Two desensitization processes of GABA receptor from rat brain. Rapid measurements of chloride ion flux using quench-flow techniques.
Two rapid phases of GABA receptor desensitization, which proceeded with a 10-fold difference in rates, were detected in two types of experiment with membrane vesicle preparations from rat cerebral cortex. The time course of GABA-mediated 36Cl- influx progressed in two phases. The 36Cl- influx was decreased, by preincubation with GABA, in two phases. Measurements were made in the time range 10-1000 ms. The major loss of channel opening activity occurred in the faster phase, which was complete in 100 ms with saturating GABA concentrations. The remaining activity decreased in a slower phase in a few seconds with a 10-fold slower rate. The faster phase of desensitization was more than 10-fold faster than previously observed and the slower phase was slightly faster than previously reported measurements with GABA receptor. Both desensitization processes had a similar dependence on GABA concentration with a half response at approximately 100 microM GABA.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002540:Cerebral Cortex / Q000032:analysis*; D002712:Chlorides / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D002712:Chlorides; D007473:Ion Channels; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid