LONG TERM EFFECTS OF ALLANTOIN ON PERIPHERAL NERVE HEALING: AN ELECTROPHYSIOLOGICAL STUDY

Background: Peripheral nerve injuries are a common health problem resulting in a decreased quality of life. Treatment of peripheral nerve injuries is complex and depends on location, intensity, and type of nerve injury. Allantoin is an antioxidant found in plants that enhance wound healing. It promotes the proliferation of cells by improving peripheral nerve function. This study aimed to investigate the long term effects of intraperitoneal (i.p.) administration of allantoin on peripheral nerve healing in an experimental sciatic nerve crush in a rat model. Materials and Methods: Twenty male Wistar albino rats were randomly divided into four groups. Control (Cont) Group did not receive any special protocol for 60 days. Crush (Cr) Group was induced to crush. Allantoin (A) Group received 10 mg/kg of allantoin i.p. for 60 days. Crush + Allantoin (Cr+A) Group was induced to crush and given 10 mg/kg of allantoin i.p. for 60 days. After 60 days all rats were sacrificed following electromyography (EMG). Results: Allantoin was revealed to enhance the peripheral nerve function in terms of amplitude and latency. Conclusion: The i.p. administration of allantoin may have a positive effect on peripheral nerve healing.

384 ureidohydantoin or glyoxyldiureide. Wound healing is a physiological process that allows injured tissues to be repaired. Allantoin has a variety of pharmacological effects, including wound healing, cell mitotic stimulation, and epithelial stimulation promoter. It has been utilized as a wound healing enhancer for many years (Araújo, Grabe-Guimarães, Mosqueira, Carneiro, & Silva-Barcellos, 2010). Since allantoin exhibits antioxidant properties, it has also been used in cosmetics and topical medicinal preparations to treat skin conditions (Selamoglu, Dusgun, Akgul, & Gulhan, 2017). Allantoin is a safe treatment that promotes cell division and epithelial tissue formation while accelerating the healing of damaged skin (Elżbieta, 2012).
In the present study, we hypothesized that long term i.p. administration of allantoin may have a beneficial effect on peripheral nerve healing due to its tissue-repair properties. In this study, we investigated the long term effects of i.p. administration of allantoin on peripheral nerve healing in an experimental sciatic nerve crush in a rat model.

Materials and Methods:-Animals
In the present study, 20 male Wistar albino rats aged 10±2 weeks (weighing 200±50 g) were obtained from the animal and experimental research center, Ondokuz Mayıs University (OMU), Samsun, Turkey. The experimental research was approved by the Ethical Committee of Ondokuz Mayıs University (OMU) under the project of long term effects of allantoin on peripheral nerve healing (number 36).
Rats were randomly divided into four groups. Each group consisted of five animals. Control (Cont) Group did not receive any special protocol for 60 days. Crush (Cr) Group was induced to crush. Allantoin (A) Group received 10 mg/kg of allantoin i.p. for 60 days. Crush + Allantoin (Cr+A) Group was induced to crush and given 10 mg/kg of allantoin i.p. for 60 days. After 60 days all rats were sacrificed.

Surgical Procedures
The surgical procedure in the study was carried out at the animal and experimental research center, Ondokuz Mayıs University (OMU), Samsun, Turkey. The rats of the crush groups were anesthetized with a mixture of ketamine and xylazine 0.1 mg/kg -0.4 mg/kg i.p. The surgical procedure was performed on the right hind limb. The area over the right hind limb was shaved and sterilized. A small incision was made to the skin of the shaved area and the right sciatic nerve was exposed in the gluteal muscle. The nerve was crushed with hemostatic forceps for 5 seconds of 50 Newton pressure. Then the incised site was sutured and sterilized.

Electrophysiological analysis
The electrophysiological analysis was done by using EMG before sacrifice. The rats were anesthetized and the area over the right hind limb was shaved and sterilized. An incision was made to the skin and the right sciatic nerve was exposed. A needle wire was placed 10 mm distal from the sciatic notch, and two monopolar electrodes were placed on the gastrocnemius rim at a distance of 2.5 cm from the needle wire. The compound muscle action potential (CMAP) was then measured on the gastrocnemius by stimulating a voltage between 0.01 mV and 10 mV.

Statistical Analysis
Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) version 21. One-way analysis of variance (ANOVA) and Tukey's post hoc test for statistical differences was used. Data are presented as mean ± SD, and a P value of less than 0.05 was considered statistically significant.

CMAP Latency
The comparison of mean latency values is shown in Table 1 and Figure 2. There was a highly significant difference between Cont and Cr groups (p < 0.01). There was a highly significant difference between Cont and Cr+A groups (p < 0.01). There was a highly significant difference between Cr and A groups (p < 0.01). There was a highly significant difference between Cr and Cr+A groups (p < 0.01). There was a highly significant difference between the A and Cr+A groups (p < 0.01). A significant difference was not found between Cont and A.

Amplitude
The comparison of mean latency values is shown in Table 2 and Figure 3. A highly significant difference was observed between Cont and Cr groups (p < 0.01). A highly significant difference was also observed between Cont and Cr+A groups (p < 0.01). There was a highly significant difference between Cr and A groups (p < 0.01). There was a highly significant difference between Cr and Cr+A groups (p < 0.01). There was a highly significant difference between the A and Cr+A groups (p < 0.01). Similar to latency, a significant difference was not found between Cont and A. 386

Discussion:-
The peripheral nerves are affected by many different conditions (Chung, Prasad, & Lloyd, 2014). Since peripheral nerve injuries are frequent, electrophysiological analysis is important for assessing nerve injury (Elfayoumy, Elgendy, Saad, & Labib, 2020). In the present study, electrophysiological analysis of CMAP including latency and amplitude was measured. Latency was significantly higher in Cr and Cr+A groups and was lower in Cont and A groups. The amplitude was significantly higher in Cont and A groups and was lower in Cr and Cr+A groups. The Cr+A group showed improvement in both latency and amplitude if compared to the Cr group. These results indicate that myelination of the nerves was significantly improved in rats administered with allantoin. Kahraman and Kahveci (2015) investigated the effect of allantoin on peripheral nerve injuries in a rat model and found that allantoin has a positive effect on wound healing (Kahraman & Kahveci, 2015

Conclusion:-
This study evaluated the effect of allantoin on peripheral nerve healing after sciatic nerve injury in rats by using electrophysiological methods. The results showed that allantoin has a positive effect on peripheral nerve healing 387 after sciatic nerve injury and enhanced peripheral nerve regeneration. The effect is based on electrophysiological data. More studies are needed to make clear the long term effects of allantoin on peripheral nerve injury.

Conflicts of Interest
The authors declare that they have no conflicts of interest.