Cazals Y, Aran J M, Hawkins J E
Hear Res. 1980 Mar;2(2):95-109. doi: 10.1016/0378-5955(80)90031-3.
Thresholds of the auditory nerve compound action potential (CAP) responses to filtered clicks from 0.5 to 40 kHz, defining a CAP frequency threshold curve, have been determined in the same guinea pigs: (1) in acute conditions, the animal still anesthetized at the end of the operation for permanent implantation of a round-window electrode, and (2) several days later in the implanted awake and unrestrained animal. The results show higher CAP thresholds for high frequencies in acute conditions as compared to chronic recordings. This difference appears above about 12.5 kHz and increases progressively to around 40 dB at 40 kHz. Similar effects, although somewhat less pronounced, were observed during anesthesia alone in already implanted guinea pigs. Thes observations could explain the discrepancies which appear between electrophysiological thresholds, acutely recorded either from single fibers or whole-nerve responses, and behavioral audiograms. Moreover, in the accurate evaluation of the cochlea, slight impairments may be masked by this phenomenon as illustrated in guinea pigs treated with low doses of ototoxic antibiotic.
在同一批豚鼠中测定了听神经复合动作电位（CAP）对0.5至40kHz滤波短声反应的阈值，从而确定了一条CAP频率阈值曲线：（1）在急性条件下，即在手术结束时动物仍处于麻醉状态，以便永久植入圆窗电极；（2）几天后在植入电极的清醒且不受束缚的动物中进行测定。结果显示，与慢性记录相比，急性条件下高频的CAP阈值更高。这种差异出现在约12.5kHz以上，并在40kHz时逐渐增加到约40dB。在已植入电极的豚鼠单独麻醉期间也观察到了类似的效应，尽管不太明显。这些观察结果可以解释在急性记录的单纤维或全神经反应的电生理阈值与行为听力图之间出现的差异。此外，在耳蜗的精确评估中，这种现象可能会掩盖轻微的损伤，如在用低剂量耳毒性抗生素治疗的豚鼠中所示。
