σ1受体与精神分裂症、抑郁症、早老性痴呆等神经精神疾病、可卡因成瘾以及学习记忆等密切相关，最新研究还表明除与上述疾病有关外，σ1受体还可用于脑胶质瘤的治疗，因此研制具有高亲和性和选择性的σ1受体显像剂，可以为中枢神经系统(CNS)神经精神疾病的早期诊断提供灵敏的分子探针。本文设计了125I标记的苄基哌嗪类（BP类）和咪唑哌啶类（MP类）两类放射性示踪剂，合成了相应的稳定配体，进行了体外受体结合分析实验，并通过脱锡化反应制备了[125I]BP-I，对其进行了正常小鼠生物分布、抑制实验。具体工作如下：1. 125I标记的苄基哌嗪类σ1受体放射性显像剂的设计、稳定化合物以及标记前体的合成和初步的体外生物评价首次设计合成了五个新型苄基哌嗪类σ1受体配体（BP-CH3，BP-F, BP-Br, BP-I，BP-NO2），这些化合物的结构均通过核磁、质谱和元素分析得到指认。体外受体结合分析实验表明，这类化合物对σ1受体具有很高的亲和性和选择性（抑制常数Ki (σ1) 在0.43 nm~0.85 nm之间，选择性Ki(σ2)/ Ki(σ1)在51.9~94.2之间 ）。由于BP-I对σ1受体具有高亲和性和选择性，因此合成了BP-I的标记前体，准备进一步研究其体内生物分布性质。2. [125I]BP-I的制备、理化性质测定和体内生物评价利用脱锡化反应对BP-I的标记前体用125I核素进行了放射性标记，经过HPLC分离后，放化产率为（50%±8%）（n=5），放化纯度达到99.5%以上。脂水分配系数测定[125I ] BP-I 的logP=2.98±0.17，该化合物的脂溶性对于脑放射性药物来说，非常适中，避免了脂溶性偏高导致非特异性结合偏高的因素。正常小鼠生物分布结果显示：15分钟的初始脑摄取较高，达到了5.03%ID/g，两个小时之后脑中还剩余3.75%ID/g，呈现一个缓慢下降的趋势，数据同时显示，含σ1受体较多的周边器官也有较高的放射性浓集。为了验证该化合物是与σ1受体特异性结合，还进行了抑制实验，抑制剂选用氟哌啶醇，在小鼠尾部静脉注射氟哌啶醇后5 min 后，再注射 [125I]BP-I，同时设置控制组，即注射生理盐水5 min后再注射[125I]BP-I，抑制组和控制组的对照结果显示，大脑放射性浓集显著降低，脑内放射性降低60%左右，并且σ1受体广泛分布的心、脾、肺的放射性浓集也明显低于控制实验中相应脏器的浓集。例如注射氟哌啶醇后，脾中的摄取降低了40%。抑制实验结果表明[125I ]BP-I在体内与σ1受体特异性结合。总的来说，设计合成的这五个化合物具有很高的亲和性和选择性，[125I ]BP-I脂溶性适中，生物分布性质良好，有潜力成为新的σ1受体显像剂。3.苄基哌嗪类σ1受体构效关系的研究本文为了解释为什么第二章所设计合成的苄基哌嗪类化合物与σ1受体有较高的亲和性和选择性，同时为了验证模型的有效性，培养了BP-Br，解析了其晶体结构，利用Accelrys DS Visualizer 2.0软件分别测量了哌嗪环上两个N原子到两个疏水基团的距离，并与模型了进行对比，结构中左边的N原子到两个疏水基团以及两个疏水基团之间的距离分别为4.127，6.495和10.527，右边的N原子到两个疏水基团以及两个疏水基团之间的距离分别为6.737，6.839和10.527。同以往研究的σ1受体药效团模型对照，哌嗪环右边的氮原子为起主要作用的碱性氮原子，所得到的距离很好的解释了为什么该配体对σ1受体的亲和性要远大于对σ2受体的亲和性，同时验证了以往模型的有效性。4.咪唑哌啶类MP-I σ1受体放射性显像剂的设计、合成首次设计合成了咪唑哌啶类化合物MP-I，中间化合物均通过核磁、质谱和元素分析得到指认，目标化合物还通过了元素分析的确认。体外受体结合分析实验表明，该化合物对σ1受体的亲和性Ki (σ1) 为15.4±7.94nM，对σ2受体的亲和性Ki (σ2) 为324±82.2nM，亚型选择性Ki（σ2）/ Ki（σ1）= 21.04 。鉴于该化合物的亲和性和亚型选择性均不是很高，所以放弃了进一步的生物分布研究。

Sigma-1 (σ1) receptors are believed to play an important role in the central nervous system. They are linked to a number of brain disorders, including schizophrenia, depression, Alzheimer’s disease, as well as ischemia. Development of radiotracers for in vivo imaging of σ1 receptors may provide much needed diagnostic tools for the above diseases.1. Design, synthesis and evaluation of the biological properties in vitro of 125I labelled σ receptor Benz-piperazine radiotracers.In the present study, we have synthesized five 4-benzyl-piperazine ligands (BP-CH3, BP-F, BP-Br, BP-I, and BP-NO2, Figure 1), determined their affinity to σ1 receptors by in vitro Radioligand binding assays. Moreover, we prepared for [125I]BP-I(1-(benzo[d][1,3]dioxol-5-ylmethyl)-4-(4-iodobenzyl)piperazine), determined its log D value, and evaluated its potential as a putative SPECT tracer for imaging of σ1 receptors by biodistribution studies in mice.The synthesized compounds were characterized by NMR, MS and EA. In vitro competition binding assays showed that all the five ligands exhibit low nanomolar affinity for σ1 receptors (σ1: Ki = 0.43 - 0.91 nM; σ2: Ki = 40 - 61 nM) and high subtype selectivity(σ2/σ1 = 52-94).[125I]BP-I was prepared in 50 ± 8% isolated radiochemical yield, with radiochemical purity of >99% by HPLC analysis after purification, via iododestannylation of the corresponding tributyltin precursor. The log D value of [125I]BP-I was found to be 2.98 ± 0.17, which is within the range expected to give high brain uptake. 2. The biological evaluation of [125I] BP-I in vivoIn biodistribution studies [125I]BP-I was found to have high initial brain uptake with 5.03%ID/g at 15 min p.i. followed by slow clearance with 2.09 %ID/g at 240 min p.i. in normal female ICR mice. The blood radioactivity levels were low with 1.34 %ID/g at 15 min and 0.72 %ID/g at 240 min p.i., resulting in high brain-to-blood ratios. Moreover, relatively high concentration of radioactivity were observed in organs known to contain σ1 receptors, including the lung, kidney, heart, and spleen. The accumulation of radioactivity (1.22 %ID/g) in the thyroid at 240 min p.i. was quite low suggesting that [125I]BP-I is relatively stable to in vivo deiodination. Administration of haloperidol 5 min prior to injection of [125I]BP-I significantly reduced the concentration of radioactivity in organs known to contain σ1 receptors with lung by 37%, kidney by 33%, heart by 32%, spleen by 47%, and brain by 63%. These findings suggest that the binding of [125I]BP-I to σ1 receptors in vivo is specific. The results warrants further evaluation of [125I]BP-I as a putative tracer for imaging σ1 receptors with SPECT.3. Pharmacophore analysis of Benz-piperazine ligand• In this part,BP-Br crystal was synthesized. Accelrys DS Visualizer 2.0 was used for measuring the distance form two N atom to the two hydrophobic groups respectively. This result displays the right N atom is the dominant basic N atom and the Benz-piperazine ligand accord with the pharmacophore model.4. Design, synthesis and evaluation of the biological properties in vitro of 125I labelled σ1 receptor ligand Benzimidazole-piperidine radiotracers.In this part，a new Benzimidazole-piperidine（MP-I） radiotracer for 125I labelling were designed and synthesized. The compounds were characterized by IR, NMR, MS analyses and elemental analysis. Competition binding assays in vitro indicated that these compounds showed high affinity and selectivity for σ1 receptor. T he Ki values of MP-I for σ1 and σ2 receptor were 15.4±7.94nM nM and 324±82.2nM respectively.The selectivity of Ki (σ1) /Ki (σ2) is 21.04. Because the affinity and selectivity for σ1 is not very high, so the radiolabeling and the biological evaluation of [125I]BP-I in vivo are not performed.