The Basics of Electrical Coupling

  • Luca Turin
Part of the NATO ASI Series book series (NSSA, volume 99)


Cells are said to be electrically coupled when ionic current injected into one cell passes to the cell’s neighbour. Fig. 1 a illustrates the electrical circuit in the simplest case, when only two cells are present. In a), the cells are simply apposed, and the membranes are assumed to be homogeneous, that is to say no junctions are present. Two microelectrodes are inserted in cell 1, the first injects current into the cell, the second measures the voltage across the cell membrane, by comparison with a reference electrode in the bath. Current pulses give rise to voltage deflections proportional to the membrane resistance (Ohm’s law). These deflections are not instantaneous, because the membrane acts as a capacitor, which is charged and discharged at each current pulse. Cell 2 is impaled with a second voltage-recording microelectrode. What does this electrode see ? In the absence of true electrical coupling, the membranes are still close enough to one another to be capacitively coupled, but no steady current can flow from one cell to another. If one looks more closely at the space separating the two membranes, it becomes clear that ions, having crossed the first membrane under the influence of the current pulse, have so to speak a choice between entering the second cell or going to earth. Even if the cells are pushed against one another, the resistance to earth is much lower than that of the other cell’s membrane, and all the current goes that way.


Tight Junction Current Pulse Electrical Coupling Voltage Deflection Appose Membrane 
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Copyright information

© Plenum Press, New York 1985

Authors and Affiliations

  • Luca Turin
    • 1
  1. 1.Station Zoologique La DarseUA 671 du CNRSVillefranche-sur-merFrance

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