Table 3.
Effect of allosteric enhancers alone and in the presence of various concentrations of GABA on the stimulation of GTPγ[35S] binding to the membranes from CHO-Gα16-hGABAB(1a,2a) cell line
| EC50 (nM) | EC50 (Enh)/EC50 (Enh+GABA) | nH | |
|---|---|---|---|
| rac-BHFF alone | 725.0±28.3 | 1.2 | |
| rac-BHFF+0.2 μM GABA | 138.0±2.1 | 5.3 | 1.3 |
| rac-BHFF+0.6 μM GABA | 110.0±3.8 | 6.6 | 0.9 |
| rac-BHFF+1.0 μM GABA | 50.0±7.4 | 12.3 | 1.0 |
| rac-BHFF+6.0 μM GABA | 23.1±3.5 | 31.4 | 1.1 |
| rac-BHFF+20.0 μM GABA | 20.3±1.6 | 35.7 | 1.6 |
| BHFI alone | 6390.0±1111.4 | 0.8 | |
| BHFI+0.2 μM GABA | 915.0±43.0 | 7.0 | 0.8 |
| BHFI+0.6 μM GABA | 438.0±61.6 | 14.6 | 0.8 |
| BHFI+1.0 μM GABA | 299.0±15.4 | 21.3 | 0.8 |
| BHFI+6.0 μM GABA | 134.0±8.4 | 47.6 | 0.7 |
| BHFI+20.0 μM GABA | 34.0±11.7 | 188.0 | 0.7 |
| (+)-BHFF alone | 556.0±4.3 | 1.0 | |
| (+)-BHFF+1.0 μM GABA | 29.7±4.0 | 18.7 | 1.0 |
| (−)-BHFF alone | 1330.0±57.0 | 1.3 | |
| (−)-BHFF+1.0 μM GABA | 142.0±3.8 | 9.4 | 1.3 |
| BHFHP alone | 712.0±23.8 | 1.6 | |
| BHFHP+1.0 μM GABA | 48.0±2.8 | 14.8 | 1.1 |
| CGP7930 alone | No effect | ||
| CGP7930+1.0 μM GABA | 4180.0±957.0 | 1.0 |
Concentration–response curves were measured in the absence and presence of 0.2, 0.6, 1, 6 and 20 μM GABA for rac-BHFF and BHFI, and in the absence and presence of 1 μM GABA for (+)-BHFF, (−)-BHFF, BHFHP and CGP7930 (see Figure 4). The EC50 and nH values are mean±s.e.mean, calculated from three independent experiments each performed in triplicate.