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Fish appetite is modulated in a complex manner by orexigenic hormones. To investigate appetite regulation, the fasting response of appetite-related hormone genes in eight brain regions was observed in yellowtail Seriola quinqueradiata, the most important aquaculture species in Japan. Gene expression of appetite-related hormones, neuropeptide Y (NPY), two agouti-related proteins (AgRP1 and AgRP2), two melanin-concentrating hormones (MCH1 and MCH2), and five cocaine- and amphetamine-regulated transcripts (CART1b, CART2a, CART2b, CART3a, and CART3b) was measured in the olfactory bulb, telencephalon, optic tectum, hypothalamus, pituitary gland, corpus cerebellum, crista cerebellum, and medulla oblongata and compared between 7-day-fasted fish and 3-h post-fed fish. Except that of cart2b, the gene expression of all appetite-related hormones was detected in all brain regions. The expression of optic tectum agrp1, mch1, mch2, and cart1b; hypothalamic agrp1; pituitary cart1b and cart3a; and corpus cerebellar npy, agrp1, and agrp2 was significantly increased after fasting. Fasting significantly reduced olfactory bulb cart1b and cart2b, optic tectum cart2b, hypothalamic cart1b, pituitary cart2a and cart3b, corpus cerebellar cart2a, and medulla oblongata agrp2 and mch2 expressions. These results suggest that brain regions other than the hypothalamus—the center of appetite—might also be involved in appetite regulation. [ABSTRACT FROM AUTHOR]