Optimization of the leak conductance in the squid giant axon

TL;DR

This study shows that the leak conductance in the squid giant axon is nearly optimal for maximizing firing frequency, especially when modeled with chloride ions, aligning with experimental measurements.

Contribution

The paper demonstrates that the leak conductance density in the squid giant axon is close to an optimal value for firing frequency, based on a theoretical Hodgkin-Huxley model with chloride ions.

Findings

Leak conductance density is near optimal for firing frequency.

Optimality depends on the assumption of chloride ions in leak current.

Temperature variations influence the optimal leak conductance.

Abstract

We report on a theoretical study showing that the leak conductance density, $\GL$, in the squid giant axon appears to be optimal for the action potential firing frequency. More precisely, the standard assumption that the leak current is composed of chloride ions leads to the result that the experimental value for $\GL$ is very close to the optimal value in the Hodgkin-Huxley model which minimizes the absolute refractory period of the action potential, thereby maximizing the maximum firing frequency under stimulation by sharp, brief input current spikes to one end of the axon. The measured value of $\GL$ also appears to be close to optimal for the frequency of repetitive firing caused by a constant current input to one end of the axon, especially when temperature variations are taken into account. If, by contrast, the leak current is assumed to be composed of separate voltage-independent sodium and potassium currents, then these optimizations are not observed.