耳蜗电刺激对听觉剥夺幼鼠学习记忆能力的实验研究

The Effects of Intracochlear Electrical Stimulation on the Learning and Memory Abilities of Auditory-deprived Rats

目的建立听力障碍和耳蜗电刺激模型，探讨听力障碍及耳蜗电刺激对幼鼠认知功能的影响。方法选用健康SD幼鼠随机分成4组：①听觉剥夺组（auditorydeprivation，AD）；②听觉剥夺＋早期耳蜗电刺激组（earlyintracochlearelectricalstimulation。JCESl）；③听觉剥夺＋晚期耳蜗电刺激组（1ateintracochlearelectricalstimulation，lCES2）；④对照组（normalcontrol，NC）。AD组、ICESl组、ICES2组在出生后第7天开始用阿米卡星500mg／kg．d皮下注射，直到出生后第16天。对听觉剥夺的幼鼠分别于生后3周龄（早期干预组，ICESl）和生后7周龄（晚期干预组，lCES2）进行电刺激，持续3小时／天，共1周。然后对各组进行行为学检测，并与同龄对照组比较。结果Morris水迷宫实验结果①定位航行试验：早期耳蜗电刺激组（ICESl组）逃避潜伏期于训练后第3天及第4天逐渐达正常水平（与对照组比较，P值均〉0．05）。明显短于听觉剥夺组（P值均〈0．05）；晚期耳蜗电刺激组（ICES2）每日逃避潜伏期虽较听觉剥夺组稍有缩短，但与正常组比较，仍明显延长（均为P〈O．05）。②空间探索实验：早期电刺激组幼鼠在平台象限的游泳时间明显长于听觉剥夺组，穿越平台的次数较听觉剥夺组明显增多（P〈0．05），达同龄正常对照组水平。而晚期电刺激组幼鼠在平台象限的游泳时间、穿越平台的次数与听觉剥夺组比较无统计学意义（P〉O．05）。结论听力丧失后学习和记忆能力受损，早期耳蜗电刺激可以改善听力障碍幼鼠的学习记忆能力。

Objective To establish an auditory deprivation and intracochlear electrical stimulation model, and to explore the influence of hearing impairment and intracochlear electrical stimulation on the cognitive function of young rats. Methods The young Sprague-Dawley rats were randomly divided into four groups：Auditory deprivation group（group I）, auditory deprivation and early intracochlear electrical stimulation group（ICES1, group II ）, auditory deprivation and late intracochlear electrical stimulation group （ICES2, group III ） and normal control group （NC,group IV）. Groups I,II and III were deafened by aminoglycoside intoxication. Amikacin was administered subcutaneously at a dosage of 500 mg/kg, from the seventh （P7）to the 16th （P16） postnatal day. Normal control group were injected saline intraperitoneally （i.p） at the same dosage and for the same course. In group II and III, animals were implanted at P3w and PTw respectively to receive intracochlear electrical stimulation. The duration of the stimulation was 3 hours each day at the same time for 7 days. Morris Water Maze （MWM） test was conducted at P4w, P8w and 1 week after electrically stimulated. Results （1） Place navigation results in MWM test： The mean escape latencies of group II（ICES1 ） had no significant difference with the normal control group on the third and the fourth day（P〉0.05）and were significantly shorter than the auditory deprivation group（P〈0.05）.The mean escape latencies of group lit（ICES2） were shorter than those of group I but still much longer than those of NC group（P〈0.05）.（2） Spatial probe test： The swimming time and crossing times through the platform quadrant in group II（ICES1） increased significantly as compared with those in group I（P〈0.05）.However, there was no significant difference in swimming time and crossing times through the platform quadrant between group Ill（ICES2） and group I （P〉O.O5）.Conclusion The learning and memory abilities of rats are impaired after auditory deprivation, while the early intracochlear electrical stimulation can help improve these abilities.