4.3. Orofacial Pain Sensitivity Tested with von Frey filaments

A set of calibrated nylon monofilaments (Stoelting, Wood Dale, Illinois, USA) was used to perform measurements before and after CFA/saline injection on all animals. Increasing strengths (rats: 0.8–12 g, mice: 0.0075–1 g) were used to measure facial mechanosensitivity. The mechanonociceptive threshold was defined as the lowest force evoking at least 2 withdrawal responses (face stroking with the forepaw or head shaking) out of 5 stimulations according to our previous paper [49]. The experimenter was not blinded for these measurements as the visible inflammatory oedema of the whisker pad cannot be hidden during the in vivo experiments.