Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
Neuroscience. 2010 Nov 24;171(1):62-78. doi: 10.1016/j.neuroscience.2010.08.036. Epub 2010 Aug 22.
Purines such as ATP act as extracellular messengers through specific purinergic receptors. Three different classes of purinergic receptors have been identified and termed P1, P2X and P2Y. The purinergic receptor subunit P2X2 is a ligand-gated ion channel that is widely expressed by neurons in the central nervous system. The aim of this study was to study the cellular localization and to identify the chemical phenotypes of ionotropic P2X2 receptor (P2X2R)-containing neurons in the rat mediobasal hypothalamus by immunohistochemistry using three different P2X2R antisera, with special reference to neurons that influence food intake and body weight. P2X2R immunoreactivity was mainly observed in cell bodies and neural extensions located in the ventromedial part of the hypothalamic arcuate nucleus, a subregion of the nucleus with a weak blood-brain barrier (BBB). At the subcellular level, P2X2R immunoreactivity was located to the periphery of individual cells, likely representing the plasma membrane. Many P2X2R-immunoreactive cell bodies in the arcuate nucleus contained the orexigenic peptides neuropeptide Y (NPY) and agouti-related protein (AgRP), and the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD). In contrast, P2X2R immunoreactive cell bodies of the arcuate nucles only occasionally contained the anorexigenic peptides α-melanocyte-stimulating hormone (α-MSH) or cocaine- and amphetamine-regulated transcript (CART), or the opioid peptide dynorphin (DYN). There was no evidence for colocalization of P2X2R with somatostatin or neuronal nitric oxide synthase (nNOS) in neurons of the arcuate nucleus. In the parvocellular part of the paraventricular nucleus, P2X2R was demonstrated in some corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH) and CART-containing neurons. In some cell bodies of the lateral hypothalamic area P2X2R was colocalized with DYN. The presence of P2X2R immunoreactivity in primarily orexigenic NPY/AgRP/GABA-containing neurons of the arcuate nucleus suggests that extracellular ATP has a regulatory action on this neuronal population located in a strategic position of the brain.
嘌呤类物质（如 ATP）通过特定的嘌呤能受体作为细胞外信使发挥作用。已经鉴定出三种不同类型的嘌呤能受体，分别命名为 P1、P2X 和 P2Y。嘌呤能受体亚基 P2X2 是一种配体门控离子通道，广泛存在于中枢神经系统的神经元中。本研究的目的是通过免疫组织化学使用三种不同的 P2X2R 抗血清来研究大鼠中脑基底部下丘脑内离子型 P2X2 受体（P2X2R）包含神经元的细胞定位，并确定其化学表型，特别关注影响食物摄入和体重的神经元。P2X2R 免疫反应性主要观察到位于下丘脑弓状核腹内侧部分的神经元细胞体和神经延伸，该区域的血脑屏障（BBB）较弱。在亚细胞水平上，P2X2R 免疫反应性位于单个细胞的外周，可能代表质膜。弓状核中的许多 P2X2R 免疫反应性细胞体含有食欲肽神经肽 Y（NPY）和刺鼠相关蛋白（AgRP）以及 GABA 合成酶谷氨酸脱羧酶（GAD）。相比之下，弓状核中 P2X2R 免疫反应性细胞体偶尔含有厌食肽α-黑素细胞刺激素（α-MSH）或可卡因和安非他命调节转录物（CART）或阿片肽强啡肽（DYN）。在弓状核神经元中没有证据表明 P2X2R 与生长抑素或神经元一氧化氮合酶（nNOS）共定位。在室旁核的小细胞部分，在一些促肾上腺皮质激素释放激素（CRH）、促甲状腺素释放激素（TRH）和 CART 含有神经元中证明了 P2X2R 的存在。在外侧下丘脑区域的一些细胞体中 P2X2R 与 DYN 共定位。P2X2R 存在于弓状核中主要是食欲肽 NPY/AgRP/GABA 含有神经元中，表明细胞外 ATP 对位于大脑战略位置的这群神经元具有调节作用。
