Assessing the noradrenergic system in normal aging: a review of methodology

Studies evaluating plasma norepinephrine in the normal elderly have found significant increases as compared to the young and middle-aged individuals. The increased plasma norepinephrine concentrations found during the normal aging process in man may be relevant to both the understanding of drug therapeutics and underlying mechanisms of the noradrenergic system in the elderly. The authors critically review the experimental design of studies that have evaluated plasma norepinephrine and age. The various conditions and methods for assessment of plasma norepinephrine concentrations, which may contribute to the finding of a hypernoradrenergic system in the aged, are examined. An attempt is made to collate the studies and develop a standardized methodology for studying the peripheral noradrenergic system in the elderly.