A bicarbonate-dependent increase in extracellular pH mediated by GABA A receptors in turtle cerebellum

Abstract

The γ-aminobutyric acid (GABA)-gated anion channel has been found to have a significant permeability to bicarbonate in isolated nerve cells and crayfish muscle. We have studied the extracellular pH of the in vitro turtle cerebellum to determine whether the extracellular pH of vertebrate brain can be modulated by GABA. Exposure to 10 −3 M GABA produced an extracellular alkaline transient with a mean amplitude of 0.054 ± 0.19 pH units ( n = 49, range 0.018–0.091 pH units). The GABA-evoked alkaline shift was blocked by picrotoxin and was dependent on the presence of HCO 3 − in the bathing media. These data suggest that GABA A receptors gate an HCO 3 −-efflux which is sufficient to modulate brain pH.