Abstract
A comparative study of the nerve structures and the density of mast cells in the heart of rats aged 3–4 and 23 months was carried out with histological and histochemical methods and the immunohistochemical markers PGP 9.5, tyrosine hydroxylase (TH), and synaptophysin. It was found that tissues innervation decreases with aging in all studied heart areas, particularly, sympathetic innervation. A decrease in sympathetic plexus density and the presence of dystrophic and degenerative changes in TH-immunopositive axon terminals were registered. It was also demonstrated that the mast cell population in old animals increases in the connective tissue of the pericardial, in the epicardium, and the myocardium of atria and ventricles region upon a decrease in sympathetic innervation. It is suggested that the increase in the number of mast cells in the heart during aging occurs in response to a deficiency in catecholamines and is related to the mast-cell secretion of biologically active substances (heparin, histamine, and serotonin), which help maintain local tissue homeostasis and adaptive and compensatory reactions of the animal heart.
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