Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, 1020 Locust Street, 368 JAH, Philadelphia, PA, 19107, USA.
Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, USA.
Brain Struct Funct. 2019 Nov;224(8):2983-2999. doi: 10.1007/s00429-019-01949-y. Epub 2019 Sep 4.
Guanylyl cyclase C (GUCY2C) is the afferent central receptor in the gut-brain endocrine axis regulated by the anorexigenic intestinal hormone uroguanylin. GUCY2C mRNA and protein are produced in the hypothalamus, a major center regulating appetite and metabolic homeostasis. Further, GUCY2C mRNA and protein are expressed in the ventral midbrain, a principal structure regulating hedonic reward from behaviors including eating. While GUCY2C is expressed in hypothalamus and midbrain, its precise neuroanatomical organization and relationship with circuits regulating satiety remain unknown. Here, we reveal that hypothalamic GUCY2C mRNA is confined to the ventral premammillary nucleus (PMV), while in midbrain it is produced by neurons in the ventral tegmental area (VTA) and substantia nigra (SN). GUCY2C in the PMV is produced by 46% of neurons expressing anorexigenic leptin receptors, while in the VTA/SN it is produced in most tyrosine hydroxylase-immunoreactive neurons. In contrast to mRNA, GUCY2C protein is widely distributed throughout the brain in canonical sites of PMV and VTA/SN axonal projections. Selective stereotaxic ablation of PMV or VTA/SN neurons eliminated GUCY2C only in their respective canonical projection sites. Conversely, specific anterograde tracer analyses of PMV or VTA/SN neurons confirmed distinct GUCY2C-immunoreactive axons projecting to those canonical locations. Together, these findings reveal two discrete neuronal circuits expressing GUCY2C originating in the PMV in the hypothalamus and in the VTA/SN in midbrain, which separately project to other sites throughout the brain. They suggest a structural basis for a role for the GUCY2C-uroguanylin gut-brain endocrine axis in regulating homeostatic and behavioral components contributing to satiety.
鸟苷酸环化酶 C(GUCY2C)是肠道-脑内分泌轴的传入中枢受体,受厌食性肠激素尿鸟苷素调节。GUCY2C mRNA 和蛋白在调节食欲和代谢稳态的主要中枢下丘脑产生。此外,GUCY2C mRNA 和蛋白在调节包括进食在内的行为愉悦奖赏的中脑腹侧被盖区表达。虽然 GUCY2C 在下丘脑和中脑表达,但它在调节饱腹感的回路中的精确神经解剖组织和关系仍不清楚。在这里,我们揭示下丘脑 GUCY2C mRNA 局限于腹前乳头核(PMV),而在中脑,它由腹侧被盖区(VTA)和黑质(SN)中的神经元产生。PMV 中的 GUCY2C 由表达厌食性瘦素受体的 46%神经元产生,而在 VTA/SN 中,它由大多数酪氨酸羟化酶免疫反应性神经元产生。与 mRNA 相反,GUCY2C 蛋白在大脑的经典 PMV 和 VTA/SN 轴突投射部位广泛分布。选择性立体定向消融 PMV 或 VTA/SN 神经元仅在其各自的经典投射部位消除 GUCY2C。相反,PMV 或 VTA/SN 神经元的特定顺行示踪分析证实了分别向这些经典位置投射的不同 GUCY2C-免疫反应性轴突。这些发现共同揭示了两个离散的神经元回路,它们分别起源于下丘脑的 PMV 和中脑的 VTA/SN,投射到大脑的其他部位。它们为 GUCY2C-尿鸟苷素肠道-脑内分泌轴在调节与饱腹感相关的稳态和行为成分的作用提供了结构基础。