Table 1.
Functional characteristics of ICOA‐9 and ICOA‐13 in HEK293 cells expressing the melatonin receptors indicated
| Receptor | Ligand | 2‐[125I]‐MLT compet. pKi | ERK act. pEC50 (Emax) | cAMP inh. pEC50 (Emax) | ß‐ARR recrut. pEC50 (Emax) |
|---|---|---|---|---|---|
| hMT1 | Melatonin | −8.61 ± 0.19 | −8.46 ± 0.41 (100 ± 9) | −9.37 ± 0.22 (100 ± 5) | −9.67 ± 0.17 (100 ± 5) |
| ICOA‐9 (3) | −5.76 ± 0.16 | > −6 (n.d.) | −9.18 ± 0.47 (49 ± 8) | −7.60 ± 0.48 (95 ± 7) | |
| ICOA‐13 (7) | −4.97 ± 0.28 | > −6 (n.d.) | −7.76 ± 0.69 (37 ± 8) | −7.13 ± 0.05 (57 ± 5) | |
| hMT2 | Melatonin | −9.3 ± 0.20 | −9.16 ± 0.57 (100 ± 8) | −9.49 ± 0.11 (100 ± 5) | −9.53 ± 0.16 (100 ± 6) |
| ICOA‐9 (3) | −7.41 ± 0.05 | −6.65 ± 0.21 (156 ± 23) | n.d. (n .d.) | −7.91 ± 0.72 (79 ± 8) | |
| ICOA‐13 (7) | −5.48 ± 0.50 | −6.58 ± 0.38 (133 ± 14) | n.d. (n.d.) | −7.76 ± 0.49 (49 ± 8) | |
| mMT1 | Melatonin | −9.42 ± 0.28 | −9.22 ± 0.86 (100 ± 14) | −9.65 ± 0.45 (100 ± 12) | n.d. |
| ICOA‐9 (3) | −6.88 ± 0.29 | −6.90 ± 0.12 (146 ± 13) | −9.88 ± 0.34 (81 ± 12) | n.d. | |
| ICOA‐13 (7) | −5.81 ± 0.33 | −7.12 ± 0.10 (164 ± 15) | −9.60 ± 0.94 (92 ± 12) | n.d. | |
| mMT2 | Melatonin | −9.52 ± 0.18 | −8.90 ± 0.47 (100 ± 9) | −10.19 ± 0.22 (100 ± 9) | n.d. |
| ICOA‐9 (3) | −7.39 ± 0.36 | −6.69 ± 0.24 (105 ± 13) | −9.60 ± 0.94 (94 ± 12) | n.d. | |
| ICOA‐13 (7) | −6.24 ± 0.29 | −7.24 ± 0.30 (84 ± 14) | −7.47 ± 0.65 (62 ± 8) | n.d. |
Concentration–response curves were analysed by non‐linear regression. Binding affinity was measured with 2‐[125I]‐MLT and is expressed as mean pKi ± SEM (M). Agonist potency is expressed as pEC50 ± SEM (M). While the maximal efficacy, Emax, is expressed as a percentage of the maximal effect observed with melatonin (=100%). Data are mean of at least three independent experiments, each of them performed using at least eight different ligand concentrations. n.d., not determined.