Catecholamines in the Brain: An Assay with Norepinephrine

Abstract

The National Institutes of Health, in Bethesda, Maryland, offers a broad range of research areas. One area which is under considerable investigation is the study of catecholamines. The following study is concerned with the catecholamine norepinephrine. A sensitive and specific radiometric method has been used to measure human plasma norepinephrine. The purpose of the following report is to describe a standardized procedure which has been developed and is in current use in the laboratory of Dr. Charles Rayfuond Lake at the Clinical Center of the National Institute of Mental Health. Levels of norepinephrine (NE) in human plasma have been determined by a radioenzymatic technique sufficiently sensitive to measure 0.014 ng NE per ml plasma. Several procedures which raise plasma NE levels have been compared and a standard procedure used to evaluate sympathetic neuronal function based on the increments in plasma NE produced by postural change and a standard amount of exertion. The mean basal level of NE in plasma of 74 resting, supine, normal subjects ranging in age from 10 to 70 (mean 32.7 years) was 0.292 ± 0.016 (± SEM) ng/ml and ranged from 0.112 to 0.738 ng/ml. There was a significant correlation between age and basal levels of NE (L.R. = 0.33, p 0.01). In 44 subjects who stood for 5 minutes after the basal sample of blood was obtained, the mean plasma level of NE increased to 0.538 + 0.044 ng/ml and further increased to 0.778 + 0.080 ng/ml after a subsequent isometric hand grip for 5 minutes.