Figure 2.

Concentration–response relationship of transient receptor potential (TRP) channel-blocking fenamates. (A) Calcium entry in TRPM3-expressing cells was measured using FLIPR^Tetra and data analysed as described in Methods. Data from a representative experiment show the effect of mefenamic acid on calcium entry in TRPC6-, TRPM2-, TRPM3- and TRPV4-expressing cells upon hyperforin (10 µM), hydrogen peroxide (5 mM), pregnenolone sulphate (35 µM) and 4α-phorbol-didecanoate (5 µM) stimulation respectively. Mefenamic acid was ineffective at suppressing TRPC6-, TRPM2- and TRPV4-mediated calcium entry, whereas the intracellular calcium concentration ([Ca²⁺]_i) remained at the initial basal level in TRPM3-expressing cells upon stimulation with pregnenolone sulphate. The data were calculated from one experiment of at least three experiments performed in quadruplicate per concentration and TRP channel. (B) In transiently transfected HEK cells expressing TRPM3, the application of pregnenolone sulphate (35 µM) results in an instantaneous increase in intracellular calcium. The application of mefenamic acid (30 µM) during the plateau phase results in a rapid decrease in [Ca²⁺]_i to basal levels. Application of vehicle had no effect. Mean value obtained from at least 20 cells of one experiment (out of five independent experiments) is shown. The grey shading represents the SEM for each data point.