Article date: 1992/11/1
PubMed ID: 1334197
Journal name: Brain research. Molecular brain research (ISSN: 0169-328X)
Cerebral cortical cultured neurons were characterized for GABA-benzodiazepine (BZ) receptor complex, and the effect of chronic exposure of cortical neurons to GABA on GABA-BZ receptor system was investigated. In the intact cells, the [3H]flunitrazepam binding was rapid and saturable, with an apparent Kd of 4.2 +/- 1.5 nM and Bmax of 776 +/- 54 fmol/mg protein. Specifically bound [3H]flunitrazepam was displaced in a concentration-dependent manner by various BZ receptor ligands such as Ro15-1788, DMCM, Ro15-4513, clonazepam, alprazolam, diazepam and zolpidem, and enhanced by GABA, muscimol and pentobarbital. GABA induced enhancement of 36Cl-influx in a concentration-dependent manner (EC50 = 9 +/- 2 microM). Chronic exposure of the cultured neurons to GABA resulted in a reduced [3H]flunitrazepam, [3H]GABA, [3H]Ro15-1788, [3H]Ro15-4513 and [35S]TBPS binding, a reduced enhancement of [3H]flunitrazepam binding by GABA, and a reduced GABA-induced 36Cl-influx susceptible to reversal by concomitant exposure of the cultures to R 5135, a GABAA-receptor antagonist. These findings indicate that cerebral cortical cultured neurons provide an ideal model to study GABA-BZ receptor complex using binding and 36Cl-influx assays, and chronic exposure of cortical cultures to GABA leads to a down-regulation of GABA-BZ receptor system. It is a GABAA receptor-mediated slow process.
Author List: Mehta A K, Ticku M K
Publication Types: Journal Article; Research Support, U.S. Gov't, P.H.S.
Substances mentioned in the article: Ionophores; Radioisotopes; Receptors, GABA-A; Chlorine; gamma-Aminobutyric Acid;
Mesh terms: Animals; Cells, Cultured; Cerebral Cortex/cytology; Chlorine; Down-Regulation/drug effects; Female; Ionophores/chemistry; Male; Mice; Mice, Inbred C57BL; Neurons/drug effects; Radioisotopes; Radioligand Assay; Receptors, GABA-A/chemistry; Time Factors; gamma-Aminobutyric Acid/pharmacology;