Figure 4. D1-mGlu5 heteromer creates an atypical D1 receptor–mediated intracellular Ca²⁺ release.

(A) HEK cell line stably expressing GcAMP6 calcium indicator and Glo cAMP-sensor, cotransfected with mGlu5 and D1 receptors. (B–E) Ca²⁺ release and cAMP production were measured in cells transfected with mGlu5, D1, or mGlu5 plus D1 receptors. Values represent mean ± SEM of 3 or 4 independent experiments. Data are expressed as a percentage of the maximal Quisq- or SKF-induced effect. (B and C) Ca²⁺ release dose-response curve induced by (B) D1 agonist (SKF81297) and (C) mGlu5 agonist Quisq. (D and E) cAMP production dose response curve induced by (D) D1 agonist SKF81297 and (E) mGlu5 agonist Quisq. (F–H) Synergistic activation of Ca²⁺ release induced by D1 and mGlu5 receptors. Cells were transfected with D1 (F), mGlu5 (G), or both receptors (H). Ca²⁺ release is here expressed as a percentage of basal levels in each transfection condition. Values represent mean ± SEM of 2 to 4 independent experiments.