Immunohistochemical study of the nervous structures of the mediastinal organs

Abstract

BACKGROUND: No studies have sufficiently evaluated the innervation of the mediastinal organs in the P1 period when the blood circulation switches from placental to pulmonary and the regulation of respiration and functioning of the cardiovascular system begin. AIM: This study aimed to conduct a comparative immunohistochemical analysis of the innervation of the mediastinal organs of newborn rats. MATERIALS AND METHODS: Immunohistochemical methods were employed for identifying neuronal markers: PGP 9.5 protein, tyrosine hydroxylase, and synaptophysin. Primary antibodies were applied to mediastinal sections after they had been deparaffinized. RESULTS: Analysis of frontal sections of the cardiopulmonary complex of rats at P1 showed that the bronchi, esophagus, great vessels (aorta and pulmonary artery trunks), veins (pulmonary and caval), adipose tissue, lymph nodes, lung fragments, and heart occupied the upper and middle sections of the mediastinum. Closely adjacent parasympathetic and sympathetic ganglia, microganglia, nerve trunks, and plexuses of nerve fibers were identified using neuronal markers in the interstitium between organs. In the upper and middle mediastinum of newborn rats, synaptic structures were identified in the ganglia and paraganglia, mixed lobules of adipose tissue, esophageal and bronchial wall, around small arteries and arterioles for the first time using immunohistochemical methods. CONCLUSION: This comparative study revealed that in the early period of postnatal development of rats, the walls of the esophagus, trachea, and main bronchi are most innervated in the mediastinum; in the myocardium and lungs, these nervous apparatuses are typically rare or absent. A high concentration of synaptic structures in the conducting myocardium has been described.