Chronic pain is one of the most debilitating conditions, affecting one out of five people worldwide. Preclinical models in rodents represent a valuable tool for the study of pathophysiological mechanisms and the discovery of new analgesic drugs. However, pain evaluation in rodents is rather challenging. Altered response to mechanical or thermal stimuli is commonly used as behavioral outcome to measure pain sensitivity. This protocol introduces a method for assessing static mechanical pain hypersensitivity in rats using an electronic von Frey (VF) test. The electronic VF is an evolution of the manual VF hairs previously described by Kim and Chung (1991). In this previous procedure, 6 calibrated nylon filaments (diameters of 0.13, 0.23, 0.31, 0.48, 0.52, and 0.59 mm, respectively) are perpendicularly applied to the plantar surface of the rat hind paw, to deliver the following defined pressures: 5.89, 9.81, 27.0, 74.4, 124, and 205 mN. Each application has to be repeated several times for each filament to determine the mechanical threshold. Comparatively, the electronic VF is relatively easy-to-use and particularly suited for pharmacological studies with precise time-points. The electronic VF can be used as a behavioural read-out for a wide range of models, including inflammatory and neuropathic pain. The following protocol was originally published in Ferrier et al. (2013), Grégoire et al. (2014) and in Ferrier et al. (2015).
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