Modulation of recombinant GABA(A) receptors by neurosteroid dehydroepiandrosterone sulfate.

Aim: To investigate whether long-term exposure to the neurosteroid dehydroepiandrosterone sulfate (DHEAS) induces adaptive changes of GABA(A) receptors related to the development of tolerance and dependence.

Methods: We compared the parameters of [(3)H]DHEAS binding and the effects of DHEAS on [(3)H]flunitrazepam binding in the membranes of HEK 293 cells, nontransfected or stably transfected with recombinant α(1)β(2)γ(2S) GABA(A) receptors. In HEK 293 cells expressing α(1)β(2)γ(2S) GABA(A) receptors, we investigated the effects of long-term DHEAS treatment on the [(3)H]flunitrazepam and [(3)H]t-butylbicycloorthobenzoate ([(3)H]TBOB) binding and on their modulation with GABA.

Results: DHEAS behaves as an allosteric antagonist of the recombinant α(1)β(2)γ(2S) GABA(A) receptors expressed in HEK 293 cells. Exposure of cells to 100 μmol/l DHEAS for 48 h did not change the number or affinity of benzodiazepine and convulsive binding sites. Long-term DHEAS treatment failed to affect functional allosteric interactions between GABA(A) receptor binding sites, as evidenced by an unchanged ability of GABA to stimulate or to inhibit [(3)H]flunitrazepam and [(3)H]TBOB binding, respectively.

Conclusion: The findings that prolonged DHEAS treatment does not produce changes in GABA(A) receptor expression and functional coupling, assumed to underlie the development of tolerance and dependence, might have importance in the long-term therapy necessary for the observed beneficial effects of DHEAS.