Stokes A H, Bernard L P, Nicklas W J, Zeevalk G D
Department of Neurology, Robert Wood Johnson Medical School-UMDNJ, 675 Hoes Lane, Piscataway, NJ 08854, USA.
J Neurosci Res. 2001 Apr 1;64(1):43-52. doi: 10.1002/jnr.1052.
Cultured rat mesencephalic neurons were used to assess the effects of gamma-aminobutyric acid (GABA) transport blockers on toxicity caused by malonate, a reversible, competitive inhibitor of succinate dehydrogenase. Previous studies utilizing an ex vivo chick retinal preparation have shown that GABA release and cell swelling are early consequences of acute energy impairment and that GABA transport blockers attenuate this toxicity. The present results demonstrate that the nonsubstrate GABA transport blocker, NO-711 (1 nM-1 microM), dose-dependently protected cultured mesencephalic dopamine (DA) and GABA neurons from malonate-induced toxicity. Similar protection was demonstrated with nipecotic acid (1 mM) and SKF89976A (100 nM), substrate and nonsubstrate GABA transport blockers, respectively. These compounds by themselves produced no signs of toxicity, although nipecotic acid caused a long-term decrease in GABA uptake not associated with toxicity. Compounds which decrease intracellular reactive oxygen species (ROS) are protective in this model, but NO-711 did not prevent the rise in intracellular ROS induced by malonate, indicating its protective effects were downstream of ROS production. Supplementation of malonate treated cultures with the GABA(A) agonist, muscimol (10 microM), increased the toxicity toward the DA and GABA neuron populations. Antagonists at the GABA(A) and glycine receptors provided partial protection to both the GABA and DA neurons. These findings suggest that the GABA transporter, GABA(A), and/or glycine channels contribute to cell damage associated with energy impairment in this model.
培养的大鼠中脑神经元用于评估γ-氨基丁酸（GABA）转运阻滞剂对丙二酸（一种琥珀酸脱氢酶的可逆性竞争性抑制剂）所致毒性的影响。此前利用离体鸡视网膜制剂进行的研究表明，GABA释放和细胞肿胀是急性能量损伤的早期后果，且GABA转运阻滞剂可减轻这种毒性。目前的结果表明，非底物GABA转运阻滞剂NO-711（1 nM - 1 μM）可剂量依赖性地保护培养的中脑多巴胺（DA）和GABA神经元免受丙二酸诱导的毒性。分别作为底物和非底物GABA转运阻滞剂的尼克酸（1 mM）和SKF89976A（100 nM）也表现出类似的保护作用。这些化合物本身未产生毒性迹象，尽管尼克酸导致GABA摄取长期下降，但这与毒性无关。在该模型中，可降低细胞内活性氧（ROS）的化合物具有保护作用，但NO-711并未阻止丙二酸诱导的细胞内ROS升高，表明其保护作用发生在ROS产生的下游。用GABA(A)激动剂蝇蕈醇（10 μM）补充丙二酸处理的培养物，会增加对DA和GABA神经元群体的毒性。GABA(A)和甘氨酸受体拮抗剂对GABA和DA神经元均提供部分保护。这些发现表明，在该模型中，GABA转运体、GABA(A)和/或甘氨酸通道与能量损伤相关的细胞损伤有关。
