Effects of haloperidol on chemoreceptor reflex ventilatory response in the rabbit

In order to obtain further evidence for the modulatory role of dopamine in chemoreceptors, effects of haloperidol, a potent dopamine antagonist, on chemoreceptor reflex ventilatory response were studied in the rabbit carotid body. An injection of 30 microgram of haloperidol into the external carotid artery induced evident ventilatory excitation which became more marked and sustained at a higher dose. The response was produced by blockade inhibitory dopamine receptors since it was completely abolished in the catecholamine depleted animals. The NaCN-induced excitation of ventilation was potentiated by prior treatment of the carotid body with haloperidol, whereas the treatment blocked the induction of the postexcitatory depression of ventilation. The results indicate the negative feedback as the most possible mechanism by which dopamine exerts its suppressor effect on chemoreceptor nerve activity.