Affinity of nicotinic agonists and antagonists for immuno-immobilized nAChR subtypes
The Kd and Ki values were derived from the curves of 125I-Epi saturation and competition binding to α 6* or (non-α 6)β 2* immuno-immobilized receptors. The curves obtained from three or four separate experiments were fitted using a nonlinear least squares analysis program. A two-site model was statistically significant (F test) for α-conotoxin MII, whereas the d-tubocurarine and cytisine data better fitted a one-site model. The numbers in parentheses represent the percentage coefficient of variation (CV).
| α6* | (non-α6)β2* | |
|---|---|---|
| pM | ||
| K d | ||
| 125I-Epibatidine | 10.2 (34) | 8.7 (25) |
| nM | ||
| K i | ||
| Cytisine | 1.43 (29) | 0.25 (42) |
| Nicotine | 5 (33) | 3.3 (36) |
| Acetylcholine | 11.3 (37) | 11.5 (32) |
| 1,1-Dimethy1-4-phenylpiperazinium | 15.7 (40) | 24 (43) |
| Dihydro-β-erythroidine | 1012 (36) | 1000 (25) |
| d-Tubocurarine | 700 (36) | 1650 (27) |
| α-Conotoxin MII | 1.1 (47) | |
| >10,000 | >10,000 | |