GABA_a-receptor function in hippocampal cells is maintained by phosphorylation factors

Gamma aminobutyric acid (GABA) mediates fast synaptic inhibition in the central nervous system by activating the chloride-permeable GABA_A channel. The GABA_A conductance progressively diminishes with time when the intracellular contents of hippocampal neurons are perfused with a minimal intracellular medium. This "run down" of the GABA-activated conductance can be prevented by the inclusion of magnesium adenosine triphosphate and calcium buffer in the intracellular medium. The amount of chloride conductance that can be activated by GABA is determined by competition between a calcium-dependent process that reduces the conductance and a phosphorylation process that maintains the conductance.