The whole-cell patch-clamp technique was used to record GABA-activated currents in freshly isolated DRG neurons. It was found that application of SP (10(-7)-10(-5) mol/L) could induce concentration dependent inward currents in some cells (4/26), while no such current was detectable in the other neurons. However, preapplication of SP could inhibit the inward currents mediated by GABAA receptor (18/22). The inhibitory effect of SP was concentration dependent and reversible, and the desensitization of GABA-activated current could also be enhanced by SP.