Protective Effects of Acupuncture Against Gentamicin-Induced Ototoxicity in Rats: Possible Role of Neurotrophin-3.

ABSTRACT

BACKGROUND The aim of this study was to investigate the protective effects of acupuncture against gentamicin-induced ototoxicity and explore the possible protective role of neurotrophin-3 (NT-3). MATERIAL AND METHODS Twenty-four rats were divided randomly into 4 groups control group, gentamicin group, neitinggong group, and tinggong group. Rats in the gentamicin, neitinggong, and tinggong groups received intraperitoneal injection of gentamicin (100 mg/kg) for 14 consecutive days. Rats in the neitinggong and tinggong groups further received acupuncture at neitinggong or tinggong acupoints once every 2 days for 20 days. Rats in the control group received intraperitoneal injection of saline. Auditory brainstem response (ABR) was tested in all rats on the day before treatment (day 0), and again on day 14 and day 20 to determine the average threshold value of ABR for each treatment group. The expression of NT-3 in the cochlear nucleus and the inferior colliculus nucleus were detected by immunohistochemical staining. RESULTS The average threshold value of ABR was significantly higher in the gentamicin group as compared with that of the control group on day 14 (P<0.05). On day 20, the average threshold values of ABR in the neitinggong and tinggong groups were significantly lower than that of the gentamicin group (P<0.05). No statistically significant differences in NT-3 expression in the cochlear nucleus were observed among the groups (P>0.05). However, the expression of NT-3 in the inferior colliculus nucleus in both the neitinggong and tinggong groups was significantly higher than that of the gentamicin group (P<0.01). CONCLUSIONS A decrease in NT-3 expression in the inferior colliculus nucleus may contribute to gentamicin-induced ototoxicity in rats. Acupuncture at neitinggong or tinggong acupoints effectively improved hearing, which was attributed partially to the rescue of NT-3 expression in the inferior colliculus nucleus. Therefore, preserving NT-3 expression in the auditory system may be a viable strategy to counteract gentamicin-induced ototoxicity.