目的  探讨外侧臂旁核（LPB）中痛觉和痒觉特异性神经元的分布特征及其下游投射通路差异。方法 使用雄性C57BL/6小鼠，通过预实验（n=24）确定四环素抑制性基因表达系统（Tet-off）的最佳诱导时间窗为7 d，随后采用Tet-off系统，结合c-Fos启动子驱动的病毒载体及Fos蛋白免疫荧光染色技术，特异性标记LPB中痛觉（LPB^pain）或痒觉（LPB^itch）激活的神经元，并分析LPB不同亚核内LPB^pain与LPB^itch的共标情况（n=7）；利用Tet-off技术结合病毒顺行示踪技术，观察并分析LPB^pain和LPB^itch神经元下游投射靶区差异（n=6）。结果 在不同时间窗内先后给予两种不同伤害性刺激可诱发LPB内大量的绿色荧光蛋白标记的病毒以及红色荧光蛋白标记的Fos表达；荧光显微镜下可见LPB^pain和LPB^itch神经元在LPB的外侧亚核（LPBE）大量共存，增强绿色荧光蛋白（EGFP）标记的痛神经元和Fos（红色）标记痒神经元共标率可达72.9%，EGFP（绿色）标记的痒神经元和Fos（红色）标记痛神经元共标率可达79.5%，而其他亚核共标率相对较低；顺行示踪结果显示，LPB^pain和LPB^itch神经元均主要投射至中央杏仁核（CeA）、中脑导水管周围灰质（PAG）、未定带（ZI）等脑区，总体投射模式高度相似。结论  LPB可以同时被痛和痒刺激激活，但不同亚核对痛、痒的处理方式有差异；LPB^pain和LPB^itch下游投射脑区基本重叠，提示中枢神经系统内痛/痒差异编码可能更多地通过分子差异而非通路差异完成。

Objective  To investigate the distribution patterns of pain- and itch-specific neurons within the lateral parabrachial nucleus (LPB), and to map their divergent downstream projection pathways. Methods  The male C57BL/6 mice were used, the optimal induction window for the tetracycline-off gene expression system (Tet-off system) was determined to be seven days through preliminary experiment (n=24). We then employed the Tet-off system, in combination with c-Fos promoter-driven viral vectors and Fos immunofluorescence histochemistry, to specifically label LPB neurons activated by pain (LPB^pain) or itch (LPB^itch) and to analyze their co-localization within LPB subnuclei (n=7). Finally, using Tet-off-based viral anterograde tracing (n=6), we compared the downstream projection targets of these two neuronal populations. Results  Sequential application of distinct noxious stimuli within defined time windows induced robust co-expression of viral vector-derived enhanced green fluorescent protein (EGFP) and Fos protein (labeled by red fluorescence) in the LPB. Microscopic analysis revealed that LPB^painand LPB^itch neurons were extensively co-localized in the external part of the lateral parabrachial nucleus (LPBE). The co-localization rate reached up to 72.9% for EGFP^＋ pain neurons with Fos^＋ itch neurons, and 79.5% for EGFP^＋ itch neurons with Fos^＋ pain neurons. Co-labelling rates in other subnuclei were relatively lower. Anterograde tracing results showed that both LPB^pain and LPB^itch neurons projected predominantly to overlapping regions, including the central amygdaloid nucleus (CeA), periaqueductal gray (PAG), zona incerta (ZI), revealing a highly similar overall projection pattern. Conclusion  While the LPB is activated by both pain and itch stimuli, its subnuclei exhibit distinct response profiles to these stimuli. The largely overlapping downstream projections of LPB^pain and LPB^itch neurons suggest that differential central encoding of pain and itch may rely more on molecular or functional mechanisms than on strictly segregated anatomical pathways.