Fig. 8.
Dopamine does not elicit a calcium response in cells co-expressing the D1R and D4R. HEK293T cells were transiently transfected with D1R + D2LR or D1R + D4R, as indicated and described in Materials and Methods. Twenty-four hours later, cells were plated in 384-well plates and assayed for calcium mobilization through stimulation by the indicated concentrations of DA. Data are expressed as a percentage of control maximum DA stimulation seen in cells transfected with D1R + D2LR only (EC50 = 162.0 nM) and are representative of two or three independent experiments done with the same assay conditions on different days. Expression of the D4R was confirmed using radioligand binding assays as described in Materials and Methods and was similar to that of the D2R. Error bars indicate S.E.M. from multiple wells within the representative experiment.