RAPID DESENSITIZATION OF ALPHA(1)BETA(1), GABA(A) RECEPTORS EXPRESSEDIN SF9 CELLS UNDER OPTIMIZED CONDITIONS

alpha(1) and beta(1) subunits of human GABA(A) receptors were expresse d in Sf9 cells using the Sf9-baculovirus system. Better expression was obtained by manipulating the system. Cell growth phase at the time of infection determined the practical range of virus titre, the period p ostinfection during which cells were useful for signal detection and t he maximal current obtained. Cells in the early exponential phase were relatively insensitive to multiplicity of infection (MOI) whereas cel ls in the mid- to late-exponential phase were highly dependent on MOI and they responded with the largest Cl- current generated by GABA. Cha nnels activated by GABA were chloride-selective. Half the maximum peak whole-cell current was obtained with 11 mu M GABA. The time course of Cl- currents activated by saturating GABA concentrations in cells inf ected with alpha(1) beta(1)-recombinant recombinant viruses was examin ed employing a rapid perfusion system which allowed whole-cell solutio n exchange in less than 1 msec. The current decay could be fitted by 3 to 4 exponentials for the first 8 sec. The initial fast current decre ase had a time constant of about 23 msec. No voltage dependence of tim e constants was detected but the whole-cell IV relation showed outward rectification. Currents were depressed by bicuculline, penicillin and picrotoxin and potentiated by pentobarbitone.