The Caudal Solitary Complex is a Site of Central CO₂ Chemoreception and Integration of Multiple Systems That Regulate Expired CO₂

The solitary complex is comprised of the nucleus tractus solitarius (NTS, sensory) and dorsal motor nucleus of the vagus (DMV, motor), which functions as an integrative center for neural control of multiple systems including the respiratory, cardiovascular and gastroesophageal systems. The caudal NTS-DMV is one of the several sites of central CO ₂ chemoreception in the brain stem. CO ₂ chemosensitive neurons are fully responsive to CO ₂ at birth and their responsiveness seems to depend on pH-sensitive K ⁺ channels. In addition, chemosensitive neurons are highly sensitive to conditions such as hypoxia (e.g., neural plasticity) and hyperoxia (e.g., stimulation), suggesting they employ redox and nitrosative signaling mechanisms. Here we review the cellular and systems physiological evidence supporting our hypothesis that the caudal NTS-DMV is a site for integration of respiratory, cardiovascular and gastroesophageal systems that work together to eliminate CO ₂ during acute and chronic respiratory acidosis to restore pH homeostasis.