Carotid chemoreflex control of blood pressure at rest and during exercise in young‐onset hypertension

Despite reports of amplified carotid chemoreflex sensitivity to hypoxia in young adults with hypertension (<40 years), it is unclear whether this equates to a direct role of this reflex in maintaining high resting and exercise blood pressures (BP). The aim of this study was to examine whether tonic carotid chemoreflex activity contributes to high resting and exercise BP in young people with untreated hypertension compared to normotensives (NTN). In 14 NTN and 14 untreated hypertensives (HTN) (aged 27 ± 6 and 28 ± 5 years, respectively) the ventilatory and haemodynamic responses to hypoxia were measured using the transient hypoxic test at rest and during submaximal steady-state upright cycle exercise (40%–50% VO_2peak). A double-blinded placebo-controlled systemic infusion of low-dose dopamine (2 mcg/kg/min) was used to inhibit the carotid chemoreflex and assess its tonic contribution to ventilation and BP at rest and submaximal exercise (mixed-model ANOVA). The hypoxic ventilatory response (HVR) at rest and submaximal cycle exercise were comparable between groups and were similarly blunted by dopamine infusion in both groups. However, at rest, there was a greater decrease in resting systolic BP (SBP) during carotid chemoreflex inhibition in the HTN group. Notably, during submaximal exercise, SBP was reduced during dopamine versus that during saline, but the decrease was similar between groups. The carotid chemoreflex appears to contribute to resting SBP in young people with untreated HTN but does not play a role in exaggerated exercise BP responses in this group.