神経膜の内表面と外表面の機能

概要

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Physiological properties of internal and external surfaces of the nerve membrane were compared applying three types of substances on both surfaces mainly using intracellularly perfused squid giant axons.<BR>First, effects of neurotoxins and enzymes were demonstrated. The neurotoxin such as tetrodoxin was only effective to external surface and blocked the nerve excitation. On the other hand, proteolytic enzymes were only effective to internal surface and prolonged the duration of action potential. This suggests that the specific reaction sites do not exist symmetrically on both sides.<BR>Secondly, effects of several kinds of ions on both surfaces were examined. Especially, external Ca stabilized the membrane, and was indispensable for maintaining excitability. On the other hand, internal Ca made the membrane unstable. By Ca perfusion within a minute, a sudden large spike was observed without any electrical stimulation. This suggests that internal and external surfaces are composed of different quality of molecules.<BR>Thirdly, effect of neutral molecules, such as glycerol, glucose, and sucrose, were examined. By adding these neutral molecules to internal and external electrolytes solutions, they regulated the ionic flux and also the time course of rising phase or falling phase of the spike according to the value of microscopic viscosity of each side.
日本膜学会の論文