It is well established that the process of nerve excitation takes place in the 70-100 Å thick membrane. However, studies on birefringence of nerve fibers and on proteins undercoating the membrane indicate that the excitation process affects the conformational state of the submembranous fibrous layer. During membrane excitation, the fibrous layer under the membrane loses the orderliness and increases its solubility.
There are many investigations which examined the effects of antimitotic drugs on the excitability. Some of them suggest importance of microtubules in maintenance of membrane excitability. Others disagree with it. In intracellularly perfused squid giant axons, a KCl- or KBr-containing solution removes almost all fibrous proteins which are closely associated with the membrane. Without these fibrous proteins, axons maintain their excitability unless the intracellular pressure is kept high. Colchicine applied intracellularly exerts its effects only when the intracellular pressure is high. Based on these experimental results, it is emphasized that the fibrous proteinacious structure near the membrane provides the membrane with mechanical rigidity and strength.
