Kelley M S, Lurie D I, Rubel E W
Virginia Merrill Bloedel Hearing Research Center and Department of Otolaryngology-HNS, University of Washington, Seattle 98195, USA.
J Comp Neurol. 1997 Dec 22;389(3):469-83.
During development, removal of neuronal input can lead to profound changes in postsynaptic cells, including atrophy and cell death. In the chicken brainstem cochlear nucleus, the nucleus magnocellularis (NM), deprivation of auditory input via unilateral cochlea removal or silencing the eighth nerve with tetrodotoxin leads to a loss of 25-30% of the neurons and the atrophy of surviving neurons. One intracellular component that may be involved in both cell atrophy and cell death is the cytoskeleton. The degradation of the cytoskeleton following deafferentation could potentially lead to either atrophy or death of NM neurons. However, little is known regarding the role of neuronal input on the cytoskeletal structure of NM neurons and whether changes in the cytoskeleton are responsible for cell death following deafferentation. The present study examined whether changes in the cytoskeleton of NM neurons occurred following cochlea removal. Several components of the cytoskeleton were analyzed following unilateral afferent deprivation. Levels of immunostaining for tubulin, actin, and microtubule-associated protein 2 (MAP-2), and levels of beta-tubulin and beta-actin mRNAs were assessed in NM neurons following cochlea removal. Our results revealed that afferent deprivation results in a rapid decrease in immunostaining for all three cytoskeletal proteins examined. These decreases were observed as early as 3 hours after cochlea removal and persisted for up to 4 days. In addition, these changes occurred in all deafferented NM neurons at the early time points, indicating that both dying and surviving NM neurons undergo a similar change in their cytoskeletons. In contrast to the decreases in immunostaining, levels of beta-tubulin and beta-actin mRNAs were not noticeably altered by deafferentation. Our findings indicate that the cytoskeleton is altered or degraded following deafferentation but that this process is not regulated at the transcriptional level.
在发育过程中，神经元输入的去除可导致突触后细胞发生深刻变化，包括萎缩和细胞死亡。在鸡脑干细胞蜗神经核中，大细胞性核（NM），通过单侧切除耳蜗剥夺听觉输入或用河豚毒素使第八神经沉默，会导致25%-30%的神经元丧失以及存活神经元的萎缩。细胞骨架可能是参与细胞萎缩和细胞死亡的一种细胞内成分。去传入神经后细胞骨架的降解可能会导致NM神经元萎缩或死亡。然而，关于神经元输入对NM神经元细胞骨架结构的作用以及细胞骨架的变化是否是去传入神经后细胞死亡的原因，人们知之甚少。本研究检测了切除耳蜗后NM神经元的细胞骨架是否发生变化。在单侧传入神经剥夺后，对细胞骨架的几个成分进行了分析。在切除耳蜗后，评估了NM神经元中微管蛋白、肌动蛋白和微管相关蛋白2（MAP-2）的免疫染色水平以及β-微管蛋白和β-肌动蛋白mRNA的水平。我们的结果显示，传入神经剥夺导致所检测的所有三种细胞骨架蛋白的免疫染色迅速减少。这些减少在切除耳蜗后3小时就可观察到，并持续长达4天。此外，这些变化在早期时间点出现在所有去传入神经的NM神经元中，表明正在死亡和存活的NM神经元在其细胞骨架中都经历了类似的变化。与免疫染色的减少相反，β-微管蛋白和β-肌动蛋白mRNA的水平并未因去传入神经而明显改变。我们的研究结果表明，去传入神经后细胞骨架会发生改变或降解，但这一过程在转录水平上不受调控。
