Table 2. [³⁵S]GTPγS Binding (G-Protein Activation) and Functional Assays.

	δ receptor		μ receptor		κ receptor		bioassay, IC50d (nM)b
compd	Emax (%)a	EC50 (nM)b	Emax (%)a	EC50 (nM)b	Emax (%)a	EC50 (nM)b	MVD (δ)	GPI (μ)
Ctrlc	142.6 ± 1.4	7.7 ± 1.9	465.2 ± 7.7	81 ± 12	202 ± 3.3	7.7 ± 1.8
Bph	219.6 ± 5.7	90.5 ± 25	178.2 ± 3.6	12 ± 4.6	108.9 ± 4.1	amb.	27 ± 15e	8.8 ± 0.3e
9	149.5 ± 2.3	7.1 ± 1.7	474.5 ± 4.1	76.2 ± 7.4	126.8 ± 4.4	480 ± 385	7.2 ± 0.8	21 ± 4
10	142.6 ± 2.8	360 ± 121	162.2 ± 3.2	230 ± 82	124.5 ± 2.7	205.1 ± 137	21% at 1 mM	4% at 1 mM

^aNet total bound/basal binding × 100 ± SEM.

^b±SEM.

^cThe control was the corresponding opioid receptor specific ligand (δ, Ile^5,6deltorphine II; μ, DAMGO; and κ, U69593).

^dConcentration at 50% inhibition of muscle contraction in electrically stimulated isolated tissues (n = 4).

^eData according to refs (19−21). amb.: ambiguous fitting since the compound did not stimulate the receptor above basal activity significantly.