Single-unit sympathetic discharge : Quantitative assessment in human hypertensive disease

Background-Reports demonstrating sympathetic hyperactivity in hypertension with the use of microneurography have been inconsistent. One possible reason is that previous studies have assessed muscle sympathetic nerve activity (MSNA) from integrated voltage waves ("bursts") recorded from multiunit discharges. We studied single units with defined vasoconstrictor properties (s-MSNA) to further characterize sympathetic output in hypertensive disease. Methods and Results-We examined 74 subjects with a wide range of arterial blood pressure that were considered to be either normal (NT), high normal (HN), or stages 1 to 3 essential hypertension (EHT-1, EHT-2/3). All had their peripheral sympathetic activity measured from both multiunit bursts and single-unit vasoconstrictor impulses. There was a significant correlation between s-MSNA and MSNA, and results of variability studies were similar. The EHT-1 and EHT-2/3 groups had greater s-MSNA and MSNA than did the matched NT group (always P