.05. iNOS: inducible nitric oxide synthase; IL1- β: interleukin-1 beta; LPS: lipopolysaccharide; SD: standard deviation; TNF-α: tumor necrosis factor alpha.