Figure 2. Perforated patch and single-channel experiments.

(A) Combined amphotericin-induced perforated-patch and Fura-2 experiments (see methods). The upper trace depicts average perforated-patch whole-cell currents using standard internal solution in the absence of ADPR (n = 3). The lower trace shows the average cellular Ca²⁺ signal measured in parallel in the same cells (n =3). Cells were superfused with standard extracellular solution devoid of Ca²⁺ and supplemented with 2 μM ionomycin for 5 sec as indicated by the two arrows, respectively. Standard voltage ramps were applied from a holding potential of 0 mV. Error bars represent S.E.M. (B) Single-channel activity of a representative cell during consecutive voltage ramps applied in the whole-cell configuration. The cell was perfused with 200 nM ADPR and two channels were active (dotted lines indicate channel open levels). A fit to the data gave a single channel conductance of 43 pS ± 0.4 pS (n = 3) at negative potentials and 63 ± 2 pS (n = 3) at positive potentials.