Table 1.
Affinity of nicotinic agonists and antagonists for immunoimmobilized nAChR subtypes
| α6β2* | α4(non α6)β2* | |
|---|---|---|
| Kd (nm) | ||
| 125I-Epibatidine | 0.034 (34) | 0.041 (25) |
| Ki (nm) | ||
| Cytisine | 0.65 (18) | 0.19 (16) |
| Nicotine | 2.5 (23) | 1.75 (23) |
| Acetylcholine | 8.0 (34) | 8.6 (23) |
| Dihydro-β-erythroidine | 524 (25) | 274 (21) |
| d-Tubocurarine | 3,110 (20) | 16,100 (28) |
| α-Conotoxin MII | 1.3 (45) | – |
| >10,000 | >10,000 | |
| Methyllycaconitine | 40 (47) | – |
| 20,800 (18) | 25,000 (23) |
Kd and Ki values were derived from curves of 125I-Epi saturation and competition binding, respectively, to α6β2* or α4(nonα6)β2
*
immunoimmobilized receptors. Curves obtained from three or four separate experiments were fitted using a nonlinear least-squares analysis program. For both α-conotoxin MII and methyllycaconitine, a two-site model was statistically significant (F test), whereas for d-tubocurarine and cytisine the data were better fitted with a one-site model. Numbers in parentheses represent percentage of coefficient of variation.