Gait Analysis of Mice Using CatWalk XT

The Noldus CatWalk XT gait analysis system (Noldus Information Technology, Leesburg, VA) was used to analyze the paw prints of mice.^{1 (link),22 ,31 (link),33 (link),38 (link)} In a dark room, mice walked across an elevated glass platform with a camera positioned underneath, facing the underside of the animal. Light illuminated the section of the paws that applied weight on the glass (Fig. 1A). Paw prints were imaged by the camera and measured using the Noldus CatWalk XT 10 software (Fig. 1B). The paw print area refers to the total area of the glass in contact with the paw, measured at the point in the step when the area of contact with the glass is maximal for that paw print. Analgesic studies in incision animals were performed in mice that had a relative paw print area in the ipsilateral paw that was no greater than 80% than of the contralateral paw; 10 of 46 mice were thus excluded based on this criterion.