Figure 4

FSK potentiates capsaicin-induced Ca²⁺ responses in FLAG-MOP/TRPV1 double stable HEK293 cells. Pre-incubation with varying concentrations of FSK (0.5–500 μM) and constant concentrations of IBMX (100 μM) caused a FSK-concentration-dependent increase in Ca²⁺ response to the injection of 300 nM capsaicin in colony 21 (△(A)) and colony 13 (■, (C)). (B and D) Individual Ca²⁺ traces after injection of 300 nM capsaicin from Fluo-3-loaded double colonies (Colony 21, (B) and Colony 13, (D)). Cells responded with a characteristic increase in intracellular Ca²⁺ after injection of capsaicin, which was increased after 15 minutes incubation with FSK and IBMX (100 μM). Data are presented as mean ± SEM with n = 4.