Neurophysiological Study on Onset Mechanism of Ear Symptoms in Temporomandibular Disorders

颞下颌关节紊乱病患者经常出现耳鸣、耳痛等耳部症状。本实验采用戊巴比妥钠（25 mg/kg）麻醉豚鼠，通过记录听性脑干反应（ABR），探讨口面区感觉输入对听神经传导的影响。将动物固定在立体定位仪上，并将带有小扬声器的耳塞插入右外耳道。从扬声器提供用于诱发ABR的声刺激作为咔哒声（频率：9 Hz）。将ABR记录电极分别贴于正中顶点（Cz）和左右乳突（A1，A2）皮下。将参比电极置于枕骨。在实验开始时，声音刺激的声压为100 dB，然后降低5 dB，直到ABR中的所有反应都减弱。ABR各波数 关于我们 方法：对10 0只SD大鼠进行100次平均声压水平和ABR平均波形的测量，并对口面区进行单次和连续矩形恒流脉冲（持续时间：lmec）电刺激。皮下注射辣椒素（100 mg/10 μl）作为化学性疼痛刺激。分别对犬牙周膜、口腔粘膜和咬肌进行电刺激和化学刺激，刺激前记录ABR作为对照。在注射30 μ1辣椒素后也记录了ABR。刺激前，ABR记录到的波I、II、III、IV、V、VI 6种反应的潜伏期均明显缩短，且随声压的降低，潜伏期缩短。化学刺激后ABR反应无明显变化。施加电刺激后的结果与化学刺激的结果相同。这些结果表明，短暂的伤害性刺激并不引起颞下颌关节紊乱病患者的耳功能障碍，如耳部症状。因此，有必要进行慢性模型动物实验，通过人工错牙合的方法建立颞下颌关节紊乱病的动物模型。实验中应注意观察口面部症状与耳功能障碍的关系。少

Ear symptoms, such as tinnitus and earache, are observed frequently in the patients of temporomandibular disorders. The aim of this study was to evaluate the influence of sensory inputs from the orofacial area on the auditory neural conduction by means of recording auditory brainstem response (ABR).Guinea-pigs were anesthetized with pentobarbital sodium (25mg/kg) intraperitoneally and used for the experiment. Animals were mounted on the stereotaxic apparatus and were inserted a earbur with a small speaker into right external auditory canal. Sonic stimulation for eliciting ABR was supplied as click sound (frequency : 9 Hz) from the speaker. Recording electrodes of ABR were attached beneath the skin at the median vertex (Cz) and the Ieft and right mastoid (Al, A2). A reference electrode was placed at occiput. Sound pressure of the sonic stimuli was 100 dB at the beginnings of the experiment and then reduced by 5 dB until all of the responses in ABR were diminished. Waves of ABR at each s … More ound pressure level were averaged 100 times and averaged waveforms of ABR were estimated.Single and train rectangle constant current pulses (duration : lmec) were applied for electrical stimulation to the orofacial regions. Subcutaneus injection of Capsicin (100mg/10 μl) was used as chemical pain stimulation. Electrical and chemical stimulation were applied to the periodontal ligaments of canine, oral mucosa and masseter muscles.Before applying stimulation, ABR was recorded as a control. ABRs were also recorded after injection of 30 μ1 of capsicin. Before stimulation, six responses ( Wave I, II, III, IV, V, VI) were obviously obserbed in recorded ABR and the latency of these responses were reduced as reducing the sound pressure. After applying the chemical stimllation, the responses of ABR were not changed. The results after applying the electrical stimulation were the same as the results of the chemical stimulation. Namely, transient electrical or chemical pain stimulation could not induce the change of ABR.These results suggest that transient noxious stimulation to the orofacial region does not cause the ear dysfunction such as ear symptoms observed in temporomandibular disorders patients. Therefore, it suggests the need of chronic model animal experiment, in which model animal with temporomandibular disorders would be made by artificial malocclusion. The relation of orofacial symptoms and ear dysfunction should be observed in thoese experiments. Less