Cardiac autonomic denervation in diabetes mellitus.

The heart is heavily innervated with sympathetic and parasympathetic nerve fibers. Although both receptor types are present in the atria and ventricles, the cholinergic receptors are located mainly in the atria and the adrenergic receptors in the ventricles. The distribution of these receptors in the ventricles is not homogenous but follows apex-to-base and epicardium-to-endocardium gradients. The adrenergic receptors are localized in the myocardium and in the coronary arteries and are of several types and subtypes. The receptors constitute 15% of the total receptors and are both postand presynaptic, whereas the -receptors constitute 85% of the receptors and are postsynaptic. In the coronary arteries, -1d and -2 are most common, whereas in the left ventricular (LV) myocardium, -1a and -1 prevail.1