Potencies of doxapram and hypoxia in stimulating carotid body chemoreceptors and ventilation in anesthetized cats

Abstract

The effects of doxapram on carotid chemoreceptor activity and on ventilation (phrenic nerve activity) were tested before and after denervation of the peripheral chemoreceptors in cats. Doxapram was found to be a potent stimulus to the carotid chemoreceptors; the stimulation produced by 1.0 mg/kg doxapram, i.v., equalled that produced by a Pa(O2) of 38 torr. Doxapram also increased phrenic nerve activity in doses as low as 0.2 mg/kg, i.v. After denervation of the peripheral chemoreceptors, doxapram in doses as large as 6 mg/kg failed to stimulate ventilation. It is concluded that (in anesthetized cats) doxapram in doses of less than 6 mg/kg increases ventilation by direct stimulation of the carotid, and probably, the aortic, chemoreceptors, not by a direct effect on the medullary respiratory center.