Relationship between food intake and expression of messenger RNA encoding aromatic amino acid decarboxylase (AADC), tyrosine hydroxylase (TH), and catechol‐O‐methyltransferase (COMPT) in channel catfish.

Obesity is linked to various metabolic disorders and associated complications, including major depressive disorder and anhedonia. How dopamine metabolism affects food intake and the development of obesity in fish, however, is not clear. Our objectives were to characterize the tissue expression of AADC, TH, and COMPT mRNA and if their expression is influenced by food intake in channel catfish. Expression of these mRNAs were examined in the brain, hypothalamus, liver, muscle, kidney, spleen, large intestine, and small intestine, as well as within different parts of the brain to examine their tissue expression profile. To study the relationship between hypothalamic expression of these mRNAs and food intake, samples were harvested at −1 hour prior to (−1), at feeding (0), and 1 hour after feeding (+1, n=4 per time point). Expression of all transcripts encoding these enzymes was detectable in all tissues examined, with increased expression in the liver. These mRNAs were more highly expressed in the hypothalamus compared to other parts of the brain examined. The expression of AADC mRNA and TH mRNA was not altered by timing of food exposure. Given that these mRNA transcripts had increased expression in the hypothalamus, the dopaminergic neural system may influence the regulation of food intake. Lack of changes of expression of these enzymes within the hypothalamus in response to food exposure may indicate that the changes in the dopamine system in response to food intake may be at the enzyme activity level rather than changes in transcription. Support or Funding Information P20 GM103418