Dopamine neuromodulation of neural synapses is a process implicated in a number of critical brain functions and diseases. Development of protocols to visualize this dynamic neurochemical process is essential to understanding how dopamine modulates brain function. We have developed a non-genetically encoded, near-IR (nIR) catecholamine nanosensor (nIRCat) capable of identifying ~2-µm dopamine release hotspots in dorsal striatal brain slices. nIRCat is readily synthesized through sonication of single walled carbon nanotubes with DNA oligos, can be readily introduced into both genetically tractable and intractable organisms and is compatible with a number of dopamine receptor agonists and antagonists. Here we describe the synthesis, characterization and implementation of nIRCat in acute mouse brain slices. We demonstrate how nIRCat can be used to image electrically or optogenetically stimulated dopamine release, and how these procedures can be leveraged to study the effects of dopamine receptor pharmacology. In addition, we provide suggestions for building or adapting wide-field microscopy to be compatible with nIRCat nIR fluorescence imaging. We discuss strategies for analyzing nIR video data to identify dopamine release hotspots and quantify their kinetics. This protocol can be adapted and implemented for imaging other neuromodulators by using probes of this class and can be used in a broad range of species without genetic manipulation. The synthesis and characterization protocols for nIRCat take ~5 h, and the preparation and fluorescence imaging of live brain slices by using nIRCats require ~6 h.

神经突触的多巴胺神经调节是与许多关键的大脑功能和疾病有关的过程。开发可视化这种动态神经化学过程的协议对于理解多巴胺如何调节大脑功能至关重要。我们开发了一种非基因编码的近红外 (nIR) 儿茶酚胺纳米传感器 (nIRCat)，能够识别背侧纹状体脑切片中约 2 µm 的多巴胺释放热点。 nIRCat 很容易通过用 DNA 寡核苷酸对单壁碳纳米管进行超声处理来合成，可以很容易地引入遗传上易处理和难处理的生物体中，并且与许多多巴胺受体激动剂和拮抗剂相容。在这里，我们描述了 nIRCat 在急性小鼠脑切片中的合成、表征和实施。我们演示了如何使用 nIRCat 对电或光遗传学刺激的多巴胺释放进行成像，以及如何利用这些程序来研究多巴胺受体药理学的影响。此外，我们还提供了构建或调整宽视野显微镜以与 nIRCat nIR 荧光成像兼容的建议。我们讨论了分析近红外视频数据的策略，以识别多巴胺释放热点并量化其动力学。该协议可以通过使用此类探针进行调整和实施，用于对其他神经调节剂进行成像，并且可以在无需基因操作的情况下用于广泛的物种。 nIRCat 的合成和表征协议需要约 5 小时，使用 nIRCat 活体脑切片的制备和荧光成像需要约 6 小时。