Chen Q, Surmeier D J, Reiner A
Department of Anatomy and Neurobiology, University of Tennessee-Memphis, Memphis, Tennessee, 38163, USA.
Exp Neurol. 1999 Sep;159(1):283-96. doi: 10.1006/exnr.1999.7135.
The excitatory input from cortex and/or thalamus to striatum appears to promote the maturation of glutamate receptors on striatal neurons, but the mechanisms by which it does so have been uncertain. To explore the possibility that the excitatory input to striatum might influence glutamate receptor maturation on striatal neurons, at least in part, by its depolarizing effect on striatal neurons, we examined the influence of chronic KCl depolarization on the development of glutamate receptor-mediated excitotoxic vulnerability and glutamate receptors in cultured striatal neurons. Dissociated striatal neurons from E17 rat embryos were cultured for 2 weeks in Barrett's medium containing either low (3 mM) or high (25 mM) KCl. The vulnerability of these neurons to NMDA receptor agonists (NMDA and quinolinic acid), non-NMDA receptor agonists (AMPA and KA), and a metabotropic glutamate receptor agonist (trans-ACPD) was examined by monitoring cell loss 24 h after a 1-h agonist exposure. We found that high-KCl rearing potentiated the cell loss observed with 500 microM NMDA or 250 microM KA and yielded cell loss with 250 microM AMPA that was not evident under low KCl rearing. In contrast, neither QA up to 5 mM nor trans-ACPD had a significant toxic effect in either KCl group. ELISA revealed that chronic high KCl doubled the abundance of NMDA NR2A/B, AMPA GluR2/3, and KA GluR5-7 receptor subunits on cultured striatal neurons and more than doubled AMPA GluR1 and GluR4 subunits, but had no effect on NMDA NR1 subunit levels. These receptor changes may contribute to the potentiation of NMDA and non-NMDA receptor-mediated excitotoxicity shown by these neurons following chronic high-KCl rearing. Our studies suggest that membrane depolarization produced by corticostriatal and/or thalamostriatal innervation may be required for maturation of glutamate receptors on striatal neurons, and such maturation may be important for expression of NMDA and non-NMDA receptor-mediated excitotoxicity by striatal neurons. Striatal cultures raised under chronically depolarized conditions may, thus, provide a more appropriate culture model to study the role of NMDA or non-NMDA receptor subtypes in excitotoxicity in striatum.
来自皮层和/或丘脑至纹状体的兴奋性输入似乎能促进纹状体神经元上谷氨酸受体的成熟，但其具体机制尚不清楚。为了探究纹状体的兴奋性输入是否至少部分通过其对纹状体神经元的去极化作用来影响纹状体神经元上谷氨酸受体的成熟，我们研究了慢性氯化钾去极化对培养的纹状体神经元中谷氨酸受体介导的兴奋毒性易感性和谷氨酸受体发育的影响。将来自E17大鼠胚胎的解离纹状体神经元在含有低（3 mM）或高（25 mM）氯化钾的巴雷特培养基中培养2周。在1小时激动剂暴露后24小时，通过监测细胞损失来检测这些神经元对NMDA受体激动剂（NMDA和喹啉酸）、非NMDA受体激动剂（AMPA和KA）以及代谢型谷氨酸受体激动剂（反式-ACPD）的易感性。我们发现，高钾培养增强了用500 microM NMDA或250 microM KA观察到的细胞损失，并在用250 microM AMPA时产生了细胞损失，而在低钾培养条件下并不明显。相比之下，高达5 mM的QA和反式-ACPD在任何一个氯化钾组中均无显著毒性作用。酶联免疫吸附测定显示，慢性高钾使培养的纹状体神经元上NMDA NR2A/B、AMPA GluR2/3和KA GluR5 - 7受体亚基的丰度增加了一倍，使AMPA GluR1和GluR4亚基增加了一倍多，但对NMDA NR1亚基水平没有影响。这些受体变化可能导致这些神经元在慢性高钾培养后NMDA和非NMDA受体介导的兴奋毒性增强。我们的研究表明，皮层纹状体和/或丘脑纹状体神经支配产生的膜去极化可能是纹状体神经元上谷氨酸受体成熟所必需的，而这种成熟对于纹状体神经元表达NMDA和非NMDA受体介导的兴奋毒性可能很重要。因此，在慢性去极化条件下培养的纹状体培养物可能为研究NMDA或非NMDA受体亚型在纹状体兴奋毒性中的作用提供更合适的培养模型。
