Surface charges on the outer side of mollusc neuron membrane

The shifts of current-voltage characteristics of sodium and calcium inward currents produced by changes in the concentration of divalent cations and in pH of the extracellular solution have been measured on isolated neurons of the mollusc Helix pomatia intracellularly perfused with potassium-free solutions. On the basis of these shifts and using Stern's theory the binding constants for the ions to charged groups have been calculated.