Figure 2. MTX activates a non-selective cationic current (I_mtx).

A, I–V curve of the basal K⁺ current present in human skin fibroblasts in the absence of MTX, the current reversal potential is −85.8 ± 4.1 mV (n = 12). B, I–V curve of the current activated by 500 pm MTX, the current reversal potential is −10.10 ± 6.4 mV (n = 10). C, comparison of the I–V curves under control conditions (•), total current after MTX application (control + MTX activated, □) and the net current activated by MTX (total – control, ▴). D, I–V curves for I_mtx obtained with physiological extracellular solution (□) and with NMDG-Cl in the external medium (n = 4, ▪). In the presence of external NMDG the current reversal potential shifts to values more negative than −100 mV. In all the cases means ± s.d. are shown. Where not shown error bars are smaller than symbols. V_h = 0 mV.