Fig. 2.
Inhibition of the α1β3γ2L receptor by sulfated steroids. (A) Comparison of apparent desensitization in the presence of 1 mM GABA, 1 mM GABA coapplied with 30 µM PS (upper panel), or 30 µM DHEAS (lower panel). The paired traces are from the same cells and normalized to the peak response to GABA in the same cell. The fitted or weighted decay time constants are: 26 seconds (GABA) and 3.6 seconds (GABA + PS) in the upper panel, and 33 seconds (GABA) and 1.3 seconds (GABA + DHEAS) in the lower panel. (B) Sample traces showing PS-induced inhibition of steady-state current elicited by 1 mM GABA. The inset indicates the time course of inhibition with peak and sustained effects shown with arrows. (C) Concentration-response relationships for PS- and DHEAS-induced inhibition of steady-state current elicited by 1 mM GABA. The data points show mean ±S.D. from 5–8 cells per condition. Each cell was exposed to a single application of steroid. The curves were fitted with Eq. 1. The fitted IC50s, values of nHill, and high-concentration asymptotes are given in the text.