Fig. 1

Depletion procedure. One fiber, bathed in a 0 Ca²⁺ medium, was electrically stimulated four times and challenged three times with the high K⁺ solution to verify its viability before treating it with CPA. In the presence of this agent, the fiber was exposed several times to 4-CmC until the responses to high K⁺ and to 4-CmC were practically abolished. In this and following figures, the dashed lines represent acquisition interruptions. A similar protocol, not entirely shown, preceded the traces of the experiments of Figs. 2, 3, 4, 5 and 8