Figure 3. Full conductance and subconductance openings of single cGMP- and Ca²⁺-dependent Cl⁻ channels in outside-out patches.

A shows a trace of single channel currents recorded from an outside-out patch at −50 mV with 10 μm cGMP and 100 nm[Ca²⁺]_i in the pipette solution. The continuous line represents the closed channel level (c), while the dotted lines denote the channel subconductance and full conductance levels. B is an all points histogram taken from the current trace shown in A. The bin width was 0.04 pA and the data were fitted by the sum of four Gaussian curves, with means of 0, −0.82, −1.71 and −2.75 pA, respectively. C, mean single channel I–V relationships for subconductance and full conductance openings of single cGMP-activated Cl⁻ channels in the presence of 10 μm cGMP and 100 nm[Ca²⁺]_i. Data are mean ±s.e.m., n= 4–6.