Figure 7. A single channel can be activated to two conductance states by coapplication of LPA and capsaicin. (A) Left: Three classes of openings from the same single channel are observed. The low conductance and high conductance are prevalently observed with capsaicin or LPA, respectively. The two types are observed when capsaicin and LPA are applied together. Middle: To quantitatively evaluate the presence of the two levels of conductance, the amplitude of each detected event is plotted as a function of its duration. Capsaicin openings (black crosses) have mean amplitude of 8 pA; LPA openings (red squares) have amplitude of 9.8 pA. Openings elicited with capsaicin and LPA together show the presence of both types of openings (blue circles), with mean amplitudes 9.8 and 8.3. The membrane potential is 60 mV. Right: All-points histograms of selected openings in the three conditions. The histogram with LPA + cap is wider because of the presence of the two types of openings with two different amplitudes. Gaussian functions have been fitted to the histograms with capsaicin and LPA alone, as a visual guide. The arrows indicate the mean amplitudes of the openings with capsaicin (black) or LPA (red). (B) Representative traces of single-channel current elicited by capsaicin 4 µM (black) or 5 µM LPA (red) in the TRPV1 mutant K710D. (C) All-points histograms in the presence of capsaicin 4 µM (black) or 5 µM LPA (red) for TRPV1-WT (left) and for TRPV1-K710D (right). The value for single-channel current amplitude for TRPV1-WT in the presence of capsaicin 4 µM was 6.84 ± 0.02 pA (n = 24) and 9.66 ± 0.02 pA (n = 10) in the presence of 5 µM LPA. For TRPV1-K710D the single-channel current amplitude elicited by capsaicin 4 µM was 6.25 ± 0.4 pA (n = 6) and 6.84 ± 0.59 pA (n = 6) for LPA 5 µM. (D) Summary of the effects of LPA on the K710D mutant. Lines between the symbols indicate mean ± SEM. Recordings were made applying up to 100, 3-s-long, 60-mV square pulses from a 0-mV holding potential; data were sampled at 50 kHz and filtered with a 3-kHz low-pass Bessel filter. Capsaicin, LPA, and the combination of both agonists were applied by perfusion with a rapid solution changer.
Figure 7.

A single channel can be activated to two conductance states by coapplication of LPA and capsaicin. (A) Left: Three classes of openings from the same single channel are observed. The low conductance and high conductance are prevalently observed with capsaicin or LPA, respectively. The two types are observed when capsaicin and LPA are applied together. Middle: To quantitatively evaluate the presence of the two levels of conductance, the amplitude of each detected event is plotted as a function of its duration. Capsaicin openings (black crosses) have mean amplitude of 8 pA; LPA openings (red squares) have amplitude of 9.8 pA. Openings elicited with capsaicin and LPA together show the presence of both types of openings (blue circles), with mean amplitudes 9.8 and 8.3. The membrane potential is 60 mV. Right: All-points histograms of selected openings in the three conditions. The histogram with LPA + cap is wider because of the presence of the two types of openings with two different amplitudes. Gaussian functions have been fitted to the histograms with capsaicin and LPA alone, as a visual guide. The arrows indicate the mean amplitudes of the openings with capsaicin (black) or LPA (red). (B) Representative traces of single-channel current elicited by capsaicin 4 µM (black) or 5 µM LPA (red) in the TRPV1 mutant K710D. (C) All-points histograms in the presence of capsaicin 4 µM (black) or 5 µM LPA (red) for TRPV1-WT (left) and for TRPV1-K710D (right). The value for single-channel current amplitude for TRPV1-WT in the presence of capsaicin 4 µM was 6.84 ± 0.02 pA (n = 24) and 9.66 ± 0.02 pA (n = 10) in the presence of 5 µM LPA. For TRPV1-K710D the single-channel current amplitude elicited by capsaicin 4 µM was 6.25 ± 0.4 pA (n = 6) and 6.84 ± 0.59 pA (n = 6) for LPA 5 µM. (D) Summary of the effects of LPA on the K710D mutant. Lines between the symbols indicate mean ± SEM. Recordings were made applying up to 100, 3-s-long, 60-mV square pulses from a 0-mV holding potential; data were sampled at 50 kHz and filtered with a 3-kHz low-pass Bessel filter. Capsaicin, LPA, and the combination of both agonists were applied by perfusion with a rapid solution changer.

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