Electrotonic Coupling between Adjacent Internodal Cells of Chara braunii : Transmission of Action Potentials beyond the Node

概要

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Many nodal cells are interposed between two internodal cells of Chara braunii. When an action potential conducted in an internode reached the node, no electrical activation in the nodal cells could be found, although an area of the membrane bordering the nodal cells in this internode was partially activated (end-membrane action potential). When the action potential approached the node along the stimulated internode, an electrotonic potential change (depolarization) was produced in the other internode. This depolarization was greatly depressed by the end-membrane action potential of the stimulated internode, so that hardly any transmission took place. The ratio of the potential change in the surface membrane of the adjoining ("postsynaptic") internode (cell b) to that of the stimulated one (cell a), the coupling ratio, Δe_b/Δe_a, can be estimated from a simple equivalent circuit of the nodal region composed of two surface-membrane resistances (R_a, R_b) and intercellular resistance (R_n). IfR_n remains the same, a higher ratio should be produced with a larger R_b, but the ratio does not depend on any change in R_a, which could be proved experimentally. Transmission of the action potential beyond the node was frequent when the coupling ratio was increased and when the threshold that elicits the action potential was lowered by immersing the node in a K or Na salt solution.
日本植物生理学会の論文