Consequences of peripheral chemoreflex inhibition with low-dose dopamine in humans

Key points Low-dose dopamine reduces the ventilatory response to acute hypoxia both in animal and in human studies. In this study we show that low-dose dopamine also attenuates the haemodynamic responses (tachycardia, hypertension) to acute hypoxia in healthy humans. Moreover, we found that dopamine withdrawal results in a temporary increase in minute ventilation. The magnitude of the increase in minute ventilation after dopamine withdrawal correlates with the degree of ventilatory response to acute hypoxia and depends on the duration of dopamine administration. Dopamine may provide a novel method for assessing differences in the level of peripheral chemoreceptor activity, which has important clinical implications given the recently reported pathological role of the carotid body in cardiovascular diseases in animals and humans. Low-dose dopamine inhibits peripheral chemoreceptors and attenuates the hypoxic ventilatory response (HVR) in humans. However, it is unknown: (1) whether it also modulates the haemodynamic reactions to acute hypoxia, (2) whether it also modulates cardiac baroreflex sensitivity (BRS) and (3) if there is any effect of dopamine withdrawal. We performed a double-blind, placebo-controlled study on 11 healthy male volunteers. At sea level over 2 days every subject was administered low-dose dopamine (2 mu g kg(-1) min(-1)) or saline infusion, during which we assessed both ventilatory and haemodynamic responses to acute hypoxia. Separately, we evaluated effects of initiation and withdrawal of each infusion and BRS. The initiation of dopamine infusion did not affect minute ventilation (MV) or mean blood pressure (MAP), but increased both heart rate (HR) and cardiac output. Concomitantly, it decreased systemic vascular resistance. Dopamine blunted the ventilatory, MAP and HR reactions (hypertension, tachycardia) to acute hypoxia. Dopamine attenuated cardiac BRS to falling blood pressure. Dopamine withdrawal evoked an increase in MV. The magnitude of the increment in MV due to dopamine withdrawal correlated with the size of the HVR and depended on the duration of dopamine administration. The ventilatory reaction to dopamine withdrawal constitutes a novel index of peripheral chemoreceptor function.