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

Peripheral (IP) and central (ICV) 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 IP or ICV injection of LPS (250 mu g/kg or 60 ng/rat, respectively). Social exploration was depressed for 6 h after IP 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 ICV LPS injection, and this was accompanied by increased immobility. These effects were totaly blocked by ICV IL-10 (300 ng/rat). Rats lost body weight after ICV LPS, and this effect was attenuated by ICV IL-10. These results indicate that IL-10 is able to modulate the production and/or action of central proinflammatory cytokines. (C) 1999 Elsevier Science Ltd. All rights reserved.