ETHANOL INCREASES GABA(A) RESPONSES IN CELLS STABLY TRANSFECTED WITH RECEPTOR SUBUNITS

Ethanol enhancement of GABA(A) receptor function has been found in som e, but not all, studies. These results suggest the existence of ethano l-sensitive and -resistant receptors that may differ in subunit compos ition, although methodological differences (e,g., Cl-36(-) flux versus membrane currents) could also contribute to the different results. To examine these possibilities, we used mouse L(tk(-)) cells stably tran sfected with alpha(1) + beta(1) or alpha(1) + beta(1) + gamma(2L) GABA (A) receptor subunit DNAs and compared Cl-36(-) flux with whole-cell, patch-clamp measurements of GABA(A) receptor function. Both techniques detected a similar modulation of the GABA receptor by ethanol, flunit razepam, and pentobarbital. The potentiating action of ethanol require d the gamma-subunit and was maximal at a concentration of 10 mM, Simil ar ethanol potentiation was obtained with brief (20 msec) or long (2 s ec) applications of GABA. Analysis of data obtained from individual ce lls expressing alpha(1) beta(1-)gamma(2L) subunits showed considerable variability in sensitivity to ethanol, particularly with concentratio ns of 30 and 100 mM, Ethanol potentiated GABA action if the cells were grown on coverslips coated with polylysine, but had no effect on GABA (A) receptors of cells grown on uncoated coverslips. Thus, ethanol act ion was influenced by the growth matrix. Taken together, these data in dicate that a gamma-subunit is necessary, but not sufficient, for etha nol sensitivity in this cell system. We suggest that posttranslational processing, particularly receptor phosphorylation, may also be import ant and that stably transfected cells will be useful in elucidating th ese events.