Anderson Christopher M, Norquist Becky A, Vesce Sabino, Nicholls David G, Soine William H, Duan Shumin, Swanson Raymond A
Department of Neurology, University of California, San Francisco, USA.
J Neurosci. 2002 Nov 1;22(21):9203-9. doi: 10.1523/JNEUROSCI.22-21-09203.2002.
Barbiturates are widely used as anesthetics, anticonvulsants, and neuroprotective agents. However, barbiturates may also inhibit mitochondrial respiration, and mitochondrial inhibitors are known to potentiate NMDA receptor-mediated neurotoxicity. Here we used rat cortical cultures to examine the effect of barbiturates on neuronal mitochondria and responses to NMDA receptor stimulation. The barbiturates tested, secobarbital, amobarbital, and thiamylal, each potentiated NMDA-induced neuron death at barbiturate concentrations relevant to clinical and experimental use (100-300 microm). By using rhodamine-123 under quenching conditions, barbiturates in this concentration range were shown to depolarize neuronal mitochondria and greatly amplify NMDA-induced mitochondrial depolarization. Barbiturate-induced mitochondrial depolarization was increased by the ATP synthase inhibitor oligomycin, indicating that barbiturates act by inhibiting electron transport sufficiently to cause ATP synthase reversal. Barbiturates similarly amplified the effects of NMDA on cytoplasmic free calcium concentrations. The cell-impermeant barbiturate N-glucoside amobarbital did not influence mitochondrial potential or potentiate NMDA neurotoxicity or calcium responses. However, all of the barbiturates attenuated NMDA-induced calcium elevations and cell death when present at millimolar concentrations. Whole-cell patch-clamp studies showed that these effects may be attributable to actions at the cell membrane, resulting in a block of NMDA-induced current flux at millimolar barbiturate concentrations. Together, these findings reconcile previous reports of opposing effects on barbiturates on NMDA neurotoxicity and show that barbiturate effects on neuronal mitochondria can be functionally significant. Effects of barbiturates on neuronal mitochondria should be considered in experimental and clinical application of these drugs.
巴比妥类药物被广泛用作麻醉剂、抗惊厥药和神经保护剂。然而，巴比妥类药物也可能抑制线粒体呼吸，并且已知线粒体抑制剂会增强NMDA受体介导的神经毒性。在此，我们使用大鼠皮质培养物来研究巴比妥类药物对神经元线粒体的影响以及对NMDA受体刺激的反应。所测试的巴比妥类药物，即司可巴比妥、异戊巴比妥和硫喷妥钠，在与临床和实验使用相关的巴比妥类药物浓度（100 - 300微摩尔）下，均增强了NMDA诱导的神经元死亡。通过在淬灭条件下使用罗丹明 - 123，显示该浓度范围内的巴比妥类药物会使神经元线粒体去极化，并极大地放大NMDA诱导的线粒体去极化。ATP合酶抑制剂寡霉素增加了巴比妥类药物诱导的线粒体去极化，表明巴比妥类药物的作用是通过充分抑制电子传递导致ATP合酶逆转。巴比妥类药物同样放大了NMDA对细胞质游离钙浓度的影响。细胞不透性的巴比妥类药物N - 葡萄糖苷异戊巴比妥不影响线粒体电位，也不增强NMDA神经毒性或钙反应。然而，当处于毫摩尔浓度时，所有巴比妥类药物都会减弱NMDA诱导的钙升高和细胞死亡。全细胞膜片钳研究表明，这些作用可能归因于在细胞膜上的作用，导致在毫摩尔巴比妥类药物浓度下阻断NMDA诱导的电流通量。总之，这些发现调和了先前关于巴比妥类药物对NMDA神经毒性的相反作用的报道，并表明巴比妥类药物对神经元线粒体的作用在功能上可能是显著的。在这些药物的实验和临床应用中，应考虑巴比妥类药物对神经元线粒体的影响。
