The external segment of the globus pallidus (GPe) is involved in the modulation of the motor output and limbic components of behavior. The circuitry by which the GPe contributes to limbic components of behavior remains unknown. While many investigations have focused on the local circuitry within the basal ganglia, numerous GPe projections to target regions outside of the basal ganglia including the midbrain, thalamus, and cortex exist and remain largely unexplored. Here, by anatomical and electrophysiological means, we investigate the projections of the GPe to the retrorubral field (RRF), a dopaminergic nucleus in the caudal midbrain, in both male and female mice. We find that the GPe targets both GABAergic and DAergic neurons in the RRF (RRFDA and RRFGABA). Viral-assisted circuit mapping to trace the cell-type-specific projection patterns of RRFDA and RRFGABA populations revealed diverging pathways. The connectivity of GPe-recipient RRFDA neurons followed the traditional medial forebrain bundle path, innervating the ventral striatum and to a lesser extent the dorsal striatum. GPe-recipient RRFGABA neurons, on the other hand, displayed broad projections targeting numerous brain regions involved in limbic function including the parabrachial nucleus, amygdala, and hypothalamus. These contrasting projection profiles reveal multiple nodes by which the GPe is disynaptically connected to the limbic system, representing novel access points for the GPe to modulate limbic components of behavior.

中文翻译：

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对 Retrorubral 场的 GPe 预测导致了 GABA 能和 DA能回路的发散。


苍白球 （GPe） 的外段参与运动输出和行为边缘成分的调节。GPe 对行为边缘成分的贡献回路仍然未知。虽然许多研究都集中在基底神经节内的局部回路上，但存在许多针对基底神经节外区域（包括中脑、丘脑和皮层）的 GPe 预测，并且在很大程度上仍未得到探索。在这里，通过解剖学和电生理学手段，我们研究了 GPe 对雄性和雌性小鼠中脑尾部中脑中的多巴胺能核 （RRF） 的投射。我们发现 GPe 同时靶向 RRF 中的 GABA 能和 DA能神经元 （RRFDA 和 RRFGABA）。用于追踪 RRFDA 和 RRFGABA 群体的细胞类型特异性投影模式的病毒辅助电路映射揭示了不同的途径。GPe 受体 RRFDA 神经元的连接遵循传统的内侧前脑束路径，支配腹侧纹状体，并在较小程度上支配背侧纹状体。另一方面，GPe 受体 RRFGABA 神经元显示出针对参与边缘功能的许多大脑区域的广泛投射，包括臂旁核、杏仁核和下丘脑。这些对比鲜明的投影剖面揭示了 GPe 与边缘系统分离连接的多个节点，代表了 GPe 调节边缘行为成分的新接入点。