Xenopus laevis oocyte: using living cells to teach the theory of cell membrane potential

We describe a student course in membrane physiology that includes demonstration of the cell membrane potential of a living cell, the Xenopus laevis oocyte. By use of K+ macroelectrodes and a computer simulation program, students are introduced to the membrane concept on the basis of ion gradients, diffusion potentials, and membrane conductances. Subsequently, some basic principles are demonstrated in living cells by measuring the cell membrane potential of a X. laevis oocyte. The dependence of the cell membrane potential on ion gradients is shown by stepwise elevation of the extracellular K+ concentration. The clinical relevance of disturbances of the K+ homeostasis is discussed in this context. The effect of changing the membrane conductance for particular ions on the cell membrane potential is demonstrated by applying a K+ channel blocker. The experiments are discussed in the context of the action of pharmaceuticals and toxins. This student course on membrane physiology has now been held for 2 yr for medical and dental students, and their response to the oocyte demonstration, as evaluated by a student questionnaire, was mainly positive.