POSSIBLE ROLE OF DOPAMINE IN VENTILATORY ACCLIMATIZATION TO HIGH-ALTITUDE

Ventilatory acclimatization to high altitude is accompanied by increas ed hypoxic (HVR) and hypercapnic (HCVR) ventilatory responses which ma y reflect increased carotid body chemosensitivity. Dopamine is an inhi bitory neuromodulator of the carotid body and its activity may be redu ced by hypoxic exposure. To determine whether decreased dopaminergic a ctivity could account for the increased chemosensitivity of acclimatiz ation, we examined the response to peripheral dopamine receptor (D-2) blockade with domperidone on HVR and HCVR in awake cats before and aft er exposure to simulated altitude of 14000 ft for 2 days. During anest hesia, we also examined the effects of domperidone on carotid body res ponses to hypoxia and hypercapnia in acclimatized and low altitude cat s. Two days' exposure to hypobaric hypoxia produced an increase in HVR and HCVR. Before acclimatization, domperidone augmented HVR and HCVR, but there wets no effect after acclimatization. In anesthetized low a ltitude cats, domperidone increased carotid body responses to hypoxia and hypercapnia, but had no effect in acclimatized cats. These results indicate that decreased endogenous dopaminergic activity may contribu te to increased ventilatory and chemoreceptor responsiveness to hypoxi a and hypercapnia during hypoxic ventilatory acclimatization.