[Changes in plasma norepinephrine levels to stepwise tilting--comparisons between the young and aged].
Plasma norepinephrine level was measured in the 9 young (22-26 years old) and the 8 aged (66-81 years old) normal volunteers in stepwise tilting. After 30 minutes rest in recumbent position, the table was tilted in stepwise manner (15 degrees, 30 degrees, 45 degrees, 80 degrees) each for 5 minutes and blood samples were taken at the end of the each angle. The changes of the level was compared between the two groups and with the data resulted from the examination of muscle sympathetic activities by microneurography. The norepinephrine level increased with the stepwise tilting and the positive linear correlation was observed between the levels and the sine values of tilting angles. The absolute levels in the aged were significantly higher than those in the young in 0 degrees, 15 degrees, and 30 degrees. The increasing rates of plasma norepinephrine (percentages of increase against the level in 0 degrees position) in the aged were significantly lower than those in the young in 45 degrees and 80 degrees. These partly resembled the character observed in the two groups in muscle sympathetic activity. However, the gradients of the mean regression lines of the two groups in plasma norepinephrine level were not significantly different, although they were clearly different in muscle sympathetic activity. This means that the difference between the young and the aged was more clearly shown in muscle sympathetic activity than in plasma norepinephrine level.
Kunimoto
M
M
Department of Neurology, Institute of Brain Research, University of Tokyo.
Aizawa
H
H
Yamasato
M
M
Mannen
T
T
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood*; D011187:Posture; D012044:Regression Analysis
D009638:Norepinephrine