Sihver W, Gillberg P G, Nordberg A
Subfemtomole Biorecognition Project, PET Centre Uppsala and Japan Science and Technology Corporation, Sweden.
Neuroscience. 1998 Aug;85(4):1121-33. doi: 10.1016/s0306-4522(97)00652-0.
The subregional localization of different nicotinic acetylcholine receptor subtypes in human cerebral cortex was estimated by quantitative in vitro autoradiography using the nicotinic ligands 3Hnicotine, [3H]cytisine and [3H]epibatidine in large whole human forebrain hemispheres. Saturation experiments in frontal cortex revealed for 3Hnicotine two binding sites with affinity constants (Kd) of 0.45 and 6.3 nM and binding site densities (Bmax) of 3.0 and 14.2 pmol/g, for [3H]cytisine one binding site with Kd of 0.19 nM and Bmax of 21.8 pmol/g, and for [3H]epibatidine one binding site with Kd of 0.011 nM and Bmax of 20.0 pmol/g. The laminar binding distributions of the three ligands were compared in different cortical areas by creating binding profiles perpendicular to the entire cortical depth. The regional autoradiographic binding patterns of the three ligands were essentially similar, with higher receptor binding in cortical layers I, III and V. In the primary sensory cortex and inferior frontal sulcus, marked binding of all ligands was observed in layer III. [3H]Cytisine showed the lowest difference between maximal and minimal binding within the gray tissue in all other areas. In the primary motor cortex, [3H]epibatidine and 3Hnicotine showed high binding in layers III and V. The 3Hnicotine binding was higher than that of the other ligands in layers I and VI of the primary motor cortex, the deeper layer V of the primary sensory cortex, layer III of the superior temporal sulcus and layer VI of the parietal cortex. A distinct band of binding of 3Hnicotine and [3H]epibatidine but not of [3H]cytisine was found in layer IIlb of the occipital cortex and layer V of the superior temporal sulcus. [3H]Epibatidine showed higher binding than the other ligands in all layers of the medial frontal, superior frontal and superior temporal sulcus. The findings with the three nicotinic ligands suggest three binding sites in the cortex with different laminar distributions. All three ligands bound to an identical receptor site, most likely the alpha4 nicotinic receptor subunit. The morphological distribution of [3H]epibatidine and 3Hnicotine binding indicate that they bind to an additional site, especially in the primary motor cortex, in layer IIIb of the occipital cortex and layer V of the superior temporal sulcus. High binding of 3Hnicotine in layers I and VI of the primary motor cortex, the deeper layer V of the primary sensory cortex, layer III of the superior temporal sulcus and layer VI of the parietal cortex may indicate a third binding site.
通过在完整的大型人类前脑半球中使用烟碱配体3H尼古丁、[3H]金雀花碱和[3H]埃博霉素进行定量体外放射自显影，估计了不同烟碱型乙酰胆碱受体亚型在人类大脑皮质中的亚区域定位。额叶皮质的饱和实验显示，3H尼古丁有两个结合位点，亲和常数（Kd）分别为0.45和6.3 nM，结合位点密度（Bmax）分别为3.0和14.2 pmol/g；[3H]金雀花碱有一个结合位点，Kd为0.19 nM，Bmax为21.8 pmol/g；[3H]埃博霉素有一个结合位点，Kd为0.011 nM，Bmax为20.0 pmol/g。通过创建垂直于整个皮质深度的结合图谱，比较了三种配体在不同皮质区域的层状结合分布。三种配体的区域放射自显影结合模式基本相似，在皮质I、III和V层中受体结合较高。在初级感觉皮质和额下回，所有配体在III层均有明显结合。在所有其他区域，[3H]金雀花碱在灰质组织内的最大结合与最小结合之间的差异最小。在初级运动皮质，[3H]埃博霉素和3H尼古丁在III和V层有高结合。在初级运动皮质的I和VI层、初级感觉皮质较深的V层、颞上沟的III层和顶叶皮质的VI层，3H尼古丁的结合高于其他配体。在枕叶皮质的IIlb层和颞上沟的V层发现了3H尼古丁和[3H]埃博霉素的一条明显结合带，但[3H]金雀花碱没有。在额叶内侧、额上和颞上沟的所有层中，[3H]埃博霉素的结合高于其他配体。三种烟碱配体的研究结果表明皮质中有三个具有不同层状分布的结合位点。所有三种配体都与同一个受体位点结合，很可能是α4烟碱受体亚基。[3H]埃博霉素和3H尼古丁结合的形态学分布表明它们还与另一个位点结合，特别是在初级运动皮质、枕叶皮质的IIlb层和颞上沟的V层。在初级运动皮质的I和VI层、初级感觉皮质较深的V层、颞上沟的III层和顶叶皮质的VI层中，3H尼古丁的高结合可能表明存在第三个结合位点。
