INTRODUCTION Tetramethylpyrazine (TMP) is a chemical compound, which has been shown to possess numerous biological features such as anticoagulation, inhibition of platelet aggregation, anti-inflammation, capillary dilatation, improvement in microcirculation, and protection against reactive oxygen radicals. The aim of the present study was to investigate the protective effect of TMP against radiation-induced ototoxicity. MATERIALS AND METHODS 40 rats were divided into four groups. The first group was irradiated for 5 days. The second group received a single dose of 140 mg/kg/day intraperitoneal TMP given to the rats 30 min before radiotherapy (RT) for 5 days. The third group received a single dose of 140 mg/kg/day i.p. TMP for 5 days, whereas the fourth group was administered saline. All rats underwent distortion product otoacoustic emission (DPOAE) and auditory brainstem response measurements before and after the application. The temporal bulla of animals was removed for immunohistopathological examination. RESULTS Signal-noise ratio values were significantly decreased in the RT group for the frequencies of 2-32 kHz after RT (p < 0.05), whereas the difference was not significant in terms of pre- and posttreatment values for the other groups. Also in the RT group, the ABR thresholds were significantly increased after treatment. In H&E staining, the mean scores for outer hair cells (OHCs), stria vascularis (SV), and spiral ganglion (SG) injuries were significantly higher in RT and RT + TMP groups than in the other groups. The mean OHCs and SV injury scores were also significantly higher in the RT group than in the RT + TMP group (p < 0.05). The number of cochleas that showed cytoplasmic caspase-3 immunoreactivity in the OHC, SV, and SG was significantly higher in RT and RT + TMP groups than in the other groups. CONCLUSION The findings of the present study suggest that TMP may have a therapeutic potential for preventing sensorineural hearing loss (SNHL) related to RT.

中文翻译：

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四甲基吡嗪减轻大鼠模型中辐射引起的耳毒性。

简介 四甲基吡嗪 (TMP) 是一种化合物，已被证明具有多种生物学特性，如抗凝、抑制血小板聚集、抗炎、扩张毛细血管、改善微循环和防止活性氧自由基。本研究的目的是研究 TMP 对辐射引起的耳毒性的保护作用。材料和方法 40 只大鼠分为四组。第一组照射5天。第二组在放疗 (RT) 前 30 分钟向大鼠腹腔注射单剂量 140 mg/kg/天的 TMP，持续 5 天。第三组接受单剂量 140 mg/kg/天 ip TMP，持续 5 天，而第四组则给予生理盐水。所有大鼠在应用前后均接受畸变产物耳声发射（DPOAE）和听觉脑干反应测量。摘除动物颞大泡进行免疫组织病理学检查。结果 RT 组在 RT 后 2-32 kHz 频率的信噪比值显着降低（p < 0.05），而其他组治疗前和治疗后值的差异不显着。同样在 RT 组中，治疗后 ABR 阈值显着增加。在 H&E 染色中，RT 组和 RT + TMP 组的外毛细胞 (OHC)、血管纹 (SV) 和螺旋神经节 (SG) 损伤的平均评分显着高于其他组。RT 组的平均 OHC 和 SV 损伤评分也显着高于 RT + TMP 组 (p < 0.05)。RT 组和 RT + TMP 组中 OHC、SV 和 SG 中显示细胞质 caspase-3 免疫反应性的耳蜗数量显着高于其他组。结论 本研究的结果表明，TMP 可能具有预防与放疗相关的感音神经性听力损失 (SNHL) 的治疗潜力。