Effect of Nerve Growth Factor on Peripheral Neuropathy in Experimental Rat Model

Abstract

Nerve growth factor (NGF) is a one of a family of neurotrophic factors, which are considered to be essential for neuronal survival and differentiation. Decrease of NGF is thought to be one possible etiology of neuropathy. The use of NGF in the treatment of peripheral neuropathies has also been researched, but has been found to cause many problems including hyperalgesia. The aim of this study is to find out possibility that NGF as a therapeutic agent for neuropathy, and the effect of exogenously administered nerve growth factor on mechanical or thermal hyperalgesia in an experimental neuropathic pain model. In this experiment, 180-200 gm, Sprague-Dawley rats of either sex, were used. As an index of neuropathy, mechanical and thermal responses were measured: the mechanical stimulation was done with 1.0, 2.0, 3.0, 4.0, and 5.0 gm von Frey filament, and thermal stimulation was done with 40C water. The responses to mechanical or thermal stimulation were increased within 24 hours after surgery, reached to the peak on the 7th day, and was maintained over 4 weeks. To measure the effect hof NGF on peripheral neuropathy, NGF was infiltrated into the transected nerve during surgery, after that NGF(50 ng) was subcutaneously injected on the proximal end of the tail everyday. Mechanical allodynia on peripheral neuropathy was disappeared with NGF application over 4 weeks. Cold or warm hyperalgesia was reversed, or more desensitized by NGF application, especially in the initial I ~2 weeks. The reversal effect of NGF on mechanical or thermal hyperalgesia also showed in rats treated with NGF for only 1 week. In summary, NGF reduced mechanical allodynia and thermal hyperalgesia on tail neuropathic pain model. These results suggest the possibility of NGF application for the treatment of neuropathic pain and possibility of a decrease in NGF as the pathogenesis of neuropathic pain, especially initial pain.