Table III.

K _i Values for the Inhibition of Mu-, Delta-, and Kappa-opioid Receptor Binding to Murine Brain Membrane Protein by TPI 1818-101 and TPI 1818-109

Radiolabeled ligands	K i (nM) ± SEM
	[3H]DAMGO (MOR)	[3H]DPDPE (DOR)	[3H]U69,593 (KOR)
TPI 1818-101	2,790 ± 741	1,930 ± 474	3,910 ± 1,640
TPI 1818-109	9,470 ± 1,210	2,210 ± 932	7,750 ± 3,830

Murine brain membrane protein was incubated with six different concentrations of each TPI compound in the presence of 0.87 nM [³H]DAMGO, 2 nM [³H]DPDPE, or 2 nM [³H]U69,593 in 50 mM Tris–HCl, pH 7.5, at 25°C as described in “MATERIALS AND METHODS.” Data are listed as the mean K _i values ± SEM from at least three experiments