Role of brain-derived neurotrophic factor in inflammatory pain in rats

Abstract

Objective To evaluate the role of brain-derived neurotrophic factor (BDNF) in inflammatory pain in rats. Methods Sixty female SD rats weighing 150-180 g in which intrathecal (IT) catheters were successfully placed without complication were randomly divided into 5 groups (n= 12 each): group Ⅰ sham operation; group Ⅱ sham operation + IT anti-BDNF antibody; group Ⅲ inflammatory pain; group Ⅳinflammatory pain + IT control IgG and group Ⅴ inflammatory pain + IT anti-BDNF antibody. Inflammatory pain was induced by injecting complete Freund's adjuvant (CFA) into ankle joint cavity of left hindpaw, while in sham operation group equal volume of normal saline was injected instead of CFA. Anti-BDNF antibody or control IgG 15 μg/10 μl was injected IT once a day for 3 days after inflammatory pain was induced. Paw withdrawal latency to thermal stimuli (PWTL) was measured one day before and at 3, 5, 7, 10 and 14 d after inflammatory pain was induced. The rat was sacrificed on 3 rd day of IT anti-BDNF antibody or control IgG injection. The lumbar segment L4-6 of the spinal cord was removed for detection of the expression of BDNF and p-ERK1/2 by immunohistochemistory and Western blot. Results Intra-articular CFA injection significantly increased the expression of BDNF and p-ERK1/2 in the spinal cord in group Ⅲ as compared with sham-operated animals in group Ⅰ . IT antiBDNF antibody injection significantly suppressed the expression of BDNF and p-ERK1/2. PWTL was significantly shortened after intra-articular CFA injection in group Ⅲ as compared with group Ⅰ . IT anti-BDNF antibody reversed the inflammation-induced thermal hyperalgesia in group Ⅴ but IT control IgG did not. Conclusion BDNF in the spinal cord may be involved in inflammatory pain through p-ERK1/2 signal transduction pathway. Key words: Brain-derived neurotrophic factor; Pain; Inflammation