Modulation of Cardiac Growth by Sympathethic Innervation: Differential Response between Normotensive and Hypertensive Rats

Sympathethic innervation of the heart develops during late gestation and is not fully mature until the end of the neonatal period. The onset of neuroeffector transmission coincides with the cessation of myocyte mitosis (Claycomb, 1976) and the beginning of cellular hypertrophy (Clubb and Bishop, 1984). This process must occur during normal development and growth but also occurs pathologically in the setting of heart disease and hypertension. Although hemodynamic load is a major stimulus for cardiac hypertrophy, it is not the sole regulatory mechanism as evidenced by hypertrophic cardiomyopathy, which occurs in the presence of presumed normal hemodynamics.