Sprague-Dawley rats repeatedly exposed to systemic injections of lipopolysaccharide (LPS), a well-known immune system activator, displayed depressive and anxiety-like behaviors alongside microglial activation and increased hippocampal expression of the pro-inflammatory cytokines IL-1β and IL-6, and the nitric oxide (NO)-producing isoenzyme inducible NO synthase (iNOS) and cyclooxygenase 2 (COX-2). This evidence concerns the gene PTGS2 and Anxiety.