Effects of dopamine and domperidone on ventilatory sensitivity to hypoxia after 8 h of isocapnic hypoxia
Acclimatization to altitude involves an increase in the acute hypoxic ventilatory response (AHVR). Because low-dose dopamine decreases AHVR and domperidone increases AHVR, the increase in AHVR at altitude may be generated by a decrease in peripheral dopaminergic activity. The AHVR of nine subjects was determined with and without a prior period of 8 h of isocapnic hypoxia under each of three pharmacological conditions: 1) control, with no drug administered; 2) dopamine (3 μg ⋅ min−1 ⋅ kg−1); and 3) domperidone (Motilin, 40 mg). AHVR increased after hypoxia ( P ≤ 0.001). Dopamine decreased ( P ≤ 0.01), and domperidone increased ( P ≤ 0.005) AHVR. The effect of both drugs on AHVR appeared larger after hypoxia, an observation supported by a significant interaction between prior hypoxia and drug in the analysis of variance ( P ≤ 0.05). Although the increased effect of domperidone after hypoxia of 0.40 l ⋅ min−1 ⋅ %saturation−1[95% confidence interval (CI) −0.11 to 0.92 l ⋅ min−1 ⋅ %−1] did not reach significance, the lower limit for this confidence interval suggests that little of the increase in AHVR after sustained hypoxia was brought about by a decrease in peripheral dopaminergic inhibition.