Practical mechanical threshold estimation in rodents using von Frey hairs/Semmes-Weinstein monofilaments: Towards a rational method

Abstract

Here, we reconsider the status quo in testing mechanical sensitivity with von Frey's hairs. The aim is to improve paw withdrawal estimates by integrating current psychometric theory, and to maximise the clinical relevance and statistical power of mechanosensory models. A wealth of research into human tactile stimulus perception may be extended to the quantification of laboratory animal behaviour. We start by reviewing each step of the test, from its design and application through to data analysis. Filament range is assessed as a whole; possible test designs are compared; techniques of filament application to mice and rats are considered; curve fitting software is introduced; possibilities for data pooling and curve fitting are evaluated. A rational update of classical methods in line with recent advances in psychometrics and supported by open source software is expected to improve data homogeneity, and Reduce and Refine animal use in accord with the '3R' principles.

Keywords: Allodynia; Esthesiometer; Rodent behaviour; Semmes–Weinstein monofilaments; Threshold estimation; Von Frey hairs.