Saturation and self-inhibition of rat hippocampal GABA(A) receptors at high GABA concentrations.

Current responses to ultrafast gamma-aminobutyric acid (GABA) applications were recorded from excised patches in rat hippocampal neurons to study the gating properties of GABA(A) receptors at GABA concentrations close to saturating ones and higher. The amplitude of currents saturated at approximately 1 mm, while the onset rate of responses reached saturation at 4-6 mm GABA. At high GABA concentrations (> 10 mm), the amplitude of current responses was reduced in a dose-dependent manner with a half-blocking GABA concentration of approximately 50 mm.

[Effect of changes in extracellular pH on GABAA receptors in neurons].

Local pH values of both intra- and extracellular liquids can be regulated by a number of mechanisms including membrane transport and metabolism. It is known that the changes of extracellular pH accompanying physiological and pathological processes are sufficient to affect several important structures such as ionic channels, transporters, receptors etc. In particular, several reports indicate that GABAA receptor is strongly modulated by this factor.