In order to test the hypothesis that carotid body (CB) chemoreception depends on the functions of
anion channels and HCO3-/Cl- exchangers, we studied the effects of the
anion channel blocker
anthracene-9-carboxylic acid (9-ANC), the
carbonic anhydrase inhibitor methazolamide, and the HCO3-/Cl- exchanger blocker 4,4 diisothiocyanatostilbene-2-2'disulfonic
acid (
DIDS) on the chemosensory discharges of cat CB, perfused-superfused in vitro at 36.5 +/- 0.5 degrees C, with a modified Tyrode
solution. The chemosensory responses to
hypoxia (PO2 approximately 50 Torr),
hypercapnia (PCO2 approximately 60 Torr, pH = 7.10),
nicotine (2-4 nmol) and NaCN (20-40 nmol) were recorded. 9-ANC (2 microM) and
DIDS (10 microM) decreased the chemosensory baseline activity, and eliminated the initial peak responses to
hypercapnia and
hypoxia and increased the time to achieve it.
Methazolamide (0.13 mM) did not alter the effect of 9-ANC. The steady state responses to
hypoxia and
hypercapnia were not diminished after 9-ANC but
DIDS lowered the responses. Responses to NaCN effects were all diminished but those to
nicotine were not affected. The results suggest that the functions of
anion channels and HCO3-/Cl- exchangers are important for the resting dischargers and for the fast responses to
hypoxia and
hypercapnia.