Table 1.
Affinities of key ammonium salts tested.
| Ammonium salt | σ-1 R affinity pKi ± SEM (n) |
σ-1 R affinity (µM) |
σ-2 R affinity pKi ± SEM (n) |
σ-2 R affinity (µM) |
σ-1 R Ki/σ-2 R Ki |
|---|---|---|---|---|---|
| Octyl | 6.1 ± 0.3 (4) | 0.80 | 5.2 ± 0.2 (3) | 6.2 | 0.13 |
| Decyl | 6.5 ± 0.4 (4) | 0.32 | 5.41 ± 0.07 (3) | 3.9 | 0.081 |
| Dipropyl | 5.6 ± 0.2 (6) | 2.6 | 4.10 ± 0.07 (3) | 79 | 32 |
| Dibutyl | 6.9 ± 0.4 (6) | 0.14 | 5.64 ± 0.07 (3) | 2.3 | 18 |
| Dipentyl17 | 7.4 ± 0.5 (6) | 0.043 | 6.9 ± 0.2* (3) | 0.12 | 3.2 |
| Dihexyl | 6.8 ± 0.6 (6) | 0.14 | 7.58 ± 0.06* (3) | 0.026 | 0.17 |
| Dioctyl | 10.3 ± 0.2 (6) | 0.000050 | 7.9 ± 0.5 (3) | 0.014 | 0.0040 |
| Tributyl | 6.9 ± 0.1 (6) | 0.13 | 5.5 ± 0.2* (3) | 3.0 | 0.040 |
| Tripentyl | 7.8 ± 0.2 (6) | 0.015 | 6.1 ± 0.1 (3) | 0.78 | 0.020 |
| Trihexyl | 8.1 ± 0.4 (6) | 0.009 | 6.63 ± 0.03 (3) | 0.23 | 0.034 |
| Bis(2-ethylhexyl) | 4.5 ± 0.3* (5) | 29 | 4.0 ± 0.2* (3) | 91 | 0.29 |
| Triisobutyl | 5.1 ± 0.6 (6) | 7.9 | 5.46 ± 0.06 (3) | 3.5 | 2.3 |
| Triisopentyl | 4.1 ± 0.4* (6) | 79 | 6.40 ± 0.09* (3) | 0.40 | 200 |
| Tetrapropyl | 2.5 ± 0.1 (3) | 3,200 | 3.5 ± 0.2* (3) | 310 | 10 |
| Tetrabutyl | 2.8 ± 0.1 (3) | 1,600 | 4.22 ± 0.08* (3) | 60 | 25 |
Affinities for the sigma-1 and sigma-2 receptors (σ-1 R and σ-2 R, respectively) are shown as pKi and Ki (µM) values from competition binding assays. Hill slopes were determined as unity for all salts tested, except those labelled *. σ-1 R Ki/σ-2 R Ki shows the ratio between Ki values. Sigma-1 receptor affinity has been previously published17. These data are reproduced from the PhD theses by J.M. Brimson44 and H. Abbas45.