Age-dependent effect of domperidone on dopamine release by the hypoxic carotid body in the rabbit.

The aim of this study was to identify the mechanisms that regulate dopamine release (DA(r)) by the hypoxic carotid body (CB) during development. CBs sampled from adult (n = 58) and 10-day-old (n = 53) rabbits were incubated for 1 h in a medium equilibrated with 8% O(2) in N(2) without or in the presence of the specific DA D(2) receptor antagonist domperidone, 0.01, 0.1 and 1 microM. DA and its major metabolite DOPAC were measured in the CB (DA(CB)) and in the medium (DA(r)) by HPLC+ED. In adults, each concentration of domperidone significantly decreased DA(CB) and increased DA(r), compared with control (p < 0.01). In contrast, in 10-day old, only the 1 microM domperidone concentration decreased DA(CB) and increased DA(r) compared with control (p < 0.001). The data show that domperidone increases CB DA(r) in response to hypoxia in a concentration- and age-dependent manner and suggest this response depends, in part, on the functional maturation of CB DA D(2) receptors.