Central injection of interleukin-13 potentiates LPS-induced sickness behavior in rats

Systemic administration of the bacterial endotoxin lipopolysaccharide (LPS) has profound depressive effects on behavior that are mediated by the inducible expression of proinflammatory cytokines such as interleukin-1 (IL-1), IL-6 and tumor necrosis factor-α (TNF-α) in the brain. To assess the regulatory effects of the anti-inflammatory cytokine IL-13 on LPS-induced sickness behavior, rats injected i.p. with LPS were administered rat recombinant IL-13 i.c.v. IL-13 (300 ng) potentiated the behavioral effects of LPS (125 μg/kg) when both molecules were co-injected. Administration of IL-13 (300 ng) 12 h prior to LPS (150 μg/kg) did not block the depressing effects of LPS on social exploration. These results indicate that IL-13 acts as a proinflammatory cytokine in the brain.