The influence of preterm birth on the development of intracardiac nerve fibers in the postnatal ontogenesis: an immunohistochemical study

Rationale. At the time of birth, the innervation of the rat heart is not complete: differentiation of neurons of the autonomic ganglia, growth of axons, and development of nerve fibers sheaths continue in the postnatal period of ontogenesis. Whether preterm birth affects the innervation of the heart has not been sufficiently studied. Aim: To perform immunohistochemical study of cardiac nerve fibers of preterm rats in the postnatal period of ontogenesis. Material and Methods. A morphological study of the development of intracardiac nerve fibers in the right and left ventricles, as well as the interventricular septum of the heart in full-term and 24-hour preterm Wistar rats on the 7th, 56th and 180th days of the postnatal period of ontogenesis was carried out. Immunohistochemical detection of PGP9.5 and tyrosine hydroxylase was carried out. The relative area of nerve fibers (PGP9.5-positive staining) and sympathetic postganglionic nerve fibers (tyrosine hydroxylase-positive staining) was determined dynamically, as well as the proportion of sympathetic nerve fibers from nerve fibers total number in the wall of the right and left ventricles, as well as the interventricular septum of the heart of full-term and 24-hour preterm rats. Results. It has been shown that on the 7th day of the postnatal period of ontogenesis in the right, left ventricle and interventricular septum of the heart in 24-hour preterm rats, the relative area of nerve fibers is reduced, compared with that in full-term animals, the differences are leveled out by the 56th day. The relative area of sympathetic postganglionic nerve fibers in the interventricular septum of 24-hour preterm rats on the 7th day of the postnatal period of ontogenesis remains lower, on the 56th day – is higher than in fullterm animals. The relative area of sympathetic postganglionic nerve fibers in the right ventricle of the heart of 24-hour preterm rats throughout the experiment remains lower, while in the left ventricle – does not differ from the parameters of full-term animals. Conclusion. There were revealed structural features of the development of intracardiac nerve fibers of the right and left ventricles of the heart, as well as the interventricular septum in 24-hour preterm rats in the postnatal period of ontogenesis, which may be the cause of a violation of the autonomic regulation of the heart.