Aerobic physical training and alterations in pressor response during norepinephrine infusion: a controlled single-subject experiment.
To test the influence of aerobic physical training on pressor response to infused norepinephrine, the present study utilized a single subject A-B-A-B withdrawal design consisting of 9-week alternating sedentary and aerobic phases (S1, A1, S2, A2). During each 9-week phase the subject underwent infusions every 3 weeks, consisting of saline, low-dose and high-dose norepinephrine (Low-NE, High-NE). Heart rate and mean arterial blood pressure were monitored continuously; resting platelet and plasma catecholamines were also measured. Infusions were conducted 48 h from the most recent exercise bout to minimize residual effects of acute exercise. Fitness level was confirmed by VO2max during graded exercise testing at the conclusion of each 9-week phase. Blood pressure during saline did not differ between aerobic and sedentary phases. However, in all but one comparison, aerobic fitness was associated with a highly significant reduction in pressor response during Low-NE as well as High-NE. Plasma norepinephrine was higher during the two aerobic phases; platelet catecholamines and plasma epinephrine showed no reliable association with fitness. Results for this subject support an attenuation of pressor response associated with aerobic conditioning.
Morrell
E M
EM
University of Michigan, Ann Arbor.
Cameron
O G
OG
Kandarian
S C
SC
Renk
C M
CM
Weder
A B
AB
Pomerleau
O F
OF
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D015444:Exercise; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects*; D010806:Physical Education and Training / Q000379:methods*; D013564:Sympathetic Nervous System / Q000187:drug effects*
D009638:Norepinephrine