[Comparative analysis of the morphologic and physiologic characteristics of nodes of Ranvier].

The intravital light microscopic study of the Ranvier node and paranodal structure was carried out in the isolated nerve fibres of Rana ridibunda. For the same fibres the electro-physiological characteristics obtained by the voltage-clamp method were compared with morphological ones. Definite correlations were found between the reduction of Na+ and K+ permeability constants and the degree of the paranodal myeline damage. The leakage conductance variations of the fibres under study did not exceed the normal range. High vulnerability of sodium and potassium systems seems to reflect a more complicated molecular organization of the electrically excitable Na+ and K+ channels as compared to nonexcitable leakage pathways. Essential changes of the Na+ channels properties caused by batrachotoxin were not accompanied by a visible alteration of the paranodal structure. The data obtained are discussed from the view point of modern ideas of the nature of axoglial relationships in myelinated nerve fibres.