ナトリウムチャンネルの種類とキネティクス

概要

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Pharmacological and molecular biological approaches for elucidating the functional proteins of Na channels have made clear that Na channel is not a single but several different identities. The electro-physiological observations; e. g 1) well-fitting by the exponential function having more than two time constants to the falling phase of sodium current in the macroscopic recording and 2) frequent opening episodes (burst) in the single channel recording, also support the notion of the presence of several types of Na channel. Recently, it has been observed that three different modes of openings of Na channel, (1) opening of channel in short duration at the very beginning of pulse, (2) frequent opening episodes in relatively long duration, and (3) null opening episode, occur in cluster in the single channel recording. This intriguing observation provides the modal gating theory that the activity of Na channel is in three different modes. The observations contradictory to the notion that Na channels function as a single unit in spite of the difference in molecular structure, as mentioned in earlier part, may well be accounted for by the modal gating theory. In other words, electrophysiological techniques will not be able to detect the difference in the molecular structure among Na channels.
日本膜学会の論文