Effects of Cu(2+), Pb (2+) and Zn (2+) on voltage-activated currents in Helix pomatia L. Neurons

Effects of Cu(2+), Pb(2+) and Zn(2+) were studied on voltage-activated Na-, Ca-, and K-currents in snail neurons. It was found that: 1. In normal physiological saline Cu(2+), Pb(2+) and Zn(2+) ions exerted complex changes on the total ionic currents; 2. All three metal ion have depressed the inward Na-currents but with different K D , moreover Pb (2+) increased Na-current at low concentrations (5 μM); 3. The inward Ca-current was also reduced. The sequence of the blocking effect of metals was different: Pb>Cu>Zn, however the steady-state inactivation was influenced only by Cu(2+); 4. Outward currents were decreased in all neurons by Cu(2+), but the effects of Pb(2+) and Zn(2+) were either depression or enhancement in different indentified neurons; 5. The possibility of binding heavy metals to wide variety of membrane proteins and the observed effects on different ionic channels suggest that the metal effect is complex and cannot be taken as a specific one to a single channel type or site of location.