Figure 10.

Potentiation of a single TRPC5 channel by Ca²⁺ in cell-attached recordings. (A) Channel activity as shown by continuous NP_o trace (averaged 10-s bins). (B) The current trace recorded −50 mV relative to the cell membrane potential. Channel openings are downward deflections from the baseline. (Bottom right) Single-channel I-V relation. (C) Expanded trace for the region indicated by the black circle in B. C and O indicate closed and open levels, respectively. (D–G) Summary of single-channel properties from nine independent patches (normalized as fold change relative to preceding condition due to baseline NP_o variability from patch to patch). The large increase in single-channel activity (NP_o) evoked by the addition of 10 mM of extracellular Ca²⁺ in D (10.42 ± 2.8-fold; n = 7; P = 0.025), resulted from (E) increased channel-opening frequency (9.76 ± 2.13-fold; n = 8; P = 0.003) and (G) channel open time (2.09 ± 0.38-fold; n = 8; P = 0.011). (F) Single-channel conductance did not change. In this figure and Fig. 11, symbols represent patches recorded in the bath solutions indicated; for clarity, patches at similar amplitudes are offset horizontally and shown in different shapes for different solution conditions. Internal solution: standard 2 Ca external with 100 µM CCh. Bath solutions: 2 Ca and 10 Ca each had 1 mM MgCl₂. Nominally Ca-free external had 3 mM MgCl₂.