Neuropeptides in atrial subepicardial ganglia of rats

The distribution of several neuropeptides in subepicardial atrial ganglia was examined in the rat heart by using immunohistochemical techniques. Some of the ganglion cells in the right atrium exhibited neuropeptide Y-immunoreactivity while no immunostaining was found with antisera against atrial natriuretic polypeptide (ANF), substance P, vasoactive intestinal polypeptide (VIP), and calcitonin gene-related peptide (CGRP). Nerve fibers in and around the ganglia showed neuropeptide Y, calcitonin gene-related peptide and vasoactive intestinal polypeptide immunoreactivities. Some of these immunoreactive fibers (substance P, calcitonin gene-related peptide, neuropeptide Y) formed relatively dense networks around blood vessels and capillaries. Atrial natriuretic polypeptide-like immunoreactivity which was present in atrial myocytes failed to show up in any neuronal elements in the rat heart.