Development Of New Approaches To Neuroimaging with PET and SPECT

开发 PET 和 SPECT 神经影像新方法

• 批准号: 7593253
• 负责人: Elliot Stein
• 金额: $ 62.18万
• 依托单位: NATIONAL INSTITUTE ON DRUG ABUSE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7593253
• 关键词: Adult; Affect; Affinity; Age; Agreement; Amphetamines; Animal Experimentation; Animals; Anxiety; Anxiety Disorders; Area; Arts; Autopsy; Behavior; Behavioral; Binding; Biological Assay; Blood; Blood specimen; Bolus Infusion; Brain; Brain region; Cerebellum; Chronic; Clinical Research; Condition; Contralateral; Corpus Callosum; Data; Development; Disease; Dissociation; Dopamine; Dopamine D2 Receptor; Dopamine Receptor; Dose; Drug usage; Exhibits; Family suidae; Female; Gated Ion Channel; High Pressure Liquid Chromatography; Hippocampus (Brain); Human; Human Volunteers; Illicit Drugs; Image; In Vitro; Individual; Infant; Infusion procedures; Injection of therapeutic agent; Invasive; Lesion; Life; Life Stress; Ligands; Literature; Macaca; Macaca mulatta; Measurement; Measures; Medial; Mediating; Mental Depression; Methodology; Methods; Midbrain structure; Modeling; Monkeys; Moods; Mothers; Mus; Muscle; Neurobiology; Nicotine; Nicotinic Antagonists; Nicotinic Receptors; Numbers; One-Step dentin bonding system; Opioid; Parkinson Disease; Pattern; Perinatal; Pharmaceutical Preparations; Phase; Plasma; Play; Pontine structure; Positron-Emission Tomography; Prefrontal Cortex; Process; Property; Prosencephalon; Pump; Radioactive; Radioactivity; Rattus; Relative (related person); Reproducibility; Rewards; Risk; Role; Running; Saimiri; Sampling; Scanning; Self Administration; Serotonin; Serotonin Receptor 5-HT1A; Sex Characteristics; Side; Smoker; Smoking Behavior; Solid; Stress; Substance abuse problem; Sus scrofa; Tail; Techniques; Testing; Thalamic structure; Thinking; Time; Tobacco smoke; Toxic effect; Up-Regulation; Venous; base; brain tissue; cingulate cortex; day; density; frontal lobe; human data; in vivo; male; method development; neuroimaging; nicotine abuse; non-smoker; nonhuman primate; novel; novel strategies; pediatric trauma; peer; preference; psychostimulant; putamen; radioligand; receptor; receptor density; research study; sex; single photon emission computed tomography; smoking cessation; volunteer

Part of this project determined if differences in nAChR density between smokers and non-smokers could be shown in vivo with PET and to determine the neuroanatomical extent of the difference. We used dynamic PET imaging with 2F-18F-A-85380 (2FA) to measure total volume of distribution (VT) in non-smokers and heavy smokers. Values for VT obtained by several modeling methods using a metabolite-corrected arterial input function for 2FA yielded similar results. The thalamus (TH), midbrain (MB), pons (P), cerebellum (CB), frontal cortex (FC), putamen (PUT) and corpus callosum (CC) were sampled. VT was significantly higher in smokers than in nonsmokers in CB, FC, MB, P and PUT. PET imaging of nAChRs suggests that it can be used to study the role of nicotine-induced upregulation of nAChRs in smoking behaviors and in smoking cessation. Quantifying nAChRs in this study required arterial blood sampling and dynamic scanning as the 2FA was administered as a bolus injection. A second part of this project evaluated the less invasive bolus plus constant infusion (B/I) paradigm for quantifying nAChRs. Volunteers underwent a bolus injection study and a study in which the 2FA was administered by B/I to evaluate the feasibility of using shorter scan times and data from venous blood. VT values from the B/I studies were very similar to those calculated from bolus studies. Test/retest showed a high reproducibility of VT measurements. We conclude that B/I methodology will be useful for clinical and research studies of human brain nAChRs. We developed a one-step solid-phase extraction (SPE) method for measuring the concentration of unmetabolized 2FA, which allowed many samples to be processed in a short period of time. SPE effectively separated 2FA from radioactive metabolites typically observed in blood plasma after 2FA administration to humans, yielding nearly identical values to those obtained with HPLC, and showed good reproducibility within and between runs. These results suggest that SPE is the method of choice for the determination of the plasma 2FA concentration when measurement of individual metabolites is not required. Male squirrel monkeys underwent quantitative studies of nAChRs with 2FA. Non-displaceable volumes of distribution (VDnd) were determined following blockade of 2FA specific binding by nicotine infusion. Binding potential (BP*) values, estimated using Cb and muscle as reference regions, were compared for reproducibility of measurements. Administration of 2 mg/kg/day nicotine via osmotic pump nearly completely saturated specific binding to nAChRs and led to a very small changes in VT in CB and muscle (-9 4% and 0 6%, respectively), suggesting limited specific binding of 2FA in these areas. VT measured in muscle in 15 monkeys was reasonably constant but VDnd in studied brain regions exceeded VT in muscles by a factor of 1.3. Applying this factor and using muscle as a reference region, BP* values calculated for studied brain regions were in a good agreement with those obtained using CB as a reference region, suggesting that nAChRs can be accurately quantified using 2FA and muscle as a reference region. To expand the capability of microPET to quantify nAChRs in the rat brain, we measured BP* in anesthetized rats that were imaged repeatedly over six months Using a B/I paradigm, 2FA was administered intravenously over 8 to 9 h. Steady state conditions developed within 5 h. A 2-h nicotine infusion initiated 2 h before the end of scanning displaced specifically bound 2FA. BP* averages for TH, forebrain, and CB were consistent with nAChR distribution in rat brain measured in vitro. Studies of nAChR occupancy determined that 0.29 nmol/kg/h nicotine occupied 50% of the nAChRs. A novel radioligand F-18 NIDA131 for imaging extrathalamic nAChRs was characterized in vitro and in vivo. The Kd and T1/2 of dissociation of NIDA522131 measured in vitro were 4.9 pM and 81 min, respectively. The in vivo patterns of radioactivity distribution for F-18NIDA522131 and 2FA were similar and matched the distribution of nAChRs. F-18NIDA522131 exhibited better in vivo binding properties than 2FA, and accumulated in monkey brain to a substantially greater extent. VT and VDnd were substantially greater than those of 2FA. The toxicity of NIDA522131 in mice was comparable to 2FA and was consistent with a 2300 fold higher affinity for alpha4beta2* nAChRs than for alpha3beta4* nAChRs. These results suggest that F-18 NIDA131 is promising for studying extrathalamic nAChR in humans. Nicotine may function as a gateway drug to illicit drug use. Nicotine produces cross sensitization to opioids in rats in a conditioned place preference (CPP) paradigm. We utilized CPP to test the hypothesis that nicotine produces behavioral cross sensitization to stimulants and demonstrated that nicotine pretreatment enhances the rewarding effects of amphetamine for at least 3 to 5 days following the cessation of nicotine, with this effect dissipating within 19 days. The underlying mechanism involves alpha4beta2 nAChRs as a competitive alpha4beta2 antagonist effectively blocks development of nicotine-induced cross sensitization. An alpha7 nicotinic antagonist also blocked cross-sensitization at doses that do not block nicotine self-administration in rats. This study clearly demonstrated that nicotine produces cross-sensitization to the rewarding effects of both psychostimulants measured with CPP. We compared D2 dopamine receptor (D2DR) occupancy by dopamine (DA) in the MPTP-unilaterally lesioned (a model of Parkinson's disease) and contralateral PUT of four pig-tailed macaques. PET and in vitro binding techniques were used to measure BP* and D2DR density (Bmax), respectively. There were relatively higher values of BP* and Bmax and less amphetamine-induced decreases in C-11raclopride binding in the lesioned compared with the contralateral PUT in each animal. The percent differences between the measurements were similar for BP* and Bmax values. As BP* is a measure of unoccupied D2DRs, these findings suggest that endogenous DA occupies a similar fraction of receptors in the lesioned PUT and contralateral PUT. Therefore, the DA occupies a greater number of D2DRs in the lesioned than in the contralateral PUT, possibly because despite a loss in available DA, there is an increase in the ratio of D2DR in the low-affinity to those in the high affinity state on the lesioned side. Childhood trauma is associated with increased risk for developing depression, anxiety, posttraumatic stress and substance abuse disorders. Rearing infant macaques with same-aged peers in the absence of adults, an established model of early adversity, induces high levels of anxiety-like behavior in monkeys. Chronic early life stress affects expression and function of 5-HT1A receptors (5HTR), which may increase vulnerability to mood and anxiety disorders. In addition, human data shows sex differences in 5HTR. Based on the hypothesis that peer-reared (PR) macaques would exhibit differences in 5HTR density (measured with 18FFPWAY and PET) relative to those raised by their mothers (MR), we evaluated these effects in male MR, female MR, male PR and female PR rhesus monkeys, at 24-29 months (corresponding to 6-7 human years). The distribution of 18FFPWAY was consistent with the known pattern of 5HTR density (highest accumulation in hippocampus and cingulate cortex, intermediate in the prefrontal cortex and the lowest in the CB) and showed a significant rearing X sex interaction. In females, BP values were elevated in the dorso-medial prefrontal cortex in the PR compared to the MR group, but in males, values were lower in medial cingulate cortex in the PR group than in the MR group, suggesting that early stress affects the number of available 5HTR differently in females and males.

该项目的一部分是确定吸烟者和非吸烟者之间 nAChR 密度的差异是否可以通过 PET 在体内显示出来，并确定差异的神经解剖学程度。我们使用动态 PET 成像和 2F-18F-A-85380 (2FA) 来测量非吸烟者和重度吸烟者的总分布容积 (VT)。使用 2FA 的代谢物校正动脉输入函数通过多种建模方法获得的 VT 值产生了类似的结果。对丘脑（TH）、中脑（MB）、脑桥（P）、小脑（CB）、额叶皮质（FC）、壳核（PUT）和胼胝体（CC）进行采样。在 CB、FC、MB、P 和 PUT 中，吸烟者的 VT 显着高于非吸烟者。 nAChR 的 PET 成像表明，它可用于研究尼古丁诱导的 nAChR 上调在吸烟行为和戒烟中的作用。本研究中 nAChR 的定量需要动脉血采样和动态扫描，因为 2FA 以推注形式进行。该项目的第二部分评估了用于量化 nAChR 的微创推注加持续输注 (B/I) 范例。志愿者接受了一项推注研究和一项通过 B/I 施用 2FA 的研究，以评估使用更短扫描时间和静脉血数据的可行性。 B/I 研究的 VT 值与推注研究计算的 VT 值非常相似。测试/再测试显示 VT 测量具有很高的可重复性。我们得出的结论是，B/I 方法将有助于人脑 nAChR 的临床和研究。我们开发了一种一步固相萃取 (SPE) 方法来测量未代谢 2FA 的浓度，该方法可以在短时间内处理许多样品。 SPE 有效地将 2FA 与放射性代谢物分离，通常在人类施用 2FA 后在血浆中观察到，产生的值与 HPLC 获得的值几乎相同，并且在运行内和运行之间表现出良好的重现性。这些结果表明，当不需要测量单个代谢物时，SPE 是测定血浆 2FA 浓度的首选方法。 雄性松鼠猴接受了 2FA 对 nAChR 的定量研究。通过尼古丁输注阻断 2FA 特异性结合后测定不可置换分布容积 (VDnd)。使用 Cb 和肌肉作为参考区域估计的结合电位 (BP*) 值，比较了测量的再现性。通过渗透泵给予 2 mg/kg/天的尼古丁，与 nAChR 的特异性结合几乎完全饱和，并导致 CB 和肌肉中的 VT 发生非常小的变化（分别为 -9 4% 和 0 6%），表明 2FA 在这些区域的特异性结合有限。 15 只猴子的肌肉中测量的 VT 相当恒定，但研究的大脑区域中的 VDnd 超过肌肉中的 VT 1.3 倍。应用该因子并使用肌肉作为参考区域，为研究的大脑区域计算的 BP* 值与使用 CB 作为参考区域获得的值非常一致，这表明可以使用 2FA 和肌肉作为参考区域准确量化 nAChR。 为了扩展 microPET 量化大鼠大脑中 nAChR 的能力，我们测量了麻醉大鼠的 BP*，这些大鼠在六个月内重复成像。使用 B/I 范式，在 8 至 9 小时内静脉注射 2FA。 5 小时内形成稳态条件。在扫描结束前 2 小时开始输注 2 小时尼古丁，置换特异性结合的 2FA。 TH、前脑和 CB 的 BP* 平均值与体外测量的大鼠脑中 nAChR 分布一致。 nAChR 占有率研究确定 0.29 nmol/kg/h 尼古丁占据了 50% 的 nAChR。 用于丘脑外 nAChR 成像的新型放射性配体 F-18 NIDA131 在体外和体内进行了表征。体外测量的NIDA522131解离的Kd和T1/2分别为4.9 pM和81分钟。 F-18NIDA522131 和 2FA 的体内放射性分布模式相似，并且与 nAChR 的分布相匹配。 F-18NIDA522131 表现出比 2FA 更好的体内结合特性，并且在猴脑中的积累程度明显更高。 VT 和 VDnd 明显大于 2FA。 NIDA522131 在小鼠中的毒性与 2FA 相当，并且与 alpha4beta2* nAChR 的亲和力比 alpha3beta4* nAChR 高 2300 倍。这些结果表明 F-18 NIDA131 有希望用于研究人类丘脑外 nAChR。 尼古丁可能充当非法药物使用的门户药物。在条件性位置偏好（CPP）范式中，尼古丁对大鼠产生对阿片类药物的交叉过敏。我们利用 CPP 来检验尼古丁对兴奋剂产生行为交叉过敏的假设，并证明尼古丁预处理可在戒烟后至少 3 至 5 天内增强安非他明的奖励效果，并且这种效果在 19 天内消失。其潜在机制涉及 α4β2 nAChR 作为竞争性 α4β2 拮抗剂，有效阻止尼古丁诱导的交叉致敏的发展。 α7 烟碱拮抗剂也能阻断交叉致敏，其剂量不阻断大鼠自我施用尼古丁。这项研究清楚地表明，尼古丁对用 CPP 测量的两种精神兴奋剂的奖励作用产生交叉敏感性。 我们比较了四只猪尾猕猴的 MPTP 单侧损伤（帕金森病模型）和对侧 PUT 中多巴胺 (DA) 的 D2 多巴胺受体 (D2DR) 占据情况。 PET 和体外结合技术分别用于测量 BP* 和 D2DR 密度 (Bmax)。与每只动物的对侧 PUT 相比，病变部位的 BP* 和 Bmax 值相对较高，安非他明引起的 C-11雷氯必利结合减少较少。 BP* 和 Bmax 值的测量值之间的百分比差异相似。由于 BP* 是未占据的 D2DR 的衡量标准，因此这些发现表明内源性 DA 在病变 PUT 和对侧 PUT 中占据相似比例的受体。因此，病变侧的 DA 比对侧 PUT 中占据更多数量的 D2DR，这可能是因为尽管可用 DA 损失，但病变侧低亲和力状态下的 D2DR 与高亲和力状态下的 D2DR 比例有所增加。 童年创伤与患抑郁症、焦虑症、创伤后应激障碍和药物滥用障碍的风险增加有关。在没有成年猕猴的情况下与同龄同伴一起抚养幼年猕猴，这是一种既定的早期逆境模型，会导致猴子出现高度的焦虑样行为。慢性早期生活压力会影响 5-HT1A 受体 (5HTR) 的表达和功能，这可能会增加患情绪和焦虑障碍的可能性。此外，人类数据显示 5HTR 存在性别差异。基于同侪饲养 (PR) 猕猴相对于其母亲 (MR) 饲养的猕猴在 5HTR 密度（使用 18FFPWAY 和 PET 测量）方面表现出差异的假设，我们在 24-29 个月（相当于人类 6-7 岁）时评估了雄性 MR、雌性 MR、雄性 PR 和雌性 PR 恒河猴的这些影响。 18FFPWAY 的分布与已知的 5HTR 密度模式一致（海马和扣带皮层中积累最高，前额叶皮层中居中，CB 中最低），并显示出显着的饲养 X 性别相互作用。在女性中，与 MR 组相比，PR 组背内侧前额叶皮层的血压值升高，但在男性中，PR 组内侧扣带皮层的血压值低于 MR 组，这表明早期压力对女性和男性可用 5HTR 数量的影响不同。