GABA-A receptor channel opening rates in excised patches of rat [correction of mouse] cortical neurons.
Patch clamp electrophysiology techniques and an ultrafast ligand exchange system (100 microseconds exchange time) were used to study opening rates of GABA-A receptor chloride channels in excised outside-out patches of fetal rat cortical neurons in culture. Receptor activation kinetics were studied using GABA (0.5 microM-10 mM) using rapid ligand exchanges. Patches contained 5-25 channels and were voltage clamped at -75 mV in symmetrical chloride solutions at room temperature. Responses were analyzed individually and as ensemble averages for each patch. Current rise times (10-90%) decreased with increased GABA concentration to a minimum of about 0.5 ms at 1 and 10 mM. Rates of channel activation at saturating GABA concentrations were similar to that recorded for miniature inhibitory currents at GABA synapses in these neurons. These data suggest that the synaptic concentration of GABA to activate GABA-A receptors in these neurons is at least 1 mM.
Twyman
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Department of Neurology, University of Utah, Salt Lake City 84112, USA.
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000502:physiology*; D018118:Chloride Channels / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D009474:Neurons / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D011963:Receptors, GABA-A / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology
D018118:Chloride Channels; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione