BLOCKADE OF ELECTRICAL-ACTIVITY PROMOTES THE DEATH OF MAMMALIAN RETINAL GANGLION-CELLS IN CULTURE
BLOCKADE OF ELECTRICAL-ACTIVITY PROMOTES THE DEATH OF MAMMALIAN RETINAL GANGLION-CELLS IN CULTURE
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DOI：
10.1073/pnas.83.24.9774
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发表时间：
1986-12-01
影响因子：
11.1
通讯作者：
LIPTON, SA
中科院分区：
文献类型：
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作者：
LIPTON, SA
在出生后的前2周，哺乳动物视网膜中高达50%的神经节细胞通常死亡。自然细胞死亡可能由几个因素引起，并且电活动已被提出作为一个关键因素。最近在体内使用眼内注射河豚毒素（TTX）的实验表明，从两个眼睛的神经节细胞之间的生存竞争是由它们的神经元活动的程度介导的。此外，神经节细胞的传入活动水平被认为是决定其存活的重要变量。为了研究由活动改变引起的细胞死亡的机制，我研究了TTX（阻断钠通道，从而阻断动作电位）或低钙/高镁（阻断递质释放，从而阻断突触活动）对体外单个神经元的电阻断作用。为此目的，鉴定的视网膜神经节细胞（RGC）从出生后的大鼠保持在文化。与之前的体内实验不同，这种方法允许控制每种药剂的精确浓度，并记录RGC的电活动。在来自出生后第2-10天（P2-10）的动物的培养物中，1 μ M TTX或0.2mM Ca/20 mM Mg导致约50%的RGC死亡，这代表那些已经显示出自发电活性的细胞，但不影响缺乏活性的RGC。然而，这些药物对P11-13动物中具有自发活动的RGC的死亡没有影响。这些发现表明，在发育的关键时期，神经元变得依赖于电活动，这种活动的停止可能导致它们的死亡。此外，从缺乏TTX的培养物中收集的条件培养基拯救了大部分经TTX处理的RGC免于死亡。因此，生存的关键因素可能代表与活动水平相关的营养因子的调节，而不是电活动本身。由于在体内，自然细胞死亡发生在相似类型和年龄的神经元中，并且与人工阻断培养物中的电活动诱导的比例相同，因此这些发现可能与视网膜中自然细胞死亡的机制密切相关。
During the first 2 postnatal weeks, up to 50% of the ganglion cells in the mammalian retina normally die. Natural cell death may result from several factors, and electrical activity has been proposed as one critical element. Recent experiments in vivo using intraocular injection of tetrodotoxin (TTX) have suggested that competition for survival between ganglion cells from the two eyes is mediated by their degree of neuronal activity. In addition, the level of activity of afferents to the ganglion cells has been postulated to be an important variable in determining their survival. To investigate the mechanism of cell death engendered by altered activity, I studied the effect of electrical blockade with TTX (to block sodium channels and thus action potentials) or low Ca/high Mg (to block transmitter release and hence synaptic activity) on individual neurons in vitro. For this purpose, identified retinal ganglion cells (RGCs) from postnatal rats were maintained in culture. Unlike the previous in vivo experiments, this approach permitted the exact concentration of each agent to be controlled and the electrical activity of the RGCs to be recorded. In cultures from animals of postnatal day 2-10 (P2-10), 1 .mu.M TTX or 0.2 mM Ca/20 mM Mg resulted in the death of about 50% of the RGCs, representing those cells that had displayed spontaneous electrical activity, but did not affect RGCs that lacked activity. However, the death of RGCs with spontaneous activity from P11-13 animals was not influenced by these drugs. These findings suggest that during a critical period of development neurons become dependent upon electrical activity, and the cessation of this activity can result in their death. In addition, conditioned medium, collected from cultures lacking TTX, rescued from death a large proportion of TTX-treated RGCs. Thus, the critical element for survival may represent modulation of a trophic factor related to the level of activity rather than electrical activity itself. Since, in vivo, natural cell death occurs in neurons of similar type and age, and in the same proportion as that induced by the artificial blockade of electrical activity in culture, these findings may be germane to the mechanism of natural cell death in the retina.