Dissecting the diversity of midbrain dopamine (DA) neurons by optotagging is a promising addition to better identify their functional properties and contribution to motivated behavior. Retrograde molecular targeting of DA neurons with specific axonal projection allows further refinement of this approach. Here, we focus on adult mouse DA neurons in the substantia nigra pars compacta (SNc) projecting to dorsal striatum (DS) by demonstrating the selectivity of a floxed AAV9-based retrograde channelrhodopsin-eYFP (ChR-eYFP) labeling approach in DAT-cre mice. Furthermore, we show the utility of a sparse labeling version for anatomical single-cell reconstruction and demonstrate that ChR-eYFR expressing DA neurons retain intrinsic functional properties indistinguishable from conventionally retrogradely red-beads-labeled neurons. We systematically explore the properties of optogenetically evoked action potentials (oAPs) and their interaction with intrinsic pacemaking in this defined subpopulation of DA neurons. We found that the shape of the oAP and its first derivative, as a proxy for extracellularly recorded APs, is highly distinct from spontaneous APs (sAPs) of the same neurons and systematically varies across the pacemaker duty cycle. The timing of the oAP also affects the backbone oscillator of the intrinsic pacemaker by introducing transient “compensatory pauses”. Characterizing this systematic interplay between oAPs and sAPs in defined DA neurons will also facilitate a refinement of DA neuron optotagging in vivo.

中文翻译：

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逆行鉴定的中脑多巴胺神经元中的光遗传学动作电位和内在起搏器相互作用

通过光标记来剖析中脑多巴胺（DA）神经元的多样性是一个有希望的补充，可以更好地识别它们的功能特性和对动机行为的贡献。具有特定轴突投射的 DA 神经元的逆行分子靶向允许进一步完善这种方法。在这里，我们通过展示 DAT-cre 中基于 floxed AAV9 的逆行通道视紫红质 eYFP (ChR-eYFP) 标记方法的选择性，重点关注成年小鼠黑质致密部 (SNc) 中投射到背侧纹状体 (DS) 的 DA 神经元老鼠。此外，我们展示了稀疏标记版本在解剖单细胞重建中的实用性，并证明表达 ChR-eYFR 的 DA 神经元保留了与传统逆行红珠标记神经元无法区分的内在功能特性。我们系统地探索了光遗传学诱发动作电位 (o AP )的特性及其与定义的 DA 神经元亚群中内在起搏的相互作用。我们发现，o AP的形状及其一阶导数作为细胞外记录的 AP 的代表，与相同神经元的自发 AP (sAP) 高度不同，并且在起搏器工作周期内系统地变化。 o AP的时间还通过引入短暂的“代偿性停顿”来影响内在起搏器的主干振荡器。表征确定的 DA 神经元中 oAP 和 sAP 之间的系统相互作用也将有助于体内 DA 神经元光标签的完善。