Kuznetsova Marina S, Higgs Matthew H, Spain William J
Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98105, USA.
J Neurosci. 2008 Nov 12;28(46):11906-15. doi: 10.1523/JNEUROSCI.3827-08.2008.
Adaptation is commonly defined as a decrease in response to a constant stimulus. In the auditory system such adaptation is seen at multiple levels. However, the first-order central neurons of the interaural time difference detection circuit encode information in the timing of spikes rather than the overall firing rate. We investigated adaptation during in vitro whole-cell recordings from chick nucleus magnocellularis neurons. Injection of noisy, depolarizing current caused an increase in firing rate and a decrease in spike time precision that developed over approximately 20 s. This adaptation depends on sustained depolarization, is independent of firing, and is eliminated by alpha-dendrotoxin (0.1 microM), implicating slow inactivation of low-threshold voltage-activated K+ channels as its mechanism. This process may alter both firing rate and spike-timing precision of phase-locked inputs to coincidence detector neurons in nucleus laminaris and thereby adjust the precision of sound localization.
适应通常被定义为对持续刺激的反应减弱。在听觉系统中，这种适应在多个层面都能观察到。然而，双耳时间差检测电路的一级中枢神经元是通过尖峰的时间来编码信息，而不是整体的放电率。我们在雏鸡大细胞神经核神经元的体外全细胞记录过程中研究了适应现象。注入有噪声的去极化电流会导致放电率增加以及尖峰时间精度下降，这种变化在大约20秒内逐渐形成。这种适应依赖于持续的去极化，与放电无关，并且可被α-树突毒素（0.1微摩尔）消除，这表明低阈值电压激活的钾离子通道的缓慢失活是其机制。这个过程可能会改变向层状神经核中重合检测器神经元的锁相输入的放电率和尖峰时间精度，从而调整声音定位的精度。
