Maturation of glycinergic inhibition in the gerbil medial superior olive after hearing onset
Maturation of glycinergic inhibition in the gerbil medial superior olive after hearing onset
复制标题
DOI：
10.1113/jphysiol.2005.094763
复制
发表时间：
2005-10-15
影响因子：
5.5
通讯作者：
Koch, U
中科院分区：
文献类型：
--
作者：
Magnusson, AK;Kapfer, C;Koch, U
内侧上橄榄（MSO）的神经元是大脑中时间最敏感的神经元。它们以微秒级的分辨率响应声音到达两耳的时间差；这些耳间时间差用于定位低频声音。除了来自每只耳朵的兴奋性输入之外，MSO 神经元还接收双耳甘氨酸投射，这在声音定位处理中起着关键作用。最近，研究表明，在听力出现后，MSO 的甘氨酸输入会经历依赖于经验的结构重组。为了探索细胞水平上声音定位发展过程中抑制的成熟，通过全细胞膜片钳记录测量了沙鼠MSO主细胞出生后（P）天P12-P25的甘氨酸电流和电位。突触甘氨酸电流在听力出现后加速到快速衰减动力学（类似于 2 ms）和上升时间（类似于 0.4 ms），在 P17 左右达到成熟。由于微型甘氨酸电流的动力学不随年龄而变化，因此较高程度的递质释放同步性可能是影响动力学加速的潜在机制。在同一时期，突触甘氨酸电位加速了四倍，这主要是由于输入阻力显着降低的结果。根据甘氨酸输入的重组，诱发的峰值电导下降了两倍以上，并且听力出现后微型事件的频率下降了三倍。在全向噪音中饲养的动物中不存在这些年龄依赖性的变化，这表明经验依赖性的突触输入修剪对于 MSO 功能抑制的成熟很重要。总而言之，MSO 中甘氨酸抑制的这些显着的发育调整很可能反映了在声音定位行为成熟过程中以极高的时间精度和保真度改进听觉线索编码的适应。
The neurones of the medial superior olive (MSO) are the most temporally sensitive neurones in the brain. They respond to the arrival time difference of sound at the two ears with a microsecond resolution; these interaural time differences are used to localize low-frequency sounds. In addition to the excitatory inputs from each ear, the MSO neurones also receive binaural glycinergic projections, which have a critical role in sound localization processing. Recently, it was shown that the glycinergic input to the MSO undergoes an experience-dependent structural reorganization after hearing onset. To explore the maturation of inhibition during the development of sound localization on a cellular level, glycinergic currents and potentials were measured in gerbil MSO principal cells from postnatal (P) day P12-P25 by whole-cell patch-clamp recordings. The synaptic glycinergic currents accelerated to rapid decay kinetics (similar to 2 ms) and rise times (similar to 0.4 ms) after hearing onset, reaching maturity around P17. Since the kinetics of miniature glycinergic currents did not change with age, it is likely that a higher degree of transmitter release synchrony is the underlying mechanism influencing the acceleration of the kinetics. During the same period, the synaptic glycinergic potentials accelerated four-fold, largely as a result of a prominent decrease in input resistance. In accordance with a reorganization of the glycinergic inputs, the evoked peak conductances decreased more than two-fold, together with a three-fold reduction in the frequency of miniature events after hearing onset. These age-dependent changes were absent in animals that had been reared in omni-directional noise, indicating that an experience-dependent pruning of synaptic inputs is important for the maturation of functional inhibition in the MSO. Taken together, these striking developmental adjustments of the glycinergic inhibition in the MSO most probably reflect an adaptation to improve the encoding of auditory cues with great temporal precision and fidelity during the maturation of sound localization behaviour.