Gene expression of appetite-related hormones: Responses to fasting in different brain regions of yellowtail Seriola quinqueradiata

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.