A. A schematic of the ASDN showing the components mediating intrinsic control. B. A single channel, cell-attached patch clamp experiment on a principal cell in the isolated, split-open ASDN showing the effects of ATP on ENaC in the apical membrane. In this experiment, inward current is downwards and the closed state is noted with C. Areas below the gray bars, 1 and 2, are shown below on a faster time scale. Data originally presented in [10]. C. Summary of these effects of ATP on ENaC open probability in isolated, split open ASDN. Experiments were similar to that shown in 1B. Data originally presented in [8]. *significant decrease vs. before treatment. D. Dose response curves showing the effects of ATP and UTP on ENaC activity in isolated, split-open ASDN. Experiments similar to that shown in 1B. Data originally presented in [10].