硫酸卡那霉素对成年大鼠的耳毒性效应

本研究旨在观察硫酸卡那霉素(kanamycin sulfate,KM)对成年大鼠的耳毒性效应。6～7周龄的雄性Sprague-Dawley(SD)大鼠40只,随机分为2组:实验组,每天腹腔注射KM(500mg/kg)2周;对照组,注射等量生理盐水2周。通过检测脑干听觉诱发电位(auditory brainstem response,ABR)观察大鼠听力改变。ABR检测结束后,分离出耳蜗进行基底膜铺片、耳蜗冰冻切片,观察耳蜗螺旋神经节细胞(spiral ganglion cells,SGCs)的密度和耳蜗形态学改变。结果显示,注射KM2周后,大鼠在各频率的听觉阈值均有明显升高,其上升幅度超过60dB;随着时间推移,KM组SGCs密度逐渐降低,Corti器结构尚存,但外毛细胞及内毛细胞均有不同程度的缺失,以外毛细胞为甚;内毛细胞缺失与SGCs的密度下降相平行。以上结果表明,6～7周龄大鼠经过KM作用2周后,听力会明显下降,达到重度耳聋甚至全聋。KM的耳毒性作用与SGCs和内外毛细胞的损伤密切相关。     

Hearing Range of White-Tailed Deer as Determined by Auditory Brainstem Response

Abstract: Basic knowledge of white-tailed deer (Odocoileus virginianus) hearing can improve understanding of deer behavior and may assist in the development of effective deterrent strategies. Using auditory brainstem response testing, we determined that white-tailed deer hear within the range of frequencies we tested, between 0.25–30 kilohertz (kHz), with best sensitivity between 4–8 kHz. The upper limit of human hearing lies at about 20 kHz, whereas we demonstrated that white-tailed deer detected frequencies to at least 30 kHz. This difference suggests that research on the use of ultrasonic (frequencies >20 kHz) auditory deterrents is justified as a possible means of reducing deer—human conflicts.     

Specialization for underwater hearing by the tympanic middle ear of the turtle, Trachemys scripta elegans

Turtles, like other amphibious animals, face a trade-off between terrestrial and aquatic hearing. We used laser vibrometry and auditory brainstem responses to measure their sensitivity to vibration stimuli and to airborne versus underwater sound. Turtles are most sensitive to sound underwater, and their sensitivity depends on the large middle ear, which has a compliant tympanic disc attached to the columella. Behind the disc, the middle ear is a large air-filled cavity with a volume of approximately 0.5 ml and a resonance frequency of approximately 500 Hz underwater. Laser vibrometry measurements underwater showed peak vibrations at 500-600 Hz with a maximum of 300 μm s(-1) Pa(-1), approximately 100 times more than the surrounding water. In air, the auditory brainstem response audiogram showed a best sensitivity to sound of 300-500 Hz. Audiograms before and after removing the skin covering reveal that the cartilaginous tympanic disc shows unchanged sensitivity, indicating that the tympanic disc, and not the overlying skin, is the key sound receiver. If air and water thresholds are compared in terms of sound intensity, thresholds in water are approximately 20-30 dB lower than in air. Therefore, this tympanic ear is specialized for underwater hearing, most probably because sound-induced pulsations of the air in the middle ear cavity drive the tympanic disc.     

Auditory evoked potentials in the Japanese monkey.

Auditory sensitivity based on auditory brain stem response (ABR), whole nerve action potential (AP), and cochlear microphonics (CM) to tone bursts of 0.5-8 kHz were compared with behavioral audiometry in the Japanese monkeys. Although sensitivity loss at 4-6 kHz was observed in these potentials, an increase in sensitivity at 8 kHz was obtained only in the ABR. Thus the sensitivity loss at 4-6 kHz originates at the peripheral system and the increased sensitivity at 8 kHz originates at the central.     

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。     

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。     

Identifying the Threshold of Iron Deficiency in the Central Nervous System of the Rat by the Auditory Brainstem Response

The deleterious effects of anemia on auditory nerve (AN) development have been well investigated; however, we have previously reported that significant functional consequences in the auditory brainstem response (ABR) can also occur as a consequence of marginal iron deficiency (ID). As the ABR has widespread clinical use, we evaluated the ability of this electrophysiological method to characterize the threshold of tissue ID in rats by examining the relationship between markers of tissue ID and severity of ABR latency defects. To generate various levels of ID, female Long-Evans rats were exposed to diets containing sufficient, borderline, or deficient iron (Fe) concentrations throughout gestation and offspring lifetime. We measured hematological indices of whole body iron stores in dams and offspring to assess the degree of ID. Progression of AN ID in the offspring was measured as ferritin protein levels at different times during postnatal development to complement ABR functional measurements. The severity of ABR deficits correlated with the level of Fe restriction in each diet. The sufficient Fe diet did not induce AN ID and consequently did not show an impaired ABR latency response. The borderline Fe diet, which depleted AN Fe stores but did not cause systemic anemia resulted in significantly increased ABR latency isolated to Peak I.The low Fe diet, which induced anemia and growth retardation, significantly increased ABR latencies of Peaks I to IV. Our findings indicate that changes in the ABR could be related to various degrees of ID experienced throughout development.     

Auditory response in rats exposed to 2,450 MHz electromagnetic fields in a circularly polarized waveguide

Rats were exposed to 2,450-MHz pulsed microwave fields in a circularly polarized waveguide. The threshold incident energy density per pulse was about 1.5 to 3 microJ/cm2 over the range 1-10 microseconds. The corresponding whole-body averaged specific absorption of energy was 0.9 to 1.8 mJ/kg per pulse. The same response was evoked when the incident energy density or absorbed energy density per pulse was the same, regardless of the pulse widths.     

Auditory role of lateral trunk channels in cobitid fishes

In cobitid fishes the anterior part of the swimbladder is encapsulated by bone to varying extent. This might diminish the auditory sensitivity of these otophysine fishes by reducing the vibrations of the swimbladder wall in the sound field. However, according to prior studies the auditory thresholds of the cobitid Botia modesta is similar to that of other otophysine fishes. According to anatomical investigation B. modesta has a cranial encapsulation of the anterior part of the swimbladder (camera aerea Weberiana) as expected and in addition special channels stretching laterally from the swimbladder to the outer body wall. These lateral trunk channels are filled with fat and lymph. They form a muscle-free acoustic window beneath the skin, which could be demonstrated by measuring the auditory brainstem response at 400 Hz, 800 Hz, 1500 Hz, and 3000 Hz. Filling the lateral trunk channels with wettex (cotton/rayon staple) resulted in an increase of the auditory thresholds by 13.6–17.6 dB, indicating mechanical damping of the swimbladder. Our experiments demonstrate that the intact lateral trunk channels enhance the hearing sensitivity of cobitid fishes. Accepted: 15 December 1999     

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.     

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。     

Effects of Boat Engine Noise on the Auditory Sensitivity of the Fathead Minnow, Pimephales promelas

Fishes are constantly exposed to various sources of noise in their underwater acoustic environment. Many of these sounds are from anthropogenic sources, especially engines of boats. Noise generated from a small boat with a 55 horsepower outboard motor was played back to fathead minnows, Pimephales promelas, for 2 h at 142 dB (re: 1 Pa), and auditory thresholds were measured using the auditory brainstem response (ABR) technique. The results demonstrate that boat engine noise significantly elevate a fish's auditory threshold at 1 kHz (7.8 dB), 1.5 kHz (13.5 dB), and 2.0 kHz (10.5 dB), the most sensitive hearing range of this species. Such a short duration of noise exposure leads to significant changes in hearing capability, and implies that man-made noise generated from boat engines can have far reaching environmental impacts on fishes.     

生后早期听觉剥夺、经验改变大鼠听皮层NMDA受体NR2B蛋白表达

应用蛋白质印迹检测技术,研究早期听觉剥夺、经验对大鼠听皮层NMDA受体NR2B蛋白表达的影响.结果表明,听觉剥夺使生后14天龄组和28天龄组动物听皮层NR2B蛋白表达水平明显下降(P<0.05,P<0.01),听觉剥夺7天后再给予纯音暴露则又使NR2B表达水平明显提高(P<0.05),呈现双向调节趋势.听觉剥夺和纯音暴露对生后42天龄组大鼠听皮层NR2B表达不再产生明显调节作用(P>0.05).结果提示,在大鼠生后发育关键期,听觉剥夺、经验可改变听皮层NMDA受体NR2B蛋白表达水平.研究结果为研究感觉功能发育可塑性的机制提供了重要实验资料.     

Auditory brainstem responses in ground squirrels arousing from hibernation

Summary Auditory brainstem responses (ABRs) were recorded in ground squirrels (Citellus lateralis) arousing from hibernation. Squirrels implanted with recording screws to record ABRs, and a thermistor to record brain temperature, were placed in a cold room at 9 °C on a 2L:22D light-dark cycle. Hibernating animals were moved from the cold room and ABRs recorded during arousal. The responses showed a gradual development of all brainstem peaks.At low temperatures there were very long latencies to the peaks. The amplitudes of the peaks increased (with fluctuations) as brain temperature increased. The data indicate that neural generators on the brainstem auditory pathway were all activated early in arousal.These results do not support the hypothesis that successive peaks appear and grow in amplitude only after previous peaks are fully developed.     

Auditory and olfactory abilities of larvae of the Indo-Pacific coral trout Plectropomus leopardus (Lacepède) at settlement

Auditory and olfactory abilities of settlement-stage larvae of the coral trout Plectropomus leopardus (Pisces: Serranidae) were tested electrophysiologically to determine if these senses are sufficiently developed to aid larvae in detection of settlement habitats on coral reefs. Plectropomus leopardus larvae detected sounds from 100 to 2000 Hz with hearing most sensitive at the frequencies of 100, 200 and 600 Hz. The olfactory response of P. leopardus was similar for the two amino acids tested and for the water conditioned by conspecifics. Auditory and olfactory abilities of P. leopardus are well developed at settlement-stage, and apparently sufficient to detect auditory and olfactory cues from reefs.     

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.     

Hidden hearing loss is associated with loss of ribbon synapses of cochlea inner hair cells

The present study aimed to observe the changes in the cochlea ribbon synapses after repeated exposure to moderate-to-high intensity noise. Guinea pigs received 95 dB SPL white noise exposure 4 h a day for consecutive 7 days (we regarded it a medium-term and moderate-intensity noise, or MTMI noise). Animals were divided into four groups: Control, 1DPN (1-day post noise), 1WPN (1-week post noise), and 1MPN (1-month post noise). Auditory function analysis by auditory brainstem response (ABR) and compound action potential (CAP) recordings, as well as ribbon synapse morphological analyses by immunohistochemistry (Ctbp2 and PSD95 staining) were performed 1 day, 1 week, and 1 month after noise exposure. After MTMI noise exposure, the amplitudes of ABR I and III waves were suppressed. The CAP threshold was elevated, and CAP amplitude was reduced in the 1DPN group. No apparent changes in hair cell shape, arrangement, or number were observed, but the number of ribbon synapse was reduced. The 1WPN and 1MPN groups showed that part of ABR and CAP changes recovered, as well as the synapse number. The defects in cochlea auditory function and synapse changes were observed mainly in the high-frequency region. Together, repeated exposure in MTMI noise can cause hidden hearing loss (HHL), which is partially reversible after leaving the noise environment; and MTMI noise-induced HHL is associated with inner hair cell ribbon synapses.     

Characteristics of auditory brainstem responses in ground squirrels

Summary Auditory brainstem responses (ABRs) were characterized at 37 °C in ground squirrels (Citellus lateralis) which were implanted with recording screws to record ABRs, and a thermistor to record brain temperature. After two weeks ground squirrels were reanesthetized and tone pips and clicks were delivered through a TDH-49 headphone.Recorded ABRs were found to vary in a predictable manner as a function of stimulus frequency and intensity. At intensities above 50 dB SPL, ABRs could be recorded over the range tested (2–32 kHz). An 8 kHz tone pip was the best frequency for recording ABRs at the lowest stimulus intensities. Latencies decreased as stimulus frequencies increased from 4 kHz to 32 kHz.     

KILLER WHALE (ORCINUS ORCA) AUDITORY EVOKED POTENTIALS TO RHYTHMIC CLICKS

Temporal auditory mechanisms were measured in killer whales ( Orcinus orca ) by recording auditory evoked potentials (AEPs) to clicks. Clicks were presented at rates from 10/sec to 1,600/sec. At low rates, clicks evoked an AEP similar to the auditory brainstem response (ABR) of other odontocetes; however, peak latencies of the main waves were 3–3.7 msec longer than in bottlenose dolphins. Fourier analysis of the ABR showed a prominent peak at 300–400 Hz and a smaller one at 800–1,200 Hz. High-rate click presentation (more than 100/sec) evoked a rate-following response (RFR). The RFR amplitude depended little on rate up to 400/sec, decreased at higher rates and became undetectable at 1,120/sec. Fourier analysis showed that RFR fundamental amplitude dependence on frequency closely resembled the ABR spectrum. The fundamental could follow clicks to around 1,000/sec, although higher harmonics of lower rates could arise at frequencies as high as 1,200 Hz. Both RFR fundamental phase dependence on frequency and the response lag after a click train indicated an RFR group delay of around 7.5 msec. This corresponds to the latency of ABR waves PIII-NIV, which indicates the RFR originates as a rhythmic, overlapping ABR sequence. The data suggest the killer whale auditory system can follow high click rates, an ability that may have been selected for as a function of high-frequency hearing and the use of rapid clicks in echolocation.