Table 2: Opioid receptor affinities of opioid ligands 51–70.

Nos.CompoundsKiμ(nM)Kiδ(nM)Kiδ/KiμReference

51Dmt-NH-(CH2)2-NH-Dmt1.43115.781[18]
52Dmt-NH-(CH2)4-NH-Dmt0.04153.41302[18]
53Dmt-NH-(CH2)6-NH-Dmt0.05346.1870[18]
54Dmt-NH-(CH2)8-NH-Dmt0.1914.878[18]
553,6-bis[Dmt-NH-CH2]-5-methyl-2(1H)-pyrazinone1.1615.713.5[19]
563,6-bis[Dmt-NH(CH2)2]-5-methyl-2(1H)-pyrazinone0.1157.2663[19]
573,6-bis[Dmt-NH(CH2)3]-5-methyl-2(1H)-pyrazinone0.04213.2307[19]
583,6-bis[Dmt-NH(CH2)4]-5-methyl-2(1H)-pyrazinone0.11423.2204[19]
593,6-bis[Dmt-Tic-NH-CH2]-5-methyl-2(1H)-pyrazinone3.760.1630.043[20]
603,6-bis[Dmt-Tic-NH(CH2)2]-5-methyl-2(1H)-pyrazinone2.830.0950.034[20]
613,6-bis[Dmt-Tic-NH(CH2)3]-5-methyl-2(1H)-pyrazinone3.080.1550.05[20]
623,6-bis[Dmt-Tic-NH(CH2)4]-5-methyl-2(1H)-pyrazinone1.740.3230.185[20]
633-[Dmt-Tic-NH(CH2)3]-6-[Dmt-Tic-NH(CH2)4]-5-methyl-2(1H)-pyrazinone1.560.160.1[20]
643-[Dmt-Tic-NH(CH2)4]-6-[Dmt-Tic-NH(CH2)3]-5-methyl-2(1H)-pyrazinone2.280.0920.04[20]
653-[Dmt-Tic-NH(CH2)2]-6-[Dmt-Tic-NH(CH2)4]-5-methyl-2(1H)-pyrazinone1.370.1070.078[20]
66bis[Dmt-Tic-NH]butane5.720.1240.021[20]
67bis[Dmt-Tic-NH]hexane1.790.1290.072[20]
68bis[Dmt-Tic-NH]decane4.861.530.315[20]
69bis[N,N-dimethyl-Dmt-Tic-NH]2.210.060.027[20]
hexane
703,6-bis[N,N-dimethyl-Dmt-Tic-NH-1.680.2870.17[20]
propyl]-5-methyl-2(1H)-pyrazinone

Opioid receptor affinities are determined using rat brain P2  synaptosomal preparations with [3H]DAMGO for μ-opioid receptors and [3H]DPDPE for  δ-opioid receptors.