Central injection of IL-10 antagonizes the behavioural effects of lipopolysaccharide in rats.

Peripheral (i.p.) and central (i.c.v.) injections of lipopolysaccharide (LPS) have been shown to induce brain expression of proinflammatory cytokines and to depress social behaviour in rats, increase duration of immobility and induce body weight loss. To determine if the anti-inflammatory cytokine, interleukin-10 (IL-10) is able to modulate these effects, recombinant rat IL-10 was injected in the lateral ventricle of the brain (30, 100, 300 ng/rat) prior to i.p. or i.c.v. injection of LPS (250 micrograms/kg or 60 ng/rat, respectively). Social exploration was depressed for 6 h after i.p. LPS injection. This effect was attenuated by IL-10 (30 and 100 ng) 2 h after injection, whereas the highest dose of IL-10 blocked the depression of social interaction for 6 h after LPS injection. IL-10 produced the same effects on the increase of immobility although the results did not reach significance. Social exploration was depressed 3 h after i.c.v. LPS injection, and this was accompanied by increased immobility. These effects were totally blocked by i.c.v. IL-10 (300 ng/rat). Rats lost body weight after i.c.v. LPS, and this effect was attenuated by i.c.v. IL-10. These results indicate that IL-10 is able to modulate the production and/or action of central proinflammatory cytokines.