Effect of stress and lipopolysaccharide on the expression of CD200, chemokine (C-X3-C motif) receptor 1 and monocyte chemoattractant protein 1 mRNAs in the substantia nigra. mRNA expression was quantified by real-time RT-PCR. (A) CD200. Lipopolysaccharide (LPS) decreased CD200 expression in nonstressed animals and increased it in stressed rats. (B) Chemokine (C-X3-C motif) receptor 1 (CX3CR1). LPS decreased CX3CR1expression in nonstressed animals, and in stressed animals the decrease was even greater. (C) Monocyte chemoattractant protein 1 (MCP-1). No significant change was observed after injection of LPS into nonstressed rats. However, the effect of LPS on MCP-1 expression in stressed animals was massive. P < 0.01 by one-way analysis of variance followed by least significant difference post hoc test for multiple range comparisons. a, compared with vehicle (V); b, compared with lipopolysaccharide (L). SL, stressed animals injected with lipopolysaccharide.