Collision of two action potentials in a single excitable cell

TL;DR

This study experimentally demonstrates that two colliding action potentials in a single excitable plant cell annihilate each other, supporting the idea that APs are nonlinear phenomena with similar collision properties across biological systems.

Contribution

It provides direct experimental evidence that action potentials in plant cells do not penetrate each other but annihilate upon collision, aligning with nonlinear wave theory.

Findings

APs in plant cells annihilate upon head-on collision

Action potentials behave as nonlinear waves

Collision behavior is consistent across biological excitable systems

Abstract

It is a common incident in nature, that two waves or pulses run into each other head-on. The outcome of such an event is of special interest, because it allows conclusions about the underlying physical nature of the pulses. The present experimental study dealt with the head-on meeting of two action potentials (AP) in a single excitable plant cell (Chara braunii internode). The membrane potential was monitored at the two extremal regions of an excitable cell. In control experiments, an AP was excited electrically at either end of the cell cylinder. Subsequently, stimuli were applied simultaneously at both ends of the cell in order to generate two APs that met each other head-on. When two action potentials propagated into each other, the pulses did not penetrate but annihilated (N=26 experiments in n=10 cells). APs in excitable plant cells did not penetrate upon meeting head-on. In the classical electrical model, this behavior is specifically attributed to relaxation of ion channel proteins. From an acoustic point of view, annihilation can be viewed as a result of nonlinear material properties the entire system. The present results suggest that APs in excitable animal and plant cells belong to a similar class of nonlinear phenomena. Intriguingly, other excitation waves in biology (intracellular waves, cortical spreading depression, etc.) also annihilate upon collision and are thus expected to follow the same underlying principles as the observed action potentials.