Distribution of dopamine beta-hydroxylase and neuropeptide Y-immunoreactive nerves in healthy equine lungs.

Immunohistochemical methods were used to determine the distribution of pulmonary nerves containing either an enzymatic marker of adrenergic nerves, dopamine beta hydroxylase, or the putative neurotransmitter neuropeptide Y in 7 equids with healthy lungs. Nerves immunoreactive for these substances were found on airway smooth muscle in nearly all the samples of healthy equine lung examined. These nerves were generally more numerous in the larger airways but could be detected even in noncartilaginous bronchioles. Pulmonary and bronchial vessels also contained numerous immunoreactive nerves. On the basis of these findings, we suggest that dopamine beta-hydroxylase- and neuropeptide Y-immunoreactive nerves may be involved in the regulation of airway and vascular diameter in equids.