Medical Scientist Training Program, University of Virginia, Charlottesville, VA 22904, USA.
J Neurochem. 2010 Apr;113(1):188-99. doi: 10.1111/j.1471-4159.2010.06588.x. Epub 2010 Jan 13.
The two main sources of serotonin available for release are expected to be newly synthesized serotonin and serotonin recycled after reuptake by the serotonin transporter. However, their relative importance for maintaining release and the time course of regulation are unknown. We studied serotonin signaling in the ventral nerve cord of the larval Drosophila CNS. Fast-scan cyclic voltammetry at implanted microelectrodes was used to detect serotonin elicited by channelrhodopsin2-mediated depolarization. The effects of reuptake were probed by incubating in cocaine, which is selective for the serotonin transporter in Drosophila. p-chlorophenylalanine, an inhibitor of tryptophan hydroxylase2, was used to investigate the effects of synthesis. Stimulations were repeated at various intervals to assess the time course of recovery of the releasable pool. Reuptake is important for the rapid replenishment of the releasable pool, on the 1 min time scale. Synthesis is critical to the longer-term replenishment (10 min) of the releasable pool, especially when reuptake is also inhibited. Concurrent synthesis and reuptake inhibition decreased both serotonin tissue content measured by immunohistochemistry (by 50%) and the initial amount of evoked serotonin (by 65%). Decreases in evoked serotonin are rescued by inhibiting action potential propagation with tetrodotoxin, implicating endogenous activity in the depletion. These results show synthesis is necessary to replenish part of the releasable serotonin pool that is depleted after reuptake inhibition, suggesting that regulation of synthesis may modulate the effects of serotonin reuptake inhibitors.
预计可用于释放的两种主要 5-羟色胺来源是新合成的 5-羟色胺和 5-羟色胺经 5-羟色胺转运体再摄取后的再循环。然而，它们对维持释放的相对重要性以及调节的时间过程尚不清楚。我们研究了幼虫果蝇中枢神经系统腹神经索中的 5-羟色胺信号。通过在植入的微电极上进行快速扫描循环伏安法来检测由通道视紫红质 2 介导的去极化引起的 5-羟色胺。通过在可卡因中孵育来探测再摄取的影响，可卡因对果蝇中的 5-羟色胺转运体具有选择性。p-氯苯丙氨酸，色氨酸羟化酶 2 的抑制剂，用于研究合成的影响。重复刺激以评估可释放池恢复的时间过程。在 1 分钟的时间尺度上，再摄取对于可释放池的快速补充很重要。合成对于可释放池的长期补充（10 分钟）至关重要，特别是当再摄取也被抑制时。同时进行合成和再摄取抑制会降低免疫组织化学测量的 5-羟色胺组织含量（降低 50%）和诱发的 5-羟色胺的初始量（降低 65%）。用河豚毒素抑制动作电位传播可挽救诱发的 5-羟色胺减少，这表明内源性活动参与了耗竭。这些结果表明，合成对于补充再摄取抑制后耗尽的部分可释放 5-羟色胺池是必要的，这表明合成的调节可能调节 5-羟色胺再摄取抑制剂的作用。
