Figure 7.

Zn²⁺ modulation of I_AcCho in ^L247Tα₇ mutant cDNA-injected oocytes. (A) Examples of inward current activated in the same oocyte by AcCho alone or by AcCho plus Zn²⁺. Note the large inward current after Zn²⁺ withdrawal. Holding potential, −100 mV. (B) Voltage-dependent inhibition of I_AcCho by Zn²⁺. Inhibition of I_AcCho (AcCho, 0.2 μM) by Zn²⁺, measured as the percentage of I_AcCho alone to that in the presence of Zn²⁺ (10 mM). Data represent mean from 6 oocytes and 2 donors. (C) I_AcCho– voltage relationship in an oocyte held at −50 mV. Peak currents evoked at various test potentials by 0.2 μM AcCho (•) or by 0.2 μM AcCho plus 1 mM Zn²⁺ (○). AcCho was applied at 3-min intervals. The solid lines are three-order polynomial fits to the data. Note that I_AcCho was reduced considerably at hyperpolarized potentials. (D) Potentiation of I_AcCho by Zn²⁺ at lower doses.