FIGURE 3.
HCO3−-independent H+ extrusion in neonatal optic nerve astrocytes. A, mean pHi changes in HEPES-aCSF following a 5-min 20 mm ammonia pulse (segment a-c). pHi recovered after return to ammonia-free conditions (segment d-e), but not completely (note thick dashed line). B, as in A; the recovery was reduced by removal of extracellular Na+ (0 Na+) and Cl− (0 Cl−). C and D, mean pHi recovery following acid load in the presence of the Na-H exchange inhibitor EIPA or the V-ATPase inhibitor bafilomycin. Both inhibitors reduced the recovery, although bafilomycin reduced it to the greatest extent. E and F, pHi recovery was prevented by the following combinations: NHE inhibitor EIPA and Cl− removal or V-ATPase inhibitor bafilomycin combined with Na+ removal. Dotted lines on A–D indicate recovery rates within the first 5 min following removal of NH4+. All values are given as mean ± S.E.