Figure 4.
Camphor does not activate currents in cells expressing several related TRP channels. A, B, Camphor (10 mm) did not activate current from a TRPV2-expressing cell. The expression of TRPV2 was confirmed by the response induced by 300 μm DPBA. C, D, Camphor (10 mm) failed to increase the basal current from a TRPV4-transfected cell. Indeed, the small constitutive activity was completely inhibited. 4-αPDD (1 μm) readily activated a doubly rectifying current characteristic of ITRPV4. E, F, TRPM8 was not activated by 10 mm camphor but by 500 μm menthol. A small outward-rectifying basal current was seen after break in (data not shown) but decayed almost completely. G, H, Application of 10 mm camphor to a cell cotransfected with mTRPC5 and the M1 receptor did not activate TRPC5 currents (ITRPC5). Subsequent application of 100 μm carbachol activated large inward and outward currents with the characteristic I–V of ITRPC5.