Effect of stress and lipopolysaccharide on lipid peroxidation in the substantia nigra. Lipid peroxidation increased in stressed animals as well as after the injection of lipopolysaccharide (LPS) in nonstressed animals. When combined, stress and LPS had an additive effect. 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 stress (S); c, compared with lipopolysaccharide (L). SL, stressed animals injected with lipopolysaccharide.