運用基因病毒追蹤方法進行藍斑核傳出前額葉皮質的連結視覺化

Abstract

中文摘要 藍斑核（LC）是哺乳動物大腦中去甲腎上腺素的主要合成中心，調節清醒、注意、壓力和高階認知控制。儘管在調節大腦功能方面起著關鍵作用，但形態學上從LC到腦皮質的連接模式仍然難以解釋。儘管最近的研究通過電生理學和RNAseq揭示了LC內的一種假設的模塊化組織，但由於先前的研究標記了大量LC神經元，因此形態學上很難區分在皮質中的單個去甲腎上腺素纖維的來源。 為了解決這個問題，我們的策略是標記少量的LC神經元並檢查它們在皮質中的投射。我們的方法是在前額葉皮質（mPFC）注射攜帶重組酶的逆行病毒，同時在LC注射攜帶重組酶依賴的螢光示踪劑的病毒。通過這種方法，我們成功地追踪了少數LC神經元，通常少於10個細胞，顯示它們不僅投射到mPFC，還在多個皮質區域中呈現廣泛和特定的投射混合。藉由其投射的模式，我們假設這兩個特定的投射代表基於它們的功能的兩種模塊化組織之一，一個用於空間識別，另一個用於運動控制。這些觀察結果提供了形態學上的證據，支持藍斑核模塊化組織的存在，並對藍斑核功能帶來了新的見解。

Abstract The Locus Coeruleus (LC) is the primary synthesis center of norepinephrine in the mammalian brain, modulating wakefulness, attention, stress, and higher-order cognitive control. Despite its pivotal role in brain function modulation, the connection pattern from the LC to the brain cortex has remained elusive. While recent research has proposed a hypothetical modular organization within the LC through electrophysiology and RNAseq, this hypothesis remains unverified morphologically due to previous studies labeling a large number of LC neurons, making it challenging to distinguish the origin of an individual norepinephrine fiber in the cortex from the LC. To address this question, we aimed to label a small number of LC neurons and examine their cortical projections. Our strategy involved injecting a retrograde virus carrying recombinase into the medial Prefrontal Cortex (mPFC) along with a virus carrying recombinase-dependent fluorescent tracer into the LC. Through this approach, we successfully traced a few LC neurons, typically fewer than 10 cells, revealing projections not only to the mPFC but also a mix of broad-range and specific projections in multiple cortical regions. Based on such observation, we hypothesize that these two specific projections represent two modular organizations based on their functions—one for spatial recognition and another for motor control. These observations provide morphological evidence supporting the existence of LC modular organization and shed new light on LC function.