Fall in intracellular pH mediated by GABAA receptors in cultured rat astrocytes.
The influence of muscimol (a specific gamma-aminobutyric acid-A (GABAA) receptor agonist) on intracellular pH (pHi) was studied in cultured rat astrocytes by means of fluorescence spectrophotometry with BCECF as the H+ indicator. In an HCO3(-)-free medium, muscimol had little effect on pHi. In a solution containing 22 mM HCO3-, muscimol produced a reversible, concentration-dependent fall in pHi with a maximum of about 0.1-0.15 units. The muscimol-induced fall in pHi was antagonized by an increase in the external K+ concentration, which suggest that the acidosis is an immediate consequence of a net efflux of HCO3- through GABAA receptor channels rather than an indirect effect caused by a change in membrane potential. The present results raise the possibility that astrocytes may participate in the regulation of extracellular pH at GABAergic synapses and contribute to activity-induced pH changes in nervous tissue.
Kaila
K
K
Department of Zoology, University of Helsinki, Finland.
Panula
P
P
Karhunen
T
T
Heinonen
E
E
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009118:Muscimol / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology*; D013050:Spectrometry, Fluorescence
D005452:Fluoresceins; D005456:Fluorescent Dyes; D011963:Receptors, GABA-A; D009118:Muscimol; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein