Presence of Ganglia and Brown Fat in Human Atrial Pericardium: Histology Characterization

Cardiac contraction is performed by contractile stimuli of the specific myocardium and by sympathetic and parasympathetic regulation, whose nerve ganglia are located at the level of the mediastinum.This study analyzes other nerve pathways organized in ganglion units in the human atrial pericardium and surrounding brown fat.Human samples from the right atrium, obtained and authorized by the Faculty of Medicine of the Universidad de Chile, were fixed in 10 % formalin for 48 hours (5 m sections).For histological analysis of the samples, routine hematoxylin and eosin and special techniques of toluidine blue, orcein, and van Gieson staining were used for the observation of Nissl bodies, elastic fibers, cytoplasm, collagen, and brown fat, respectively.Immunohistochemistry techniques were used to recognize the presence of neurofilaments and S100 protein (DAB).The histological and immunocytochemical analysis revealed the presence of a ganglion composed of globose neurons that reacted positively to the recognition of neurofilaments, distinctive elements of the cytoskeleton of neurons.The cells surrounding the neurons were shown to be positive for S100 protein.Additionally, subepicardial brown fat was observed.The study concludes by demonstrating and describing the presence of well-formed ganglia in the subepicardial connective tissue, with abundant brown fat.The presence of ganglia and brown fat could explain some symptoms and pathologies of unknown origin, such as angina and sudden death.