Previously, we identified a population of neurons in the hindbrain tegmentum, bordering the locus coeruleus (LC). We named this population the pre-locus coeruleus (pre-LC) because in rats its neurons lie immediately rostral to the LC. In mice, however, pre-LC and LC neurons intermingle, making them difficult to distinguish. Here we use molecular markers and anterograde tracing to clarify the location and distribution of pre-LC neurons in mice, relative to rats. First, we co-localized the transcription factor FoxP2 with the activity marker Fos to identify pre-LC neurons in sodium-deprived rats and show their distribution relative to surrounding catecholaminergic and cholinergic neurons. Next, we used sodium depletion and chemogenetic activation of the aldosterone-sensitive HSD2 neurons in the nucleus of the solitary tract (NTS) to identify the homologous population of pre-LC neurons in mice, along with a related population in the central lateral parabrachial nucleus. Using Cre-reporter mice for Pdyn, we confirmed that most of these sodium-depletion-activated neurons are dynorphinergic. Finally, after confirming that these neurons receive excitatory input from the NTS and paraventricular hypothalamic nucleus, plus convergent input from the inhibitory AgRP neurons in the arcuate hypothalamic nucleus, we identify a major, direct input projection from the medial prefrontal cortex. This new information on the location, distribution, and input to pre-LC neurons provides a neuroanatomical foundation for cell-type-specific investigation of their properties and functions in mice. Pre-LC neurons likely integrate homeostatic information from the brainstem and hypothalamus with limbic, contextual information from the cerebral cortex to influence ingestive behavior.

中文翻译：

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大鼠和小鼠的蓝斑前神经元

以前，我们在后脑被盖中发现了一群神经元，与蓝斑 (LC) 接壤。我们将这个群体命名为前蓝斑（pre-LC），因为在大鼠中，它的神经元立即位于 LC 的嘴部。然而，在小鼠中，前 LC 和 LC 神经元混合在一起，使它们难以区分。在这里，我们使用分子标记和顺行追踪来阐明小鼠中前 LC 神经元相对于大鼠的位置和分布。首先，我们将转录因子 FoxP2 与活性标记 Fos 共同定位，以识别钠剥夺大鼠中的前 LC 神经元，并显示它们相对于周围儿茶酚胺能和胆碱能神经元的分布。下一个，我们使用孤束核 (NTS) 中醛固酮敏感性 HSD2 神经元的钠耗竭和化学遗传学激活来识别小鼠中前 LC 神经元的同源群体，以及中央外侧臂旁核中的相关群体。使用 Pdyn 的 Cre-reporter 小鼠，我们证实这些钠耗尽激活的神经元中的大多数是强啡肽。最后，在确认这些神经元接收来自 NTS 和室旁下丘脑核的兴奋性输入，加上来自下丘脑弓状核中抑制性 AgRP 神经元的会聚输入后，我们确定了来自内侧前额叶皮层的主要直接输入投射。这些关于位置、分布的新信息，和输入到前 LC 神经元为细胞类型特异性研究它们在小鼠中的特性和功能提供了神经解剖学基础。前 LC 神经元可能将来自脑干和下丘脑的稳态信息与来自大脑皮层的边缘、上下文信息整合在一起，以影响摄取行为。