Figure. Concentration-dependent activation of MTNR1A by melato­nin. Reporter cells were transfected with either the expression plasmid for melato­nin receptor 1A (MTNR1A) or the mock plasmid and treated with various concentrations of melato­nin. Data points shown are the mean ± SEM of an experiment performed in triplicate, and the curve is a fit to Hill equation with an EC50 of 100 pM.