. 2021 Apr 6;22(7):3779. doi: 10.3390/ijms22073779

Table 3.

Mu agonist-induced [³⁵S]GTPγS binding in Chinese Hamster Ovary (CHO) cells stably expressing mouse, rat and human mu opioid receptor gene (Oprm1) 7TM C-terminal variants.

	Ligand
	DAMGO		Morphine		β-Endorphin		Dynorphin A		Endomorphin 1		Endomorphin 2		[Met]⁵Enkephalin-Arg⁶-Phe⁷		Ref.
	EC₅₀ (nM)	%Max	EC₅₀ (nM)	%Max	EC₅₀ (nM)	%Max	EC₅₀ (nM)	%Max	EC₅₀ (nM)	%Max	EC₅₀ (nM)	%Max	EC₅₀ (nM)	%Max
Mouse
mMOR-1	68 ± 4	100	23 ± 2	102 ± 5	64 ± 7	97 ± 2	34 ± 9	109 ± 7	26 ± 4	98 ± 8	72 ± 11	124 ± 8	53 ± 3	118 ± 15	[73]
mMOR-1A	70 ± 3	100	19 ± 4	91 ± 2	111 ± 27	83 ± 3	150 ± 36	73 ± 6	42 ± 13	69 ± 2	97 ± 28	76 ± 3	133 ± 9	75 ± 4	[73]
mMOR-1C	62 ± 4	100	23 ± 5	75 ± 4	123 ± 19	44 ± 3	140 ± 19	76 ± 10	83 ± 20	68 ± 15	122 ± 46	62 ± 15	60 ± 17	51 ± 2	[73]
mMOR-1D	62 ± 6	100	82 ± 34	99 ± 3	73 ± 18	105 ± 6	100 ± 41	102 ± 6	47 ± 21	94 ± 8	137 ± 24	92 ± 5	170 ± 16	94 ± 3	[73]
mMOR-1E	48 ± 4	100	41 ± 13	116 ± 4	113 ± 25	130 ± 3	113 ± 9	129 ± 9	80 ± 4	85 ± 9	52 ± 26	86 ± 8	131 ± 19	94 ± 10	[73]
mMOR-1B1	39 ± 8	100	100 ± 38	104 ± 38	113 ± 47	69 ± 21	137 ± 69	83 ± 23	57 ± 23	68 ± 19	197 ± 95	90 ± 0			[75]
mMOR-1B2	85 ± 18	100	76 ± 13	82 ± 8	163 ± 22	84 ± 5	210 ± 25	81 ± 6	126 ± 29	82 ± 8	187 ± 23	92 ± 4			[75]
mMOR-1B3	100 ± 14	100	51 ± 6	91 ± 3	75 ± 19	93 ± 2	147 ± 56	90 ± 6	99 ± 1	97 ± 2	110 ± 6	80 ± 3			[75]
mMOR-1B5	89 ± 13	100	53 ± 4	87 ± 7	83 ± 27	80 ± 4	197 ± 32	75 ± 3	89 ± 13	86 ± 7	155 ± 8	82 ± 4			[75]
mMOR-1F	50 ± 6	100	44 ± 17	76 ± 13	26 ± 6	74 ± 7	40 ± 8	73 ± 3	44 ± 18	113 ± 5	68 ± 18	107 ± 4	29 ± 9	94 ± 16	[73]
mMOR-1O	60 ± 19	100	85 ± 31	66 ± 23	6 ± 1	141 ± 8									[77]
mMOR-1P	133 ± 23	100	58 ± 9	115 ± 23	24 ± 5	55 ± 3									[77]
Rat
rMOR-1	12 ± 3	100			4 ± 2	105.58			14 ± 4	137.34					[74]
rMOR-1A	13 ± 5	100			13 ± 5	100.57			15 ± 3	116.48					[74]
rMOR-1C1	74 ± 22	100			48 ± 4	154.94			54 ± 8	161.80					[74]
rMOR-1D	125 ± 26	100			91 ± 14	146.02			100 ± 26	128.32					[74]
Human
hMOR-1	120 ± 17	100	21 ± 4	97.57	4 ± 1	68.75	296 ± 16	36.46							[76]
hMOR-1A	161 ± 21	100	30 ± 2	121.31	8 ± 2	71.31	36 ± 1	63.93							[76]
hMOR-1B1	255 ± 46	100	41 ± 5	64.41	25 ± 6	57.97	63 ± 17	50.51							[76]
hMOR-1B2	1028 ± 68	100	77 ± 9	80.00	73 ± 10	97.84	292 ± 66	97.84							[76]
hMOR-1B3	549 ± 86	100	86 ± 19	65.44	33 ± 11	61.78	98 ± 27	39.38							[76]
hMOR-1B4	341 ± 65	100	38 ± 5	71.68	19 ± 2	65.32	58 ± 14	40.75							[76]
hMOR-1B5	936 ± 233	100	90 ± 18	61.46	55 ± 2	92.01	158 ± 15	81.60							[76]
hMOR-1Y	571 ± 255	100	100 ± 20	88.05	43 ± 3	73.18	100 ± 21	77.26							[76]

[³⁵S]GTPγS binding assay was performed with membranes prepared from CHO cells stably expressing indicated splice variants, as described in indicated references. The percentage of maximum stimulation (% Max) of the agonists was normalized with that of DAMGO.