Figure 2.

Electrophysiological recordings of wild-type TRPV1 and G564S mutant channels. (a) Representative currents from inside-out patches in HEK293a cells expressing wild-type TRPV1 (upper traces) and G564S mutant channels (lower traces) in response to stimulation by 1-μM capsaicin (CAP) or inhibition by 130 mM Ba²⁺ to assess the level of leak currents at −70 mV. Note that the G564S mutant channel showed little activation, then a dramatic block by Ba²⁺. (b) Ratios of initial basal current amplitude to maximal current amplitude evoked by CAP in the TRPV1 wild-type and mutant channels (n = 7, ***p < 0.001, unpaired Student’s t test). (c) Upper traces are representative whole-cell current traces in response to 100-ms voltage steps from −120 mV to +180 mV for wild-type TRPV1 and G564S mutant channels. Lower traces are normalized conductance–voltage relationships for wild-type TRPV1 and G564S mutants (n = 13–18). Note the dramatic leftward shift of the G564S mutant channel. (d) Representative recordings of whole-cell current responses of HEK293a cells expressing wild-type TRPV1 (upper) or G564S mutant channels (lower) evoked by two consecutive applications of 1-μM capsaicin at −70 mV. The G564S mutant channels displayed no acute desensitization. (e) Current ratios of second to first CAP application for wild-type and mutant TRPV1 (n = 13–14, ***p < 0.001, unpaired Student’s t test). (f) Inward current densities induced by first and second capsaicin application for wild-type and mutant TRPV1 (n = 13–14, *p < 0.05, ***p < 0.001, unpaired Student’s t test). TRPV: transient receptor potential vanilloid.