Table 1.

Affinity values (Ki) for the binding to human κ-, rat μ, or rat δ-opioid receptors.

Compounds	µ binding affinity Ki (nM)	δ binding affinity Ki (nM)	κ binding affinity Ki (nM)
Dezocine	1.46 ± 0.10	398.6 ± 43.25	22.01 ± 1.52
DAMGO	2.30 ± 0.02	—	—
DPDPE	—	4.36 ± 0.69	—
U50,488 H,	—	—	0.91 ± 0.20

Membranes were incubated with varying concentrations of ligands in the presence of 2.0 nM [³H]DAMGO, 1.1 nM [³H]DPDPE and 1.5 nM [³H]U69593. Data are expressed as the mean ± SEM for at least three independent experiments performed in triplicate.