Synergetic Protective Effects Of Nitric Oxide Synthase Inhibitor Combined With Brain-derived Neurotrophic Factor On Cochlear Hair Cell Against Gentamicin Ototoxicity

Objective To investigate if a nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) combined with a neurotrophin brain-derived neurotrophic factor (BDNF) provide synergetic protection on cochlear hair cells (HCs) against gentamicin (GM) ototoxicity and try to find out the mechanism of synergetic protection in order to provide some experiment evidence for protection on deafness caused by drugs.Methods Cochlear organotypic culture technique is used. Twenty Wistar rats of post-natal 4-5 days (forty ears) were divided into five groups, four each group (eight ears). Cochlear basilar membrane were cultured in normal medium for 24 hours. Then Change new medium, respectively contained A: normal medium; B: GM; C: GM+L-NAME; D: GM+BDNF; E: GM+L-NAME+BDNF, and incubated for another 24 hours. All samples were fixed, fluorescently labeled, and examined, photographed under a fluorescence microscope. Quantify the present hair cells.Results The survival rate of IHC and OHC of normal medium, group A, is 97.0%±4.0% and 98.7%±2.7%; The survival rate of IHC and OHC of group B is 4.3%±5.1% and 4.1%±1.8%; The survival rate of IHC and OHC of group C and D are 47.9%±6.5% and 46.2%±15.9%; 44.9%±13.0% and 48.7±11.7%; The survival rate of IHC and OHC of group E is 95.0%±2.3% and 96.8%±1.1%. Analysis statistically survival rate of IHC and OHC: group B, C and D are lower than A (P<0.01). There are no difference between C and D, but they are significantly higher than B (P<0.01). Group E and A have no difference, but E is higher than C and D, the difference between them was statistically significant (P<0.01).Conclusion Both L-NAME and BDNF individually reduced the cochlear hair cells damage in vitro caused by GM but the combination of L-NAME and BDNF was more successful in preventing the damage.