Wang Xiaoying, Baumann Michael H, Xu Heng, Morales Marisela, Rothman Richard B
Clinical Psychopharmacology Section, Intramural Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, USA.
J Pharmacol Exp Ther. 2005 Sep;314(3):1002-12. doi: 10.1124/jpet.105.088476. Epub 2005 Jun 3.
We showed that the serotonin (5-HT) neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) reduces brain tissue 5-HT, decreases expression of 5-HT transporter (SERT) protein, and increases expression of glial fibrillary acidic protein (GFAP). In contrast, doses of (+/-)-3,4-methylenedioxymethamphetamine (MDMA) that decrease brain tissue 5-HT fail to alter expression of SERT or GFAP. Using a new and highly sensitive anti-SERT antibody, we determined whether MDMA alters the subcellular distribution of SERT protein by measuring SERT expression in endosomes and plasma membranes 2 weeks after MDMA administration. Rat brain tissues (caudate, cortex, and hippocampus) were collected 3 days and 2 weeks after MDMA (7.5 mg/kg i.p., every 2 h x 3 doses) or 5,7-DHT (150 microg/rat i.c.v.) administration. Representative results from cortex are as follows. At both 3 days and 2 weeks postinjection, MDMA decreased tissue 5-HT (65%) and had no effect on GFAP expression. MDMA increased heat shock protein 32 (HSP32; a marker for microglial activation) expression (30%) at 3 days, but not 2 weeks. MDMA did not alter SERT expression at either time point and did not alter SERT levels in either endosomes or plasma membranes (2 weeks). 5,7-DHT decreased tissue 5-HT (80%), increased HSP32 expression at both time points (about 50%), and increased GFAP expression at 2 weeks (40%). 5,7-DHT decreased SERT expression (33%) at 2 weeks, but not at 3 days. These findings indicate that a dosing regimen of MDMA that depletes brain 5-HT does not alter SERT protein expression or the distribution of SERT between endosomes and the plasma membrane and does not produce detectable evidence for neurotoxicity.
我们发现，血清素（5-羟色胺，5-HT）神经毒素5,7-二羟基色胺（5,7-DHT）可降低脑组织中的5-HT水平，减少5-羟色胺转运体（SERT）蛋白的表达，并增加胶质纤维酸性蛋白（GFAP）的表达。相比之下，能降低脑组织5-HT水平的（±）-3,4-亚甲基二氧甲基苯丙胺（MDMA）剂量，却无法改变SERT或GFAP的表达。我们使用一种新型且高灵敏度的抗SERT抗体，通过在MDMA给药2周后测量内体和质膜中的SERT表达，来确定MDMA是否会改变SERT蛋白的亚细胞分布。在MDMA（7.5毫克/千克腹腔注射，每2小时一次，共3剂）或5,7-DHT（150微克/大鼠脑室内注射）给药后的第3天和第2周，收集大鼠脑组织（尾状核、皮质和海马体）。皮质的代表性结果如下。在注射后第3天和第2周，MDMA均降低了组织中的5-HT水平（65%），且对GFAP表达无影响。MDMA在第3天增加了热休克蛋白32（HSP32；小胶质细胞活化的标志物）的表达（30%），但在第2周未增加。MDMA在两个时间点均未改变SERT表达，也未改变内体或质膜中的SERT水平（第2周）。5,7-DHT降低了组织中的5-HT水平（80%），在两个时间点均增加了HSP32的表达（约50%），并在第2周增加了GFAP的表达（40%）。5,7-DHT在第2周降低了SERT表达（33%），但在第3天未降低。这些发现表明，耗尽脑内5-HT的MDMA给药方案不会改变SERT蛋白表达或SERT在内体与质膜之间的分布，也不会产生可检测到的神经毒性证据。
