Table 2.
Opioid binding in wild-type, heterozygous, and exon 11 knockout mice: Mu receptor competition studies
| Ligand |
Ki, nM |
||
|---|---|---|---|
| Wild type (+/+) | Heterozygote (+/−) | Homozygote (−/−) (knockout) | |
| Morphine | 0.51 ± 0.01 | 0.53 ± 0.06 | 0.62 ± 0.16 |
| M6G | 2.41 ± 0.41 | 2.72 ± 0.17 | 1.98 ± 0.21 |
| 6-Acetylmorphine | 4.61 ± 1.46 | 3.46 ± 0.34 | 2.57 ± 0.17 |
| Methadone | 1.36 ± 0.46 | 0.91 ± 0.35 | 0.96 ± 0.39 |
| Fentanyl | 0.82 ± 0.12 | 1.15 ± 0.39 | 0.57 ± 0.18 |
| Naloxone | 0.99 ± 0.25 | 0.90 ± 0.11 | 0.43 ± 0.03 |
| DPDPE | 257.7 ± 39.6 | 151.7 ± 47.9 | 158.7 ± 36.7 |
| U50,488H | >1,000 | >1,000 | >1,000 |
Competition studies were carried out in brain membranes from wild-type, heterozygous, and knockout mice with the μ agonist ([3H]DAMGO), as previously described (27). IC50 values were determined and converted to Ki values. Results are the means ± SEM of at least 3 independent determinations.