Borue Xenia, Cooper Stephanie, Hirsh Jay, Condron Barry, Venton B Jill
Medical Scientist Training Program, University of Virginia, Charlottesville, VA 22904, USA.
J Neurosci Methods. 2009 May 15;179(2):300-8. doi: 10.1016/j.jneumeth.2009.02.013. Epub 2009 Mar 4.
Serotonin signaling plays a key role in the regulation of development, mood and behavior. Drosophila is well suited for the study of the basic mechanisms of serotonergic signaling, but the small size of its nervous system has previously precluded the direct measurements of neurotransmitters. This study demonstrates the first real-time measurements of changes in extracellular monoamine concentrations in a single larval Drosophila ventral nerve cord. Channelrhodopsin-2-mediated, neuronal type-specific stimulation is used to elicit endogenous serotonin release, which is detected using fast-scan cyclic voltammetry at an implanted microelectrode. Release is decreased when serotonin synthesis or packaging are pharmacologically inhibited, confirming that the detected substance is serotonin. Similar to tetanus-evoked serotonin release in mammals, evoked serotonin concentrations are 280-640nM in the fly, depending on the stimulation length. Extracellular serotonin signaling is prolonged after administering cocaine or fluoxetine, showing that transport regulates the clearance of serotonin from the extracellular space. When ChR2 is targeted to dopaminergic neurons, dopamine release is measured demonstrating that this method is broadly applicable to other neurotransmitter systems. This study shows that the dynamics of serotonin release and reuptake in Drosophila are analogous to those in mammals, making this simple organism more useful for the study of the basic physiological mechanisms of serotonergic signaling.
血清素信号传导在发育、情绪和行为的调节中起着关键作用。果蝇非常适合用于研究血清素能信号传导的基本机制，但此前其神经系统的小尺寸阻碍了对神经递质的直接测量。本研究展示了对单个果蝇幼虫腹神经索细胞外单胺浓度变化的首次实时测量。利用通道视紫红质-2介导的神经元类型特异性刺激来引发内源性血清素释放，并通过植入微电极处的快速扫描循环伏安法进行检测。当血清素合成或包装受到药理学抑制时，释放量会减少，这证实了检测到的物质是血清素。与哺乳动物中破伤风诱发的血清素释放类似，果蝇中诱发的血清素浓度在280 - 640纳摩尔之间，具体取决于刺激时长。在给予可卡因或氟西汀后，细胞外血清素信号传导会延长，表明转运调节了血清素从细胞外空间的清除。当将通道视紫红质-2靶向多巴胺能神经元时，可以测量到多巴胺释放，这表明该方法广泛适用于其他神经递质系统。本研究表明，果蝇中血清素释放和再摄取的动态过程与哺乳动物中的类似，使得这种简单的生物体对于研究血清素能信号传导的基本生理机制更有用。
