Larsen P J, Sheikh S P, Jakobsen C R, Schwartz T W, Mikkelsen J D
Institute of Medical Anatomy, Department B, Copenhagen, Denmark.
Eur J Neurosci. 1993 Dec 1;5(12):1622-37. doi: 10.1111/j.1460-9568.1993.tb00231.x.
Using monoiodinated radioligands of peptide YY (PYY), and the recently introduced neuropeptide Y (NPY) analogue [Leu31, Pro34]NPY, receptor binding sites of the Y1 and Y2 type were localized in the rat brain by quantitative in vitro autoradiography. The binding specificity and affinity of both radiolabelled ligands were analysed by ligand binding studies employing rat brain membrane homogenates from cerebral cortex and hippocampus. Using in situ hybridization histochemistry, the regional distribution and cellular localization of mRNA encoding the Y1 receptor were investigated in rat brain sections and compared to the distribution of Y1-specific binding sites. PYY binds to both Y1 and Y2 receptors, while long C-terminal fragments such as NPY13-36 and NPY-16-36 bind preferentially to Y2 receptors. [Leu31,Pro34]NPY is a specific agonist for Y1 receptors. Highest densities of [125I]PYY binding sites were found in the cerebral cortex, the thalamus, the lateral septum, the hippocampus and the mesencephalic dopaminergic areas. In order to block putative Y2 receptors, a series of [125I]PYY binding experiments was performed in the presence of NPY13-36 (1 microM), a Y2 preferring C-terminal fragment. High densities of binding sites remained present in the cerebral cortex, the thalamus and the medial mammillary nucleus when NPY13-36 was present in the incubation medium. Furthermore, these areas were highly enriched with [125I][Leu31,Pro34]NPY binding sites. In contrast, the hippocampal complex had its binding capacity reduced by approximately 50%, while the lateral septum and mesencephalic dopaminergic areas had their binding capacities reduced even further. Linear regression analysis showed a high degree of correspondence between [125I][Leu31,Pro34]NPY binding and that obtained with [125I]PYY in the presence of 1 microM NPY13-36, suggesting that the two independent approaches to visualizing Y1 binding sites are comparable. In situ hybridization histochemistry revealed high levels of Y1 mRNA in the granular cell layer of the hippocampal dentate gyrus, several thalamic nuclei and the hypothalamic arcuate nucleus. Moderate levels of Y1 mRNA were seen in the frontoparietal cortex, several thalamic nuclei, the hippocampal pyramidal layers, the subiculum, the olfactory tubercle, the claustrum and a number of hypothalamic nuclei. The mesencephalon, the amygdala and most basal ganglia showed very low levels of hybridization. The present study further clarifies the anatomical distribution of multiple NPY binding sites within the central nervous system of the rat, and extends earlier suggestions that Y1 and Y2 receptor types are present within the central nervous system.
利用肽YY（PYY）的单碘化放射性配体以及最近引入的神经肽Y（NPY）类似物[Leu31, Pro34]NPY，通过定量体外放射自显影法在大鼠脑中定位Y1和Y2型受体结合位点。采用来自大脑皮层和海马体的大鼠脑膜匀浆进行配体结合研究，分析了两种放射性标记配体的结合特异性和亲和力。利用原位杂交组织化学技术，研究了大鼠脑切片中编码Y1受体的mRNA的区域分布和细胞定位，并与Y1特异性结合位点的分布进行了比较。PYY与Y1和Y2受体均结合，而长C末端片段如NPY13 - 36和NPY - 16 - 36优先与Y2受体结合。[Leu31,Pro34]NPY是Y1受体的特异性激动剂。在大脑皮层、丘脑、外侧隔、海马体和中脑多巴胺能区域发现了最高密度的[125I]PYY结合位点。为了阻断假定的Y2受体，在存在Y2偏好的C末端片段NPY13 - 36（1 microM）的情况下进行了一系列[125I]PYY结合实验。当孵育介质中存在NPY13 - 36时，大脑皮层、丘脑和内侧乳头核中仍存在高密度的结合位点。此外，这些区域富含[125I][Leu31,Pro34]NPY结合位点。相比之下，海马复合体的结合能力降低了约50%，而外侧隔和中脑多巴胺能区域的结合能力降低得更多。线性回归分析表明，在存在1 microM NPY13 - 36的情况下，[125I][Leu31,Pro34]NPY结合与[125I]PYY获得的结合高度一致，这表明两种可视化Y1结合位点的独立方法具有可比性。原位杂交组织化学显示，海马齿状回颗粒细胞层、几个丘脑核和下丘脑弓状核中Y1 mRNA水平较高。在额顶叶皮层、几个丘脑核、海马锥体细胞层、下托、嗅结节、屏状核和一些下丘脑核中可见中等水平的Y1 mRNA。中脑、杏仁核和大多数基底神经节显示出非常低的杂交水平。本研究进一步阐明了大鼠中枢神经系统内多个NPY结合位点的解剖分布，并扩展了先前关于中枢神经系统中存在Y1和Y2受体类型的观点。
