Weaver C E, Wu F S, Gibbs T T, Farb D H
Laboratory of Molecular Neurobiology, Department of Pharmacology, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118-2394, USA.
Brain Res. 1998 Aug 24;803(1-2):129-36. doi: 10.1016/s0006-8993(98)00640-4.
Excessive stimulation of the N-methyl-d-aspartate (NMDA)-type glutamate receptor has been implicated in the neuronal death resulting from focal hypoxia-ischemia. Certain neurosteroids, steroids synthesized de novo in the central nervous system (CNS), have been shown to modulate the action of neurotransmitters at their cellular receptors. Pregnenolone sulfate (PS) is an abundant neurosteroid that enhances the current evoked by NMDA. Using the Ca2+-sensitive fluorescent dye, Fluo-3, AM, and a trypan blue exclusion assay, we evaluated the ability of PS to modulate NMDA-induced changes in intracellular free calcium concentration ([Ca2+]i) and neuronal death in primary cultures of rat hippocampal neurons. The results demonstrate that PS potentiates NMDA-induced increases in [Ca2+]i by 150%. Further, PS exacerbates the MK-801-sensitive neuronal death produced by acute (PS EC50=37 microM) or chronic NMDA exposure, reducing the EC50 of NMDA from 13 to 4 microM under chronic exposure conditions, whereas pregnenolone is ineffective. Our results show that PS, or related sulfated neurosteroids, may play a role in the onset of excitotoxic neuronal death in vivo.
N-甲基-D-天冬氨酸（NMDA）型谷氨酸受体的过度刺激与局灶性缺氧缺血导致的神经元死亡有关。某些神经甾体，即中枢神经系统（CNS）中新合成的甾体，已被证明可调节神经递质在其细胞受体上的作用。硫酸孕烯醇酮（PS）是一种丰富的神经甾体，可增强NMDA诱发的电流。我们使用对Ca2+敏感的荧光染料Fluo-3、AM和台盼蓝排斥试验，评估了PS调节NMDA诱导的大鼠海马神经元原代培养物中细胞内游离钙浓度（[Ca2+]i）变化和神经元死亡的能力。结果表明，PS使NMDA诱导的[Ca2+]i增加增强了150%。此外，PS加剧了急性（PS的半数有效浓度[EC50]=37 microM）或慢性NMDA暴露所产生的对MK-801敏感的神经元死亡，在慢性暴露条件下将NMDA的EC50从13 microM降低至4 microM，而孕烯醇酮则无效。我们的结果表明，PS或相关的硫酸化神经甾体可能在体内兴奋性毒性神经元死亡的发生中起作用。
