The measurement of plasma noradrenaline before and after tilt in young and old healthy subjects

Using a modified sensitive and specific radioenzymatic method we have determined the normal range for plasma noradrenaline in healthy, elderly individuals. The effects of tilt on the cardiovascular system and on plasma noradrenaline responses were found to be different compared with healthy young controls. The elderly had higher resting plasma noradrenaline concentrations with an exaggerated response to head-up tilt. In spite of this higher sympathetic drive, the cardiovascular responses in the elderly were attenuated.