Expression of mGlu1 and mGlu5 receptors in cells transfected with mGlu1 or mGlu5 cDNA in the absence or presence of mGlu2, mGlu3 receptors or GRK2-C-ter cDNA is shown in (A). Stimulation of PI hydrolysis by DHPG and/or LY379268 in cells expressing mGlu1 or mGlu5 receptors with or without mGlu2 or mGlu3 receptors is shown in (B). The effect of GRK2-C-ter on the synergism between mGlu3 and mGlu1 or mGlu5 receptors is shown in (C). In (B) and (C), values are mean ± S.E.M. of 3–9 determinations. p < 0.05 (Two-way ANOVA + Bonferroni test) * vs. the respective basal and # vs. the respective DHPG alone (B 1: F(1,16) = 4.69 for transfection factor and F(3,16) = 43.93 for treatment factor; B2: F(1,16) = 11.39 for transfection factor and F(3,16) = 112.73 for treatment factor; B3: F(1,25) = 2.17 for transfection factor and F(3,25) = 27.00 for treatment factor; B4: F(1,47) = 1.04 for transfection factor and F(3,47) = 41.17 for treatment factor; C1: F(1,25) = 4.89 for transfection factor and F(3,25) = 28.97 for treatment factor; C2: F(3,29) = 30.78 for treatment factor).