Effects of BDNF and NT-3 on hair cell survival in guinea pig cochlea damaged by kanamycin treatment

THE aim of this study was to determine whether neurotrophic factors such as brain derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) would p rotect auditory hair cells from ototoxicity by aminoglycoside antibiotic. T wenty-seven Wistar guinea pigs were divided into three groups of nine anima ls each. BDNF and NT-3 (100 mu g/ml) were delivered into the right scala ty mpani of guinea pig cochlea through a cannula-osmotic pump device. Artifici al perilymph (AP) was used as control. Immediately after implantation of th e device, each animal was given five successive doses of kanamycin (400 mg/ kg). At 15, 30 and 60 days after infusion, surviving inner and outer hair c ells were counted at each turn of every cochlea with a Philips 515 scanning electron microscope. Multiple comparison tests were carried out among the groups, using ANOVA and Dunnett T3/Tukey HSD. Protective effects of NT-3 on hair cells were observed at 30 and 60 days after kanamycin injection. BDNF had no protective effect on hair cells at 15 and 60 days, but some at 30 d ays. This study suggests that NT-3 and BDNF may protect against cochlear ha ir cell damage caused by kanamycin treatment. Possible mechanisms for the o toprotective effects were discussed. No single mechanism postulated can exp lain fully the results seen in this study. It is possible that the mechanis ms act in concert to produce the observed effects, or there are as yet undi scovered mechanisms or secondary messengers responsible for the otoprotecti ve effects. NeuroReport 10:2067-2071 (C) 1999 Lippincott Williams & Wilkins .