Effect of temperature on sensory and motor conduction of the rat tail nerves

Summary Aims of the study To assess the effect of temperature upon conduction velocity, amplitude and signal energy of the sensory and motor rat tail nerves. Materials and methods Sensory and motor responses were recorded from the tail nerves in 10 adult rats at different temperatures, starting from 40 °C and cooling down to 16 °C in steps of 2 °C. Results The conduction velocity of the various components of the orthodromic sensory response was directly and linearly related to temperature (fastest fibres ranged from 47.7 down to 19.7 m/s), with Q10 values of approximately 1.30, suggesting that all fibres, regardless of their diameter, were equally sensitive to changes in temperature. The motor conduction was similarly affected with a Q10 value of 1.28 and a velocity range from 24.2 down to 9.6 m/s. Amplitude and energy of the sensory responses were inversely related to temperature, reaching their maximum at 16 °C. Energy was by far the most temperature sensitive parameter, with a Q10 of approximately 3 both for fast or slow conducting fibres. Amplitude and energy of the motor responses also showed an inverse correlation with temperature, but were influenced by a more complex set of factors (neuromuscular synapse, muscle membrane) than the simple neural conduction. Conclusions Besides providing new normative data upon conduction in the rat tail nerves at different temperatures, our results suggest that this method may represent an excellent tool to study models of peripheral-nerve conduction in vivo under various physiological and pathological conditions.