Pifl C, Drobny H, Reither H, Hornykiewicz O, Singer E A
Institute of Biochemical Pharmacology, University of Vienna, Austria.
Mol Pharmacol. 1995 Feb;47(2):368-73.
The effects of amphetamine and cocaine were studied in [3H]-dopamine-loaded and superfused COS-7 cells transfected with either the cDNA of the plasmalemmal dopamine transporter ("DAT cells") or the cDNA of the vesicular amine transporter ("VAT cells"), or with both transporters ("DAT/VAT cells"). Amphetamine (0.01-100 microM, added for 4 min of superfusion) led to a concentration-dependent increase in dopamine release in DAT cells, as well as in DAT/VAT cells. The EC50 of the effect of amphetamine on DAT cells was 1.1 +/- 0.6 microM; the effect on DAT/VAT cells did not reach a plateau in the concentration range tested. With longer exposure to amphetamine, dopamine efflux from DAT cells reached a peak and quickly returned to baseline, in spite of the continued presence of the drug, whereas in DAT/VAT cells and in VAT cells the effect was sustained. Cocaine (up to 100 microM) did not exert any effect of its own in DAT cells or VAT cells but inhibited the amphetamine-induced release of dopamine from DAT cells in a competitive manner. In DAT/VAT cells cocaine and its analogue (-)-2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane caused an efflux of dopamine resembling that caused by amphetamine but quantitatively much smaller. The rank order of potency was the same as in uptake experiments [(-)-2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane > cocaine]. The effect of cocaine was mimicked by the reduction of chloride. The results indicate that there is a plasmalemmal component and a vesicular component in the dopamine-releasing action of amphetamine. The releasing action of cocaine is dependent on the existence of a vesicular pool of the neurotransmitter and seems to be linked to inhibition of the plasmalemmal dopamine transporter.
在转染了质膜多巴胺转运体cDNA（“DAT细胞”）、囊泡胺转运体cDNA（“VAT细胞”）或两种转运体cDNA（“DAT/VAT细胞”）的[³H] - 多巴胺负载且进行超灌流的COS - 7细胞中，研究了苯丙胺和可卡因的作用。苯丙胺（0.01 - 100微摩尔，添加后超灌流4分钟）导致DAT细胞以及DAT/VAT细胞中多巴胺释放呈浓度依赖性增加。苯丙胺对DAT细胞作用的半数有效浓度（EC50）为1.1±0.6微摩尔；在所测试的浓度范围内，对DAT/VAT细胞的作用未达到平台期。长时间暴露于苯丙胺时，尽管药物持续存在，但DAT细胞中的多巴胺流出达到峰值并迅速恢复到基线水平，而在DAT/VAT细胞和VAT细胞中，该作用持续存在。可卡因（高达100微摩尔）在DAT细胞或VAT细胞中自身未产生任何作用，但以竞争性方式抑制苯丙胺诱导的DAT细胞中多巴胺释放。在DAT/VAT细胞中，可卡因及其类似物（ - ） - 2β - 甲氧羰基 - 3β - （4 - 氟苯基）托烷引起的多巴胺流出类似于苯丙胺引起的，但在数量上要小得多。效价顺序与摄取实验相同[（ - ） - 2β - 甲氧羰基 - 3β - （4 - 氟苯基）托烷＞可卡因]。可卡因的作用可通过降低氯离子来模拟。结果表明，苯丙胺的多巴胺释放作用中存在质膜成分和囊泡成分。可卡因的释放作用取决于神经递质囊泡池的存在，并且似乎与质膜多巴胺转运体的抑制有关。
