Ephaptic Transmission and Conduction Velocity of an Action Potential in Chara Internodal Cells Placed in Parallel and in Contact with One Another

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When two separated Chara internodal cells were kept in contact over a length of 14 mm or more in moist air, an action potential of one cell could be transmitted to the other cell in about 40% of cases (ephaptic transmission). The action potential of the former cell was sometimes eliminated transiently when a new action potential was elicited in the latter cell. The new action potential reactivated the former cell. The conduction velocity of the action potential was reduced from 0.30±0.11 cm/s (mean±SD) to 0.15 ±0.05 cm/s by ephaptic transmission of the action potential. Substitution of an artificial pond water for moist air or contact over a shorter length (4 mm instead of 14 mm or more) between the two cells reduced the coupling ratio, the ratio of the change in membrane potential of one cell to that of the other cell, and no transmission was observed. After ephaptic transmission, the action potentials of the two cells were conducted at almost the same velocity along the cells. The velocity was increased to 0.68 ±0.06 cm/s by simultaneous conduction of the action potentials in the two adjacent cells. When the simultaneously conducted action potentials reached the node of one cell, at the point at which another cell made contact, they were able very frequently to trigger a new action potential in the adjoining cell.
日本植物生理学会の論文