Receptor occupancy by agonist under the various desensitizing conditions at muscarinic receptors
| Desensitizing drug | Receptor occupancy | Desensitization |
|---|---|---|
| % | ||
| 10−4 M Acetylcholine | 99.0 | 100.0 |
| 10−4 M Acetylcholine + 4.79 × 10−6 M quinacrine | 96.8 | 50.0 |
| 10−4 M Acetylcholine + 1.38 × 10−5 M chloroquine | 95.1 | 50.0 |
| 10−4 M Acetylcholine + 1.20 × 10−4 M tetracaine | 89.4 | 50.0 |
| 10−4 M Acetylcholine + 1.00 × 10−3 M procaine | 49.8 | <50.0 |
| 9.3 × 10−7 M Acetylcholine | 48.2 | 50.0 |
| 10−4 M Acetylcholine + 2.80 × 10−8 M atropine | 51.5 | 50.0 |
Receptor occupancy was calculated by use of a one-site model. Desensitization induced by 10−4 M acetylcholine was used as control. Receptor occupancy was calculated for the conditions that induced 50% desensitization, which was obtained either by adding inhibitor drug (local anesthetic or atropine at a concentration of IC50 for desensitization) or by reducing the concentration of desensitizing agent (9.3 × 10−7 M acetylcholine).