Hernández Rosendo G, Silva-Hucha Silvia, Morcuende Sara, de la Cruz Rosa R, Pastor Angel M, Benítez-Temiño Beatriz
Departamento de Fisiología, Facultad de Biología, Universidad de SevillaSevilla, Spain.
Front Neurosci. 2017 Jul 11;11:399. doi: 10.3389/fnins.2017.00399. eCollection 2017.
Extraocular motoneurons resist degeneration in diseases such as amyotrophic lateral sclerosis. The main objective of the present work was to characterize the presence of neurotrophins in extraocular motoneurons and muscles of the adult rat. We also compared these results with those obtained from other cranial motor systems, such as facial and hypoglossal, which indeed suffer neurodegeneration. Immunocytochemical analysis was used to describe the expression of nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3 in oculomotor, trochlear, abducens, facial, and hypoglossal nuclei of adult rats, and Western blots were used to describe the presence of neurotrophins in extraocular, facial (buccinator), and tongue muscles, which are innervated by the above-mentioned motoneurons. In brainstem samples, brain-derived neurotrophic factor was present both in extraocular and facial motoneuron somata, and to a lesser degree, in hypoglossal motoneurons. Neurotrophin-3 was present in extraocular motor nuclei, while facial and hypoglossal motoneurons were almost devoid of this protein. Finally, nerve growth factor was not present in the soma of any group of motoneurons, although it was present in dendrites of motoneurons located in the neuropil. Neuropil optical density levels were higher in extraocular motoneuron nuclei when compared with facial and hypoglossal nuclei. Neurotrophins could be originated in target muscles, since Western blot analyses revealed the presence of the three molecules in all sampled muscles, to a larger extent in extraocular muscles when compared with facial and tongue muscles. We suggest that the different neurotrophin availability could be related to the particular resistance of extraocular motoneurons to neurodegeneration.
眼外运动神经元在诸如肌萎缩侧索硬化等疾病中能抵抗退化。本研究的主要目的是确定成年大鼠眼外运动神经元和肌肉中神经营养因子的存在情况。我们还将这些结果与从其他确实会发生神经退行性变的颅神经运动系统（如面神经和舌下神经）所获得的结果进行了比较。免疫细胞化学分析用于描述成年大鼠动眼神经核、滑车神经核、展神经核、面神经核和舌下神经核中神经生长因子、脑源性神经营养因子和神经营养素-3的表达情况，蛋白质免疫印迹法用于描述上述运动神经元所支配的眼外肌、面部（颊肌）和舌肌中神经营养因子的存在情况。在脑干样本中，脑源性神经营养因子存在于眼外运动神经元和面部运动神经元的胞体中，而在舌下运动神经元中的含量较少。神经营养素-3存在于眼外运动核中，而面部和舌下运动神经元几乎不含这种蛋白质。最后，尽管在位于神经毡的运动神经元树突中存在神经生长因子，但在任何一组运动神经元的胞体中均未检测到。与面神经核和舌下神经核相比，眼外运动神经元核中的神经毡光密度水平更高。神经营养因子可能起源于靶肌肉，因为蛋白质免疫印迹分析显示，在所有采样肌肉中均存在这三种分子，与面部肌肉和舌肌相比，眼外肌中的含量更高。我们认为，不同的神经营养因子可用性可能与眼外运动神经元对神经退行性变的特殊抵抗力有关。
