体温过高对大鼠脑干听觉诱发电位和中潜伏期反应的影响

目的 :探讨体温过高对大鼠脑干听觉诱发电位 (BAEP)和听觉中潜伏期反应 (MLR )的影响。方法 :诱发电位仪颅表记录大鼠BAEP和MLR ;体表物理升温法逐步升高麻醉大鼠体温 ,传感探头式数字体温计监测大鼠直肠体温 ;主要观察BAEP和MLR的波峰潜伏期 (PL)、波峰间潜伏期 (IPL)和波幅随体温升高而发生的变化及它们消失的临界体温。结果 :BAEP各波PL及Ⅰ Ⅱ、Ⅰ Ⅲ、Ⅰ ⅣIPL随体温升高 ( 3 7～ 41.5℃ )而逐步缩短 ,但当体温升高至 42℃和超过 42℃时各波PL及Ⅰ Ⅱ、Ⅰ ⅣIPL不再继续缩短 ,并略有反向延长 ;MLR各波PL和P1 P3、P2 P3IPL也随体温升高 ( 3 7～ 43℃ )而缩短。随体温升高 ,BAEP和MLR波幅的主要表现为降低 ,特别是在体温升高至42℃以后。BAEP和MLR在体温 ( 4 3 .1± 0 .5)℃时出现不可逆性消失 ,且两者同步消失。结论 :体温过高对大鼠BAEP和MLR有相似的显著影响 ,体温过高至一临界值时会造成BAEP和MLR的不可逆性损害。     

正常和卡那霉素中毒豚鼠听觉脑干诱发反应及频率跟随反应的比较研究

通过测定阈值和频谱分析,比较了正常和卡那霉素中毒后豚鼠听觉脑干反应(ABR)及频率跟随反应(FFR)的特性.正常FFR的非线性随刺激频率的减低而增加,表现为高次谐波的出现.从频谱中基频成分的峰很容易识别FFR阈值.卡那霉素作用后,高频FFR首先受到影响,波幅下降,阈值显著升高.低频FFR受到影响较小.同一动物ABR阈值尚未变化时高频FFR的基频峰值已下降,乃至消失.实验结果表明FFR对耳毒性药物中毒反应由于其包含有频率特性比ABR更灵敏,更便于定量分析.     

大鼠脑干听觉诱发电位和中潜伏期反应的生后发育

目的：探讨大鼠脑干听觉诱发电位（BAEP）和听觉中潜伏期反应(MLR)生后发育模式的异同。方法：在同一批新生SD纯种大鼠连续10周同时观察BAEP和MLR生后发育的变化。结果：BAEP和MLR分别在生后14d和17d出现;BAEP各波峰潜伏期（PL）随鼠龄增长而递减,生后3－4周是PL缩短的主要时期,I波PL在生后29d达成年值,其余各波PL在生后70d全部达成年值;首次出现的MLR,其Po和Na两波PL已达成年值,而Pa、Nb和Pb和PL也随鼠龄增长而缩短,但生后20－23d很快就达成年值;BAEP的Ⅰ、Ⅲ、Ⅳ波和MLR的Nb、Pb波波幅在生后3－4周期间迅速递增,且峰值明显大于成年值,然后逐渐回降。结论：大鼠MLR和BAEP生后发育的模式基本相同,但MLR各波PL较早达成年值。     

犬脑干缺血兴奋性氨基酸含量的改变对BAEP影响的初步研究

犬脑干缺血兴奋性氨基酸含量的改变对ＢＡＥＰ影响的初步研究岳桂明邓志宽（第三军医大学新桥医院神经内科,重庆６３００３７）目前的研究已经证实,兴奋性氨基酸（Ｅｘｃｉｔａｔｏｒｙａｍｉｎｏａｃｉｄｓ,ＥＡＡｓ）在脑缺血损伤中起重要病理作用。由于脑干内神经核...     

高胆红素血症新生大鼠脑干听觉诱发电位快慢成分的变化

目的：探讨高胆红素血症新生大鼠脑干听觉诱发电位快成分（FC-BAEP）和慢成分（SC-BAEP）及脑干神经元线粒体超微结构的异常变化。方法：生后7天SD大鼠随机分为对照组（C组,17只）和两个实验组（T1和T2组,各17只）。T1和T2组大鼠生后7天和10天腹腔注射2g/L胆红素溶液,第二次腹腔注射6h后随机抽出7只断头取血用微量胆红素仪检测血清胆红素,其余大鼠生后17天和20天用诱发电位仪检测FC-BAEP和SC-BAEP,生后20天灌注固定、取耳蜗核进行透射电镜观察。结果：T1和T2组大鼠于生后10天腹腔注射6h后,血清胆红素浓度明显升高;T1和T2组大鼠生后17天三种刺激重复率（10/s,40/s,80/s）引导的FC-BAEP,除Ⅱ-Ⅳ波峰间潜伏期（IPL）外,各波波峰潜伏期（PL）和IPL显著延长,且T2组大鼠各波PL较T1组显著延长;T1和T2组大鼠生后20天三种刺激重复率引导的FC-BAEP,除刺激重复率10/s和40/s引导的Ⅱ-ⅣIPL外,各波PL和IPL显著延长;T1和T2组大鼠生后17天与20天刺激重复率10/s引导的SC-BAEP的PL显著延长,且T2组大鼠生后17天SC-BAEP的PL较T1组显著延长;T1和T2组大鼠耳蜗核电镜观察可见神经元线粒体肿胀变形、膜模糊不清和嵴断裂等。结论：高胆红素血症新生大鼠FC-BAEP和SC-BAEP及脑干神经元线粒体超微结构有显著异常变化,FC-BAEP与SC-BAEP的PL和IPL是早期监测胆红素诱发的听觉和脑损伤的客观灵敏指标。     

慢性缺氧性脑病诱发电位、行为与caspase-3凋亡蛋白表达的变化

目的:探讨大鼠慢性间断性缺氧后,脑诱发电位与慢性缺氧性脑损伤的关系,探讨脑诱发电位对缺氧性脑病的评估价值.方法:在建立慢性间断性缺氧大鼠模型的基础上,雄性SD大鼠随机分成缺氧组(H组)和对照组(N组),H组随机分为缺氧2周组(H2组)和缺氧4周组(H4组)2个亚组;应用Morris水迷宫检测各组大鼠的学习记忆能力;测定各组大鼠的脑干听觉诱发电位(BAEP)和短潜伏期体感诱发电位(SLSEP).免疫组织化学法检测caspase-3凋亡蛋白表达的变化.结果:缺氧组BAEP和SEP各波的峰潜伏期和峰间峰潜伏期比对照组明显延长,差异有显著性意义,缺氧组BAEP和SEP的变化与学习记忆能力和caspase-3凋亡蛋白表达有相关性.结论:BAEP和SEP的改变与慢性缺氧性脑损伤及损伤的程度明显相关,是反映缺氧性脑损伤比较敏感的指标.     

兔脑温升高时听觉诱发电位的变化

兔单侧颈总动脉血体外加温灌流可选择性地升高脑温。在脑温升高3℃过程中,听觉脑干诱发电位成分Ⅰ的峰潜伏期无明显改变,成分Ⅱ～Ⅵ及听觉中潜伏期诱发电位成分Pa的峰潜伏期则逐渐缩短,其中Pa变化最早和最显著;Ⅰ～Ⅲ,Ⅲ～Ⅵ和Ⅵ～Pa峰间期的缩短,以Ⅵ～Pa变化最早、最显著。经脑复温而仍存活的兔,缩短的峰潜伏期可逐渐恢复,当脑复温至加温前水平时,Ⅱ、Ⅴ和Ⅵ峰潜伏期及Ⅲ～Ⅵ峰间期较加温前延长。结果表明,兔脑温升高可使听觉中枢传导径路上各级神经元的传导功能增强,而脑复温时,增强的传导功能逐渐降低,随后,部分神经元的传导功能低于加温前水平。     

卡那霉素耳慢性中毒对豚鼠耳蜗毛细胞中Bcl-2表达的影响

目的:探讨卡那霉素耳慢性中毒对豚鼠耳蜗毛细胞中Bcl-2表达的影响。方法:取20只豚鼠随机分为2组,实验组连续14d肌肉注射硫酸卡那霉素,200mg/(kg.d),对照组连续14d等量肌肉注射生理盐水,停药14d处死动物后制作耳蜗标本,处死前检测其ABR的变化,免疫组化及原位杂交法测定Bcl-2的表达。结果:豚鼠卡那霉素耳慢性中毒后,ABR阈值较对照组明显上升,Bcl-2阳性表达减低,与对照组比较差异有显著性(P<0.05)。结论:卡那霉素耳慢性损害可能与抑制Bcl-2的表达有关。     

脑干听觉诱发电位与后循环TIA及脑干梗死的相关性研究

目的:研究脑干听觉诱发电位(BAEP)与后循环短暂性脑缺血发作(TIA)及脑干梗死的相关性。方法:选取我院收治的后循环TIA患者46例作为TIA组,选取同期收治的脑干梗死患者44例作为脑干梗死组,选取同期健康体检者49例作为健康组,TIA组和脑干梗死组均在发病后1周内进行BAEP检查,健康体检者在体检时进行BAEP检查,比较3组的Ⅰ、Ⅲ、Ⅴ波的潜伏期(PL)及Ⅰ-Ⅲ、Ⅲ-Ⅴ、Ⅰ-Ⅴ波峰间的潜伏期(IPL)。结果:TIA组BAEP异常率71.74%,脑干梗死组BAEP异常率56.82%,健康组BAEP异常率24.49%,TIA组患者BAEP异常率高于健康组,差异有统计学意义(P0.05)。脑干梗死组BAEP异常率高于健康组,差异有统计学意义(P0.05)。TIA组患者PL的Ⅰ、Ⅲ、Ⅴ水平均高于健康组,差异有统计学意义(P0.05)。TIA组患者IPL的Ⅰ-Ⅲ、Ⅲ-Ⅴ、Ⅰ-Ⅴ水平均高于健康组,差异有统计学意义(P0.05)。脑干梗死组患者PL的Ⅰ、Ⅲ、Ⅴ水平均高于健康组,差异有统计学意义(P0.05)。脑干梗死组患者IPL的Ⅰ-Ⅲ、Ⅲ-Ⅴ、Ⅰ-Ⅴ水平均高于健康组,差异有统计学意义(P0.05)。脑干梗死组患者IPL与PL均明显高于TIA组(P0.05)。结论:BAEP与后循环TIA及脑干梗死存在相关性,并且较为敏感,是优秀的诊断方法之一。     

有关猫交叉听力及其对检测耳影响的初步研究

目的研究猫的交叉听力现象及其产生机理,初步探讨交叉听力对检测耳ABR振幅的影响。方法用彻底破坏一侧耳蜗的方法,观察16只听力正常家猫的交叉听力现象及其对检测耳的影响。结果①当短声强度≥75dB(SPL)时,开始出现交叉听力波形,声强增至95dB时,交叉听力波形最典型。②95dB短声产生的交叉听力波形可被40或45dB(SPL)的稳态白噪声（SWN）完全屏蔽掉。③在同一时间轴中比较95dB短声诱发的ABR和交叉听力波形,发现交叉听力之波谷恰与ABR之pⅢ、pⅣ波峰相对应。④两耳均正常时对侧耳负荷的40dBSWN可使95dB短声诱发的ABR之pⅢ、pⅣ波振幅增大,且具统计学意义（P＜0.01）。结论交叉听力对ABR振幅的影响取决于两者的波峰与波谷在同一时间轴上的对应情况,声强较大时记录到的ABR,实质上是交叉听力与刺激侧产生的ABR在同一时间轴上的综合电位。     

甘肃鼢鼠和根田鼠听域研究

用电生理学方法对甘肃鼢鼠和根田鼠的听性脑干反应(ABR)的反应阈值做了测定,以确定甘肃鼢鼠和根田鼠听域.结果 表明甘肃鼢鼠听力敏感频率为12 kHz,根田鼠的听力敏感频率为16～32 kHz.甘肃鼢鼠和根田鼠听性脑干电位测定结果表明地下鼠和地面鼠低频高频听力阈值存在差异,地下鼠对中低频声波敏感.     

Behavioral determination of stimulus pair discrimination of auditory acoustic and electrical stimuli using a classical conditioning and heart-rate approach

Acute animal preparations have been used in research prospectively investigating electrode designs and stimulation techniques for integration into neural auditory prostheses, such as auditory brainstem implants and auditory midbrain implants. While acute experiments can give initial insight to the effectiveness of the implant, testing the chronically implanted and awake animals provides the advantage of examining the psychophysical properties of the sensations induced using implanted devices. Several techniques such as reward-based operant conditioning, conditioned avoidance, or classical fear conditioning have been used to provide behavioral confirmation of detection of a relevant stimulus attribute. Selection of a technique involves balancing aspects including time efficiency (often poor in reward-based approaches), the ability to test a plurality of stimulus attributes simultaneously (limited in conditioned avoidance), and measure reliability of repeated stimuli (a potential constraint when physiological measures are employed). Here, a classical fear conditioning behavioral method is presented which may be used to simultaneously test both detection of a stimulus, and discrimination between two stimuli. Heart-rate is used as a measure of fear response, which reduces or eliminates the requirement for time-consuming video coding for freeze behaviour or other such measures (although such measures could be included to provide convergent evidence). Animals were conditioned using these techniques in three 2-hour conditioning sessions, each providing 48 stimulus trials. Subsequent 48-trial testing sessions were then used to test for detection of each stimulus in presented pairs, and test discrimination between the member stimuli of each pair. This behavioral method is presented in the context of its utilisation in auditory prosthetic research. The implantation of electrocardiogram telemetry devices is shown. Subsequent implantation of brain electrodes into the Cochlear Nucleus, guided by the monitoring of neural responses to acoustic stimuli, and the fixation of the electrode into place for chronic use is likewise shown.     

Ion channel mechanisms underlying frequency-firing patterns of the avian nucleus magnocellularis: A computational model

We have previously shown that late-developing avian nucleus magnocellularis (NM) neurons (embryonic [E] days 19–21) fire action potentials (APs) that resembles a band-pass filter in response to sinusoidal current injections of varying frequencies. NM neurons located in the mid- to high-frequency regions of the nucleus fire preferentially at 75 Hz, but only fire a single onset AP to frequency inputs greater than 200 Hz. Surprisingly, NM neurons do not fire APs to sinusoidal inputs less than 20 Hz regardless of the strength of the current injection. In the present study we evaluated intrinsic mechanisms that prevent AP generation to low frequency inputs. We constructed a computational model to simulate the frequency-firing patterns of NM neurons based on experimental data at both room and near physiologic temperatures. The results from our model confirm that the interaction among low- and high-voltage activated potassium channels (K_LVA and K_HVA, respectively) and voltage dependent sodium channels (Na_V) give rise to the frequency-firing patterns observed in vitro. In particular, we evaluated the regulatory role of K_LVA during low frequency sinusoidal stimulation. The model shows that, in response to low frequency stimuli, activation of large K_LVA current counterbalances the slow-depolarizing current injection, likely permitting Na_V closed-state inactivation and preventing the generation of APs. When the K_LVA current density was reduced, the model neuron fired multiple APs per sinusoidal cycle, indicating that K_LVA channels regulate low frequency AP firing of NM neurons. This intrinsic property of NM neurons may assist in optimizing response to different rates of synaptic inputs.     

Fine mapping of Ahl3 affecting both age-related and noise-induced hearing loss

A region in the vicinity of D17Mit119 on mouse chromosome 17 harbors a susceptibility gene, designated as Ahl3, to age-related hearing loss (AHL). We produced congenic lines of C57BL/6 background that substituted regions around D17Mit119 with MSM-derived ones, and examined auditory brainstem response (ABR) thresholds for their hearing capacity at 6 and 12months of age. Three congenic lines carrying the approximately 14-Mb region between D17Mit274 and D17Mit183 retained normal hearing at 12months of age whereas two congenic lines not carrying this region tended to lose hearing at that age. We also investigated noise-induced hearing loss (NIHL) in congenic lines at 1, 7 and 14days after exposure to the noise of 100dB for 1h. Most congenic mice carrying the 14-Mb region did not exhibit permanent threshold shift (PTS) whereas mice not carrying this region exhibited a strong tendency of PTS, indicating the role of Ahl3 in susceptibility to NIHL. These results indicate that Ahl3 exists within the 14-Mb region and affects not only AHL but also NIHL.