Brain Distribution of Key Neuropeptides Involved in Appetite Control in Atlantic Salmon, Salmo Salar (L.)
Authors: Lai Floriana , Kalananthan Tharmini , Berg Gunnar M. , Murashita Koji , Gomes Ana Silva , Handeland Sigurd O. , Rønnestad Ivar 
Published: June 2021

The physiological mechanisms that control food intake in the brain of mammals consist of orexigenic and anorexigenic neuronal populations that integrate both central and peripheral signals and play a pivotal role on the control of appetite. The neuropeptide Y (NPY) and agouti‐related proteins (AgRP) are neuropeptides expressed and secreted by the orexigenic neurons, while anorexigenic neurons synthesizes and releases proopiomelanocortin (POMC) and Cocaine‐ and amphetamine‐regulated transcript (CART) neuropeptides. These central signals controlling the appetite system are integrated in complex neuronal nucleus within the hypothalamus, but other brain regions are also involved.Several studies indicate that analogue control systems are conserved among vertebrates, although limited information is available for teleost species. The expression of these neuropeptides has been correlated with food intake, hunger and satiety, in several fish species. However, the majority of these studies analyzed the whole brain, thereby limiting our understanding on which brain areas are involved in teleost appetite control. This is particularly important, because these neuropeptides are involved in other physiological and behavioral functions. For e.g., NPY expressed in the neural circuits in amygdala and hippocampus of mammals has been shown to be involved in fear and anxiety behaviours. However, in teleosts, very few attempts have been made to specific locate in which brain areas the neuropeptides related to appetite control are expressed.In this study, we analyzed the mRNA distribution level of the key neuropeptides npy, agrp‐1 and agrp‐2, cart, pomc‐a1, ‐a2, a2s and ‐b in six brain regions of Atlantic salmon (Salmo salar), a commercially key species in the Norwegian aquaculture. In addition, we analyzed the response of these neuropeptides after 3 days of fasting in a pilot study.Our data show that both anorexigenic and orexigenic neuropeptides genes are expressed in the six brain regions analyzed at very different levels. npy, cart and agrp‐2 showed a high mRNA expression in the forebrain. In contrast to this, agrp‐1 had high expression in the hypothalamus, pituitary and saccus vasculosus. For all pomc genes, the pituitary had considerable much higher expression compared to the other brain regions. With the exception of the pituitary, the hypothalamus was the brain region with the highest expression in pomc‐a genes, followed by the saccus vasculosus. A preliminary comparison between fed and fasted fish did not indicate significant differences in the mRNA expression of the key neuropeptides in the hypothalamus.These results indicate that to understand the teleosts neuropeptides involvement in appetite control their spatial and temporal expression in the brain needs to be fully characterized.Support or Funding InformationFunded by Regional Research Fund Vest (RFFV 259183; Greenbag) and Research Council of Norway (NFR. 267626 LeuSENSE).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.