Modeling the effects of elevated temperatures on action potential propagation in unmyelinated axons

Infrared lasers (λ=1.87 μm) are capable of inducing a thermally mediated nerve block in Aplysia and rat nerves. While this block is spatially precise and reversible in sensory and motor neurons, the mechanism of block is not clearly understood. Model predictions show that, at elevated temperatures, the rates of opening and closing of the voltage gated ion channels are disrupted and normal functioning of the gates is hindered. A model combining NEURON with Python is presented here that can simulate the behavior of unmyelinated nerve axons in the presence of spatially and temporally varying temperature distributions. Axon behavior and underlying mechanism leading to conduction block is investigated. The ability to understand the photothermal interaction of laser light and temperature dependence of membrane ion channels in-silico will help speed explorations of parameter space and guide future experiments testing the feasibility of selectively blocking pain conduction fibers (Photonic Analgesia of Nerves (PAIN)) in humans.