Central nervous system control of cardiorespiratory nasopharyngeal reflexes in the rabbit

The role of different central nervous regions in the reflex apnea, bradycardia, and mesenteric vasoconstriction evoked by nasopharyngeal stimulation with cigarette smoke was examined in unanesthetized shamoperated, thalamic, and pontine rabbits with intact and sectioned carotid sinus and aortic nerves (CS and AN). Apnea occurred in all preparations. In pontine animals with intact CS and AN, the heart rate response was reduced but not the mesenteric vasoconstriction. The role of suprabulbar and bulbospinal regions became more apparent when individual components of the input profile were examined in animals with controlled ventilation. The bradycardia and mesenteric vasoconstriction evoked by apnea without smoke, but not by smoke without apnea, were reduced in pontine animals. Prior section of the CS and AN attenuated the response in all neural preparations but to the least extent when cerebral hemispheres were intact. The data indicate that the respiratory reflex is predominantly integrated at bulbospinal sites, but the cardiovascular reflex is integrated at both bulbospinal and suprabulbar sites, or is integrated at bulbospinal and modulated from suprabulbar sites.