Distribution of the hypothalamic cardioactive hormone "G"-protein complex (PCG) in neuronal elements of the heart in intact and vagotomized rats.

The distribution of the protein-carrier of one of the coronary dilatatory glycopeptides, neurohormone "G" (PCG) in rat heart was examined by immunohistochemistry. PCG-immunoreactive nerve fibers and varicosities were found around cardiac ganglion cells and in close topographical contact with coronary vessels and capillaries of the heart. The anatomical localization of the PCG-containing neuronal fibers was similar that of calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY); however, the intensity of the stainings were different. In contrast to NPY immunostainings, cardiac ganglion cells did not show any PCG immunoreactivity. Some of the small, SIF cell-like NPY immunopositive neurons were also immunostained to PCG. In the atrial cardiomyocytes, only ANP exhibited fairly intensive immunoreactivity. Fourteen days after vagotomy, no considerable changes were found in the distribution of PCG and other neuropeptides investigated in cardiac neurons and nerve fibers. The presence of PCG in cardiac neuronal elements suggests a possible role of this peptide in cardiovascular regulations.