Electrophysiological characterization of α1β2N265Cγ2L GABAA receptors.

Panel A: GABA concentration response in oocytes. Data points are mean ± sd (n ≥4) peak currents normalized to maximal GABA (1 mM) responses. Lines through data represent fits to logistic equations (Eq. 1, Methods). Open symbols: GABA alone; EC50 = 31±4.7 µM; nH = 1.75±0.088. Filled symbols: GABA plus 3.2 µM etomidate; EC50 = 30±3.2; nH = 1.67±0.068; maximum response = 1.06±0.01. Panel B: Etomidate agonism concentration response in oocytes. Data points are mean ± sd (n ≥4) peak currents normalized to maximal GABA (1 mM) responses. The line represents a logistic fit. EC50 = 35±5.7 µM; nH = 2.5±1.1; maximum response = 0.020±0.007. Panel C: Spontaneous channel gating activity in an oocyte, assessed using picrotoxin (PTX). No outward current during PTX application was observed. Current elicited with 1 mM GABA in the same cell is also displayed. Panel D: Estimation of maximal GABA efficacy in oocytes. GABA (3 mM; white bar) alone elicits a current that is enhanced about 5% with co-application of alphaxalone (2 µM; black bar). Average results for GABA efficacy are reported in Table 1.