Dual influence of temperature on compound nerve action potential

Compound neural action potentials (NAPs) were recorded from N. suralis and the digital nerves of N. medianus in man using the antidromic technique. The nerves were cooled either at the site of the recording ("local cooling") avoiding temperature change proximally, or between the stimulating and recording electrodes ("segmental cooling") avoiding temperature change at the recording site. Local cooling was followed by a pronounced increase in NAP amplitude and rise time without any change in the onset latency. The values of Q10 were identical for both amplitude and rise time changes. Segmental cooling caused a definite fall in the amplitude of NAP and a slight increase in its rise time. The practical consequences of the dual temperature effect on NAP are discussed.