Fig. 1. Original trace from an experiment investigating baroreflex sensitivity showing the effects of a bolus injection of sodium nitroprusside (SNP, 3 μg/kg) on arterial pressure (determined by volume plethysmography) and muscle sympathetic activity (MSA). Bursts are indicated by dots . The decrease in diastolic pressure of 20 mmHg is followed by a marked increase in MSA. Correlating MSA burst area with diastolic arterial pressure during the decrease in blood pressure on a beat-to-beat basis allows determination of baroreflex sensitivity. ECG = electrocardiogram.