Table I.
Effect of Agonists on the Desensitization Rate Constant of Diliganded AChR
| θ | τc P o | k O +D | n | |||||
|---|---|---|---|---|---|---|---|---|
| ms | ||||||||
| Acetylcholine (50 μM) | 45.0 | 222 ± 65 | 4.5 ± 1.0 | 4 | ||||
| Carbamylcholine (200 μM) | 5.1 | 320 ± 98 | 3.1 ± 0.7 | 7 | ||||
| Tetramethylammonium (200 μM) | 5.4 | 312 ± 83 | 3.2 ± 0.6 | 6 |
θ is the gating equilibrium constant (opening/closing), τc P o is the corrected cluster duration multiplied by the probability of being open in the cluster, and k O +D is the inverse of this value, which equals the desensitization rate constant for diliganded AChR. The desensitization rate constant does not vary between these agonists. All experiments in 142 mM KCl, −100 mV.