REPETITIVE ACTION POTENTIALS IN NITELLA INTERNODES

Typical spontaneous action potentials can be elicited in 10–100mM NaCl or LiCl solution. The period of repetition is 0.5–2seconds and the action potential generally consists of a rapidspike alone. Similar spontaneous action potentials are alsodemonstrated by adding either 1 mM EDTA (pH 6.6) or 2 mM ATP(pH 6.6) to the artificial pond water. In these cases, however,the period of repetition is much longer and the action potentialis of a normal shape, a rapid spike being followed by a slowtransient depolarization. The period of repetition and the sizeof the action potential decrease with the elevation of the vacuolarpotential level. The cause of the spontaneous firing is supposedto be the removal of Ca⁺⁺ from the outer surface of the Nitellamembrane. (Received May 18, 1966; )