The stimulatory effect of neuropeptide Y on growth hormone expression, food intake, and growth in olive flounder (Paralichthys olivaceus)

Neuropeptide Y (NPY) is a 36-amino acid peptide known to be a strong orexigenic (appetite-stimulating) factor in many species. In this study, we investigated the effect of NPY on food intake and growth in the olive flounder (Paralichthys olivaceus). Recombinant full-length NPY was injected intraperitoneally into olive flounder at the dose of 1 mu g/g body weight; phosphate buffered saline was used as the negative control. In a long-term experiment, NPY and control groups were injected every fifth day over a period of 30 days. In a short-term experiment, NPY and control groups were given intraperitoneal injections and maintained for 24 h. Food intake and growth rates were significantly higher in fish injected with recombinant NPY than in the control fish (P < 0.05). Higher growth hormone (GH) and NPY mRNA transcript levels were observed in both experiments, indicating a stimulatory effect of NPY on GH release. These findings demonstrate that NPY is an effective appetite-stimulating factor in olive flounder with the potential to improve the growth of domestic fish species and enhance efficiency in aquaculture.