• Takafumi Sakuma, Hiroto Kamoda, Masayuki Miyagi, Tetsuhiro Ishikawa, Gen Arai, Yawara Eguchi, Miyako Suzuki, Yasuhiro Oikawa, Yoshihiro Sakuma, Go Kubota, Kazuhide Inage, Takeshi Saino, Sumihisa Orita, Kazuyo Yamauchi, Gen Inoue, Kazuhisa Takahashi, and Seiji Ohtori.
• Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Inohana, Chuo-ku, Chiba, Japan.
• Spine. 2013 Jul 1;38(15):E919-24.

Study DesignAssessment of pain-related behavior and immunohistology of the dorsal root ganglion in a rat model.ObjectiveTo investigate pain-related behavior in a rat model of nerve crush plus inflammation using the CatWalk system.Summary Of Background DataA definitive method for evaluating animal models of lumbar disease has not been established. Von Frey testing has often been used in this type of study, but the reliability remains in question. The CatWalk system is a computer-assisted apparatus for analyzing gait that provides an automated way to assess gait function during pain. However, there have been few reports using this system for models of lumbar disease.MethodsFourteen rats were divided into 2 groups: a treatment group and a sham group. For the treatment group, nucleus pulposus was applied to the sciatic nerve and the sciatic nerve was pinched. Two different methods for assessment of pain-related behavior, von Frey testing and CatWalk analysis, were used before surgery and at 4 and 7 days after surgery. Immunohistochemistry was used to examine calcitonin gene-related peptide expression in L4 to L6 dorsal root ganglia.ResultsNo significant differences were found between the treatment and sham control groups using von Frey testing. However, significant differences in 4 parameters were found between the 2 groups using the CatWalk system (P < 0.05). The proportion of calcitonin gene-related peptide-immunoreactive neurons was higher in the treatment group than in the control group (P < 0.05).ConclusionOur results demonstrate that the CatWalk system is useful for the measurement of pain-related behavioral change in our rat model in which nociception was indicated at a cellular level. Although further studies are needed, we think that this system is a valid alternative method for the evaluation of models of lumbar disease in rodents.

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