The nerve distribution in the testis of the cat

The autonomous innervation of the feline testis was investigated by immunohistochemistry and a modified acetylcholinesterase technique. The nerves reach the testis mainly by two routes: (1) with testicular artery and pampiniform plexus to the cranial extremity (funicular contribution), (2) from the epididymal tail to the caudal extremity (caudal contribution). Within the tunica albuginea the funicular contribution supplies the cranial two thirds, whereas the caudal third of the tunica receives its nerves via the ligamentous connection between testis and epididymal tail. The nerve bundles accompanying the testicular artery give branches to the arterial wall and the pampiniform plexus. When reaching the cranial testicular pole the bundles separate; the majority of them pass into the centrally located mediastinum testis, another large portion enters the tunica albuginea, particularly on its epididymal side. The septula testis are innervated from both sides, that is from the mediastinum and from the tunica albuginea. In the cat, contrary to other mammals, all septula are innervated. Furthermore, nerve fibers occur regularly within the testicular lobules. Generally, the testicular nerves of the cat are unmyelinated and mainly vascular nerves, but fibers are also found within the connective tissue compartments of the testis. The vast majority of all autonomous testicular nerves are postjunctional sympathetic fibers. Terminal ramifications of cholinergic fibers are exclusively observed in the wall of medium-sized arterioles within mediastinum, septula and lobuli testis. Neuropeptide Y is the most frequent peptidergic transmitter in feline testicular vascular plexuses. The amount of calcitonin gene-related peptide-positive fibers is also remarkably high in the testis, but prefers a location within the stroma of the tunica albuginea, mediastinum and septula. In the cat, Leydig cells occur not only in intertubular locations, but also as intratunical and mediastinal Leydig cells. In all three localizations solitary nerve fibers are observed between Leydig cell groups. These fibers are generally dopamin-beta-hydroxylase- and tyrosine hydroxylase-positive, some contain calcitonin gene-related peptide and, very few, substance P.