The antiallodynic effect of Neurotropin is mediated via activation of descending pain inhibitory systems in rats with spinal nerve ligation.

Background: Neurotropin, a nonprotein extract isolated from inflamed skin of rabbits inoculated with vaccinia virus, is widely used in Japan to treat chronic pain such as neuropathic pain. Although some studies have been conducted on the mechanism of the antiallodynic action of Neurotropin, this mechanism has yet to be adequately clarified.

Methods: The left fifth lumbar nerve of rats was tightly ligated with silk sutures under pentobarbital anesthesia.

Mechanisms of analgesic action of neurotropin on chronic pain in adjuvant-induced arthritic rat: roles of descending noradrenergic and serotonergic systems.

Neurotropin((R)), a non-protein extract from the inflamed skin of rabbits inoculated with vaccinia virus, has been clinically used as an analgesic drug for treatment of chronic pain. In this study, we investigated the analgesic mechanisms of Neurotropin in the adjuvant-induced arthritic rat, a chronic pain model with inflammation. Neurotropin caused dose-dependent inhibition of hyperalgesia in the adjuvant-induced arthritic rat after single intravenous (10 - 100 NU/kg) and oral (30 - 200 NU/kg) administration.