The effects of vitamin B 12 and diclofenac and their combination on cold and mechanical allodynia in a neu ropathic pain model in rats

The present study was performed to investigate the effects of long-term intraperitoneal(IP) injection of vitamin B12and diclofenac in separate and combined treatments on cold andmechanical allodynia in a neuropathic pain model in rats. Neuropathic pain was induced bycrush injury in right tibial nerve. Acetone spray and von Frey tests were used to obtain coldand mechanical allodynia responses, respectively, on day 11 after nerve crush. Normal saline,vitamin B12and diclofenac were injected intraperitoneally for 10 consecutive days aftersurgery. Normal saline treated rats showed cold and mechanical allodynia responsesafternerve crush.Vitamin B12at doses of50, 100 and 200 μg kg-1anddiclofenac at a dose of 2 mg kg-1produced antiallodynic effects. Antiallodynic effects were not observed when subanalgesicdoses of vitamin B12(25 μg kg-1) and diclofenac (0.25 mg kg-1) were used together. Byincreasing the dose of vitamin B12to an effective dose (100 μg kg-1), antiallodynic effects wereobserved when compared with diclofenac (0.25 mg kg-1) alone. The results indicated thatvitamin B12and diclofenac produced neuropathic pain suppressing effects. Moreover, apotentiation effect was observed between vitamin B12and diclofenac.