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 venti latory response (AHVR). Because low-dose dopamine decreases AHVR and domper idone increases AHVR, the increase in AHVR at altitude may be generated by a decrease in peripheral dopaminergic activity. The AVNR of nine subjects w as determined with and without a prior period of 8 h of isocapnic hypoxia u nder each of three pharmacological conditions: 1) control, with no drug adm inistered; 2) dopamine (3 mu g.min(-1).kg(-1)); and 3) domperidone (Motilin , 40 mg). AHVR increased after hypoxia (P less than or equal to 0.001). Dop amine decreased (P less than or equal to 0.01), and domperidone increased ( P less than or equal to 0.005) AHVR. The effect of both drugs on AHVR appea red larger after hypoxia, an observation supported by a significant interac tion between prior hypoxia and drug in the analysis of variance (P less tha n or equal to 0.05). Although the increased effect of domperidone after hyp oxia of 0.40 l.min(-1).%saturation(-1) [95% confidence interval(CI) -0.11 t o 0.92 l.min(-1).%(-1)] did not reach significance, the lower limit for thi s confidence interval suggests that little of the increase in AHVR after su stained hypoxia was brought about by a decrease in peripheral dopaminergic inhibition.