TABLE 1

Binding affinities measured in HEK 293 cells expressing MT₁ and MT₂ receptors

HEK 293 cells expressing MT₁-Rluc or MT₂-YFP or both together at a 1:1 ratio were incubated with ¹²⁵I-MLT and various concentrations of the indicated compounds. K_i values were calculated as described under Materials and Methods. Data are means ± S.E. of three independent experiments each performed in duplicate.

Ligands	K_i			K_i Ratio
Ligands	MT₁-Rluc	MT₂-YFP	MT₁-Rluc + MT₂-YFP (Ratio 1:1)	MT₁/MT₂	MT₁/(MT₁ + MT₂)	MT₂/(MT₁ + MT₂)
	nM
Melatonin	0.36 ± 0.1	0.48 ± 0.1	1.13 ± 0.5	0.7	0.3	0.4
S20098	0.78 ± 0.2	0.08 ± 0.05	1.64 ± 1.5	9.7	0.5	0.05
S22153	39.4 ± 9.0	13 ± 3	31.7 ± 8.9	3	1.2	0.4
S20928	244 ± 105	210 ± 81	281 ± 114	1.2	0.9	0.7
4P-PDOT	53.5 ± 13	2 ± 0.3	1.40 ± 0.4	26	75	1.4
			70.3 ± 15 (2nd site)		0.7	0.02
Luzindole	31.6 ± 7.0	12.3 ± 4.3	10 ± 1.7	2.6	3.2	1.2
S24773	295 ± 26	3.70 ± 1.7	0.60 ± 0.1	80	491	6.2
			192 ± 23 (2nd site)	1.5		0.01