TABLE 5

Stimulation of [35S]GTPγS binding in mMOR-1 splice variants

Basal [35S]GTPγS binding was assessed in membranes from cells stably transfected with the indicated variants after stimulation of [35S]GTPγS binding by the indicated drug. The maximal stimulation, defined as the percentage increase over basal binding, and the dose of drug needed to elicit 50% of the maximal response (EC50) were calculated as described under Materials and Methods. Results are the means ± S.E.M. of at least three independent determinations.

Ligand mMOR-1 mMOR-1B1 mMOR-1B2 mMOR-1B3 mMOR-1B5
EC50 EC50/Ki % Max EC50 EC50/Ki % Max EC50 EC50/Ki % Max EC50 EC50/Ki % Max EC50 EC50/Ki % Max
DAMGO 68 ± 4 38 100 39 ± 8 28 100 85 ± 18 65 100 100 ± 14 56 100 89 ± 13 89 100
Morphine 23 ± 2 4.3 102 ± 5 100 ± 38 18.9 104 ± 38 76 ± 13 19.5 82 ± 8 51 ± 6 34 91 ± 3 53 ± 4 37.9 87 ± 7
M6G 75 ± 18 11.7 122 ± 9 527 ± 245 52.2 117 ± 15 150 ± 6 17.9 71 ± 5 83 ± 19 21.2 82 ± 7 85 ± 18 16.3 88 ± 9
Dynorphin A 34 ± 9 3.2 109 ± 7 137 ± 69 9.4 83 ± 23 210 ± 25 6.1 81 ± 6 147 ± 56 16.9 90 ± 6 197 ± 32 22.4 75 ± 3
β-Endorphin 64 ± 7 7.6 97 ± 2 113 ± 47 16.6 69 ± 21 163 ± 22 33.3 84 ± 5 75 ± 19 24.1 93 ± 2 83 ± 27 14.6 80 ± 4
Endomorphin 1 26 ± 4 12.3 98 ± 8 57 ± 23 5.3 68 ± 19 126 ± 29 25.2 82 ± 8 99 ± 1 30.9 97 ± 2 89 ± 13 20.7 86 ± 7
Endomorphin 2 72 ± 11 17.1 124 ± 8 197 ± 95 15.9 90 ± 0 187 ± 23 22.3 92 ± 4 110 ± 6 34.4 80 ± 3 155 ± 8 14.6 82 ± 4