Brew H M, Forsythe I D
Department of Cell Physiology and Pharmacology, University of Leicester, United Kingdom.
J Neurosci. 1995 Dec;15(12):8011-22. doi: 10.1523/JNEUROSCI.15-12-08011.1995.
The medial nucleus of the trapezoid body (MNTB) relays auditory information important for sound source localization. MNTB neurons faithfully preserve the temporal patterning of action potentials (APs) occurring in their single giant input synapse, even at high frequencies. The aim of this work was to examine the postsynaptic potassium conductances that shape the transfer of auditory information across this glutamatergic synapse. We used whole cell patch techniques to record from MNTB neurons in thin slices of rat brainstem. Two types of potassium conductance were found which had a strong influence on an MNTB neuron's postsynaptic response. A small low voltage threshold current, Id, limited the response during each EPSP to a single brief AP. Id was specifically blocked by dendrotoxin (DTX), resulting in additional APs during the tail end of the EPSP. Thus DTX degraded the temporal fidelity of synaptic transmission, since one presynaptic AP then led to several postsynaptic APs. A second conductance was a fast delayed rectifier with a high voltage activation threshold, that rapidly repolarised APs and thus facilitated high frequency AP responses. Together, these two conductances allow high frequency auditory information to be passed accurately across the MNTB relay synapse and separately, such conductances may perform analogous functions elsewhere in the nervous system.
梯形体内侧核（MNTB）传递对声源定位很重要的听觉信息。MNTB神经元能忠实地保留在其单个巨大输入突触中发生的动作电位（AP）的时间模式，即使在高频情况下也是如此。这项工作的目的是研究塑造听觉信息通过这个谷氨酸能突触传递的突触后钾离子电导。我们使用全细胞膜片钳技术在大鼠脑干薄片中的MNTB神经元上进行记录。发现了两种对MNTB神经元突触后反应有强烈影响的钾离子电导。一种小的低电压阈值电流Id，将每个兴奋性突触后电位（EPSP）期间的反应限制为单个短暂的AP。Id被树突毒素（DTX）特异性阻断，导致在EPSP的尾端出现额外的AP。因此，DTX降低了突触传递的时间保真度，因为一个突触前AP随后会导致几个突触后AP。第二种电导是具有高电压激活阈值的快速延迟整流器，它能迅速使AP复极化，从而促进高频AP反应。这两种电导共同作用，使高频听觉信息能够准确地通过MNTB中继突触传递，并且在其他地方，这样的电导可能在神经系统中执行类似的功能。
