Inhibitory effect of 8B203580 on neuropathic pain behaviors induced by lumbar 5 ventral rhizotomy in rats

Previous studies have shown that selective injury to motor fiber, but keeps primary sensory afferents intact, induced abnormal pain behaviors to a similar extent as the rat received lumbar 5 spinal nerve ligation (L5 SNL). Severallines of evidence suggest that the p38 activation in the nociceptive pathway contributes to the development of inflammatory and nerve injury induced neuropathic pain. Whereas, the role of p38 activation in the pain facilitation induced by the motor fiber injury is still unclear. In the present study, the lumbar 5 ventral rhiwtomy (L5 VR) was performed in rats, and the animals were treated with SB203580, an inhibitor of activated p38, intrathecal injection started at before and after the surgery. The pain-related behaviors were tested to elucidate the effect of SB203580. The results showed that L5 VR induced a robust and long-lasting mechanical allodynia and thermal hyprogesia in bilateral hind paws in rats started on day 1 and persisted for more than 4 weeks. Intrathecal injection of SB203580 10 minutes before L5 VR and once daily thereafter until 14th day significantly reduced the mechanical allodynia and blocked the development of thermal hyperalgesia in bilateral hind paws. Post-treatment with SB203580 performed at the first day and 8th day also clearly alleviated the established neuropathic pain following L5 YR. Taken together, the above data indicate that p38 activation might be playing an important role in the induction and maintenance of the neuropathicpain induced by the selective motor fiber injury. [Life ScienceJournal. 2007; 4 (1): 32 - 36] (ISSN: 1097- 8135).