Etomidate, propofol and diazepam potentiate GABA-evoked GABAA currents in a cell line derived from human glioblastoma

GABA(A) receptors are pentameric chloride ion channels that are opened by GABA. We have screened a cell line derived from human glioblastoma, U3047MG, for expression of GABA(A) receptor subunit isoforms and formation of functional ion channels. We identified GABA(A) receptors subunit alpha 2, alpha 3, alpha 5, beta 1, beta 2, beta 3, delta, gamma 3, pi, and theta mRNAs in the U3047MG cell line. Whole-cell GABA-activated currents were recorded and the half-maximal concentration (EC50) for the GABA-activated current was 36 mu M. The currents were activated by THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) and enhanced by the benzodiazepine diazepam (1 mu M) and the general anesthetics etomidate and propolol (50 mu M). In line with the expressed GABA(A) receptors containing at least the alpha 3 beta 3 theta subunits, the receptors were highly sensitive to etomidate (EC50=55 nM). Immunocytochemistry identified expression of the alpha 3 and beta 3 subunit proteins. Our results show that the GABA(A) receptors in the glial cell line are functional and are modulated by classical GABA(A) receptor drugs. We propose that the U3047MG cell line may be used as a model system to study GABA(A) receptors function and pharmacology in glial cells. (C) 2014 Elsevier B.V. All rights reserved.