Peripheral chemoreceptors in respiratory oscillations

The hypothesis that instability of cardiorespiratory control may depend on the response and sensitivity of carotid body chemoreceptors to arterial blood gases was studied in anesthetized cats under three different experimental conditions. 1) Following administration of the peripheral dopamine receptor blocker [domperidone (0.6-0.8 mg X kg-1, iv)], carotid chemoreceptor activity and its sensitivity to CO2 during hypoxia increased, leading to cardiorespiratory oscillations at low arterial PO2 in four of eight cats. Inhalation of 100% O2 promptly decreased chemoreceptor activity and eliminated the oscillations. Inhalation of CO2 stimulated the chemoreceptor activity and ventilation but did not eliminate the oscillations. Bilateral section of carotid sinus nerves abolished the cardiorespiratory oscillations. The implication is that the dopaminergic system in the carotid body keeps chemoreceptor responses to blood gas stimuli suppressed and hence cardiorespiratory oscillations damped. 2) Hypotension and circulatory delay induced by the partial occlusion of venous return led to cardiorespiratory oscillations at low but not at high arterial PO2. 3) A few cats developed cardiorespiratory oscillations without any particular experimental intervention. These oscillations were independent of arterial PO2 and chemoreceptor activity. Thus it is reasonable to conclude that the peripheral chemoreflex can play a critical role in developing cardiorespiratory oscillations in certain instances.