Effects of dopamine superfusion on the activity of rabbit carotid chemoreceptors in vitro

The effect of different concentrations (0.001, 0.01, 0.1 and 1 mM) of dopamine on chemo-afferent activity was studied in the rabbit carotid body superfused in vitro. Excitation was the sole effect observed: it was always present for dopamine tests at 0.1 and 1 mM but was found in only 4 out of 9 tests at 0.01 mM and in 1 out of 5 tests at 0.001 mM. By comparison with a natural stimulus like hypoxia, dopamine excitation was delayed and had a much slower time course. Dopamine antagonists, (+)-butaclamol and haloperidol did not affect the responses to dopamine and to hypoxia. The results were not significantly altered when CO2 was added to the superfusing medium. It is concluded that dopamine is not a likely excitatory transmitter for chemoreception in the rabbit carotid body.