Effects of Topiramate on the Chronic Constriction Injury Model in the Rat

We studied the effects of topiramate at a relatively low dose of 20 mg/kg/d in rats that underwent chronic constriction injury (CCI) to the sciatic nerve. Fourteen rats underwent CCI and were then divided into two groups: one treated with topiramate and the other with an equal volume of saline. A further group of six rats was sham operated and treated with topiramate. Rats were examined over a period of 13 days for the presence of mechanoallodynia (von Frey hairs) and mechanohyperalgesia (pinprick test) and then euthanized and the degree of nerve injury was assessed by measuring the expression of neuropeptide Y (NPY) in dorsal root ganglia with enzyme-linked immunosorbent assay. Topiramate, at a lower dose than previously reported, significantly delayed the onset of allodynia and both delayed and attenuated the peak hyperalgesia observed. NPY levels were not significantly different between the operated groups. Perspective: Topiramate is employed in various pain conditions and this study suggests that lower doses may be effective in neuropathic pain. Clinically this may mean reduced side effects. Additionally the potential of topiramate as a neuroprotectant is studied and, although the results were negative, this area needs further research.