Table 1.

Binding affinities and functional activities of bifunctional peptide derivatives at δ/μ opioid receptors and NK1 receptors

				Opioid agonist activities						NK1 antagonist activities
	radioligand binding assays			[35S]GTPγS binding assays				MVD (δ)	GPI (μ)	radioligand binding assays			GPI
	hDORa,b	rMORa, c	Ki(μ) /Ki(ν)	hDORa		rMORa		Opioid agonist		hNK1d, e	rNK1d, f	Ki(rNK1) /Ki(hNK1)	Substance P antagonist
no	Ki (nM)g	Ki (nM)g		EC50 (nM)h	Emax (%)i	EC50 (nM)h	Emax (%)i	IC50 (nM)j	IC50 (nM)j	Ki (nM)g	Ki (nM)g		Ke (nM)k
1l	4.7	0.29	0.062	27	87	10	36	21	26	0.0057	4.2	740	59
2	58	11	0.19	160	87	59	70	13	430	0.050	1.6	32	250
3	1.6	33	21	0.38	77	25	38	6.0	1100	0.34	0.58	1.7	13
4	4.5	0.050	0.011	3.4	68	5.5	58	9.5	60	0.0040	0.042	11	10
5	11	0.20	0.018	25	41	41	16	33	120	0.47	4.9	10	30
6	35	37	1.1	150	14	100	14	43	520	0.12	0.15	1.3	38
7	310	49	0.16	280	33	23	34	300	840	0.030	15	500	5.0
8	56	3.2	0.057	6.7	78	7.1	58	180	210	0.20	230	1200	52
9	100	180	1.8	91	36	170	26	5.5% 1μM	3.3% 1μM	0.0040	2.9	730	49
10	0.80	0.30	0.38	12	27	1.6	49	400	20% 1μM	0.016	0.28	18	110
11	64	2.4	0.038	24	50	5.2	50	41	120	0.85	92	110	22
Biphalinm	2.6	1.4	0.54	1.1	83			2.7	8.8
DAMGOn						37	150
L-732,138o										0.73	130	180	250

^aCompetition analyses were carried out using membrane preparations from transfected HN9.10 cells that constitutively expressed the DOR and MOR.

^b[³H]DPDPE; K_d = 0.45 ± 0.1 nM.

^c[³H]DAMGO; K_d = 0.50 ± 0.1 nM.

^dCompetition analyses were carried out using membrane preparations from transfected CHO cells that constitutively expressed rat or human NK1 receptors.

^e[³H]Substance P; K_d = 0.16 ± 0.03 nM.

^f[³H]Substance P; K_d = 0.40 ± 0.17 nM.

^gThe data were collected from at least two independent experiments performed in duplicate. The K_i values are calculated using the Cheng and Prusoff equation to correct for the concentration of the radioligand used in the assay.

^hThe EC₅₀ values were determined from the non-linear regression analysis of data collected from at least two independent experiments performed in duplicate.

ⁱ[Total bound − Basal]/[Basal − Non-specific] × 100.

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

^kInhibitory activity against the substance P induced muscle contraction in the presence of 1 μM naloxone, Ke: concentration of antagonist needed to inhibit substance P to half its activity (n = 4).

^lReference 11.

^mReference 15.

ⁿReference 9a.

^oReference 9c.