Antinociceptive effect of the novel compound OT-7100 in a diabetic neuropathy model.

We previously reported that OT-7100 (5-n-butyl-7-(3,4,5-trimethoxybenzoylamino)pyrazolo[1,5-alpha]pyrimidine) had antinociceptive potency in various animal models. To further characterize this compound, the present study examined the effects of OT-7100 on mechanical hyperalgesia and motor nerve conduction velocity in streptozotocin-induced diabetic rats. OT-7100 significantly increased the nociceptive threshold in the diabetic rat in a dose-dependent manner. Gabapentin (anticonvulsant agent) and insulin strongly increased the nociceptive threshold but gabapentin increased it above normal levels. An aldose reductase inhibitor slightly increased the nociceptive threshold at a high dose. We also measured glucose levels and motor nerve conduction velocity in OT-7100-treated rats. Insulin decreased glucose levels but OT-7100 had no effect on glucose levels or on motor nerve conduction velocity. These results suggest that OT-7100 alleviates hyperalgesia in a diabetic neuropathy model in a different manner from gabapentin or aldose reductase inhibitor and may be a new treatment for the pain associated with peripheral nerve injury.