Brain derived neurotrophic factor (BDNF) contributes to the pain hypersensitivity following surgical incision in the rats

Background: The pathogenic role of brain derived neurotrophic factor (BDNF) in the incisional pain is poorly understood. The present study explores the role of the BDNF in the incision-induced pain hypersensitivity. Methods: A longitudinal incision was made in one plantar hind paw of isoflurane-anesthetized rats. Dorsal root ganglias (DRG) and spinal cords were removed at various postoperative times (1-72 h). Expression pattern of BDNF was determined by immunohistochemistry and double-labeling immunofluorescence. Lidocaine-induced blockade of sciatic nerve function was used to determine the importance of afferent nerve activity on BDNF expression in the DRG and spinal cord after incision. BDNF antibody was administered intrathecally (IT) or intraperitoneal (IP) to modulate the spinal BDNF or peripheral BDNF after incision. Results: After hind-paw incision, the BDNF was upregulated in the ipsilateral lumbar DRG and spinal cord whereas thoracic BDNF remained unchanged in response to incision. The upregulated BDNF was mainly expressed in the large-sized neurons in DRG and the neurons and the primary nerve terminals in the spinal cord. Sciatic nerve blockade prevented the increase of BDNF in the DRG and spinal cord. IT injection of BDNF antibody greatly inhibited the mechanical allodynia induced by incision whereas IP administration had only marginal effect. Conclusion: The present study showed that incision induced the segmental upregulation of BDNF in the DRG and spinal cord through somatic afferent nerve transmission, and the upregulated BDNF contributed to the pain hypersensitivity induced by surgical incision.