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CO₂-H⁺ Chemoreceptors: Where Are They, What Do They Do?
Sponsored by the APS Respiration Section

Elegant studies in the 50s, 60s, and 70s provided strong evidence that CO₂-H⁺ chemoreception was restricted to sites near the ventrolateral medullary surface. However, several recent studies suggest that CO₂-H⁺ chemoreceptors are located at widespread sites in the brainstem, and that the carotid bodies are a major determinant of the ventilatory response to increased CO₂-H⁺ in awake mammals. These findings have posed several questions, some of which will be addressed by the speakers in this symposium. Are all chemoreceptors capable of influencing breathing, and do they only influence breathing? Do the physiologic responses to changes in chemoreceptor activity differ between anesthetized, awake, and asleep states? Is there a hierarchy among chemoreceptors in their influence on breathing? Do chemoreceptors at all brainstem sites have the same response characteristics? Are all brainstem chemoreceptors uniform in their neurochemical phenotype? Why did chemosensitivity develop at widespread brain sites? Are the carotid bodies primary CO₂-H⁺ chemoreceptors, or does the carotid body provide a tonic input to medullary neurons that is necessary for the normal response to central chemoreceptors?