title: Avian intrapulmonary chemoreceptor discharge rate is increased by anion exchange blocker 'DIDS'.
abstract: Avian intrapulmonary chemoreceptors (IPC) are neurons that sense lung P(CO(2)) and provide phasic feedback for the control of breathing in birds. To try to understand mechanisms of CO(2) transduction and intracellular pH regulation in IPC, the anion exchange inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) was used to block transmembrane Cl(-)/HCO(3)(-) transport. Single-unit IPC discharge rates were measured at steady intrapulmonary CO(2) levels and during step changes in CO(2) in 15 anesthetized, unidirectionally ventilated adult mallard ducks (Anas platyrhynchos). Measurements were repeated after giving 50, 100 and 200 micromol/kg cumulative i.v. dosages of DIDS. Mean IPC discharge rates at steady (tonic) P(CO(2)) levels were significantly increased by 100 and 200 micromol/kg DIDS, but not by 50 micromol/kg DIDS. Mean dynamic (phasic) IPC responses to CO(2) steps were not significantly affected by DIDS. Results indicate that the DIDS-sensitive Cl(-)/HCO(3)(-) membrane exchanger is involved with tonic CO(2) signal transduction in IPC. However, because some individual IPC were unaffected by DIDS, yet still altered their discharge rate with CO(2), additional mechanisms besides the Cl(-)/HCO(3)(-) exchange are probably required for CO(2) chemotransduction in IPC.
authors.affiliation: Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Shoemaker
authors.forename: S C
authors.initials: SC
authors.lastname: Hempleman
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology*; D000136:Acid-Base Equilibrium / Q000187:drug effects; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood / Q000494:pharmacology; D002628:Chemoreceptor Cells / Q000187:drug effects*; D027963:Chloride-Bicarbonate Antiporters / Q000037:antagonists & inhibitors*; D004372:Ducks / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D008168:Lung / Q000187:drug effects*; D009411:Nerve Endings / Q000187:drug effects; D011956:Receptors, Cell Surface; D013268:Stimulation, Chemical
chemical_list: D027963:Chloride-Bicarbonate Antiporters; D011956:Receptors, Cell Surface; D002245:Carbon Dioxide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid