The sympatho-adrenal tone and reactivity in human hypertension

In the last two decades, remarkable advances have permitted a better understanding of the modulation of sympathetic tone and reactivity at the sympathetic nerve and at the effector cell levels. In man, several indirect approaches have permitted to suggest the possibility of increased sympathetic nerve activity and reactivity in an important subgroup of essential hypertensive patients. The demonstration of significant correlations between circulating levels of sympathetic transmitters and various parameters of cardiovascular functions supports the hypothesis of a participation of the sympathetic system in the maintenance of an elevated blood pressure in those patients. Moreover, several experimental evidences have indicated that the sensitivity of cardiovascular effector cells may be altered in hypertensive patients. The blunted beta receptor responsiveness and the normal or enhanced alpha receptor responsiveness which were observed suggest the possibility of an imbalance between adrenergic receptor functions in hypertension, which may explain the preferential alpha 1 modulation of blood pressure through changes in peripheral resistance in hypertensive patients. Such an abnormality could contribute to the development of cardiac and vascular wall hypertrophy during the evolution of hypertension. These studies therefore suggest that a variety of sympathetic dysfunctions could play a role in the development, maintenance and evolution of human essential hypertension.