The assessment of sympathetic nervous function in human stress research.

The methods currently available for measuring sympathetic nervous system activity in human stress research are critically reviewed. The advantages and limitations of catecholamine measurements in plasma and urine are considered. The contribution of skeletal muscle sympathetic activity to noradrenaline concentration in venous blood represents a serious drawback of this measure, and under many circumstances, urinary assay may reflect arterial catecholamine levels more accurately. The potential benefits of assessing noradrenaline clearance are described. Other methods of assessing sympathetic activity are also reviewed, including microneurographic techniques and the use of pharmacological blockade. General recommendations are given about the methods of greatest value in human stress research.