Influence of oestradiol on distribution of VIP-and NPY-positive nerve fibers and VIP and NPY concentrations in the porcine female reproductive tract

The pattern of distribution of nerve fibers containing vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) in the oviduct and uterine horn was compared in ovariectomized (OVX) gilts administered oestradiol or placebo. Compared to controls, VIP-positive nerve fibers were scarce in the muscular layer and submucosa and absent under the luminal epithelium of the oviduct and uterine horn by 24 hours after oestradiol administration. Their number was steadily returning to the number visible in control animals by 72 hours after hormone administration, except that the nerve fibers located under the luminal eptihelium were still absent. NPY-positive nerve fibers were slightly more numerous by 24 hours after the oestradiol administration, but their number was falling to the number visible in control gilts by 72 hours after oestradiol administration. There were surprising discrepancies between the visible number of nerve fibers and quantitative measurements of VIP and NPY concentrations in the oviduct and uterine horn. Administration of oestradiol increased VIP concentration in the ampulla of the oviduct and perioviductal and middle part of the uterine horn, which then gradually decreased. However, VIP level in the isthmus of the oviduct and paracervical part of the uterine horn decreased after oestradiol. Oestradiol also decreased NPY concentration in the isthmus of the oviduct and the middle and perioviductal part of the uterine horn, but increased NPY concentration in the paracervical part of the uterine horn. The NPY concentration in the ampulla of the oviduct was similar among gilts.