Allostery and Permeability of Postsynaptic Membranes

Abstract

As it is well known, the synaptic membrane of many conducting cells can be triggered by acetylcholine as well as by the electrical stimulation of the presynaptic structures. It is generally assumed that the acetylcholinesterase is an enzyme playing a very important and specific role at the synapse by controlling the amount of acetylcholine that can be bound to the postsynaptic membrane. It is also accepted that a structure called the acetylcholine-receptor is part of the structural architecture of the postsynaptic membrane. When acetylcholine is bound to the receptor it induces a change in the configuration of the receptor leading to the permeability change that is responsible for the action potential and action current. For many years acetylcholinesterase has been used as a model for the receptor molecule and much work has been devoted to study the effect of compounds known to affect the electrical activity, on the catalytic properties of acetylcholinesterase (1). To relate the effect of various compounds on the catalytic properties of acetylcholinesterase to their effect on the intact membrane, the use of the electric organ of certain fishes has been of great value. More specifically, the isolated electroplax of the electric eel has proven to be an excellent tool for the study of the biochemical aspects of the generation of bio-electric potentials C2). This preparation is rather unique in the sense that it is possible to measure on a single cell not only the ion fluxes associated with the electrical activity but also and independently the electrical activity of the postsynaptic membranes and of the conducting membrane. Thus by inserting microelectrodes inside the isolated cell, it is possible to study the effect of various compounds, Known to affect the acetylcholine-cholinesterase system, on the generation of bioelectric potentials.

This work has been aided by a grant no 790 from the “Fonds de la Recherche Scientifique Fondamentale Collective” and a “Crédit aux Chercheurs” from the “Fonds National de la Recherche Scientifique”.