Insulin is known to exert its anorectic effect in mammals by reducing expression of the orexigenic signal neuropeptide Y (NPY) in the arcuate nucleus. However, the neural pathways by which insulin regulates food intake in fish are not well known. Bearing in mind that the actions of insulin and NPY on food intake in fish are similar to those observed in mammals, we studied the possible influence of insulin on NPY gene expression in the hypothalamus of rainbow trout. The NPY mRNA content of the

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... pothalamus-preoptic area (H-POA) was determined by qPCR, 12 h and 24 h after intracerebroventricular (i.c.v.) administration of a single dose of insulin (90 µg kg-1). Anorectic activity was observed 24 h after insulin administration, along with a slight, but significant, reduction in NPY mRNA levels, suggesting that NPY is not a relevant target for insulin-induced inhibition of food intake in rainbow trout.