Sziklai I, He D Z, Dallos P
Department of Communication Sciences and Disorders, Physiology Northwestern University, Evanston, IL 60208, USA.
Hear Res. 1996 May;95(1-2):87-99. doi: 10.1016/0378-5955(96)00026-3.
Outer hair cells (OHC) from high- and low-frequency regions were separately isolated from guinea pig cochleas. The cells were inserted with their ciliary pole first into a partitioning microchamber so that only 20-50% of the cell length was excluded. Somatic length changes due to transcellular electrical stimulation were measured at the cuticular plate in the inserted portion of the cells. Transfer curves of electromotility of the OHCs were obtained by both a series of brief (2.5 ms) and longer (30 ms) square pulses with opposite polarity and linearly increasing size from 40 to 280 mV in both negative and positive directions. Alterations in the transient and steady-state electromotility transfer curves were examined by application of acetylcholine (ACh) and gamma-aminobutyric acid (GABA) to the synaptic pole. ACh, in the concentration range of 10-30 microM, evoked a significant magnitude and gain increase of electromotility in both transient and steady-state responses without a measurable shift in the operating point of the displacement-voltage transfer curve. A tonotopic response magnitude difference is found for ACh challenge. Basal turn OHCs responded with greater magnitude increase (+90% increase from control) than apical turn OHCs (+40%). GABA exerted an opposite effect, again in a location-dependent manner. Magnitude response decreased about 30% for long cells and 14% for short ones. Atropin, a muscarinic receptor antagonist, completely blocked the increase in electromotility response due to ACh. However, D-tubocurarine, a nicorinic receptor antagonist, while not blocking the ACh effect, altered the cell's apparent operating point. Bicuculline methiodide, a GABAA-receptor antagonist, completely arrested GABA influences on the electromotility response. These results suggest that both ACh and GABA can change the electromotile activity of OHCs, in a tonotopically biased manner. ACh challenge evokes greater magnitude responses in basal turn OHCs, whereas GABA induces greater motility response decrease in apical turn OHCs. The control of the gain and magnitude of electromotility by the transmitter substances appear to involve at least two mechanisms. One is probably related to conformational changes of the voltage-to-movement converter molecules and a change in their number in an effective operational pool, the other operates via changing the electrical resistance of the basolateral cell membrane.
从豚鼠耳蜗中分别分离出高频和低频区域的外毛细胞（OHC）。将细胞的纤毛极先插入分隔微腔中，使得只有20 - 50%的细胞长度被排除在外。在细胞插入部分的角质板处测量跨细胞电刺激引起的体细胞长度变化。通过一系列短暂（2.5毫秒）和较长（30毫秒）的方波脉冲获得OHC的电运动传递曲线，脉冲具有相反的极性，且在正负方向上从40到280毫伏线性增加幅度。通过将乙酰胆碱（ACh）和γ-氨基丁酸（GABA）施加到突触极来检查瞬态和稳态电运动传递曲线的变化。在10 - 30微摩尔浓度范围内，ACh在瞬态和稳态反应中均引起电运动的显著幅度和增益增加，而位移 - 电压传递曲线的工作点没有可测量的偏移。发现ACh刺激存在音调定位反应幅度差异。基底转OHC的反应幅度增加更大（比对照增加90%），而顶转OHC的增加幅度为40%。GABA产生相反的效果，同样以位置依赖的方式。长细胞的幅度反应降低约30%，短细胞降低14%。毒蕈碱受体拮抗剂阿托品完全阻断了由于ACh引起的电运动反应增加。然而，烟碱受体拮抗剂筒箭毒碱虽然没有阻断ACh的作用，但改变了细胞的表观工作点。GABAA受体拮抗剂甲基荷包牡丹碱完全阻止了GABA对电运动反应的影响。这些结果表明，ACh和GABA都可以以音调定位偏向的方式改变OHC的电运动活性。ACh刺激在基底转OHC中引起更大的幅度反应，而GABA在顶转OHC中诱导更大的运动反应降低。递质物质对电运动增益和幅度的控制似乎涉及至少两种机制。一种可能与电压 - 运动转换分子的构象变化及其在有效操作库中的数量变化有关，另一种通过改变基底外侧细胞膜的电阻起作用。
