Afferent influences on brain stem auditory nuclei of the chicken: cessation of amino acid incorporation as an antecedent to age-dependent transneuronal degeneration.
Afferent influences on brain stem auditory nuclei of the chicken: cessation of amino acid incorporation as an antecedent to age-dependent transneuronal degeneration.
复制标题
对鸡脑干听觉核的传入影响：停止氨基酸掺入是年龄依赖性跨神经元变性的先决条件。
DOI：
10.1002/cne.902310308
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Rubel,EW
中科院分区：
文献类型：
--
作者：
Steward,O;Rubel,EW
以往的研究表明，鸟类听觉系统的外周受体（耳蜗）的去除导致听觉中继神经元的跨神经元变性的大细胞核（NM）的脑干。可在12小时内观察到的退化的早期表现是RNA的组织化学染色（尼氏染色）的减少;这种减少可能反映NM神经元内蛋白质合成活性的改变。本研究通过确定耳蜗切除是否导致靶神经元中蛋白质前体的改变并入来评估这种可能性，所述靶神经元表现出跨神经元变性，如果是，那么变化出现的时间有多早。在17只10日龄鸡和2只66周龄成熟鸡中单侧切除耳蜗，并在耳蜗切除后0.5、1.5、3、6、12和24小时评价NM神经元中蛋白前体的掺入。每只鸡接受静脉注射3 H亮氨酸，并在注射前体后存活30分钟。然后准备大脑进行放射自显影。通过计数覆盖在每个细胞体上的颗粒和确定颗粒密度/μ m2的神经元横截面积来确定NM中神经元的掺入程度。我们发现，突触输入被沉默的听觉中继神经元在耳蜗移除后30分钟内表现出蛋白质合成的显著减少;亮氨酸掺入减少了约50%。在取出耳蜗后3至24小时处死的雏鸡中，尽管其邻居的重标记和大脑对侧的所有NM神经元的重标记，但一些神经元（约1/3）完全未被标记。剩余的神经元表现出约15%的减少，与对侧（对照）NM中的细胞相比，在掺入。尽管在所有存活时间段掺入量明显减少，但直到耳蜗取出后6小时，尼氏染色才持续减少。有没有变化，蛋白质前体掺入成年鸟类的耳蜗，这是符合相对缺乏transneuronal变性后，在成熟时去除耳蜗。结果表明，在年轻动物中，靶神经元内的蛋白质代谢可能通过活动相关事件进行非常快速的跨神经元调节。
Previous studies of the avian auditory system have revealed that removal of the peripheral receptor (the cochlea) leads to a transneuronal degeneration of auditory relay neurons in nucleus magnocellularis (NM) of the brain stem. An early manifestation of the degeneration which can be observed within 12 hours is a decrease of histochemical staining for RNA (Nissl staining); such a decrease could relect an alteration in protein synthetic activity within the NM neurons. The present study evaluates this possibility by determining whether the cochlea removal led to an alteration incorporation of protein precursors in the target neurons which exhibit transneuronal degeneration and if so, how early the changes appeared. The cochlea was removed unilaterally in seventeen 10‐day‐old chicks and two 66‐week‐old mature chickens, and incorporation of protein precursors was evaluated in the neurons of NM at 0.5, 1.5, 3, 6, 12, and 24 hours following the cochlea removal. Each chick received an intravenous injection of 3H leucine, and was allowed to survive for 30 minutes after the injection of precursor. The brains were then prepared for autoradiography. The extent of incorporation by neurons in NM was determined by counting grains overlying each cell body and determining grain density/μm2of neuron cross‐sectional area.We found that auditory relay neurons whose synaptic inputs have been silenced exhibit dramatic decreases in protein synthesis within 30 minutes after removal of the cochlea; leucine incorporation was reduced by about 50%. In chicks sacrificed 3 to 24 hours after removal of the cochlea, some neurons (about 1/3) were entirely unlabeled despite heavy labeling of their neighbors and heavy labeling of all NM neurons on the opposite side of the brain. The remaining neurons exhibited about a 15% reduction in incorporation in comparison with the cells in the contralateral (control) NM. While the decreases in incorporation were apparent at all survival intervals, there was no consistent decrease in Nissl staining until 6 hours after cochlea removal. There were no changes in protein precursor incorporation following removal of the cochlea in adult birds, a result which is in keeping with the relative absence of transneuronal degeneration following removal of the cochlea at maturity. The results suggest a very rapid transneuronal regulation of protein metabolism within target neurons in young animals, perhaps by activity‐related events.