Neurochemical metabolic pathways display regional and age-specific expression patterns in the chicken intestinal...

Poultry intestinal neurophysiology is increasingly understood to directly influence performance, health, food safety, and other aspects of production. Monoamine neurochemicals, including the indoleamines and catecholamines, have been demonstrated to mediate production-relevant challenges. Hence, there is immense practical utility in understanding the enzymatic pathways surrounding neurochemical production and breakdown. Although the gut is a major source of peripheral monoamine neurochemicals in the bird, little attention has been directed towards characterizing the metabolic pathways involved in local enteric neurochemical synthesis, transport, and catabolism. As such, the present study sought to determine the presence and regional distribution within the chicken intestinal tract of key enzymes and transporters responsible for the production, transport, and breakdown of neurochemicals including serotonin, dopamine, and norepinephrine, and if this biogeography changes with age of the bird. To accomplish this, we utilized ileal, cecal, and colon tissues from chickens at 14 and 28 d. Following tissue protein extraction, protein lysates were run using the Jess immunoassay system for identification and quantification of target proteins. While all measured enzymes and transporters were detected within each region of the chicken intestinal tract, many targets revealed region-specific differences in expression. Monoamine oxidases A/B and DOPA-decarboxylase showed greatest (p < 0.05) expression in the ileum compared to the ceca and colon. Catechol-O-methyltransferase (COMT) showed isoform specific differences (p < 0.05) between the ceca and colon. Tyrosine hydroxylase and tryptophan hydroxylase-1 showed differences (p < 0.05) between regions. Dopamine beta-hydroxylase was elevated in the ceca (p < 0.05) compared to the ileum and colon. The serotonin and norepinephrine transporters were not significantly (p > 0.05) different between regions. As the present study is the first to demonstrate the presence of several key neurochemical metabolic steps, including COMT, in the chicken gut our data provide poultry researchers a biogeography of the neurochemical metabolic pathways in the chicken intestinal tract. The characterization and mapping of key steps in neurochemical metabolism within the poultry gut is expected to enable the development of useable targets that control enteric and systemic neurochemical concentrations.