Demonstration of Two Stable Potential States in the Squid Giant Axon Under Tetraethylammonium Chloride

Abstract

1. Intracellular injection of tetraethylammonium chloride (TEA) into a giant axon of the squid prolongs the duration of the action potential without changing the resting potential (Fig. 3). The prolongation is sometimes 100-fold or more. 2. The action potential of a giant axon treated with TEA has an initial peak followed by a plateau (Fig. 3). The membrane resistance during the plateau is practically normal (Fig. 4). Near the end of the action potential, there is an apparent increase in the membrane resistance (Fig. 5D and Fig. 6, right). 3. The phenomenon of abolition of action potentials was demonstrated in the squid giant axon treated with TEA (Fig. 7). Following an action potential abolished in its early phase, there is no refractoriness (Fig. 8). 4. By the method of voltage clamp, the voltage-current relation was investigated on normal squid axons as well as on axons treated with TEA (Figs. 9 and 10). 5. The presence of stable states of the membrane was demonstrated by clamping the membrane potential with two voltage steps (Fig. 11). Experimental evidence was presented showing that, in an "unstable" state, the membrane conductance is not uniquely determined by the membrane potential. 6. The effect of low sodium water was investigated in the axon treated with TEA (Fig. 12). 7. The similarity between the action potential of a squid axon under TEA and that of the vertebrate cardiac muscle was stressed. The experimental results were interpreted as supporting the view that there are two stable states in the membrane. Initiation and abolition of an action potential were explained as transitions between the two states.

Thresholds and Plateaus in the Hodgkin-Huxley Nerve Equations

“…This synthetic process, carried out with the aid of the analog computer, leads to a better understanding of the complete system than can be obtained by considering all the variables at once, and suggests how modifications in the separate equations will affect the behavior of the complete system. In particular, it becomes obvious how plateau-type action potentials can be produced, resembling those obtained experimentally from heart (Weidmann (1957)), frog node (Spyropoulos (1956)), frog muscle (Falk and McGrath (1958)), and squid axon (Tasaki and Hagiwara (1957)). …”

“…The plateau potentials of Tasaki and Hagiwara (1957) are, however, not at this level, but are in the neighborhood of -5 0 my. To get such lower plateau levels following the spike, it is necessary to reintroduce h (or n) as a third variable.…”

“…In this section a comparison will be made between the computations of a modified H-H system and the experimental results of Tasaki and Hagiwara (1957) obtained from squid axons injected with TEA (tetraethylammonium chloride). The computed curves for the plateau action potential, its abolition, and the refractoriness following a plateau, agree well with experiment, although the corresponding conductance changes do not.…”

“…A result which illustrates this distinction is the partial duplication of Tasaki and Hagiwara's (1957) results obtained from squid axons injected with tetraethylammonium chloride (TEA). The plateau, its abolition, and subsequent refractoriness are well reproduced by the equations, after suitable modification.…”

Solutions of the Hodgkin‐huxley Equations for Squid Axon Treated With Tetraethylammonium and in Potassium‐rich Media

“…There are some quantitative discrepancies between predicted and observed behaviour. Inspection of the published records of Tasaki and Hagiwara (1957) shows that the membrane potential at tiie crest of the spike is somewhat lower than the predicted value of -114 mV. The computed action potentials also show a small notch separating the spike and plateau which is not seen in the experimental records.…”