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

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 (38 ± 10 vs. 29 ± 0.9 burst per min, P