一氧化氮合酶抑制剂和神经营养因子3对噪声暴露下豚鼠耳蜗的保护作用

Protection from noise-induced hearing loss by a nitric oxide synthase inhibitor and neurotrophin 3 in the guinea pig cochlea

目的观察一氧化氮合酶抑制剂——N-硝基左旋精氨酸甲酯(N^G-nitro-L-argininemethyl ester,L-NAME)和神经营养因子3(neurotrophin 3,NT3)对噪声性听力损失的保护作用。方法80只雄性杂色豚鼠按区组随机分为非噪声组(n=20)和噪声暴露组(n=60),噪声暴露组又分为生理盐水组(n=20)、L-NAME 组(n=20)、L-NAME+NT3组(n=20)。L-NAME 组和 L-NAME+NT3组动物在噪声暴露(4 kHz 倍频程、声压级115 dB,5 h)之前2 d 和噪声暴露前30 min 给予 L-NAME10 mg/kg(腹腔注射),生理盐水组动物给予等体积的生理盐水。NT3(10μ/ml)在噪声暴露前4 d 经微量渗透泵(200μl,0.5 μl/h)输入到 L-NAME+NT3组动物的右侧耳蜗鼓阶,持续到噪声暴露后10 d。噪声暴露前和暴露后10 d 测试听性脑干反应(auditory brainstem response,ABR),暴露后3 d 测试耳蜗组织一氧化氮(nitric oxide,NO)水平,最后一次 ABR 测试后计数耳蜗毛细胞的存活率。结果无噪声暴露组动物无明显的听力改变和毛细胞缺失;生理盐水组动物的 ABR 阈移、毛细胞缺失率及耳蜗组织 NO 水平均高于 L-NAME 组和 L-NAME+NT3组,差异有统计学意义(P 值均<0.01);与 L-NAME 组相比,L-NAME+NT3组豚鼠的 ABR 阈移减小,差异有统计学意义(P<0.01),而耳蜗组织NO 水平和毛细胞缺失率差异则没有统计学意义(P=0.197及 P=0.095)。结论与单独给予 L-NAME 相比,联合使用 NT3可以更大程度减轻噪声对豚鼠耳蜗的损伤。

Objective To observe the protective effect of nitric oxide synthase inhibitor-N^G-nitro-L-arginine methyl ester （ L-NAME ） with or without neurotrophin 3 （ NT3 ） on hearing in acoustic trauma. Methods Eighty pigmented male guinea pigs were randomly divided into two groups： sham-exposed group （n =20） and noise-exposed group. The latter was divided into three subgroups： saline group（n =20）, L- NAME group（n =20）and L-NAME ＋ NT3 group（n =20）. Two days consecutively and 30 min before noise exposure （4 kHz octave band noise at 115 dB SPL for 5 h）, subjects in L-NAME and L-NAME ＋ NT3 groups received an introperitoneal injection of 10 mg/kg; animals in saline group received the same dosage of physiological saline at the same time. Four days before noise exposure, NT3 in artificial perilymph was delivered to the right scala tympani via a mini-osmitic pump in noise ＋ L-NAME ＋ NT3 group. Auditory brainstem responses （ABR） were measured before and 10 days following noise exposure. The cochlear tissue was assayed for nitric oxide （NO） level 3 days after noise exposure. Protection was assessed physiologically by the change in ABR threshold shift, and histologically by outer hair cell （OHC） survival. Results The hearing thresholds and the number of OHC were relatively stable in sham-exposed group. The obvious threshold shift and OHC loss were observed in the noise-exposed groups. The hearing thresholds, NO level of cochlear tissue and OHC loss in the noise ＋ saline group were significantly higher than those in the noise ＋ L-NAME group （P 〈 0. 01 ） and noise ＋ L-NAME ＋ NT3 group （ P 〈 0. 01 ）. N33 provided an additive functional （ P 〈 0. 01 ）, but not morphological protection with L-NAME （ P = 0. 095 ） . Conclusion Compared to L-NAME alone, a combination of L-NAME and NT-3 can provide an additional protection against acoustic trauma in the guinea pig cochlear.