Calcitonin gene-related peptide-, neuropeptide Y- and tyrosine hydroxylase-immunoreactive nerve fibers in the human umbilical cord.

The distribution of nerve fibers positive for calcitonin gene-related peptide (CGRP), which is a vasodilator peptide, neuropeptide Y (NPY), which is a vasoconstrictor peptide, and tyrosine hydroxylase (TH), which is a key enzyme for the synthesis of the neurotransmitter of adrenergic nerves, was studied in the fetal side, middle part, and placental side of the human umbilical cord using immunohistochemistry. In the fetal side of the umbilical cord, CGRP-, NPY-, and TH-positive fibers were observed in the smooth muscle of the media of the umbilical artery and in the margins of the Wharton jelly. They were not observed around the umbilical vein or in the middle part or placental side of the umbilical cord. These results demonstrate the presence of the vasoactive peptides CGRP and NPY, as well as of the enzyme TH in the fetal side of the umbilical vessel. The presence of CGRP and NPY suggests the involvement of these peptides in the regulation of the umbilical and placental circulation.