Xie Tao, Tong Liqiong, McLane Michael W, Hatzidimitriou George, Yuan Jie, McCann Una, Ricaurte George
Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21224, USA.
Neuropsychopharmacology. 2006 Dec;31(12):2639-51. doi: 10.1038/sj.npp.1301031. Epub 2006 Jan 25.
We studied in vivo expression of the serotonin transporter (SERT) protein after 3,4-methylenedioxymethamphetamine (MDMA), p-chloroamphetamine (PCA), or fenfluramine (FEN) treatments, and compared the effects of substituted amphetamines to those of 5,7-dihydroxytryptamine (5,7-DHT), an established serotonin (5-HT) neurotoxin. All drug treatments produced lasting reductions in 5-HT, 5-HIAA, and [(3)H]paroxetine binding, but no significant change in the density of a 70 kDa band initially thought to correspond to the SERT protein. Additional Western blot studies, however, showed that the 70 kDa band did not correspond to the SERT protein, and that a diffuse band at 63-68 kDa, one that had the anticipated regional brain distribution of SERT protein (midbrain>striatum>neocortex>cerebellum), was reduced after 5,7-DHT and was absent in SERT-null animals, was decreased after MDMA, PCA, or FEN treatments. In situ immunocytochemical (ICC) studies with the same two SERT antisera used in Western blot studies showed loss of SERT-immunoreactive (IR) axons after 5,7-DHT and MDMA treatments. In the same animals, tryptophan hydroxylase (TPH)-IR axon density was comparably reduced, indicating that serotonergic deficits after substituted amphetamines differ from those in SERT-null animals, which have normal TPH levels but, in the absence of SERT, develop apparent neuroadaptive changes in 5-HT metabolism. Together, these results suggest that lasting serotonergic deficits after MDMA and related drugs are unlikely to represent neuroadaptive metabolic responses to changes in SERT trafficking, and favor the view that substituted amphetamines have the potential to produce a distal axotomy of brain 5-HT neurons.
我们研究了3,4-亚甲基二氧甲基苯丙胺（摇头丸）、对氯苯丙胺（PCA）或芬氟拉明（FEN）处理后血清素转运体（SERT）蛋白的体内表达情况，并将取代苯丙胺的作用与5,7-二羟基色胺（5,7-DHT，一种已确定的血清素（5-HT）神经毒素）的作用进行了比较。所有药物处理均导致5-HT、5-羟吲哚乙酸（5-HIAA）和[³H]帕罗西汀结合持续减少，但最初认为与SERT蛋白相对应的70 kDa条带密度无显著变化。然而，进一步的蛋白质印迹研究表明，70 kDa条带并不对应于SERT蛋白，而在63 - 68 kDa处有一条弥散条带，其具有SERT蛋白预期的脑区分布（中脑>纹状体>新皮层>小脑），在5,7-DHT处理后减少，在SERT基因敲除动物中不存在，在摇头丸、PCA或FEN处理后也减少。使用与蛋白质印迹研究相同的两种SERT抗血清进行的原位免疫细胞化学（ICC）研究表明，在5,7-DHT和摇头丸处理后，SERT免疫反应性（IR）轴突丧失。在同一动物中，色氨酸羟化酶（TPH）-IR轴突密度也相应降低，这表明取代苯丙胺后的血清素能缺陷与SERT基因敲除动物不同，SERT基因敲除动物的TPH水平正常，但在没有SERT的情况下，5-HT代谢会出现明显的神经适应性变化。总之，这些结果表明，摇头丸及相关药物导致的持久血清素能缺陷不太可能代表对SERT转运变化的神经适应性代谢反应，支持取代苯丙胺有可能导致脑5-HT神经元远端轴突切断的观点。
