Table 1

Affinities (K_i, nM) of ring-constrained orvinols for μ-, δ-, and κ-opioid binding sites in mouse brain homogenates

	K_i
	μ	δ	κ
	nM
BU 46	0.60 ± 0.05	0.86 ± 0.08	1.02 ± 0.10
BU 47	0.88 ± 0.20	1.45 ± 0.19	2.75 ± 0.10
BU 61	0.55 ± 0.06	1.78 ± 0.11	1.79 ± 0.10
BU 95	0.48 ± 0.19	1.41 ± 0.19	3.20 ± 1.00
BU 96	1.50 ± 0.15	1.31 ± 0.39	2.99 ± 0.50
Buprenorphine^1-a	0.57 ± 0.05	1.30 ± 0.03	2.00 ± 0.30

Displacement studies were performed for 60 min at 25°C as described in Materials and Methods with 1 nM [³H]DAMGO (μ), 2 nM [³H]DPDPE (δ), and 0.5 nM [³H]CI977 (κ). K_i values were determined from IC₅₀values. Slopes of displacement curves were not significantly different from unity. Data represent means ± S.E. from at least three determinations each performed in triplicate.

↵1-a Performed in guinea pig brain homogenates.