Figure 1.

Camphor activates heterologously expressed rat TRPV1. A, Structure of the (+) and (–) stereoisomers of camphor. B, Both camphor stereoisomers activated rTRPV1. The weaker action of (–)-camphor in comparison with (+)-camphor was likely the result of tachyphylaxis. Ramp currents were evoked by 400 ms voltage ramps from –100 to +100 mV applied every 4 s. Each symbol represents the current amplitude at +60 mV (red triangles) and –60 mV (black circles). Note the zero current level (indicated by blue dashed line). C, rTRPV1 was activated by camphor, anandamide, and capsaicin. Capsazepine (10 μm) strongly inhibited the anandamide-induced currents. D, Effect of camphor on rTRPV1-mediated current elicited by voltage steps (protocol shown in the top panel).