Comparison of pharmacological properties of nAChR ligand binding in membrane homogenates from KXα3β4R2 cell and rat forebrain
| Drug | KXα3β4R2 cell | Rat forebrain | Ratio (Ki for KXα3β4R2/Ki for rat forebrain) | ||
|---|---|---|---|---|---|
| Ki | nH | Ki | nH | ||
| nm | nm | ||||
| (±)-Epibatidine | 0.38 ± 0.07 | 0.99 ± 0.09 | 0.053 ± 0.002 | 0.96 ± 0.01 | 7 |
| (+)-Anatoxin-A | 52.9 ± 4.2 | 0.99 ± 0.03 | 6.51 ± 0.53 | 0.92 ± 0.04 | 8 |
| A85380 | 73.6 ± 6.3 | 0.88 ± 0.07 | 0.097 ± 0.023 | 0.96 ± 0.10 | 759 |
| Cytisine | 195 ± 14 | 0.85 ± 0.02 | 1.03 ± 0.14 | 0.75 ± 0.05 | 189 |
| (−)-Nicotine | 475 ± 52 | 0.89 ± 0.08 | 7.22 ± 1.23 | 0.82 ± 0.07 | 66 |
| Acetylcholine | 881 ± 154 | 0.82 ± 0.08 | 32.8 ± 10.5 | 0.84 ± 0.03 | 27 |
| Carbachol | 3,839 ± 276 | 0.83 ± 0.05 | 428 ± 57 | 0.84 ± 0.07 | 9 |
| d-Tubocurarine | 22,929 ± 3,800 | 0.79 ± 0.061-a | 2,237 ± 1,011 | 0.63 ± 0.021-b | 10 |
| DHβE | 218,622 ± 32,734 | 1.09 ± 0.08 | 28.9 ± 15.2 | 0.62 ± 0.021-b | 7,565 |
| Hexamethonium | >1,000,000 | 102,864 ± 7,632 | 0.85 ± 0.02 | ||
| Mecamylamine | >1,000,000 | >1,000,000 | |||
Competition binding experiments were carried out as described in Experimental Procedures using ≈500 pm [3H]EB. Hill coefficients (n H) and IC50 values (not shown) of competition binding curves were estimated by Hill plot. The inhibition constants (K i) were calculated according to the Cheng-Prusoff equation (1973). The K d values of [3H]EB used in the calculation were 300 pm for KXα3β4R2 cells and 50 pm for rat forebrain. Values shown are the mean ± standard error of three to five independent measurements.