Fig. 2.

Block by Fe²⁺ of currents carried by Ca²⁺ with the I-V protocol. A, sample records, shown in 20-mV increments (3-kHz Gaussian filter). B, I-V relationships with the protocol used in A, with the same cells as in Fig. 1. C, I-V relationships on an expanded scale. D, chord conductances calculated from the data in B. E, inhibition by Fe²⁺, determined as chord conductance ratios and fitted to the model described by Woodhull (1973). Data near the reversal potential are not shown. Symbols shown in B apply to B to E.