Table 2. EC₅₀ and E_max Values for the Stimulation of [³⁵S]GTPγS Binding and IC₅₀ and I_max Values for the Inhibition of Agonist-Stimulated [³⁵S]GTPγS Binding to the Human μ and δ Opioid Receptors^a.

	agonism				antagonism
	μ		δ		μ		δ
compd	EC50 (nM)	Emax (%)	EC50 (nM)	Emax (%)	IC50 (nM)	Imax (%)	IC50 (nM)	Imax (%)
1	19 ± 1.9	84 ± 10	c	6.8 ± 1.8	b	b	1.3 ± 0.031	95 ± 1.1
2	0.90 ± 0.032	92 ± 4.0	2.8 ± 0.60	44 ± 6.1	b	b	b	b
3	33 ± 2.9	52 ± 5.5	c	4.5 ± 0.85	460 ± 93	43 ± 3.3	0.95 ± 0.058	93 ± 2.2
4	63 ± 3.5	34 ± 6.4	c	0.4 ± 1.43	820 ± 150	65 ± 1.1 at 25 μMe	1.0 ± 0.28	86 ± 5.0
5	61 ± 15	16 ± 2.5	c	3.1 ± 0.43	810 ± 27.0	74 ± 6.9	1.6 ± 0.76	79 ± 3.8
6	d	d	c	13 ± 1.0	d	d	5.2 ± 0.13	78 ± 2.7
7	4.8 ± 0.16	45 ± 1.2	c	−1.9 ± 0.17	b	b	8.3 ± 0.26	100 ± 7.4
8	22 ± 6.8	43 ± 6.6	c	−1.4 ± 0.14	b	b	2.3 ± 0.27	99 ± 3.3

^aSee Methods section. Data are the mean E_max and EC₅₀ values (SEM from at least three separate experiments, performed in triplicate). For calculation of the E_max values, the basal [³⁵S]GTPγS binding was set at 0%.

^bNo inhibition.

^cNot active.

^dNot tested.

^eCompound 4 at a concentration of 25 μM inhibited 65% ± 1.1% of DAMGO-stimulated [³⁵S]GTPγS binding. An IC₅₀ value was not reported because higher concentrations could not be used without having the DMSO vehicle interfere with the assay. A concentration of 200 nM DAMGO, which gave 96% ± 3.1% stimulation, was used to measure inhibition of DAMGO-stimulated [³⁵S]GTPγS binding. A concentration of 100 nM U50,488, which gave 64% ± 1.9% stimulation, was used to measure inhibition of U50,488-stimulated [³⁵S]GTPγS binding, and 10 nM SNC 80, which gave 66% ± 4.3% stimulation, was used to measure inhibition of [³⁵S]GTPγS binding, mediated by the δ opioid receptor.