Nerve structures of the heart and their immunohistochemical characterization in 10-week-old porcine foetuses.

The aim of the present study was to investigate the distribution of neuronal perikarya and nerve fibres and their chemical coding in the heart of 10-week-old porcine foetuses. The foetuses, obtained from a local slaughterhouse, were fixed by immersion in 4% buffered (pH 7.4) paraformaldehyde. Cryostat sections of the hearts were processed for single- or double-labelling immunofluorescence methods using antibodies against protein gene product (PGP) dopamine beta-hydroxylase (DβH), acetylcholine vesicular transporter (VAChT) and calcitonin gene-related peptide (CGRP). Numerous clusters of the PGP-positive nerve cells were observed throughout the heart wall. The majority of the clusters were found beneath the epicardium around the root of the aorta, pulmonary trunk and main veins. Some single PGP-positive neurons or small clusters of nerve cells were observed in the epicardium of heart atria and ventricles. The richest network of PGP-positive nerve fibres was observed in the base of the heart near the main cardiac blood vessel openings. Many bundles of PGP-positive nerve fibres were observed throughout the four cardiac chambers. Double-immunohistochemical staining revealed that the majority of the neurons contained immunoreactivity to VAChT, some of them stained for CGRP and the single neuronal somata were DβH-positive. The nerve fibres supplying the heart expressed immunoreactivity to DβH, VAChT or CGRP. The distribution and neurochemical coding of the nerve structures in ten-week-old foetuses are different from those observed in the hearts of juvenile pigs.