Department of Human & Animal Physiology, Lomonosov Moscow State University, Leninskie Gory 1/12, 119991 Moscow, Russia.
Cells. 2019 Jul 22;8(7):762. doi: 10.3390/cells8070762.
The aim of this study was to compare the acute effects of thrombin and brain-derived neurotrophic factor (BDNF) on spontaneous miniature endplate potentials (MEPPs) and multiquantal evoked endplate potentials (EPPs) in mouse neuromuscular junctions (NMJs) of m. diaphragma and m. EDL. Intracellular microelectrode recordings of MEPPs and EPPs were used to evaluate the changes in acetylcholine (ACh) release in mature and newly-formed mouse NMJs. Thrombin (1 nM) increased the amplitude of MEPPs and EPPs by 25-30% in mature and newly-formed NMJs. This effect was due to an enhanced loading of synaptic vesicles with ACh and increase of ACh quantal size, since it was fully prevented by blocking of vesicular ACh transporter. It was also prevented by tropomyosin-related kinase B (TrkB) receptors inhibitor ANA12. Exogenous BDNF (1 nM) mimicked thrombin effect and increased the amplitude of MEPPs and EPPs by 25-30%. It required involvement of protein kinase A (PKA) and mitogen-activated protein kinase (MEK1/2)-mediated pathway, but not phospholipase C (PLC). Blocking A adenosine receptors by ZM241385 abolished the effect of BDNF, whereas additional stimulation of A receptors by CGS21680 increased MEPP amplitudes, which was prevented by MEK1/2 inhibitor U0126. At mature NMJs, BDNF enhanced MEPPs frequency by 30-40%. This effect was selectively prevented by inhibition of PLC, but not PKA or MEK1/2. It is suggested that interrelated effects of thrombin/BDNF in mature and newly-formed NMJs are realized via enhancement of vesicular ACh transport and quantal size increase. BDNF-induced potentiation of synaptic transmission involves the functional coupling between A receptor-dependent active PKA and neurotrophin-triggered MAPK pathway, as well as PLC-dependent increase in frequency of MEPPs.
本研究旨在比较凝血酶和脑源性神经营养因子（BDNF）对小鼠膈肌和 EDL 肌运动终板（NMJ）自发性微小终板电位（MEPPs）和多量子诱发终板电位（EPPs）的急性影响。通过细胞内微电极记录 MEPPs 和 EPPs，评估成熟和新形成的小鼠 NMJ 中乙酰胆碱（ACh）释放的变化。凝血酶（1 nM）使成熟和新形成的 NMJ 中的 MEPPs 和 EPPs 幅度增加 25-30%。这种作用是由于 ACh 囊泡的加载增强和 ACh 量子大小增加所致，因为其被囊泡 ACh 转运体阻断完全阻止。它也被 tropomyosin-related kinase B (TrkB) 受体抑制剂 ANA12 阻止。外源性 BDNF（1 nM）模拟凝血酶的作用，并使 MEPPs 和 EPPs 的幅度增加 25-30%。它需要涉及蛋白激酶 A（PKA）和丝裂原活化蛋白激酶（MEK1/2）介导的途径，而不是磷脂酶 C（PLC）。用 ZM241385 阻断 A 腺苷受体消除了 BDNF 的作用，而 CGS21680 对 A 受体的额外刺激增加了 MEPP 幅度，这被 MEK1/2 抑制剂 U0126 阻止。在成熟的 NMJ 中，BDNF 使 MEPPs 的频率增加 30-40%。这种作用被 PLC 抑制选择性地阻止，但不是 PKA 或 MEK1/2。这表明凝血酶/BDNF 在成熟和新形成的 NMJ 中的相互关联作用是通过增强囊泡 ACh 运输和量子大小增加来实现的。BDNF 诱导的突触传递增强涉及 A 受体依赖性活性 PKA 和神经营养因子触发的 MAPK 途径之间的功能偶联，以及 PLC 依赖性 MEPPs 频率增加。
