Lead inhibits the voltage-activated calcium current of Aplysia neurons.

Lead is a potent and reversible inhibitor of the voltage-dependent calcium current of Aplysia neurons in a concentration range (1-1000 microM) similar to that which elicits toxic effects in man. The threshold for inhibition is 1 microM and the dissociation constant about 90 microM. The inhibition is due to reduction of the peak current amplitude, and not due to alteration of the voltage dependence of the activation or inactivation. The effect of lead is specific to the calcium current as the delayed rectifier potassium and the sodium currents are not affected by concentrations of lead (200 microM) which give near-maximal inhibition. The calcium current of Aplysia neurons appears similar to the current flowing through the mammalian L-type calcium channel. This suggests that inhibition of the investigated calcium channel may contribute to the toxic effects of lead in mammals.