Evaluation of ketamine, nimodipine, gabapentin and imipramine in partial sciatic nerve transection model of neuropathic pain in rat: an experimental study.

The aim of this research is to study the effects of nimodipine, gabapentin, ketamine and imipramine in the partial sciatic nerve transection (PST) model of neuropathic pain in rats. PST was produced in young Wistar rats of either sex by partial destruction of the sciatic nerve. A decrease in the latency to paw withdrawal reaction on the hot plate was considered as development of neuropathy. The drugs were given daily from the third day of the procedure, and evaluation was done on days 7, 14, 21 and 28. There was a significant decrease (p < 0.05) in the paw withdrawal response in the nimodipine group from day 14 onward when compared with the control group. In the ketamine and imipramine group, this response was seen from day 21 onward. The effect persisted till the end of the study. There was no improvement in the gabapentin group. The results of our study show that nimodipine (dihydropyridine calcium channel blocker), ketamine (NMDA antagonist) and imipramine (tricyclic antidepressant) modulated hyperalgesia and allodynia in the PST model of neuropathy. Gabapentin (an alpha-2 delta calcium subunit blocker) did not show any effect in this model of neuropathy. The widespread use of gabapentin in various types of neuropathic pain thus needs to be reevaluated.