El-Masry et al., IJPSR, 2013; Vol. 4(2): 666-670 ISSN: 0975-8232 Available online on www.ijpsr.com 666 IJPSR (2013), Vol. 4, Issue 2 (Research Article) Received on 17 October, 2012; received in revised form, 29 November, 2012; accepted, 30 January, 2013 EFFECTS OF CAPSAICIN ON RAT SCIATIC NERVE IN VINCRISTINE-INDUCED NEUROPATHIC PAIN MODEL Thanaa A. El-Masry * 1 , Magda E. El Sayaad 1 , Ibrahim A. Gaaboub 2 and Wafaa M. Fouda 1 Department of Pharmacology & Toxicology, Faculty of Pharmacy, Tanta University 1 , Egypt Department of Plant Protection, Faculty of Agriculture, Banha University 2 , Egypt ABSTRACT Capsaicin, the pungent ingredient of red pepper, is used topically to treat different types of neuropathic pain, in rat model of vincristine induced neuropathic pain we tried to investigate the effect of capsaicin on sciatic nerve through electrophysiological and histopathological studies. We found that treatment of animals with vincristine results in significant decrease in sciatic nerve conduction velocity and degeneration of the nerve fibers, where combined treatment of vincristine and capsaicin showed highly significant decrease in sciatic nerve conduction velocity and degeneration of the nerve fibers compared with that treated with vincristine only. In new trial, we tried to investigate the effect of direct capsaicin titration on sciatic nerve fibers that results in nearly abolishment of nerve conduction velocity. All of these findings may illustrate the mechanism of capsaicin effect through afferent nerves degeneration. INTRODUCTION: The pungent ingredient of red pepper, Capsaicin, is used topically in treatment of post-hepatic neuralgia, diabetic neuropathy and osteoarthritis 1 . Capsaicin therapeutic effects are based on modification of sensory nerve endings. Capsaicin renders animals and man insensitive to further noxious stimuli after initial irritation 2 . Examination of the function of sensory neurons specifically peripheral C- fibers can be mediated by capsaicin .it was found that capsaicin high doses cause desensitization to chemical stimuli, loss of neurogenic inflammation, and depletion of neuropeptides. Analgesic (and anti-inflammatory) effects of capsaicin can be accounted for by a rapid degeneration/ destruction of sensory ganglion cell axons and/or peripheral and central axon terminals, these effects were suggested due to the rapid onset and the long duration of the antinociceptive effect of vanilloids 3, 4, 5, 6, 7 . Indeed, independent laboratories experimental data support the notion that capsaicin antinociceptive effects, administered through different routes, are associated with degenerative changes within the different domains of the nociceptive primary sensory neuron and the consequent loss of peripheral or central nociceptor specific macromolecules and receptors 4, 8 . One of the most common chemo- therapeutic drugs used to treat various types of malignancies is vincristine 9, 10 . Its major dose-limiting side effect is neurotoxicity that requires discontinuation of treatment and thus greatly affects the survival of cancer patients 11, 12, 13 . In this study, we investigate the degenerative effects of capsaicin on sciatic nerve by systemic repeated doses of capsaicin in vincristine induced neuropathy model through electrophysiological study and histo- pathological examination of sciatic nerve. Keywords: Capsaicin, Vincristine, Electrophysiology, Neuropathic Pain Correspondence to Author: Thanaa A. El-Masry Department of Pharmacology & Toxicology, Faculty of Pharmacy, Tanta University, Egypt E-mail: fofo_pharm2007@yahoo.com