Electrophysiological, biochemical and ultrastructural effects of radiotherapy on normal rat sciatic nerve

Abstract

Purpose: The aim of the present study was to evaluate the electrophysiological, biochemical and ultrastructural changes on the rat sciatic nerve after radiotherapy.Material and Methods: Thirty male Wistar albino rats were divided into three groups as: Control group (n = 10), Group I: 3 months after radiotherapy (n = 10), and Group II: 6 months after radiotherapy (n = 10). Groups I and II were irradiated with a 60Co gamma source. A dose of 20 Gy in 10 fractions was applied to Groups I and II. Compound motor action potentials (CMAP) were recorded in all groups. Superoxide dismutase (SOD) and catalase (CAT) activities and malondialdehyde (MDA) levels were measured in the sciatic nerve of rats using the biochemical methods. Ultrastructural changes were determined by electron microscopy.Results: In Groups I and II, the amplitude of CMAP was significantly lower and the latency was significantly higher than that of the control group. There were no significant differences between Groups I and II regarding the CMAP amplitude and latency. The MDA levels were significantly increased, whereas the SOD and CAT activities were significantly decreased in experimental groups when compared with the control group. However, there were no significant changes in these parameters between Groups I and II. Degeneration in myelinated nerve fibers was observed ultrastructurally only in the experimental groups. Significant changes were observed between the control group and experimental groups in terms of ultrastructural myelin grading score and axonal damage score. No significant differences were found between Groups I and II.Conclusions: These findings indicated that the dose of 20 Gy in 10 fractions radiotherapy caused neuropathic damages in normal rat sciatic nerve 3 and 6 months after irradiation.