Effect of Partial Sciatic Nerve Injury on the Response to Formalin Test in Rats

Abstract

Background: Different types of injury to the sciatic nerve branches produces different levels of each kind of nociception. In this study, we undertook to identify the nature of the partial sciatic nerve injury that affects nociceptive reaction to subcutaneous formalin injection, and to determine the branch of the sciatic nerve involved. Methods: Sprague-Dawley rats were randomly divided into 4 groups, control group (n = 9) in which a sham operation was performed, a sural nerve transection group (n = 5), a tibial nerve transection group (n = 5), and a common peroneal nerve transection group (n = 5). Under enflurane anesthesia, sural, tibial, or common peroneal nerves were injured and responses to formalin test were compared for the four groups 24 hours after surgery. Results: Pain behavior in the tibial and common peroneal nerve transected groups reduced in phase 2, but not in phase 1, while sural nerve transected group showed no change in response in either phase. Conclusions: Tibial and common peroneal nerves mainly affect phase 2 reaction in the formalin test in this partial sciatic nerve injury model.