Human hypertension, sympathetic activity and the selfish brain

Despite the harmful consequences of high blood pressure (hypertension; e.g. stroke, renal failure, dementia and even death), the underlying physiological mechanisms that cause the onset of hypertension are poorly understood. The most established finding is that hypertension occurs alongside activation of the sympathetic nervous system, yet exactly what triggers this in humans is ambiguous. This review discusses evidence for elevated sympathetic nerve activity, particularly in human hypertension, and revisits an historical theory regarding the aetiology underlying human hypertension that was proposed by Seymour Kety and John Dickinson in the 1940s-1950s. My research group hypothesizes that elevated sympathetic nerve activity and hypertension develop as a fundamental mechanism to maintain adequate cerebral blood flow, which is now termed Cushing's mechanism or the selfish brain hypothesis. Moreover, it goes against the traditional belief that high cerebrovascular resistance is a consequence of hypertension; we propose that this elevated resistance drives hypertension. This review discusses historical and new evidence in animals and humans supporting this hypothesis. In particular, unique human data indicating a higher prevalence of congenital cerebral vascular abnormalities in hypertension are considered.