DISTRIBUTION OF CALCITONIN-GENE-RELATED PEPTIDE, ATRIAL-NATRIURETIC-PEPTIDE AND NEUROPEPTIDE-Y IN THE RAT-HEART

Calcitonin gene-related peptide (CGRP) is a novel neuropeptide, predic ted on the basis of structural analysis of the rat calcitonin gene. It is a neurotransmitter which has been suggested to take part in sensor y transmission. In this study, we have examined the distribution of th is peptide, alpha-atrial natriuretic peptide immunoreactivity (irANP) and neuropeptide Y (NPY) within different regions of the rat heart. At tempts were also made to compare the distributions of these peptides i n the regions examined, through different methods of immunocytochemist ry and further comparing these results with those obtained through rad ioimmunoassay. The distributions of the peptides in the atria were sim ilar to results obtained with radioimmunoassay, but there were no myoc ytes containing irANP in the ventricles with immunocytochemistry as op posed to radioimmunoassay. While the staining obtained for irANP in th e atrium was more intense in the right, CGRP and NPY nerve fibres were two to three times more abundant in the left atrium. The high local c oncentration of a vasoconstrictor peptide in the region of coronary ve ssels may suggest that it is involved in the control of vascular smoot h muscle tone. The method of choice with the immunocytochemical studie s was that of the susa wax technique for irANP. Caution should therefo re be observed when interpreting results based only on a single staini ng technique.