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. 2017 Nov;92(5):556–563. doi: 10.1124/mol.117.109595

Fig. 2.

Fig. 2.

Activation of the α1β2γ2L GABAA receptor by GABA, propofol, or combinations of GABA and propofol. (A) Concentration-response relationships for activation by GABA or propofol. The data show mean ± S.E.M. from seven (GABA) or five (propofol) cells. The Poest value was determined as described in Materials and Methods. The curves were generated by fitting pooled data to eq. 1. The best-fit parameters are KGABA = 35 μM and cGABA = 0.0045 for GABA (R2 of the fit 0.9997), and KProp = 19 μM and cProp = 0.139 for propofol (R2 = 0.9956). (B) An isobologram for receptor activation by GABA or propofol, calculated to produce a response with a Po value of 0.5. The two axial points (open symbols) are connected with a straight line. The filled circles show GABA and propofol concentration combinations predicted to produce responses with a Po value of 0.5. (C) Summary of electrophysiological recordings. The graph shows response ratios (mean ± S.E.M. from five to nine cells) vs. 1 mM GABA + 50 μM propofol for 1) 26 μM GABA (0.51 ± 0.05; P = 0.9 for comparison with the expected ratio of 0.50), 2) 99 μM propofol (0.46 ± 0.06; P = 0.52), 3) 2 μM GABA + 4.7 μM propofol (0.49 ± 0.06; P = 0.9), 4) 5 μM GABA + 2.1 μM propofol (0.45 ± 0.03; P = 0.20), 5) 10 μM GABA + 0.94 μM propofol (0.49 ± 0.04; P = 0.76), 6) 15 μM GABA + 0.46 μM propofol (0.52 ± 0.05; P = 0.67), or 7) 20 μM GABA + 0.19 μM propofol (0.55 ± 0.03; P = 0.20). The dashed line shows the expected response of 0.5. (D) Sample current traces showing responses to 1 mM GABA (G) + 50 μM propofol (P) expected to produce a Po value of 1, and 26 μM GABA, 99 μM propofol, or various combinations of GABA + propofol expected to produce a Po value of 0.5. The traces in each set are from the same cell.