Studies on ionic transport mediated by carriers and channels are proposed to further understanding of the molecular factors underlying ion permeation, voltage gating, and anomalous rectification in membranes of excitable cells. More specifically, the experimental analysis of the electrical properties of lipid bilayer membranes induced by the cyclic depsipeptide, beauvericin, will be extended to those mediated by its structurally related analogs, enniatins A and B, and a suitable model will be elaborated to interpret the data. Theoretical studies on permeation mediated by carriers will also be extended to encompass the effects of diffusion and homogeneous reaction on the membrane conductivity, and zero-current potential. In addition, ion permeation in channels will be investigated both theoretically and experimentally. Conventional description of the fluxes will be generalized to allow for ionic interaction and multiple occupancy, and the expectations of the theory will be tested by studying the properties of the single pore of alamethicin. The same theoretical framework will be used to interpret the blocking effects of Cs ion on the "inward" rectifying channels of starfish egg cell membranes, for which a model has been recently proposed.