The effect of novocaine on the electrical activity of nodes of Ranvier in high and low pH solutions.

The minimal concentrations of procaine which block the action potentials of a single Ranvier node were determined under decreased and increased pH in the bathing solution. The changes in concentrations of the basic [B] and cationic [BH+] form of procaine with pH were of monotonic character: [B] drops and [BH+] grows with pH increase. The dependence of membrane excitability (fraction of channels are able to excite) on pH was nonmonotonic; it is low under increased and decreased pH. On the basis of these data the hypothesis that the membrane of the Ranvier node may interact with a definite form of procaine is rejected. T he quantitative analysis shows that the membrane interacts with both the basic and cationic forms of procaine but the efficiency of this interaction is different.