Fig. 4.
Single-channel activation properties of the wild-type concatemeric γβα-βα receptor. A, relationship between the effective opening rate and GABA concentration. The effective opening rate is the inverse duration of the GABA concentration-dependent closed-time component. Each symbol corresponds to data from one patch. The curve was fitted to the Hill equation. The best-fit parameters are as follows: β (maximal effective opening rate) = 2950 ± 686 s-1, EC50 = 1452 ± 488 μM, nH = 1.4 ± 0.1. The dashed line is from previous data on α1β2γ2L receptors (Steinbach and Akk, 2001), with the following best-fit parameters: β = 1883 ± 686 s-1, EC50 = 359 ± 162 μM, nH = 1.7 ± 0.2. B, relationship between the intracluster open probability (Po) and GABA concentration. Each symbol corresponds to data from one patch. The curve was fitted to the Hill equation. The best-fit parameters are as follows: Pomax = 0.88 ± 0.03, EC50 = 83 ± 10 μM, nH = 1.4 ± 0.2. The dashed line is from previous data on α1β2γ2L receptors (Steinbach and Akk, 2001), with the following best-fit parameters: Pomax = 0.82 ± 0.04, EC50 = 70 ± 9 μM, nH = 1.2 ± 0.2.