Changing role of the autonomic nervous system in human hypertension.

Pathophysiological effects of the autonomic nervous system are clearly seen in young patients with a high cardiac output and borderline hypertension. As the hypertension progresses, there is a change from the hyperkinetic circulation in borderline hypertension to the increased vascular resistance seen in established hypertension. This hemodynamic transition is caused by decreased beta-adrenergic responsiveness and decreased end-diastolic distension of the heart combined with an increased alpha-adrenergic responsiveness of the resistance vessels. In parallel, the sympathetic tone decreases in the course of hypertension. This transition in sympathetic tone can be explained by the hypothesis of the 'blood pressure seeking properties of the brain'. The central nervous system 'seeks' to maintain a higher pressure. When vascular overresponsiveness sets in, less sympathetic drive is needed to maintain a neurogenic hypertension. Sympathetic overactivity in borderline hypertension is associated with overweight subjects, insulin resistance and dyslipidemia. This suggests a new area of research to investigate the basis of metabolic abnormalities in hypertension.