The ionophore function of γ-aminobutyric acidA (GABAA) receptors was studied by whole-cell patch clamp electrophysiology in primary cultures of rat cerebral cortex. Chloride ions were replaced for SCN- (thiocyanate) and HCO3- (bicarbonate) ions. The EC50 values of the GABAA agonist muscimol (HCO3->Cl->SCN-) varied parallel with the free energies of dehydration of the anions, while the inhibition constants of the GABAA antagonist bicuculline methiodide were not affected. These findings might be relevant in the interpretation of the contribution of HCO3- versus Cl- currents to the pharmacological differences between depolarizing and hyperpolarizing GABA responses.
- Dehydration of anions
- GABAergic depolarization
- γ-aminobutyric acid (GABA) receptor-ionophore function
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