Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
J Neurophysiol. 2013 Jun;109(12):2866-82. doi: 10.1152/jn.00021.2013. Epub 2013 Mar 27.
The development of auditory temporal processing is important for processing complex sounds as well as for acquiring reading and language skills. Neuronal properties and sound processing change dramatically in auditory cortex neurons after the onset of hearing. However, the development of the auditory thalamus or medial geniculate body (MGB) has not been well studied over this critical time window. Since synaptic inhibition has been shown to be crucial for auditory temporal processing, this study examined the development of a feedforward, GABAergic connection to the MGB from the inferior colliculus (IC), which is also the source of sensory glutamatergic inputs to the MGB. IC-MGB inhibition was studied using whole cell patch-clamp recordings from rat brain slices in current-clamp and voltage-clamp modes at three age groups: a prehearing group [postnatal day (P)7-P9], an immediate posthearing group (P15-P17), and a juvenile group (P22-P32) whose neuronal properties are largely mature. Membrane properties matured substantially across the ages studied. GABAA and GABAB inhibitory postsynaptic potentials were present at all ages and were similar in amplitude. Inhibitory postsynaptic potentials became faster to single shocks, showed less depression to train stimuli at 5 and 10 Hz, and were overall more efficacious in controlling excitability with age. Overall, IC-MGB inhibition becomes faster and more precise during a time period of rapid changes across the auditory system due to the codevelopment of membrane properties and synaptic properties.
听觉时间处理的发展对于处理复杂声音以及获取阅读和语言技能非常重要。在听觉开始后，听觉皮层神经元的神经元特性和声音处理发生了巨大变化。然而，在这个关键的时间窗口内，听觉丘脑或内侧膝状体（MGB）的发育并没有得到很好的研究。由于已经表明突触抑制对于听觉时间处理至关重要，因此本研究检查了从下丘（IC）到 MGB 的前馈 GABA 能连接的发育，IC 也是 MGB 的感觉谷氨酸能输入的来源。使用电流钳和电压钳模式在三个年龄组（P7-P9 的预听组、P15-P17 的即时听后组和 P22-P32 的幼年组）的大鼠脑切片中进行全细胞膜片钳记录，研究了 IC-MGB 抑制。在所有研究的年龄中都存在 GABAA 和 GABAB 抑制性突触后电位，并且幅度相似。抑制性突触后电位对单刺激的反应更快，对 5 和 10 Hz 的训练刺激的抑制作用较小，并且随着年龄的增长，对兴奋性的控制效果总体上更为有效。总体而言，由于膜特性和突触特性的共同发育，IC-MGB 抑制在听觉系统快速变化的时间段内变得更快、更精确。
