Cotinine Effects on Peripheral Nerve Injuries: An Experimental Study

Aim: Cigarette smoking is a common addictive manner and one of the greatest threats to health. Nicotine is one of the main components of cigarette. The aim of this study was to reveal the effect of cotinine which is an active metabolite of nicotine, on peripheral nerve injury in rats. Material and Methods: We studied 42 male adult albino-Wistar rats that were divided into three groups with simple randomization method. Group 1 were given Cotinine® (C-5923-sigma) intraperitoneally, at a dose of 0.3 mg/kg/day for 21 days. Group 2 were given ethyl alcohol, the solvent of Cotinine in the same way, dose and period. Group 3 were subjected to sciatic nerve compression injury by a clip, which has a closing pressure of 50 gr/cm2. Group 1 and 2 were subjected to the same type of injury at the end of 21 days. Four weeks later after trauma, both three groups were sacrificed and injured sciatic nerve sections are taken for histopathological analysis. Results: It was observed that cotinine aggravated the traumatic degeneration and as privileged caused to fibrosis. In the Schwann cells of thick-myelinated fibers exhibited higher grades of degeneration and mitochondrial augmentation. According to the multiple comparison results, the number of Wallerian degenerations in the trauma group was significantly lower than in both the drug-control (p=0.016) and drug (p<0.001) groups. This situation was estimated as a response to oxidative stress. Conclusion: This study reveals that peripheral nerve regeneration after traumatic injury may be affected negatively in smokers.