Immunohistochemical and biological evidence for a neuromodulator function of neuropeptide Y in the human oviduct.

By means of the peroxidase-antiperoxidase technique the existence of neuropeptide Y-immunoreactivity (NPY-IR) in nerve fibers of the normal human uterine tube was established. NPY-IR fibers are found to supply vascular and non-vascular smooth muscles of the uterine tube. In both systems the density of NPY-IR nerves is markedly high. The NPY-IR nerves exhibit a predominance for the arterial portion of the oviductal vasculature in the serosal, the muscle and the mucosal layer. Furthermore in the mucosal layer, some NPY-IR fibers occur in contact with the surface epithelium. In-vitro experiments with helical strips of the human uterine tube reveal no significant effects of NPY alone of the different parameters (resting tension, frequency and amplitude of spontaneous contractions) of mechanical activity while it seems to act in combination with acetylcholine. Thus, the distinct innervation patterns of the NPY-IR nerve fibers as well as the results obtained by bioassay may suggest a neuromodulator function of this neuropeptide in the human uterine tube. In this respect, NPY may play an important role in the transport of the eggs through the tube.