Affinities of GR196429 and other melatonin receptor analogs to compete for radiolabeled melatonin binding to native and recombinant high-affinity melatonin receptors
| Compound | CHO-hmt1 | CHO-hMT2 | Human Cerebellum | Guinea Pig Superior Colliculus | Guinea Pig Hypothalamus |
|---|---|---|---|---|---|
| Melatonin | 10.08 ± 0.05 | 9.72 ± 0.11 | 9.41 ± 0.12 | 9.59 ± 0.05 | 9.61 ± 0.20 |
| GR196429 | 9.85 ± 0.06 | 9.79 ± 0.07 | 9.25 ± 0.11 | 9.21 ± 0.10 | 9.47 ± 0.18 |
| S-20098 | 10.36 ± 0.04 | 10.47 ± 0.07 | 9.38 ± 0.14 | 10.00 ± 0.05 | 10.01 ± 0.10 |
| 2-l-melatonin | 10.91 ± 0.04 | 10.28 ± 0.05 | 10.47 ± 0.06 | 10.52 ± 0.03 | 10.36 ± 0.06 |
| 6-Cl-melatonin | 9.17 ± 0.06 | 9.84 ± 0.08 | 8.57 ± 0.15 | 9.33 ± 0.10 | 9.13 ± 0.23 |
| 6-OH-melatonin | 9.26 ± 0.03 | 8.77 ± 0.06 | 8.65 ± 0.13 | 7.99 ± 0.07 | 7.60 ± 0.15 |
| Luzindole | 6.60 ± 0.05 | 7.84 ± 0.08 | 6.60 ± 0.11 | 6.03 ± 0.21 | 6.17 ± 0.19 |
| N-acetyl-serotonin | 7.10 ± 0.05 | 6.83 ± 0.04 | 6.52 ± 0.07 | 6.40 ± 0.11 | 6.46 ± 0.19 |
Values are pKi ± S.E.M. from duplicate determinations in three to eight experiments.
Data in CHO membranes obtained using [3H]-melatonin. Data in human and guinea pig tissues determined using 2-[125I]-iodomelatonin. No slope values were significantly different from unity, with the exception of 2-iodomelatonin at mt1 receptors (1.38 ± 0.09, P < .05).