It was in 1939, just before the outbreak of World War II, when Alan Hodkin and Andrew
Huxley first recorded an action potential from a squid giant axon. Yet, understanding
why there are varied sizes, shapes, and numbers of action potentials elicited by dif-
ferent neurons and how these neurons transition from one mode of firing to another
remains an important research pursuit of current-day neuroscience. With the advent
of molecular cloning, we now know there are hundreds of ion channel genes particu-
larly expressed in the brains of higher animal systems. The immense diversity of firing
properties of neurons within the central and peripheral nervous systems can be in large
part attributable to the vast number of ion channel genes. We now appreciate that stable
neuronal network responses to diverse environmental stimuli are also likely due to the
availability of multiple ion channel genes. With the ever-increasing number of pharma-
cological tools, including naturally occurring toxins and transgenic animal models, we
are starting to understand the contributions different ion channels make to neuronal
firing and network responses.