A sympathetic component of baroreflex function in patients with essential hypertension.
1. The baroreflex-mediated changes in plasma norepinephrine (NE) and heart period (RR interval) to phenylephrine (PE)-evoked pressor and nitroprusside (NP)-evoked depressor stimulations were studied in 19 patients with chronic essential hypertension, 12 with borderline hypertension and in 11 age-matched normal controls. 2. Intravenous infusion of PE at a rate of 0.25-1.0 microgram/kg/min induced dose-related increases in mean arterial pressure (MAP) and in RR interval and a decrease in plasma NE. Similarly, NP infusion at a rate of 0.1-0.4 microgram/kg/min evoked the opposite changes in each variable. The reflex sensitivity was defined as the slope of linear regression between the changes in RR interval and MAP (RR/MAP) and between those in plasma NE (% of the baselines) and MAP (%NE/MAP). 3. Both RR/MAP and %NE/MAP for pressor and depressor stimulations were reduced below values found in normal subjects, in both chronic and borderline hypertensives. 4. The values of %NE/MAP was negatively related to the basal plasma NE during falls in blood pressure (r = -0.401, P less than 0.05). 5. The %NE/MAP may be a useful index of the sympathetic component of baroreflex sensitivity. A decrease in %NE/MAP in hypertensive and borderline hypertensive patients suggests a blunted sensitivity of the sympathetic constrictor reflexes.
Meguro
Y
Y
Second Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Miura
Y
Y
Kimura
S
S
Noshiro
T
T
Sugawara
T
T
Takahashi
M
M
Watanabe
H
H
Sano
N
N
Ohzeki
T
T
Shimizu
K
K
D000328:Adult; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000097:blood; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*
D009599:Nitroprusside; D010656:Phenylephrine; D009638:Norepinephrine