Nerve excitability: transition from descriptive phenomenology to chemical analysis of mechanisms.

The electrical activity by which impulses are conducted along nerve and muscle fibers, is carried by Na-and K-ions moving across the excitable membranes due to increased ion permeability. -- A biochemical approach, initiated to elucidate the mechanism of the permeability changes, centered around the analysis of the properties and functions of the proteins, including enzymes, directly associated with the role of AcCh, in the excitable membrane. The results necessitated a fundamentally reformed concept of the role of AcCh. The four proteins specifically associated with the function of AcCh form a cycle which controls the rapid ion permeability changes of the membrane and permits the ion fluxes through dynamic gateways. A model has been elaborated that integrates biochemical, biophysical, and thermodynamic data; it permits the interpretation of many electrophysiological data in molecular terms. AcCh has basically the same function in conducting and synaptic parts of excitable membranes. The new concept has replaced the purely descriptive phenomenology of nerve impulse propagation by the analysis of the chemical mechanisms of nerve excitability and bioelectricity.