Synthesis and Evaluation of 8-[^(131)I]Iodo-substituted Imidazopyridine Derivative as Single Photon Emission Computed Tomography Tracer for Peripheral Benzodiazepine Receptors

A novel N-methyl, N-phenyl-[6-chloro-2-（4-chlorophenyl）-8-iodoimidazo[1, 2-a]- pyridine-3-yl]acetamide （compound Ⅴ） was synthesized, radiolabelled with 131I and evaluated in vitro. In vitro cell uptake studies showed that MDA-MB-231 cells yield four-fold higher specific uptake of [^131I]-compound Ⅵ than MCF-7 cells, corresponding to the increased expression of PBR in MDA-MB-231 cells. Blocking studies significantly reduced the MDA-MB-231 cells uptake of [^131I]-compound Ⅵ. It indicated that [^131I]-compound Ⅵ might be a potential SPECT radioligand for imaging of PBR.

3-Arylisothiazoloquinols as potent ligands for the benzodiazepine site of GABA_(A) receptors

3-Arylisothiazolo[5,4-b]quinolin-4(9H)-ones and 3-arylisoxazolo[5,4-b]quinolin-4(9H)-ones were synthesized and assayed for affinity for the benzodiazepine binding site of the GABAA receptors. While the 3-arylisothiazoloquinolin-4-ones were found to be potent ligands, with affinities (expressed as the affinity Ki value) down to 1 nM, the 3-arylisoxazoloquinolin-4-ones are less potent. This is suggested to depend on sterical repulsive interaction of the 3-arylisoxazoloquinolin-4-ones with the receptor essential volume of the binding site, and a higher electron density at the nitrogen in the azole ring (N-2) as well as the carbonyl oxygen in the isothiazoloquinolin-4-ones enabling them to interact stronger with hydrogen bond donor sites at the binding site.

The Role of Ca^(2+) and Cyclic AMP in the Modulation of BenzodiazepineReceptor on Aldosterone Secretion

PK11195, a ligand of peripheral-type benzodiazepine receptor can stimulate thealdosterone secretion of isolated adrenal glomerulosa cell: this effect could be abolished by nifedipinewhich mainly blocks the calcium channel in plasma membrane, but could not be abolished bydantrolene, a selective blocker of mitochondria calcium channel. Even under the condition of themaximum stimulative effects on aldosterone secretion, PK11195 could not change the cyclic AMP（cAMP） content in isolated glomerulosa cells. These results indicated that in the modulatory mecha-nism of benzodiazepine receptor on aldosterone secretion, the intracellular messenger might be theCa2+ from extracellular Ca2+ pool, but not the Ca2+ from mitochondria Ca2+ pool or cAMP.

<i>Commentary</i>: Benzodiazepine (BZD) and Related BZD-Receptor Agonists: Basic Science Reasons to Limit to Four Weeks or Less

Benzodiazepines and related benzodiazepine-receptor agonists such as the pyrazolopyrimidinezalepl -on;?the imidazopyridine zolpidem;and the cyclopyrroloneszopiclone and eszopiclone, are among the most widely prescribed drugs, and for a variety of conditions. Surprisingly: 1) there are only a few conditions for which there is a good evidence basis, 2) efficacy has only been well demonstrated for short-term use (i.e., less than 4 weeks), and 3) much less is known about the basic science of these drugs than is widely believed. We suggest that the use of these drugs beyond four or less weeks exceeds the available knowledge base, so best-practice use suggests that the prescribing of these drugs for most patients should be limited to only short-term use until more is known about the basic pharmacology of their actions in the brain and in the periphery.

High- and Low-Rearing Rats Differ in the Brain Excitability Controlled by the Allosteric Benzodiazepine Site in the GABA_(A) Receptor

Rearing is an exploratory behavior induced by novelty, such as exposure to an open field. Stimulation of certain brain regions, including the hippocampus, induces both rearing and clonic convulsions. Brain excitability is controlled by gamma-aminobutyric acid (GABA) inhibitory neurotransmission through its ionotropic GABAA/allosteric benzodiazepine site. Drugs that decrease GABAA receptor fast inhibitory neurotransmission induce clonic convulsions and rearing when injected into the hippocampus. Therefore, individual differences in rearing behavior may be related to the susceptibility to clonic convulsions, which could involve differences in brain excitability controlled by GABAA/allosteric benzodiazepine site receptors. Adult, male Wistar rats were divided into high- (HR) and low-rearing (LR) groups based on the number of rearings in the open field test. Groups of HR and LR rats were challenged with convulsant drugs that antagonize GABA neurotransmission via different mechanisms of action (3-mercaptopropionic acid, a glutamate decarboxilase inhibitor;bicuculline, a GABAA receptor antagonist;pentylenetetrazol and picrotoxin, both GABAA receptor chloride channel blockers and DMCM, a benzodiazepine inverse agonist). The convulsant doses that induced 50% of clonic convulsions were determined for each drug. The LR rats had a higher susceptibility (a lower convulsant dose 50%) to clonic convulsions induced by DMCM than the HR rats, but there were no differences between the groups in the susceptibility to tonic convulsions induced by the same drug. There were no significant differences in the convulsant dose 50% for clonic convulsions between the groups for all other drugs injected. In another experiment, additional HR and LR rats were injected with a sedative-hypnotic dose of diazepam, which caused a significantly higher hypnotic effect (sleeping-time) in the LR rats than in the HR rats. The LR group was also shown to have a significantly lower density of [3H]-Flunitrazepam bound to the GABAA receptor in hippocampal membranes. Our data suggest that inter-individual differences in rearing are related, at least in part, to the GABA inhibitory neurotransmission controlled by the benzodiazepine allosteric site in the GABAA receptor.

Involvement of flumazenil-insensitive benzodiazepine binding site in benzodiazepine-induced anesthesia in zebrafish larvae

OBJECTIVE To identify the involvement of flumazenil-insensitive benzodiazepine(BZD) binding site in mediating BZD-induced immobility.The distribution of this nonclassical binding site and its key amino acid residues in GABAAreceptors(GABAARs) were also investigated.METHODS Using a zebrafish larvae locomotion model,we investigated the detailed dose-dependent effects of diazepam and other BZDs on zebrafish larvae behaviors,with a focus on their high-dose effects.We then evaluated the influence of the classical BZD antagonist flumazenil,GABAARs antagonist bicuculline,and the antagonist of a proposed BZD binding site in α4/6β3δ subtype receptor Ro15-4513 on BZDs induced immobility.Using wholecell patch clamp electrophysiological recordings on recombinant GABAARs,we investigated the modulation of diazepam alone or combined with flumazenil on GABA-elicited current in wildtype and mutated receptors.RESULTS Diazepam dose-dependently decreased the locomotor activities of zebrafish larvae at doses of 0.4,2,10,20,30,50 and 75 mg·L^(-1).The hypolocomotion(sedation-like state) induced by diazepam at10 and 20 mg·L^(-1) were effectively antagonized by flumazenil with EC150 of 0.086 mg·L-and1.295 mg·L^(-1),while the immobility(anesthesialike state) induced by diazepam at 30 mg·L^(-1) was abolished by bicuculline(3 mg·L^(-1)),but not affected by flumazenil(even at concentration up to150 mg·L^(-1)) or Ro15-4513(100 mg·L^(-1)).The immobility induced by clonazepam and lorazepam(100 mg·L^(-1)) was also resistant to flumazenil(100 mg·L^(-1)).In the α1β2γ2 subtype receptor expressed in HEK293 T cells,diazepam dose-dependently potentiated GABA-elicited current,and this potentiation was effectively antagonized by flumazenil(100 μmol·L^(-1)).However,in α1β2 subtype receptor,diazepam(150 μmol·L^(-1)) induced potentiation was insensitive to flumazenil(100 μmol·L^(-1)),but was abolished by the mutation of β2 N265 I.CONCLUSION These results provide direct in vivo evidence for the nonclassical binding sites,which may be located at the second transmembrane domain of GABAAR,mediate BZD-induced anesthesia.

Flumazenil-insensitive benzodiazepine effects in vitro and in vivo

OBJECTIVE To identify benzodi⁃azepine(BZD)effects that are insensitive to the classical BZD binding site antagonist,flumazenil.Whether the flumazenil-insensitive BZD effects have selectivity on different GABAA receptor sub⁃types was also investigated.METHODS The high-concentration effects of BZDs and their sensitivity to flumazenil were determined on recombi⁃nant synaptic(α1β2γ2,α2β2γ2,α5β2γ2)and extra-synaptic(α4β2δ)GABAA receptors using the voltage-clamp electrophysiology technique.The in vivo evaluation of flumazenil-insensitive BZD effects was conducted in mice loss of right reflex(LORR)test.RESULTS Diazepam induced a biphasic potentiation for theα1β2γ2,α2β2γ2 andα5β2γ2 receptor channels,but did not affect theα4β2δreceptor.In contrast to the nanomolar com⁃ponent of potentiation,the second potentiation elicited by micromolar diazepam was insensitive to flumazenil.Midazolam,clonazepam,and loraz⁃epam at 200μmol·L-1 exhibited similar flumaze⁃nil-insensitive effects onα1β2γ2,α2β2γ2 andα5β2γ2 receptors,whereas the potentiation induced by 200μmol·L-1 zolpidem or triazolam was abol⁃ished by flumazenil.Consistent with the in vitro results,flumazenil antagonized the zolpidem(50 mg·kg-1)-induced LORR,but not those induced by 50 mg·kg-1 diazepam or 100 mg·kg-1 midazolam.CONCLUSION The existence of non-classical BZD binding sites on certain GABAA receptor subtypes and the flumazenil-insensitive effects depend on the chemical structures of the allosteric modulators.

Treating Insomnia in Older Adult Patients: Limiting Benzodiazepine Use

As aging comes, an increased prevalence of medical maladies and chronic pain independently or interactively disrupt sleep, which in turn can exacerbate either one. Furthermore, anxiety about pain can further negatively impact sleep. Fortunately, good quality sleep can improve pain management. Because benzodiazepine receptor agonists (including the “Z” drugs) can reduce anxiety and improve sleep, they seem a convenient choice. However, their use in this population, particularly for more than short-term (guidelines range from 2 to 6 weeks max), is not recommended because of increased likelihood of falls, further disruption of sleep, dependence, and problems with discontinuation (withdrawal). Besides, this population is often likely to take concomitant medication for pain or other central nervous system depressants leading to potentially serious and even life-threatening interactions involving synergistic amplification of respiratory depression (opioids being a particularly dangerous interaction). Therefore, insomnia in older adults should ideally be treated with a non-benzodiazepine receptor agonist;if indicated, they may be used, but should be closely monitored and tapered to avoid long-term adverse problems (direct or from withdrawal). Older adult patients with insomnia may be more optimally treated with sleep aids that do not interact with the GABAA receptor.

BENZODIAZEPINE RECEPTORS IN ISOLATED ADRENAL GLOMERULOSA CELLS

In our experiments the isolated rat adrenal glomerulosa cells displayed perlpheral-type benzodiazepine receptors, which could bind to [3H] PKl1195 with an apparent equilibrium dissociation constant （KD） of 9.4±2.8 nmol/L and a maximal binding capacity (Bmax) of 5.6q-1.8 pmol/106 cells. The effects of five ligands: PKl1195, Ro5--4846, flunitrazepam, diazepam and clonazepam on aldosterone secretion responses of isolated glomerulosa cells to anglotensin Ⅱ or extracellular potassium ions were observed. The logarithm of EO50 for these ligands as stimulators was well correlated with the logarithm of their Ki value for [3H] PK11195 binding, suggesting that the stimulative effects might be mediated by the benzodiazepine receptor in isolated glomerulosa cells.

Mechanism-based design of 2,3-benzodiazepine inhibitors for AMPA receptors

2,3-Benzodiazepine(2,3-BDZ) compounds represent a group of structurally diverse,smallmolecule antagonists of(R,S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid(AMPA)receptors.Antagonists of AMPA receptors are drug candidates for potential treatment of a number of neurological disorders such as epilepsy,stroke and amyotrophic lateral sclerosis(ALS).How to make better inhibitors,such as 2,3-BDZs,has been an enduring quest in drug discovery.Among a few available tools to address this specific question for making better 2,3-BDZs,perhaps the best one is to use mechanistic clues from studies of the existing antagonists to design and discover more selective and more potent antagonists.Here I review recent work in this area,and propose some ideas in the continuing effort of developing newer 2,3-BDZs for tighter control of AMPA receptor activities in vivo.

Distribution of benzodiazepine receptor in rat brain

Benzodiazepines (BZs) are anxiolytic drugs which are commonly used in clinics; however, their mechanism of actions is still unclear. Since the late 1970s, receptors for benzodiazepine (BZ-R) were discovered in rat brain and it was found that the action strength of BZs in the central nervous system (CNS) is related to the affinity of BZ-R. There was much evidence which indicated that BZ-R,γ-aminobutyric acid type A (GABA_A) receptor, and supermolecular complex of the chloride ion (Cl^-) channel interact with

吲哚衍生物I_(20)的抗焦虑作用及机制研究

目的 研究外周型苯二氮卓受体配基吲哚衍生物I2 0的抗焦虑作用及作用机制。方法 在小鼠高架十字迷宫模型和小鼠明暗箱模型上评价I2 0 的抗焦虑活性 ,用放免法测定给予不同剂量的I2 0 在不同时间点大鼠血清中神经类固醇孕酮的含量。结果 I2 0 (1mg·kg-1,ip)能增加小鼠在开臂内运动时间百分率和小鼠穿箱次数 ,在小鼠高架十字迷宫与明暗箱模型上显示出抗焦虑作用 ;I2 0 在实验剂量下 (2 0mg·kg-1,ip)对小鼠自主活动性无影响 ,表明该化合物在抗焦虑的剂量下无镇静的副作用。放免测定结果表明 ,I2 0 能剂量依赖与时间依赖地增加大鼠血清中孕酮的含量。结论 I2 0 可能是通过与外周型苯二氮卓受体结合 ,增加体内神经类固醇孕酮的释放 ,间接调控GABAA

焦虑症γ-氨基丁酸受体机制与药物干预研究进展

焦虑症是一种常见的精神类疾病,随着社会压力的日益加大,发病率逐渐升高。以往研究证实,焦虑症与γ-氨基丁酸受体有关,现阶段又发现γ-氨基丁酸受体的多个亚型参与了焦虑症的病理生理过程。该文综述了γ-氨基丁酸受体不同亚型在焦虑症发病机制中所起作用及不同机制下药物干预的研究进展。

黄芩茎叶黄酮作为GABA_A受体BZD结合部位配体(英文)

目的从黄芩地上部分中寻找活性成分。方法利用各种柱色谱 (硅胶、SephadexLH 2 0、D10 1大孔吸附树脂和聚酰胺 )分离黄芩地上部分的活性成分。结果从黄芩地上部分的水提取物中分离得到 7种黄酮类化合物。其中白杨素对GABAA 受体的BZD结合部位有较高的亲和力 ,其IC50 值为 0 6 7μmol/L。 7种黄酮类化合物亲和力的排列顺序为 :白杨素 >汉黄芩苷元 >红花素 >黄芩素 >5 ,6 ,7 三羟基 4′ 甲氧基黄酮 >异红花素 >白杨素 7 葡萄糖醛酸苷。

侧脑室注射蝇蕈醇和荷包牡丹碱对大鼠异氟烷最低麻醉浓度的影响

大鼠侧脑室置管后 2 d,观察 icv GABAA 受体激动剂蝇蕈醇和 (或 )其拮抗剂荷包牡丹碱对麻醉箱内异氟烷最低有效浓度 (反映最低肺泡有效浓度 )和翻正反射恢复时间的影响 .结果表明 icv5mmol· L-1蝇蕈醇 2 μL明显降低箱内异氟烷最低麻醉浓度 ,延长大鼠翻正反射恢复时间 ;icv0 .5mmol·L-1荷包牡丹碱 2μL对异氟烷的最低麻醉浓度和翻正反射恢复时间皆无影响 ,但可部分拮抗蝇蕈醇降低异氟烷最低麻醉浓度和延长翻正反射恢复时间的作用 .以上实验结果提示 ,蝇蕈醇和异氟烷间有协同作用 ,但脑内的 GABAA 受体可能不是异氟烷全麻作用的主要靶位 .

血小板膜与脑细胞线粒体和突触体外周型苯二氮卓受体的相关性及生物学意义

目的:探讨衰老过程中脑细胞线粒体和突触体外周型苯二氮卓受体(PBRs)的动态变化以及与外周血血小板膜PBRs相关性的生物学意义。方法:实验动物分为3月龄、12月龄和24月龄3组。动物断头取血后,迅速取脑。采用梯度离心技术提取大脑皮质线粒体和海马突触体,低渗溶血法制备外周血血小板膜。应用放射配基[3H]PK11195结合实验测定PBR结合活力。结果:3组比较,大脑皮质线粒体(F=194.6)、海马突触体(F=94.2)、外周血血小板膜(F=162.2)[3H]PK11195结合活性差异均有显著性(P<0.001)。随着鼠龄增加,上述指标显著下降。外周血血小板膜[3H]PK11195结合活性与大脑皮质线粒体(r=0.894)、海马突触体(r=0.893)[3H]PK11195结合活性比较差异均具有显著性(P<0.001)。结论:大脑皮质线粒体、海马突触体PBRs水平呈增龄下降改变,外周血血小板膜[3H]PK11195结合活性能够反映脑组织该指标的变化。

2-芳基-3-吲哚取代乙酰胺类衍生物的合成及抗焦虑活性

目的 合成 2 芳基 3 吲哚取代乙酰胺类化合物 ,从中筛选有抗焦虑作用而无镇静、肌松等副作用的活性化合物。方法 由取代苯和琥珀酸酐经傅 克反应得到取代苯甲酰基丙酸 ,取代苯甲酰基丙酸和氯甲酸乙脂生成混合酸酐 ,再和相应的胺反应得到取代酰胺 ,取代酰胺和取代苯肼经费歇尔反应得到目标化合物。结果 得到新化合物 2 0个。结论 初步受体结果表明 ,多数化合物均与外周苯二氮受体有较强结合 ,在小鼠高架十字迷宫试验中发现一些化合物有明显的抗焦虑作用 ,且不能拮抗印防己毒素 (PTX)诱发的惊厥作用 。

苯二氮类受体的结构功能与苯二氮类耐受性和依赖性机制的研究进展

ＧＡＢＡＡ受体是脑内重要的抑制性受体。该受体是由５种亚基组成的五聚体大分子，目前已知的亚基种类共有６类１９种。苯二氮艹卓类通过作用于ＧＡＢＡＡ受体发挥其药理作用，而其慢性使用引起的耐受性和依赖性也与ＧＡＢＡＡ受体的改变密切相关，包括ＧＡＢＡＡ受体功能和数量的改变以及亚基的转录水平和翻译后的变化。本文简要综述了ＧＡＢＡＡ受体的功能结构及苯二氮艹卓类耐受性和依赖性的分子机制。

黄芪对感染血吸虫小鼠脑组织外周型苯二氮卓受体表达的影响

目的探讨黄芪对感染血吸虫小鼠脑组织外周型苯二氮卓受体表达的影响。方法采用黄芪注射液腹腔注射,在小鼠感染血吸虫满8周开始治疗,疗程12周,注射生理盐水作阴性对照。应用实时监测荧光定量PCR技术,于感染满8周、12周和20周检测脑组织外周型苯二氮卓受体mRNA的表达水平。结果黄芪治疗组小鼠脑外周型苯二氮卓受体mR-NA水平在感染12周和20周时均明显低于同期对照组(P<0.01),与正常组比较无显著差异(P>0.05);黄芪治疗组治疗前、中和后脑外周型苯二氮卓受体mRNA水平比较差异无统计学意义,而对照组治疗前后差异显著。结论黄芪可降低血吸虫病小鼠脑组织外周型苯二氮卓受体mRNA表达,提示黄芪可能通过此机制对肝性脑病有一定的治疗作用。

GABA_A五种亚型受体与BZ配基的3D-QSAR研究

GABAA受体是中枢神经系统内重要的抑制性受体,有广泛的神经生理活性.由于镇静/抗惊厥药物在临床上的广泛应用,使得其中苯并二氮杂作用位点尤为重要.我们用比较分子场法(CoMFA)对一系列咪唑苯并二氮杂类化合物(BZ)与五种重组受体亚型的亲和力进行了结构活性关系研究,得到的一组模型都有较高的交叉验证系数.并在此基础上,建立了非交叉验证的一组PLS模型.用该组模型对随机选择的6个化合物组成的测试集进行了预测,都得到了相当满意的结果,表明所建立的一组模型具有良好的预测能力.本研究对于设计高亲和力的BZ受体的配基和研究GABAA受体的模型有指导意义.