Histaminergic and dopaminergic traits in the human carotid body.

Carotid body (CB) chemoreceptors are the main sensors detecting systemic hypoxia. Studies in animals revealed that dopamine and histamine may serve as transmitters between the chemoreceptor cells and the afferent nerve. To gain insight whether histamine and dopamine could play a role in the human CB and thus be important for the understanding of breathing disorders, we have investigated the chemosensory traits in human CBs from nine subjects of different ages obtained at autopsy. Immunohistochemistry revealed expression of histidine decarboxylase, vesicular monoamine transporter 2, histamine receptors 1 and 3 in virtually all chemosensory cells within the glomeruli of different ages. By contrast, catecholaminergic traits (tyrosine hydroxylase and vesicular monoamine transporter 1) were only detected in a subset of CB chemosensory cells at each age group while dopamine D2 receptors were expressed in the great majority of them. Our data suggest that histamine along with catecholamines may serve as transmitters between chemoreceptor cells and the afferent nerve in humans as well.