Tonic activity of carotid body chemoreceptors contributes to the increased sympathetic drive in essential hypertension

Abstract

Carotid chemoreceptors provoke an increase in muscle sympathetic nerve activation (MSNA) in response to hypoxia; they are also tonically active during normoxic breathing. The contribution of peripheral chemoreceptors to sympathetic activation in hypertension is incompletely understood. The aim of our study was to investigate the effect of chemoreceptor deactivation on sympathetic activity in untreated patients with hypertension. A total of 12 untreated hypertensive males and 11 male controls participated in this randomized, crossover, placebo-controlled study. MSNA, systolic blood pressure(BP), diastolic BP, heart rate (HR), electrocardiogram, hemoglobin oxygen saturation (Sat%) and respiratory movements were measured during repeated 10-min periods of respiration with 100% oxygen or 21% oxygen in a blinded fashion. Compared with controls, hypertensives had higher resting MSNA (3810 vs. 290.9 burst per min, P0.05), systolic BP (15012 vs. 12410 mm Hg, P 0.001) and diastolic BP (9210 vs. 779 mm Hg, P0.005). Breathing 100% oxygen caused significant decrease in MSNA in hypertensive patients (3810 vs. 268 burst per min and 1000 vs. 9010 arbitrary units, P0.05) and no change in controls (299 vs. 277 burst per min and 1000 vs. 9611 arbitrary units). BP, respiratory frequency and end tidal CO 2 did not change during chemoreceptor deactivation with hyperoxia. HR decreased and Sat% increased in both the study groups. These results confirm the role of tonic chemoreceptor drive in the development of sympathetic overactivity in hypertension. © 2012 The Japanese Society of Hypertension All rights reserved.