Takahashi Taiki, Kimoto Tetsuya, Tanabe Nobuaki, Hattori Taka-aki, Yasumatsu Nobuaki, Kawato Suguru
Department of Biophysics and Life Sciences, Graduate School of Arts and Sciences, University of Tokyo at Komaba, Meguro, Tokyo, Japan.
J Neurochem. 2002 Dec;83(6):1441-51. doi: 10.1046/j.1471-4159.2002.01251.x.
This work reports the first demonstration that corticosterone (CORT) has a rapid and transient effect on NMDA receptor-mediated Ca2+ signaling in cultured rat hippocampal neurons. Using single cell Ca2+ imaging, CORT and agonists of glucocorticoid receptors were observed to modulate the NMDA receptor-mediated Ca2+ signals in a completely different fashion from pregnenolone sulfate. In the absence of steroids, 100 micro m NMDA induced a transient Ca2+ signal that lasted for 30-70 s in 86.1% of the neurons prepared from postnatal rats (3-5 days old). After pre-treatment with 0.1-100 micro m CORT for 10-20 min, NMDA induced extremely prolonged Ca2+ elevation. This prolonged Ca2+ elevation was terminated by the application of MK-801 and followed by washing out of CORT. The proportion of CORT-modulated neurons within the NMDA-responsive cells increased from 25.1 to 95.5% when the concentration of CORT was raised from 0.1 to 50 micro m. Substitution of BSA-conjugated CORT produced essentially the same results. When hippocampal neurons were preincubated with 10 micro m cortisol and 1 micro m dexamethasone for 20 min, a very prolonged Ca2+ elevation was also observed upon NMDA stimulation. The CORT-prolonged Ca2+ elevation caused a long-lasting depolarization of the mitochondrial membrane, as observed with rhodamine 123. In contrast, incubation with 100 micro m pregnenolone sulfate did not considerably alter the time duration of NMDA-induced transient Ca2+ elevation, but caused a significant increase in the peak amplitude of Ca2+ elevation in hippocampal neurons. These results imply that high levels of CORT induce a rapid and non-genomic prolongation of NMDA receptor-mediated Ca2+ elevation, probably via putative membrane surface receptors for CORT in the hippocampal neurons.
本研究首次证明皮质酮（CORT）对培养的大鼠海马神经元中N-甲基-D-天冬氨酸（NMDA）受体介导的Ca2+信号具有快速且短暂的作用。通过单细胞Ca2+成像观察到，CORT和糖皮质激素受体激动剂对NMDA受体介导的Ca2+信号的调节方式与硫酸孕烯醇酮完全不同。在无类固醇的情况下，100 μM NMDA在86.1%的新生大鼠（3 - 5日龄）制备的神经元中诱导出持续30 - 70秒的短暂Ca2+信号。用0.1 - 100 μM CORT预处理10 - 20分钟后，NMDA诱导出极其延长的Ca2+升高。这种延长的Ca2+升高通过应用MK - 801终止，随后洗去CORT。当CORT浓度从0.1 μM提高到50 μM时，NMDA反应性细胞中CORT调节的神经元比例从25.1%增加到95.5%。用牛血清白蛋白（BSA）偶联的CORT替代产生了基本相同的结果。当海马神经元用10 μM皮质醇和1 μM地塞米松预孵育20分钟后，在NMDA刺激下也观察到非常延长的Ca2+升高。如用罗丹明123观察到的，CORT延长的Ca2+升高导致线粒体膜的持久去极化。相反，用100 μM硫酸孕烯醇酮孵育并没有显著改变NMDA诱导的短暂Ca2+升高的持续时间，但导致海马神经元中Ca2+升高的峰值幅度显著增加。这些结果表明，高水平的CORT可能通过海马神经元中假定的CORT膜表面受体诱导NMDA受体介导的Ca2+升高的快速非基因组延长。
