Activation properties of receptors expressed in Xenopus oocytes
The table gives the EC50 (best-fit parameter ± uncertainty of the fit) and Hill coefficients (nH) of GABA concentration-response curves fitted to averaged data from four to six cells using the Hill equation. IGABA (mean ± S.D.) was determined as the peak response to the highest GABA concentration tested in concentration-response measurements. Maximal Poest was calculated as ratio of IGABA to the response to saturating concentration of pentobarbital in the absence or presence of DS-2, whichever generated the largest response. In the case of α4β2 receptors that are not potentiated by DS-2, alfaxalone replaced DS-2. Maximal Poest provides an estimate of gating efficacy of GABA.
| Receptor | GABA EC50 | nH | IGABA | Maximal Poest |
|---|---|---|---|---|
| µM | nA | |||
| α4β2δ | 0.010 ± 0.001 | 0.8 ± 0.1 | 2265 ± 829 | 0.53 |
| δ-β2-α4 + β2-α4 | 3.5 ± 0.6 | 1.3 ± 0.2 | 186 ± 91 | 0.06 |
| β2-α4 + δ | 4.6 ± 0.2 | 1.2 ± 0.1 | 325 ± 176 | 0.08 |
| β2-δ-β2 + β2-α4 | 1.2 ± 0.7 | 0.9 ± 0.4 | 8 ± 3 | 0.08 |
| β2-δ-α4 + β2-α4 | 55 ± 17 | 1.3 ± 0.4 | 66 ± 73 | 0.13 |
| β2-δ + α4 | 0.17 ± 0.02 | 1.0 ± 0.1 | 1131 ± 221 | 0.46 |
| α4β2 | 0.71 ± 0.32 | 0.7 ± 0.2 | 770 ± 330 | 0.31 |