Figure 5.

Measurement of IP production as a function of extracellular Mg²⁺ concentration at mGPRC6A and 5-HT_2C. (a) Response to Mg²⁺ measured in cells transiently co-expressing mGPRC6A and Gα_qG66D in the absence or presence of 30 μM L-Orn (∼EC₂₅). The response to maximal concentration (10 mM) of L-Orn in the presence of 1 mM Mg²⁺ was used as control. (b) Response to Mg²⁺ measured in cells transiently expressing the 5-HT_2C receptor, in the absence or presence of 2 nM 5-HT (∼EC₂₅). The response to maximal concentration (1 μM) of 5-HT in the presence of 1 mM Mg²⁺ was used as control. All experiments were performed in the presence of 1 mM Ca²⁺. The formation of IP was determined as described under Methods. Results are expressed as CPM and are means±s.d. of triplicate determinations of a single representative experiment. Two additional experiments gave similar results. Asterisks indicate significant differences from the measurements where only Ca²⁺ was present: ^**P<0.01 (ANOVA followed by Dunnett's test).