Responsiveness of VR1 and mutants to capsaicin.
(A) Normalized current responses by the sequential
application of 1 μM and 10 μM capsaicin to cells expressing either
VR1 receptors or VR1-E648Q receptors. The interstimulus interval was
always longer than 5 min. (B) Capsaicin dose-response
data for VR1 and mutants. Each point represents the mean ± SEM
for 2EVC data from at least four independent oocytes. The solid and
dashed lines are optimized fits to the Hill equation. Open symbols
indicate the relative Po values obtained
from single-channel records of VR1 (□), E648Q
(○), and E636Q (Δ). (C) Current-voltage
relationship for VR1, E648Q, E636Q, and D646N. Steady-state currents
were recorded at a series of voltages in the presence and absence of 10
μM capsaicin. Plots are normalized to maximal steady-state currents.
Error bars (SEM) are omitted for the sake of clarity but were always
less than 0.18I/Imax.