Catecholaminergic innervation of the equine ureter.

The aim of the present study was to determine the distribution and density of catecholaminergic nerve fibres and cells in the equine ureter by using immunohistochemical techniques to localise the enzyme tyrosine-hydroxylase (TH). TH-immunoreactive (TH-IR) nerve fibres entered the wall of the ureter as adventitial nerve trunks accompanying the blood vessels. These trunks repeatedly branched as they coursed through the muscular layer towards the epithelium, forming muscular, perivascular and subepithelial nerve plexuses. TH-IR nerve fibres were especially numerous in the pelvic and intravesical ends of the ureter. TH-IR cells have also been identified in the equine ureteral wall, usually grouped as adventitial and intramural nerve ganglia. The results of the present study demonstrated that the equine ureter, like that of other mammals, possesses a rich autonomic supply of catecholaminergic (TH-IR) nerve fibres. These morphological data support a role for the autonomic nervous system in the control of ureteral peristalsis.