Effects of lipopolysaccharide treatment on feeding of goldfish: role of appetite-regulating peptides.

The gram-negative bacteria-derived endotoxin lipopolysaccharide (LPS) is known to play an important role in immune and neurological manifestations during bacterial infections. In mammals, peripheral or brain administration of LPS induces anorexia and is thought to exert its effects through activation of pro-inflammatory cytokines. In this study, we investigated the effects of peripheral (intraperitoneal, IP) and central (intracerebroventricular, ICV) injections of LPS on food intake of goldfish. Fish treated IP with 10, 25, 50, 100 or 250 ng/g LPS or ICV with 1, 10 and 100 ng/g LPS showed a significant dose-dependent decrease in food intake, compared to the saline-treated fish. We also examined the brain mRNA expression of several hypothalamic appetite-related neuropeptides in response to the administration of LPS. IP injections of LPS (100 ng/g) induced a decrease in NPY expression and an increase in CCK, CRF and CART expression. These results indicate that LPS is a potent anorexigenic factor in goldfish and that this endotoxin induces a reduction in appetite, at least in part, by influencing gene expression of appetite-related neuropeptides.