Figure 1.

ACh activation of Ca²⁺-dependent Cl⁻ current in a single pancreatic acinar cell. Small monovalent cations (Na⁺ and K⁺) were replaced by NMDG⁺ in both the bath and pipette solutions, as shown in the cartoon representing the recording configuration. (A) Repetitive depolarizing voltage pulses to 0 from the holding potential of −30 mV were applied, so that two quasisimultaneous current recordings, at −30 mV (black trace) and 0 mV (red trace) were obtained. The equilibrium potential for both NMDG⁺ and Cl⁻ was 0 and whereas a clear inward current is elicited by ACh (10 μM) at −30 mV, there is virtually no current response to be seen at 0 mV. During ACh stimulation, in the period indicated, extracellular NMDG⁺ was replaced by Na⁺, but this had no effect on the inward current, indicating that all of the inward current is carried by Cl⁻ outflow. (B) During ACh (10 μM) stimulation, step voltage pulses from the holding potential of 0 up to −80 or 80 mV were applied, at the peak (a) and later in the response (b). The I–V relationships are plotted in C. The black squares are from Ba, whereas the green triangles and red circles are from the beginning and end, respectively, of the pulses shown in Bb. Note the different time-dependent patterns of the currents and the different shapes of the I–V relations (C) at the peak (Ba) and later (Bb) in the ACh response.