Table 3. In Vitro Pharmacological Profiles of Morphine and UMB 425^a.

	Ki ± SEM (nM)			EC50 ± SEM (nM)			% Emax ± SEM			pA2
	μ	δ	κ	μ	δ	κ	μ	δ	κ	δ
morphine	1.7 ± 0.34	87 ± 6.6	69 ± 1.3	38 ± 4.9	316.5 ± 4.9b	484 ± 213b	81 ± 2.3	103 ± 7b	62 ± 7b	nd
UMB 425	3.2 ± 0.14	208 ± 18	212 ± 21	35 ± 3.7	n/e	n/e	73 ± 7.3	nd	nd	(−0.91)

^aReceptor binding and [³⁵S]GTPγS functional activity for morphine and UMB 425 are summarized for studies performed in CHO cell membranes stably transfected and overexpressing the human μ, δ, and κ opioid receptors. Competition binding for compounds were performed in triplicate of duplicates and reported as mean K_i values ± SEM. Mean EC₅₀ and %E_max values ± SEM for the [³⁵S]GTPγS functional assays were performed in triplicate of duplicates. pA₂ is defined as the negative logarithm of antagonist concentration needed to shift the dose response curve by a factor of 2. A slope of at or near −1 is indicative of competitive antagonism for the drug at the receptor.

^bReference (32). n/e = no effect, nd = not determined.