Table 1: Difference in binding affinities of MT1, MT2 or MT3 receptors.
| Function | Ramelteon Affinity | Melatonin Affinity | |
| MT1 (humans) | Initiation of sleep | Ki = 14 | Ki = 80 |
| MT2 (humans) | Regulation and maintenance of circadian rhythm | Ki = 112 | Ki = 383 |
| MT1/MT2 ratio | Lower number identifies greater selectivity for MT1 over MT2 | 0.13 | 0.21 |
| MT3 (hamsters) | Modulates the enzyme: Quinone reductase 2 | Ki = 2650 | Ki = 24 |