ACTION POTENTIAL OF NITELLA INTERNODES

The ionic current during a non-propagating action potentialis analysed from the voltage clamp experiments. The shape ofthe action potential of the Nitella internode can be reconstructedfrom the data of the voltage clamp experiments. The N-shapedcurrent-voltage characteristics (I-V curve) of the Nitella membraneis not constant with time as it is in the tunnel diode, butdecays with time, converging finally into a delayed rectificationcurve. The temporal locus of the potential at which each I-Vcurve crosses the voltage axis coincides almost exactly withthe action potential. The membrane resistance which is calculatedfrom the slope of the I-V curve at each intersection with thevoltage axis also changes in parallel to the action potential.Such correlations are found in the Nitella not only in the pondwater, but also in high Na, high Ca or high Mg medium, wherethe shape of the action potential is modified in various ways.It is highly probable that the action potential is a locus ofthe change of the membrane potential so that the net membranecurrent may be maintained at zero after the transient modificationof the membrane structure by stimulation. (Received June 30, 1966; )