Inhibition of 5-[125I]iodo-A-85380 binding by nAChR and non-nAChR ligands
| nAChR Ligands | Ki, nM | Non-nAChR Ligands | Ki, nM |
|---|---|---|---|
| Agonists | Atropine | >25,000 | |
| (−)-Epibatidine | 0.009 ± 0.001 | Physostigmine | >25,000 |
| 5-Iodo-A-85380 | 0.010 ± 0.001 | DFP | >1,000,000 |
| A-85380 | 0.015 ± 0.002 | Naloxone | >25,000 |
| (−)-Cytisine | 0.16 ± 0.02 | Apomorphine | >25,000 |
| (−)-Nicotine | 0.96 ± 0.06 | Haloperidol | >25,000 |
| Acetylcholine | 4.0 ± 0.1 | ||
| (+)-Nicotine | 10 ± 1 | ||
| Carbachol | 73 ± 6 | ||
| Antagonists | |||
| Dihydro-β-erythroidine | 7.4 ± 0.8 | ||
| Curare | 730 ± 70 | ||
| α-Bungarotoxin | >2,500 | ||
| Mecamylamine | >25,000 |
Rat brain P2 membrane fractions (10–11 μg of protein) were incubated in a total volume of 0.2 ml with 130 pM 5-[125I]iodo-A-85380 and 9 to 11 concentrations of competitors for 4 h at 22°C and analyzed as described in Experimental Procedures. The inhibition constants (K i values) were calculated by the Cheng-Prusoff equation from measured IC50 values using aK d value of 10 pM for 5-[125I]iodo-A-85380 binding. In all assays, the pseudo-Hill coefficients (nH ) did not differ significantly from 1. Data represent mean ± S.E. obtained from four to six experiments per compound. Experiments were performed in duplicate.