Distribution and immunohistochemical characteristics of neurons in the porcine caudal mesenteric ganglion projecting to the vas deferens and seminal vesicle.

Combined retrograde tracing (using fluorescent tracer Fast Blue) and double-labelling immunofluorescence were used to study the distribution and immunohistochemical characteristics of neurons in the porcine caudal mesenteric ganglion projecting to the vas deferens and seminal vesicle. The distribution and immunohistochemical properties of neurons projecting to both organs were similar. As revealed by retrograde tracing, Fast Blue-positive neurons were located within the left and right ganglia, with a distinct predominance in the ipsilateral one. In the ipsilateral ganglion, the majority of the neurons were located caudally, along the dorso-lateral ganglionic border, suggesting a somatotopic organization of the ganglion. Immunohistochemistry revealed four populations of retrogradely labelled neurons (from the largest to the smaller one): tyrosine hydroxylase-positive/neuropeptide Y-negative (TH+/NPY-), TH+/NPY+, TH-/NPY-, TH-/NPY+. With respect to their surrounding nerve fibres, two subpopulations of the dye-labelled neurons could be distinguished. The small one consisted of solitary neurons receiving a strong calcitonin gene-related peptide- and Leu5-enkephalin-, and a less intense vasoactive intestinal peptide-immunoreactive innervation. The remaining neurons were poorly supplied by singular nerve fibres containing some of the investigated peptides. We conclude that the caudal mesenteric ganglion should be considered as a prominent source of adrenergic and/or NPY-positive innervation for the porcine male reproductive tract.