Abstract Objective Melanocortin-4 receptors (MC4Rs) are key regulators of energy homeostasis and adipose deposition in the central nervous system. Considering that MC4R expression regions and function-related research mainly focus on the paraventricular nucleus (PVN), little is known about their distribution throughout the mouse brain, although its messenger RNA distribution has been analyzed in the rat. Therefore, MC4R protein localization in mouse neurons was the focus of this study. Methods MC4R protein distribution was assessed in mice through immunofluorescence and Western blotting. Results MC4R was differentially expressed throughout the arcuate nucleus (ARC), nucleus of the solitary tract (NTS), raphe pallidus (RPa), medial cerebellar nucleus, intermediolateral nucleus, and brainstem. The highest MC4R protein levels were found in the ARC and ventromedial hypothalamic nucleus, while they were significantly lower in the parabrachial nucleus and NTS. The lowest MC4R protein levels were found in the PVN; there was no difference in the protein levels between the area postrema and RPa. Conclusions These data provide a basic characterization of MC4R-expressing neurons and protein distribution in the mouse brain and may aid further research on its role in energy homeostasis.

中文翻译：

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小鼠大脑中黑皮质素 4 受体通路的神经解剖学

摘要 目的黑皮质素4受体（MC4Rs）是中枢神经系统能量稳态和脂肪沉积的关键调节因子。考虑到 MC4R 表达区域和功能相关研究主要集中在室旁核 (PVN)，尽管其信使 RNA 分布已在大鼠中进行了分析，但对其在整个小鼠大脑中的分布知之甚少。因此，MC4R 蛋白在小鼠神经元中的定位是本研究的重点。方法通过免疫荧光和Western blotting评估小鼠MC4R蛋白分布。结果MC4R在弓状核(ARC)、孤束核(NTS)、苍白中缝(RPa)、小脑内侧核、中间外侧核和脑干中均有差异表达。在ARC和下丘脑腹内侧核中发现最高的MC4R蛋白水平，而在臂旁核和NTS中它们显着降低。PVN 中的 MC4R 蛋白水平最低；极区和RPa之间的蛋白质水平没有差异。结论 这些数据提供了小鼠大脑中表达 MC4R 的神经元和蛋白质分布的基本特征，可能有助于进一步研究其在能量稳态中的作用。