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. 2008 Mar;131(3):227–243. doi: 10.1085/jgp.200709868

Figure 6.

Figure 6.

Spermine and spermidine are inefficient blockers of the HCN2 current. (A) Plateau tail currents obtained from the TEVC and IOPC experiments shown in Figs. 1 and Figs.5 were normalized with respect to the amplitudes of the currents observed at −200 mV and plotted with respect to the observed (TEVC) and the command potential (IOPC). Data are plotted as mean ± SEM. The errors around the voltage in TEVC were always smaller than the symbols. The inset shows an expanded view of the IV relations at depolarized potentials. (B) Representative recording obtained upon stepping to +200 mV in the absence and presence of 10 μM spermidine (SPD) and normalized open channel IV relationships in the absence (n = 6) and presence of 10 μM SPD (n = 3) or spermine (SPM, n = 5) determined using the protocol described in Fig. 5 and plotted as mean ± SEM versus the command potential. Test steps were applied at 4 Hz from an activation potential of −155 mV in the absence of added divalent ions and the presence of 1 mM EGTA, 1 mM EDTA, and 30 μM cAMP with K as the only alkali metal on either side of the membrane ([K]OUT 117 mM; [K]IN 121 mM).