Postnatal maturation of carotid body and type I cell chemoreception in the rat.
The site of postnatal maturation of carotid body chemoreception is unclear. To test the hypothesis that maturation occurs synchronously in type I cells and the whole carotid body, the development of changes in the intracellular Ca2+ concentration responses to hypoxia, CO2, and combined challenges was studied with fluorescence microscopy in type I cells and compared with the development of carotid sinus nerve (CSN) responses recorded in vitro from term fetal to 3-wk animals. Type I cell responses to all challenges increased between 1 and 8 days and then remained constant, with no multiplicative O2-CO2 interaction at any age. The CSN response to hypoxia also matured by 8 days, but CSN responses to CO2 did not change significantly with age. Multiplicative O2-CO2 interaction occurred in the CSN response at 2-3 wk but not in younger groups. We conclude that type I cell maturation underlies maturation of the CSN response to hypoxia. However, because development of responses to CO2 and combined hypoxia-CO2 challenges differed between type I cells and the CSN, responses to these stimuli must mature at other, unidentified sites within the developing carotid body.
D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D002118:Calcium / Q000378:metabolism; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000494:pharmacology; D002344:Carotid Body / Q000166:cytology / Q000196:embryology / Q000254:growth & development*; D015687:Cell Hypoxia; D002628:Chemoreceptor Cells / Q000196:embryology / Q000254:growth & development* / Q000502:physiology; D004594:Electrophysiology; D006863:Hydrogen-Ion Concentration; D008856:Microscopy, Fluorescence; D010100:Oxygen / Q000008:administration & dosage; D051381:Rats