Xie D H, Henson O W
Department of Cell Biology and Anatomy, University of North Carolina, Chapel Hill 27599, USA.
Hear Res. 1998 Oct;124(1-2):60-8. doi: 10.1016/s0378-5955(98)00122-1.
The activity of the medial olivocochlear (MOC) efferent system in mustached bats, Pteronotus p. parnellii, was studied by monitoring changes in the mechanical properties of the cochlea. The changing properties were expressed by the decay time (DT) of cochlear microphonic potentials produced by transient-induced ringing (Henson et al., 1995). Tape-recorded roost noise (biosonar and communication sounds) produced sudden, marked decreases in DT when presented to the contralateral ear of animals adapted to the quiet. When the animals were first removed from their roosts the DT was relatively short (1.2-1.5 ms) but this gradually lengthened by about 0.5-1.0 ms as they rested in a quiet chamber. The time required to reach a stable, quiet-adapted state after noise exposure varied with SPL and exposure time; in many experiments recovery was in the range of 90-120 min. When quiet-adapted bats were isolated and allowed to fly and echolocate for 20 min, the DTs measured within a few minutes after the end of the flight were also short and only slowly returned to longer preflight values. The administration of a single dose of gentamicin, which blocks MOC effects, greatly reduced the amount of suppression (damping) observed after periods of noise and echolocation sound exposure. We conclude that tonic MOC activity is induced by the natural vocalizations and roost noise and this activity probably regulates and protects the highly resonant cochlear partition.
通过监测耳蜗力学特性的变化，研究了髯蝠（Pteronotus p. parnellii）内侧橄榄耳蜗（MOC）传出系统的活动。变化的特性通过瞬态诱发振铃产生的耳蜗微音器电位的衰减时间（DT）来表示（Henson等人，1995）。当将磁带记录的栖息处噪声（生物声纳和交流声音）呈现给适应安静环境的动物的对侧耳朵时，DT会突然显著下降。当动物刚从栖息处移出时，DT相对较短（1.2 - 1.5毫秒），但当它们在安静的房间休息时，DT会逐渐延长约0.5 - 1.0毫秒。噪声暴露后达到稳定的安静适应状态所需的时间随声压级和暴露时间而变化；在许多实验中，恢复时间在90 - 120分钟范围内。当将适应安静的蝙蝠隔离并让其飞行和回声定位20分钟后，在飞行结束后几分钟内测量的DT也较短，并且仅缓慢恢复到飞行前的较长值。单次给予阻断MOC效应的庆大霉素，大大降低了在噪声和回声定位声音暴露一段时间后观察到的抑制（阻尼）量。我们得出结论，自然发声和栖息处噪声可诱导持续性MOC活动，并且这种活动可能调节和保护高度共振的耳蜗隔。
