Effects of different afferent nerve injury on development of neuropathic pain and its relationship with brain-derived neurotrophic factor in spinal cord and dorsal root ganglion in rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of different afferent nerve injury on development of neuropathic pain and its relationship with brain-derived neurotrophic factor (BDNF) in spinal cord and dorsal root ganglion (DRG) in rats. Methods Twenty-four male SD rats aged 2 months weighing 200-250 g were randomly divided into 3 groups:group Ⅰ sham operation (group S); group Ⅱ sural nerve injury (group SUR) and group Ⅲ gastrocnemius-soleus nerve injury (group GS). Sural nerve and gastrocnemius-soleus nerve were transected in group SUR and GS respectively. Paw withdrawal threshold to von Frey filament stimulation was measured the day before and at day 3 and 7 after operation. The animals were killed at postoperative day 7 after the measurement of paw withdrawal threshold. The ipsllateral L5 DRG and L5 segment of the spinal cord were removed. BDNF expression in the spinal dorsal horn was determined. The percentage of BDNF positive neurons and ATF-3 positive neurons in the total DRG neurons and the percentage of BDNF positive neurons in the damaged neurons (ATF-3 positive) were calculated. Results Mechanical hyperalgesia developed after transection of gastrocnemius-soleus muscle in group GS. Mechanical pain threshold was sinificantly lower, while BDNF expression in the spinal dorsal horn and the percentage of BDNF positive neurons in total DRG neurons were significantly higher in group GS than in group S and SUR (P ＜ 0.01). There was no significant difference in all variables between group SUR and S (P＞0.05). There was no significant difference in the percentage of ATF-3 positive neurons in the total DRG neurons between group GS and SUR (P ＞ 0.05), but the percentage of BDNF positive neurons in the damaged neurons (ATF-3 positive) was significantly higher in group GS than in group SUR (P ＜ 0.05). Conclusion Transection of the afferent nerve innervating muscle can produce neuropathic pain through up-regulation of BDNF expression in spinal dorsal horn and DRG in rats, while transection of the afferent nerve innervating skin can not.