Autonomic nervous system to the airways of horses: Parasympathetic and sympathetic nerves
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Abstract
The neural networks of the cervicothoracic autonomic nervous system (ANS) branches to the upper airways and lungs are poorly described in horses. The purpose of this study was to anatomically identify and define the cervical and thoracic ANS network to pulmonary airways. Nerve branches in the regions of interest were dissected in 16 horses. Sections of the vagus nerve were stained for identification of tyrosine hydroxylase immunoreactive fibers. The results showed that ANS innervating equine airways is more developed in the right side, with parasympathetic and sympathetic nerves presenting connecting ipsilateral branches at the thoracic level between the vagus nerve, the middle-cervical (MCG) and the cervicothoracic (CTG) sympathetic ganglia. Vagus branches to the lungs are primarily ipsilateral and contain adrenergic fibers originating from the MCG and CTG. Newly described nerve branches of the cervicothoracic region in horses, including the para-recurrent laryngeal nerve were also identified.