Central administration of insulin-like growth factor-1 inhibits lipopolysaccharide-induced sickness behavior in mice

To assess the possible modulatory effects of insulin-like growth factor-1 (IGF-1) on the brain effects of proinflammatory cytokines, male CD-1 mice were injected into the lateral ventricle of the brain with a behaviorally depressing dose (100 ng) of the cytokine inducer lipopolysaccharide (LPS) and their response to various doses of IGF-1 (0, 100 and 1000 ng) was measured during behavioral tests carried before and at various time intervals after treatment. LPS induced a profound behavioral depression that was abrogated by the higher dose of IGF-1 tested. Since the behavioral effects of LPS are mediated by the local synthesis and results of proinflammatory cytokines, these results indicate that IGF-1 interferes with the production and/or action of proinflammatory cytokines in the brain.