Hypothalamic agrp and pomc mRNA Responses to Gastrointestinal Fullness and Fasting in Atlantic Salmon (Salmo salar, L.)

Abstract

The orexigenic agouti-related protein (AgRP) and the anorexigenic pro-opiomelanocortin (POMC) are crucial players in the control of feed intake in vertebrates, yet their role in teleosts has not been fully established. Triplicate groups of Atlantic salmon (<i>Salmo salar</i>) post smolts were subjected to (1) fasting for 3 days (fast) and (2) normal feeding (fed), resulting in a significant (<i>p</i> < 0.05) upregulation of hypothalamic <i>agrp1</i> transcripts levels in the fast group. Moreover, the mRNA abundance of <i>agrp1</i> was significantly (<i>p</i> < 0.05) correlated with the stomach dry weight content. Corresponding inverse patterns were observed for <i>pomca2</i>, albeit not statistically significant. No significant differences were found for the other paralogues, <i>agrp2</i> and <i>pomca1</i> and <i>b,</i> between fed and fast groups. The significant correlation between stomach fullness and <i>agrp1</i> mRNA expression suggests a possible link between the stomach filling/distension and satiety signals. Our study indicates that hypothalamic <i>agrp1</i> acts as an orexigenic signal in Atlantic salmon.