Figure. Concentration-dependent activation of GRM4 by L-glutamic acid. Reporter cells were transfected with either the expression plasmid for glutamate metabo­tropic receptor 4 (GRM4) or the mock plasmid and treated with various concentrations of L-glutamic acid. 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 34 µM.