[Basic principles of the organization of ion channels determining the electric stimulation of the neuronal membrane].

The paper provides comparative characteristics for different types of electrically operated ionic channels in the neuronal membrane of invertebrate (molluscs) and vertebrate (rats) animals. It was shown that ion-selecting characteristics of sodium channels are identical for all the investigated membranes. In addition, main selective filter of calcium channels also possesses a similar characteristic; apart of it they have an external binding group which prevents the influx of monovalent cations into the channel and thus maintains its selectivity towards divalent cations. A natural intermediate modification of ionic channels is found, which has no such external binding group. There are two different mechanisms of maintenance of electrically operated ionic channels in a functioning state--a metabolically-independent and metabolically-dependent one. In the latter case in order to preserve the ability of the channel for activation, it is essential to maintain a certain level of cAMP inside the cell which determines, in turn, the presence of corresponding membrane proteins in a phosphorylated state. This mechanism of regulation of the function of electrically operated ionic channels is also identical in both invertebrate and vertebrate membranes. It is suggested that the molecular structures providing the electrical excitability represent the most ancient product of evolution used for the generation of basic forms of nervous activity in all types of nerve cells of existing animal species.