Histological study on the distribution of autonomic nerves in the human heart

To investigate the distribution of autonomic nerves in the human heart, six autopsied hearts without cardiovascular disease were studied by a histochemical method for acetylcholinesterase (AChE) and by an immunohistochemical method for tyrosine hydroxylase (TH). The density of nerve distribution was microscopically calculated by the point-counting method to evaluate regional distribution of the autonomic nerves. There were more AChE-positive nerves and TH-positive nerves in the atrium than in the ventricle, and more at the base than at the apex in the ventricle. There were more AChE-positive nerves in the subendocardial area than in the subepicardial area of the myocardium. In the atrium, AChE-positive nerves were more numerous than TH-positive nerves. On the other hand, there were more TH-positive nerves than AChE-positive nerves in the ventricle. Predominancy of the distribution density at the anterior to the posterior wall of the ventricle was observed for TH-positive nerves. The different distribution patterns of sympathetic and parasympathetic nerves could modify cardiac performance under both physiologic and pathologic conditions.