Increased sensitivity of rabbit carotid body chemoreceptors to dopamine after chronic treatment with domperidone

An increase in specific dopamine D 2 receptor binding sites was observed in membranes prepared from the carotid bodies of rabbits treated for 8 weeks and then withdrawn for 4–9 days from the D 2 antagonist domperidone (2–5 mg/kg per day). Recordings of chemoreceptor afferent discharge from the carotid body also revealed that this change in receptor density was accompanied by an increased sensitivity to the chemodepressant effects of exogenous dopamine. The chemoreceptor responsiveness of the carotid body to hypoxia is blunted in rabbits treated chronically with domperidone, but this can be restored to normal by an acute dose of the D 2 antagonist. These experiments provide evidence that is compatible with a chemo-inhibitory role for endogenous dopamine in the rabbit's carotid body. Furthermore, these results suggest that the carotid body provides a useful model for the functional studies of dopamine D 2 receptors.