Membrane properties in small cutaneous nerve fibers in humans

INTRODUCTION: Assessment of membrane properties is important for understanding the mechanisms of painful peripheral neuropathy, developing new diagnostic techniques, and for screening/profiling of analgesics that target ion channels.

METHODS: Small cutaneous nerves were activated electrically by small diameter (0.2mm) cathodes, and large nerves were activated by ordinary patch electrodes. This new perception threshold tracking (PTT) method combines perception threshold assessment and stimulation paradigms from conventional threshold tracking.

RESULTS: The strength-duration time-constant of large fibers (580µs±160µs) was lower than the time constant of small fibers (1060µs±690µs; P<0.01, paired t-test). Threshold electrotonus showed similar threshold reductions to sub-threshold pre-pulses, except for 80ms hyperpolarizing pre-pulses, to which small fibers showed less threshold reduction than large fibers (rmANOVA, Bonferroni, P=0.006).

CONCLUSION: This study is a reliable method to investigate the membrane properties of small cutaneous nerve fibers in humans and may be used in clinical settings as a diagnostic or profiling tool. This article is protected by copyright. All rights reserved.