Carotid body dopaminergic mechanisms are functional after acclimatization to hypoxia in goats

Ventilatory acclimatization to sustained hypoxia (VASH) is the time-dependent increase in ventilation that occurs during prolonged exposure to hypoxia. We tested the hypothesis that carotid body (CB) dopaminergic mechanisms are down-regulated during VASH, which would allow CB afferent discharge and ventilation to increase beyond the initial response to hypoxia. Domperidone (DOM; 1.0 mg.kg-1) was administered intravenously to block CB dopamine (DA) receptors after VASH was complete in awake goats. DOM caused a significant augmentation of the ventilatory response to hypoxia in acclimatized goats, failing to support the hypothesis. We conclude that inhibitory CB dopaminergic function is not significantly reduced following prolonged hypoxia, and that down-regulation of CB dopaminergic mechanisms may not be involved in VASH in the goat.