A new approach to analysis of synchronized sympathetic nerve activity

Renal sympathetic nerve activity (RSNA) recorded from the multifiber preparation is a continuously fluctuating variable in terms of period and amplitude, reflecting a coordinated tonic level of output from the vasomotor center. Yet current methods of analysis cannot simultaneously measure both of these parameters. A new accurate technique for assessing changes in global sympathetic activity is required. We made a novel application of a computerized peak detection algorithm (Cluster program) to recordings of synchronized sympathetic nerve discharges. The procedure was applied to this new area to retrieve information about the characteristics of synchronized RSNA. Peaks in synchronized RSNA activity were detected from short-term (20 ms) integrated recordings in which voltage changes had been digitized at 200 Hz and stored on computer. The program scanned the data series for significant increases followed by significant decreases in a small cluster of voltage values. The program permits the input of the cluster sample sizes for the test peaks and pre- and postpeak nadirs and also the minimum height to be defined as a peak. Once each synchronized RSNA peak had been detected, its corresponding amplitude, width, and peak-to-peak interval were calculated. The program successfully characterized RSNA in a group of eight cats and yielded results comparable to other analysis techniques. The peak-to-peak interval period showed two modes of synchronized discharge, one related to the cardiac cycle and a faster 8- to 14-Hz frequency. The synchronized peak amplitude and width showed unimodal frequency distributions. The relationship between each of the three variables was examined; only the peak height and width were significantly related to each other.(ABSTRACT TRUNCATED AT 250 WORDS)