Fig. 5.

Competition curves for inhibition of specific ¹²⁵I-Mel binding by melatonin and its analogues in NIH3T3 cells stably expressing either rat MT1 or MT2. Cell lysates were incubated with 100 pM ¹²⁵I-Mel and various concentrations of 2-iodomelatonin (I-Mel), melatonin, 6-hydroxymelatonin, luzindole, or N-acetyl-5-hydroxytryptamine (NAS). Non-specific binding was determined in the presence of 20 μM melatonin. Competition binding with various ligands in NIH3T3 cells transfected with either rat MT1 (a) or MT2 (b). The data shown are mean values of four experiments for each drug. The K _i values are listed in Table 3