  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.
