心理应激对大鼠多巴胺受体功能的影响及酪氨酸的干预作用

目的 探讨心理应激对大鼠中枢多巴胺受体功能的影响以及酪氨酸的干预作用。方法 用Communication Box模型对大鼠进行连续14天、每天30min的心理应激，并经饲料给予250、500、1000mg／kg三个剂量的酪氨酸干预。采用放射性配基结合分析法测定不同应激时间的中脑腹侧被盖区（VTA）、伏隔核（Nac）、前额皮质（mPFC）等脑区多巴胺D1、D2受体的最大结合容量（Bmax）和平衡解离常数（Kd）。结果 心理应激组mPFC、Nac区D2受体最大结合容量较对照组有明显下降（P〈O．05），mPFC区D2受体最大结合容量也有明显的下降（P〈O.05）。与心理应激组相比，酪氨酸500mg／kg干预组mPFC区D2受体最大结合容量升高（P〈0．05），1000mg／kg干预组VTA、mPFC区D2受体最大结合容量升高（P〈0．05）。心理应激及酪氨酸干预组D1、D2受体平衡解离常数无明显差别。结论 心理应激能够降低mPFC、Nac区D2受体最大结合容量，酪氨酸干预能够提高心理应激时mPFC、VTA区的D1，受体最大结合容量。心理应激对不同脑区D2受体功能的影响可能不同。     

中隔核毁损对MAP大鼠颞叶皮质多巴胺受体的影响

目的 :探讨立体定向中隔核毁损对甲基苯丙胺 (MAP)大鼠脑颞叶皮质多巴胺D2受体表达的影响。方法 :4 0只SD大鼠随机分为对照组、MAP组、MAP +毁损组和MAP +假毁损组 ,每组各 10只 ;采用经腹腔注射MAP制备精神分裂症MAP模型 ,立体定向 -射频毁损中隔核 ,免疫组织化学ABC法观察颞叶皮质多巴胺受体 2型的表达。结果 :与对照组比较 ,MAP组及MAP+假毁损组大鼠颞叶皮质多巴胺受体 2型表达有非常显著性差异 (P <0 .0 1) ;MAP +毁损组大鼠颞叶皮质多巴胺受体 2型阳性细胞数目与对照组比较差异无显著性 (P >0 .0 5 )。结论 :中隔核毁损可以抑制使用MAP而诱发的颞叶皮质多巴胺受体 2型表达的亢进。     

阿扑吗啡阻抗6-羟基多巴胺毁损纹状体的实验研究

 目的 探讨阿扑吗啡是否对6-羟基多巴胺毁损纹状体帕金森病鼠模型有神经保护作用.方法 6-羟基多巴胺毁损大鼠左侧纹状体,在毁损前15 min阿扑吗啡(10mg/kg,皮下注射),连续注射11 d.毁损2周后,分别进行行为学(苯丙胺引起的旋转数目)和神经化学(高压液相测定纹状体多巴胺及代谢物含量)的研究.结果 阿扑吗啡能降低苯丙胺引起的向损伤侧旋转的数目.而且,显著减低多巴胺的损耗使其恢复到正常,并使DOPAC/DA比率恢复到正常.结论 在6-羟基多巴胺毁损纹状体模型中,阿扑吗啡不仅改善运动功能,而且,恢复纹状体的多巴胺含量.     

多巴胺D2受体乃131I-epidepride显像对帕金森病的临床研究

目的 评价多巴胺D2受体显像剂131I-(s)-(-)-N-[(1-乙基-2-吡咯烷基)甲基]-5-碘-2,3-二甲氧基苯甲酰胺(epidepride)对帕金森病(PD)的临床应用价值.方法 PD患者38例(H/YⅠ～Ⅳ级,病程4个月～6年),健康对照组12例,静脉注射131I-epidepride 18.5 MBq 3 h后行SPECT显像,并应用感兴趣区(ROI)技术计算纹状体/枕叶放射性(ST/OC)比值,分析ST/OC比值与PD患者临床严重程度的相关性.采用SPSS 10.0软件对数据进行校正t检验,配对t检验及Spearman相关分析.结果 对照组131I-epidepride显像示双侧纹状体内有高度放射性浓聚,纹状体显示清晰,双侧基本对称,额叶、颞叶、顶叶、枕叶及小脑放射性较低.与健康对照组比较,PD患者ST内131I-epide-pride浓聚增加,但差异无统计学意义.早期PD患者(H/Y Ⅰ级)病侧肢体的对侧ST放射性显著增加、体积增大(壳核尤为显著),与同侧ST相比差异有统计学意义(t=7.89,P＜0.05).ST/OC比值与PD临床严重程度(H/Y分级)无明显相关性(r=0.12,P＞0.05).结论 多巴胺D2受体131I-Epi-depride SPECT显像有助于了解PD患者ST内突触后膜的多巴胺D2受体变化,PD患者D2上调,在偏侧PD中以病变对侧壳核尤为显著.ST/OC比值与PD临床严重程度无相关性.     

Raclopride在帕金森病PET中的应用

帕金森病是发生于中年以上的中枢神经系统的变性疾病，由于多巴胺产生不足，引起多巴胺D2受体功能异常。Raclopride(雷氯必利)对中枢神经系统D2受体具有高度的选择性和亲和力，是研究D2受体分布的理想示踪剂。^11C-raclopride PET可在分子水平直观地显示D2受体的分布、密度及变化情况，对帕金森病的病情分析、序列运动的多巴胺机制分析、运动波动合并症的机制分析、药物作用机制分析、外科治疗的机制分析等方面具有重要意义。     

杏仁核和扣带回毁损对拟精神分裂症大鼠边缘区D2受体的影响

目的探讨立体定向杏仁核和扣带回的联合毁损对甲基苯丙胺(MAP)大鼠脑内边缘区多巴胺D2受体表达的影响.方法40只SD大鼠随即分为对照组、模型组、假手术组和手术组,每组各10只;采用经腹腔注射MAP制备精神分裂症MAP模型,立体定向-射频毁损杏仁核和扣带回,原位杂交法观察边缘区D2受体的表达.结果与对照组比较,模型组及假手术组大鼠边缘区D2受体阳性细胞有非常显著性差异(P<0.01);手术组(14.2±5.1)大鼠边缘区D2受体阳性细胞数目与对照组比较差异无显著性(P＞0.05).结论杏仁核和扣带回的联合毁损可以抑制使用MAP而诱发的边缘区D2表达的亢进.     

天麻对帕金森病模型大鼠行为学、生物化学的影响

 目的 探讨天麻剂量对帕金森病模型大鼠行为学及生物化学的影响及防治的机制.方法 采用6-羟基多巴胺大鼠模拟帕金森病,治疗2周后,分别进行行为学(阿朴吗啡引起的旋转数目)和神经化学(高压液相测定纹状体多巴胺及代谢物含量)的研究.结果 天麻小剂量组能降低阿朴吗啡引起的向损伤对侧旋转的数目,而且显著减少多巴胺的损耗,使其它含量恢复正常.结论 在6-羟基多巴胺毁损纹状体模型中,天麻小剂量组不仅运动功能改善,而且,可恢复纹状体的多巴胺含量.     

GM1在流体冲击致大鼠脑损伤后对谷氨酸受体变化的作用

目的探讨大鼠急性脑损伤后神经书苷脂Monosialotetrahexosylganglioside（GMI）对谷氨酸受体活性变化的作用。方法采用成年雄性Wistar大鼠左颅顶液压冲击伤模型，受体放射配基结合分析法（RBA）测量双侧海马谷氨酸受体（GluR）活性，干-湿重法测量双侧脑组织水含量。结果大鼠脑损伤后GMI能显著降低伤后脑水含量的升高；抑制伤后早期GluR的最大结合量（Bmax）的增高和平衡解离常数（KD）降低，后期未发生Bmax降低和KD升高，与伤前水平基本相同；且假损伤动物GM1组与对照组或生理盐水组间GluR活性的比较，无显著差异（P＞0．05）。结论早期应用GMI能有效地拮抗GluR滥用性激活导致的兴奋性毒性，从而有效阻止脑水肿以及继发性脑损伤的发生，同时GM1对正常脑组织中GluR的活性无影响，因此具有临床应用价值。     

早期帕金森病患者脑多巴胺D2受体131I-epidepride SPECT显像

目的探讨脑多巴胺D2受体131I-epidepride SPECT显像在早期帕金森病(PD)中的临床价值.方法对10例正常对照者、46例早期未经替代治疗的PD患者[Hoehn&Yahr(H-Y)Ⅰ级22例,H-YⅡ级24例]行多巴胺D2受体131I-epidepride SPECT显像,用感兴趣区技术计算纹状体与枕叶、额叶的放射性比值[(ST-OC)/OC和(ST-FC)/FC].结果正常对照者双侧纹状体摄取无明显差异.PD H-YⅠ级、Ⅱ级患者起病肢体对侧纹状体(ST-OC)/OC和(ST-FC)/FC较同侧均明显上调;随病情加重,纹状体(ST-OC)/OC和(ST-FC)/FC均逐渐增高,与对照组差异明显.结论人脑多巴胺D2受体131I-epidepride SPECT显像有助于PD的早期诊断.     

早期帕金森病中多巴胺转运体的显像及其与D_2受体显像比较

目的 :了解早期帕金森病患者大脑内多巴胺转运体及多巴胺D2 受体的变化情况。材料和方法 :7例早期帕金森病患者和 7例正常人进行大脑12 3 I β CIT/SPECT显像 ;其中 5例进行12 3 I β IBZM /SPECT显像。计算纹状体与小脑的放射性比值 ,分析双侧纹状体中 β CIT和IBZM的特异性摄取。 结果 :7例患者症状对侧和症状同侧纹状体 18小时的 β CIT特异性摄取指数为 2 .3± 0 .4和 4.1± 0 .3 ,纹状体的非对称指数为 2 3 .3± 6.8;其中 5例患者症状对侧和症状同侧纹状体的12 3 I IBZM特异性摄取指数分别为 1.8± 0 .2和 1.7± 0 .2 ,非对称指数为 2 .0± 0 .1。结论 :早期帕金森病患者双侧纹状体中多巴胺转运体的丢失比D2 受体的变化更早 ,更明显。     

Upregulation of putaminal dopamine D2 receptors in early Parkinson's disease: a comparative PET study with [11C] raclopride and [11C]N-methylspiperone.

Dopamine D2 receptor function was assessed in a PET study with 2 dopamine D2 receptor PET ligands, [11C]raclopride (RAC) and [11C]N-methylspiperone (NMSP), in early Parkinson's disease. METHODS: Seven patients with early Parkinson's disease and 5 healthy volunteers were studied. Each underwent PET both with reversible [11C]RAC and with irreversible [11C]NMSP. RESULTS: Upregulation of dopamine D2 receptors in the putamen contralateral to the predominant symptoms of Parkinson's disease was confirmed using both [11C]RAC and [11C]NMSP. Uptake of [11C]RAC in the contralateral putamen was 105% of uptake in the opposite putamen (P = 0.020). For [11C]NMSP, uptake in the contralateral putamen was 105% of uptake in the ipsilateral putamen (P = 0.011). No significant differences between Parkinson's disease patients and healthy volunteers were detected in any of the studied brain regions using either [11C]RAC or [11C]NMSP. No significant differences between [11C]RAC and [11C]NMSP uptake were detected in the striatum, whereas in the extrastriatal regions, [11C]NMSP showed significantly higher uptake than [11C]RAC both in healthy volunteers and in Parkinson's disease patients. CONCLUSION: This study confirms an increase in dopamine D2 receptors in the putamen contralateral to the predominant symptoms, compared with the ipsilateral putamen, in early Parkinson's disease. This increase was seen both with reversible ligand [11C]RAC and with irreversible ligand [11C]NMSP and thus does not seem a consequence of depleted endogenous dopamine.     

Bilateral increase in striatal dopamine D<Subscript>2</Subscript> receptor density in the 6-hydroxydopamine-lesioned rat: a serial in vivo investigation with small animal PET

Unilateral destruction of the substantia nigra by local application of 6-hydroxydopamine (6-OHDA) serves as an animal model for Parkinson's disease. In this study, the changes in neostriatal dopamine D(2) receptor density were investigated with a small animal positron emission tomograph (PET) before and after 6-OHDA lesion. PET scans were performed in 14 rats after injection of the D(2) receptor radioligand [(18)F] N-methylbenperidol. After the first scan (day 0), nigrostriatal pathways were lesioned by unilateral injections of 6-OHDA. Further PET scans were performed on days 2 and 14 post-lesion. For both striata, B(max) values were determined from saturation binding curves with non-linear regression analysis. In the striatum ipsilateral to the lesion, B(max) initially amounted to 19.3+/-1. 9 fmol/mg (mean+/-SD) and increased to 19.7+/-2.2 and 29.9+/-5.7 fmol/mg on days 2 and 14 post-lesion, respectively. Contralateral B(max) values increased from 19.2+/-2 fmol/mg prior to the lesion to 21.2+/-2.9 and 28.6+/-5.7 fmol/mg on days 2 and 14, respectively. On day 14, the ipsilateral saturation binding curve differed from the ipsilateral pre-lesion curve (P=0.04; F test). When the contralateral pre-lesion saturation binding curve was compared with the contralateral post-lesion curve on day 14, a P value of 0.08 was obtained. This first serial in vivo imaging study of 6-OHDA-lesioned rats showed a time-dependent increase in striatal D(2) receptor density on both sides, the increase being more pronounced ipsilateral to the lesion. This result implies that compensatory mechanisms in the intact hemisphere contribute to regenerative processes following nigrostriatal dopaminergic denervation. Overall, our findings show the feasibility of repetitive in vivo studies of striatal receptor density with a small animal tomograph. Moreover, the applied in vivo saturation binding technique provides a versatile method for the quantification of time-dependent changes in the concentration of receptor binding sites.     

In vitro evaluation of nicotinic acetylcholine receptors with 2-[18F]F-A85380 in Parkinson's disease

Nicotinic acetylcholine receptors (nAChR) are involved in many physiological functions and appear to be affected in neurodegenerative diseases like Alzheimer's disease and Parkinson's disease (PD). Here, we describe the in vitro evaluation of nAChRs in PD with 2-[18F]F-A85380, a ligand with high affinity to the beta2 nAChR subunit. Autoradiography with 2-[18F]F-A85380 in untreated rat brain corresponded to the known distribution of alpha4beta2 nAChRs with high uptake in the thalamus, moderate uptake in the striatum and cortex and low uptake in the cerebellum (47%, 43% and 19% of the thalamus, respectively). The localization of alpha4beta2 nAChRs in the striatum was investigated in rodents with unilateral lesion of the substantia nigra. 2-[18F]F-A85380 binding was significantly reduced in the striatum ipsilateral to the lesion side (to 64% of the contralateral side), indicating that a fraction of alpha4beta2 nAChRs is located on dopaminergic terminals, whereas another fraction resides on striatal interneurons or cortical afferents. Similarly, in human brain sections of PD patients, 2-[18F]F-A85380 uptake was significantly reduced not only in the caudate and putamen but also in the thalamus (approximately 30% of the binding of control brain in all three regions); within the striatum, nAChRs in the putamen were significantly more severely affected as in the caudate. The observed pattern of alpha4beta2* nAChR loss demonstrates the potential of 2-[18F]F-A85380 for further investigations of this positron emission tomography ligand for in vivo studies of alpha4beta2* nAChRs in PD.     

Measurement of D2 dopamine receptor-specific carbon-11-YM-09151-2 binding in the canine brain by PET: importance of partial volume correction.

Carbon-11-YM-09151-2 binds highly selectively to D2 dopamine receptors in the brain. Using this ligand, D2 dopamine receptor density (Bmax) and affinity (Kd) in canine striatum were measured. After administering various doses of the ligand in nine experiments, regional uptake was followed by repeated PET scanning for up to 80 min. D2 dopamine receptor specific binding at equilibrium was defined as striatal minus occipital activity after partial volume correction. Bmax and Kd were estimated by Scatchard analysis to be 40.3 pmole/ml of tissue and 22.9 nM, respectively. When a low mass dose of the ligand was administered, the bound-to-free ligand ratio in the striatum at equilibrium was consistent with the Bmax/Kd value obtained from the Scatchard analysis. The present study demonstrates the importance of partial volume correction and the Bmax/Kd measurement in a single PET study with carbon-11-YM-09151-2.     

Measurement of striatal and thalamic dopamine D2 receptor binding with 11C-raclopride

11C-Raclopride is a widely used positron emission tomography (PET) tracer for measurement of striatal D2 dopamine receptor binding characteristics. Recently, 11C-raclopride has also been used for quantification of thalamic D2 receptor binding. We studied reproducibility and validity issues on the thalamic D2 binding measurements using healthy volunteer test-retest data and simulated data. Eight healthy male volunteers received 11C-raclopride as a bolus injection in a standard test-retest design using 3-dimensional PET. The displacement of thalamic 11C-raclopride binding by the D2 receptor antagonist haloperidol was studied in two female schizophrenic patients. With regards to reproducibility and reliability, thalamic 11C-raclopride binding could be described with a simplified reference tissue model resulting in binding potentials (BPs) between 0.38 and 0.66. In comparison, the model failed to describe 11C-raclopride binding consistently in temporal cortex due to low specific signal. Measurement of thalamic 11C-raclopride BP was reproducible with a test-retest variability of 7.6+/-6.2% and reliable with an intraclass correlation coefficient (ICC) of 0.87. Comparable ICCs were observed in caudate and putamen (0.84-0.96). With regard to validity, subchronic low dose haloperidol treatment reduced specific 11C-raclopride binding equally in putamen and thalamus but a higher dose induced clearly higher D2 receptor occupancy in putamen than in thalamus. Noise simulations indicated that this can partly be explained by an over-estimation of thalamic D2 receptor BP in noisy conditions (low signal, high occupancy). The D2 receptor BP in putamen was clearly more resistant to noise. We conclude that the reproducibility and reliability of thalamic 11C-raclopride BP is good and equal to, or only slightly less than, those observed in caudate or putamen. However, the signal-to-noise ratio for quantification may become too low especially in receptor occupancy-type studies, leading to an artefactual underestimation of measured D2 receptor occupancy.     

Quantification of dopamine transporter by 123I-PE2I SPECT and the noninvasive Logan graphical method in Parkinson's disease.

(E)-N-(3-iodoprop-2-enyl)-2beta-carbomethoxy-3beta-(4'-methyl-phenyl) nortropane (PE2I), a cocaine analog, is a new, highly specific tracer for imaging dopamine transporter labeled with (123)I for in vivo SPECT. Its reversible binding on dopamine transporter and its rapid kinetics allow quantification of its binding potential according to a 3-compartment model. For quantification of distribution volume of reversible tracer, Logan developed a noninvasive and graphical method that allows accurate estimation of binding potential. In this study, we performed (123)I-PE2I SPECT on healthy volunteers and patients with Parkinson's disease (PD) to validate the Logan graphical method for quantification of (123)I-PE2I binding and to analyze the relationship between (123)I-PE2I SPECT and clinical features of this frequent degenerative disease. METHODS: Eight PD patients (3 women, 5 men; mean age, 64 +/- 7.9 y; disease duration range, 1-8 y, Hoehn and Yahr stage range, 1-2.5) and 8 age-matched healthy volunteers (4 women, 4 men; mean age, 61.5 +/- 9.5 y) were included in 2 centers and studied with SPECT. Four sequential SPECT imaging sessions of 15-min duration were performed from 5 to 65 min after bolus injection of 140 +/- 30 MBq of (123)I-PE2I. RESULTS: The kinetics of PE2I in healthy volunteers and PD patients were rapid, and the Logan graphical method allowed quantification of distribution volume ratio (DVR) in the caudate nucleus and putamen. (123)I-PE2I striatal specific binding was significantly reduced in PD patients, compared with healthy volunteers, in the caudate and putamen. The decrease of DVR in the putamen was significantly and inversely correlated to disease duration and Hoehn and Yahr stage. In asymmetric PD patients, (123)I-PE2I uptake was significantly more reduced in the putamen contralateral to the side with predominant clinical symptoms. However, (123)I-PE2I uptake was also significantly reduced in the ipsilateral putamen, compared with that in healthy volunteers, suggesting that (123)I-PE2I SPECT can detect nigrostriatal degeneration before the appearance of clinical symptoms. CONCLUSION: Our data indicate that the Logan graphical method is accurate for noninvasive quantification of PE2I and that (123)I-PE2I SPECT is a useful quantitative method for accurate estimation of nigrostriatal dopaminergic nerve terminal degeneration. The close relationships between SPECT findings and clinical data suggest that this method is useful for objectively following the progression of PD and for assessing the effect of potential neuroprotective treatments. Finally, our findings suggest that (123)I-PE2I SPECT can be used for preclinical and early diagnosis of PD.     

Adenosine A<Subscript>2A</Subscript> receptor imaging with [<Superscript>11</Superscript>C]KF18446 PET in the rat brain after quinolinic acid lesion: Comparison with the dopamine receptor imaging

We proposed [11C]KF18446 as a selective radioligand for mapping the adenosine A2A receptors being highly enriched in the striatum by positron emission tomography (PET). In the present study, we investigated whether [11C]KF18446 PET can detect the change in the striatal adenosine A2A receptors in the rat after unilateral injection of an excitotoxin quinolinic acid into the striatum, a Huntington's disease model, to demonstrate the usefulness of [11C]KF18446. The extent of the striatal lesion was identified based on MRI, to which the PET was co-registered. The binding potential of [11C]KF18446 significantly decreased in the quinolinic acid-lesioned striatum. The decrease was comparable to the decrease in the potential of [11C]raclopride binding to dopamine D2 receptors in the lesioned striatum, but seemed to be larger than the decrease in the potential of [11C]SCH 23390 binding to dopamine D1 receptors. Ex vivo and in vitro autoradiography validated the PET signals. We concluded that [11C]KF18446 PET can detect change in the adenosine A2A receptors in the rat model, and will provide a new diagnostic tool for characterizing post-synaptic striatopallidal neurons in the stratum.     

Alpha-2-adrenoreceptor density on intact platelets and adrenaline-induced platelet aggregation in endurance- and nonendurance-trained subjects

Alpha-2-adrenoreceptor density on intact platelets was evaluated in 17 sportsmen, 8 of whom were endurance-trained athletes. Receptor density was determined as being equivalent to 3H-Yohimbine, specifically bound on intact platelets. Adrenaline-induced aggregation of platelets in vitro was additionally ascertained. Bmax (maximal binding) and KD (dissociation constant) were significantly lower in endurance-trained athletes (148 fmol per 10(9) platelets, KD = 0.92 nmol) than in the nine nonendurance-trained individuals (284 fmol, KD = 1.79 nmol, P less than 0.01), amounting to 89 receptors per cell (endurance-trained subjects) and 171 (nonendurance-trained subjects). No significant change of receptor density or affinity was observed subsequent to exhaustive exercise in the group of eight endurance-trained individuals. Bmax values and oxygen uptake capacity correlated negatively (r = -0.78, P less than 0.001) and Bmax values and induced platelet aggregation in vitro positively (r = 0.79, P less than 0.001). Data may indicate a reduced sensitivity of platelets in endurance-trained subjects.     

肿瘤坏死因子致伤无菌大鼠对脑组织β受体及磷脂酶A_2活性的影响

用放射配基结合分析法测定了经腹腔注射重组人肿瘤坏死因子α型(TNFα)致伤的无菌大鼠脑细胞膜肾上腺素能β受体,同时用ELISA法测定了血中TNFα水平,用生化法测定脑细胞组织膜磷脂酶A_2(PLA_2)活性。结果表明,外原性重组人的TNFα在整体状况下能增加脑组织β受体数量,激活膜PLA_2,同时血中TNFα水平亦高于对照组。