Characterization of catecholaminergic and serotonergic pathways in the trachea of the chicken and turkey.

The avian trachea is a critical component of respiration and vocalization, as well as pathogen defense and immunity. Tracheal neuroimmune pathways involving serotonin and catecholamines are well established in mammals. Although earlier work identified an endocrine system in the avian tracheal epithelium involved in dopamine metabolism, little remains known regarding the neurophysiological systems of the trachea in poultry species. As such, the present study sought to characterize the pathways involved in the synthesis, transport, and breakdown of indolamines and catecholamines in the trachea of the chicken and turkey. Trachea was collected from chickens and turkeys at 3 weeks of age. Following tissue protein extraction, protein lysates were analyzed using the Jess immunoassay system for the identification and quantification of target proteins. Targeted proteins included catechol-O-methyltransferase, monoamine oxidases A and B, serotonin and norepinephrine transporters, dopamine decarboxylase (DDC), dopamine beta hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase-1 (TPH-1). All enzymes and transporters were consistently detected in the trachea of both the chicken and turkey. These findings establish that neurochemical metabolic pathways are present in the trachea of poultry species. As serotonin and catecholamines are known to drive pathogen response, affect cilial movement, as well as regulate inflammation, the results presented herein are expected to inform future applications that seek to target serotonergic and catecholaminergic pathways within the respiratory tract and gut-respiratory axis across poultry species.