Animal Physiology Group, Department of Biology, University of Kaiserslautern Kaiserslautern, Germany.
Chair for Applied Mathematical Statistics, Department of Mathematics, University of Kaiserslautern Kaiserslautern, Germany ; Center for Mathematical and Computational Modeling, University of Kaiserslautern Kaiserslautern, Germany.
Front Neural Circuits. 2014 Mar 10;8:14. doi: 10.3389/fncir.2014.00014. eCollection 2014.
Short-term plasticity plays a key role in synaptic transmission and has been extensively investigated for excitatory synapses. Much less is known about inhibitory synapses. Here we analyze the performance of glycinergic connections between the medial nucleus of the trapezoid body (MNTB) and the lateral superior olive (LSO) in the auditory brainstem, where high spike rates as well as fast and precise neurotransmission are hallmarks. Analysis was performed in acute mouse slices shortly after hearing onset (postnatal day (P)11) and 8 days later (P19). Stimulation was done at 37°C with 1-400 Hz for 40 s. Moreover, in a novel approach named marathon experiments, a very prolonged stimulation protocol was employed, comprising 10 trials of 1-min challenge and 1-min recovery periods at 50 and 1 Hz, respectively, thus lasting up to 20 min and amounting to >30,000 stimulus pulses. IPSC peak amplitudes displayed short-term depression (STD) and synaptic attenuation in a frequency-dependent manner. No facilitation was observed. STD in the MNTB-LSO connections was less pronounced than reported in the upstream calyx of Held-MNTB connections. At P11, the STD level and the failure rate were slightly lower within the ms-to-s range than at P19. During prolonged stimulation periods lasting 40 s, P19 connections sustained virtually failure-free transmission up to frequencies of 100 Hz, whereas P11 connections did so only up to 50 Hz. In marathon experiments, P11 synapses recuperated reproducibly from synaptic attenuation during all recovery periods, demonstrating a robust synaptic machinery at hearing onset. At 26°C, transmission was severely impaired and comprised abnormally high amplitudes after minutes of silence, indicative of imprecisely regulated vesicle pools. Our study takes a fresh look at synaptic plasticity and stability by extending conventional stimulus periods in the ms-to-s range to minutes. It also provides a framework for future analyses of synaptic plasticity.
短期可塑性在突触传递中起着关键作用，并且已经在兴奋性突触上进行了广泛的研究。关于抑制性突触的了解要少得多。在这里，我们分析了梯形体中髓质（MNTB）和外侧上橄榄（LSO）之间的甘氨酸能连接在听觉脑干中的性能，其中高尖峰率以及快速和精确的神经传递是其特征。分析是在出生后第 11 天（P11）和 8 天后（P19）在急性小鼠切片中进行的。刺激在 37°C 下进行，频率为 1-400 Hz，持续 40 s。此外，在一种名为马拉松实验的新方法中，采用了非常长时间的刺激方案，包括 10 次 1 分钟的挑战和 1 分钟的恢复期，分别为 50 和 1 Hz，因此持续时间长达 20 分钟，刺激脉冲超过 30,000 个。 IPSC 峰值幅度表现出短期抑郁（STD）和频率依赖性的突触衰减。未观察到易化作用。在 MNTB-LSO 连接中，STD 程度比在上游 Held-MNTB 连接的 calyx 中报道的要小。在 P11 时，STD 水平和故障率在 ms 到 s 的范围内比 P19 略低。在长达 40 s 的长时间刺激期间，P19 连接在 100 Hz 以下的频率下几乎无故障地保持传输，而 P11 连接仅在 50 Hz 以下保持传输。在马拉松实验中，P11 突触在所有恢复期内都能从突触衰减中重复恢复，这表明在听力开始时具有强大的突触机制。在 26°C 时，传输严重受损，在几分钟的沉默后包含异常高的幅度，表明囊泡池调节不精确。我们的研究通过将传统的 ms 到 s 范围内的刺激时间延长至几分钟，对突触可塑性和稳定性进行了新的研究。它还为未来的突触可塑性分析提供了框架。
