Neurotoxicology Research Group, Institute for Risk Assessment Sciences (IRAS), Utrecht University, P.O. Box 80.177, NL-3508 TD Utrecht, The Netherlands.
Neurotoxicology. 2012 Mar;33(2):255-60. doi: 10.1016/j.neuro.2011.09.003. Epub 2011 Oct 4.
Reversal of the dopamine (DA) membrane transporter is the main mechanism through which many drugs of abuse increase DA levels. However, drug-induced modulation of exocytotic DA release by electrical (depolarization) and neurochemical inputs (e.g., acetylcholine (ACh)) may also contribute. We therefore investigated effects of methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and meta-chlorophenylpiperazine (mCPP) (1-1000 μM) on these inputs by measuring drug-induced changes in basal, depolarization- and ACh-evoked intracellular calcium concentrations (Ca(2+)) using a dopaminergic model (PC12 cells) and Fura 2 calcium imaging. The strongest drug-induced effects were observed on cholinergic input. At 0.1mM all drugs inhibited the ACh-evoked Ca(2+) increases by 40-75%, whereas ACh-evoked Ca(2+) increases were nearly abolished following higher drug exposure (1mM, 80-97% inhibition). Additionally, high MDMA and mCPP concentrations increased basal Ca(2+), but only following prior stimulation with ACh. Interestingly, low concentrations of methamphetamine or amphetamine (10 μM) potentiated ACh-evoked Ca(2+) increases. Depolarization-evoked Ca(2+) increases were also inhibited following exposure to high drug concentrations, although drugs were less potent on this endpoint. Our data demonstrate that at high drug concentrations all tested drugs reduce stimulation-evoked increases in Ca(2+), thereby probably reducing dopaminergic output through inhibition of electrical and cholinergic input. Furthermore, the increases in basal Ca(2+) at high concentrations of MDMA and mCPP likely increases dopaminergic output. Similarly, the increases in ACh-evoked Ca(2+) upon cholinergic stimulation following exposure to low concentrations of amphetamines can contribute to drug-induced increases in DA levels observed in vivo. Finally, this study shows that mCPP, which is regularly found in ecstasy tablets, is the most potent drug regarding the investigated endpoints.
多巴胺（DA）膜转运蛋白的逆转是许多滥用药物增加 DA 水平的主要机制。然而，电（去极化）和神经化学输入（例如乙酰胆碱（ACh））诱导的药物诱导的胞外 DA 释放也可能起作用。因此，我们通过使用多巴胺能模型（PC12 细胞）和 Fura 2 钙成像来测量药物诱导的基础、去极化和 ACh 诱发的细胞内钙浓度（[Ca2+]（i））变化，研究了甲卡西酮、苯丙胺、3,4-亚甲二氧基甲基苯丙胺（MDMA）、3,4-亚甲二氧基苯丙胺（MDA）和间氯苯哌嗪（mCPP）（1-1000μM）对这些输入的影响。在 0.1mM 时，所有药物对 ACh 诱发的 [Ca2+]（i）增加的抑制作用最强，为 40-75%，而在更高药物暴露（1mM，80-97%抑制）后，ACh 诱发的 [Ca2+]（i）增加几乎被完全消除。此外，高浓度的 MDMA 和 mCPP 增加了基础 [Ca2+]（i），但仅在 ACh 刺激后才会增加。有趣的是，低浓度的甲卡西酮或苯丙胺（10μM）增强了 ACh 诱发的 [Ca2+]（i）增加。然而，高浓度的药物也抑制了去极化诱发的 [Ca2+]（i）增加。我们的数据表明，在高药物浓度下，所有测试的药物都减少了刺激诱发的 [Ca2+]（i）增加，从而可能通过抑制电和胆碱能输入来减少多巴胺能输出。此外，高浓度的 MDMA 和 mCPP 引起的基础 [Ca2+]（i）增加可能会增加多巴胺能输出。同样，在低浓度的苯丙胺暴露后，在 ACh 刺激下引起的 [Ca2+]（i）增加可能有助于解释体内观察到的药物诱导的 DA 水平增加。最后，这项研究表明，mCPP 是一种经常在摇头丸片剂中发现的药物，它是研究终点中最有效的药物。
