Multiple measures of axonal excitability in peripheral sensory nerves: an in vivo rat model.

Excitability measurements on human motor and sensory nerves have provided new insights into axonal membrane changes in peripheral nerve disorders. The aim of this study was to establish an in vivo rat preparation suitable for threshold tracking of sensory nerve action potentials (SNAPs) to model clinical sensory nerve excitability studies. In Sprague-Dawley rats anesthetized with ketamine and xylazine, current stimuli were applied to the base of the tail and SNAPs recorded from distal needle electrodes. Multiple excitability data were obtained as previously described for human nerves and compared to recordings from the motor tail axons and to sensory recordings from human median and ulnar nerves. The pattern of excitability changes in rats was broadly similar to that in humans, although some parameters differed significantly. Individual recordings were stable for at least 3 h. These data show that the rat tail enables excitability properties of sensory as well as motor axons to be studied experimentally, e.g., in models of nerve disease and during pharmacological interventions.