Reversal of respiratory responses to dopamine after dopamine antagonists.

The effects of dopamine (DA) antagonists upon resting ventilation and ventilatory reactions to DA, apomorphine, hyperoxia and hypoxia were studied in pentobarbitone-anesthetized cats. Intravenous administration of spiroperidol, haloperidol, perphenazine and chlorpromazine increased resting ventilation, the intensity and duration of the effect being dependent on the dose of the blocker. The enhanced ventilation was associated to increased frequency of chemosensory discharges recorded from one carotid nerve, and it was absent from section of the four buffer nerves. The drugs also provoked a dose-dependent block of the transient chemosensory inhibitions and ventilatory depressions induced by DA or apomorphine. In addition, spiroperidol and perphenazine reversed the inhibitory reactions to DA into excitatory ones, the ventilatory responses being abolished by section of carotid and aortic nerves. The ventilatory depressions caused by a few breaths of 100% O2 and the ventilatory excitations onset by a few breaths of 100% N2 persisted after applying DA blockers. Results indicate that DA antagonists enhance ventilation by increasing peripheral chemosensory drive and may invert DA-induced reflex withdrawal into transient ventilatory excitation, without reversing the reflex ventilatory depression provoked by hyperoxia.