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.     

乌鸡黑色素对6-OH-DA诱导帕金森病大鼠模型的神经保护作用

目的 探讨乌鸡黑色素对于6-羟多巴胺(6-OH-DA)单侧损毁纹状体诱导的帕金森病模型大鼠的神经保护作用及其机制.方法 将60只SD大鼠造模成功后,随机分为对照组、6-OH-DA诱导的帕金森病单纯模型组和治疗组,治疗组分别按6 mg/kg或20 mg/kg乌鸡黑色素灌胃给药,1次/d,共3w.然后比较各组中脑黑质多巴胺能神经元的数目、纹状体酪氨酸羟化酶(TH)阳性神经纤维的数量、阿朴吗啡诱导的旋转行为以及大鼠自主运动情况的差异.结果 6 mg/kg和20 mg/kg乌鸡黑色素灌胃给药能显著减少6-OH-DA所导致的中脑黑质多巴胺能神经元的死亡,减少纹状体TH阳性神经纤维的丢失,并有效改善阿朴吗啡诱导的旋转行为.结论 乌鸡黑色素能缓解6-OH-DA诱导的中脑黑质多巴胺能神经元的损伤,对于帕金森病有潜在的治疗作用.     

6-羟多巴胺毁损鼠脑内谷氨酸脱羧酶定量分析

 目的 探讨6-羟多巴胺毁损黑质及鹅膏氨蕈酸毁损脚内核对纹状体(STR)和苍白球(GP)内γ-氨基丁酸能神经元活动的影响.方法 应用免疫组织化学方法 和显微图像分析方法 ,对正常对照鼠、6-羟多巴胺毁损鼠、脚内核毁损的6-羟多巴胺毁损鼠相关脑区内的GAD65免疫反应阳性产物进行定量分析研究 .结果 6-羟多巴胺毁损鼠STR和GP中GAD65阳性反应产物的平均灰度明显低于正常对照组(P<0.05);而脚内核毁损可使STR内GAD65的反应产物平均灰度显著升高 ,甚至高于正常对照组(P<0.05),使GP升高到正常水平.结论 GAD65 对于基底节内γ-氨基丁酸能功能的调节起重要作用.     

运动通过调节纹状体A2AR/D2DR表达改善帕金森病模型大鼠行为功能障碍

目的:揭示纹状体腺苷2A型受体(A2AR)、多巴胺Ⅱ型受体(D2DR)在运动干预改善帕金森病(PD)模型大鼠行为功能障碍中的作用。方法:选用雄性SD大鼠,随机分为假手术组(Control组,n=22)、假手术运动组(Control+Ex组,n=22)、帕金森组(PD组,n=38)和帕金森运动组(PD+Ex组,n=38)。注射6-羟基多巴胺(6-OHDA)建立偏侧PD大鼠模型,术后24 h对运动组大鼠进行4周跑台运动干预(11 m/min,30 min/day,5 days/week),通过阿扑吗啡(APO)诱导旋转行为和黑质酪氨酸羟化酶(TH)表达鉴定PD大鼠模型可靠性。采用荧光定量PCR和免疫荧光技术检测纹状体A2AR和D2DR基因转录和蛋白表达;通过A2AR拮抗剂SCH联合D2DR激动剂QUIN干预进一步证实PD大鼠行为功能改善与纹状体A2AR-D2DR表达之间的相关性。结果:注射6-OHDA大鼠健侧旋转圈数与损毁侧旋转圈数差值>100 r/30 min,黑质TH表达较Control组降低(P<0.001),符合PD大鼠模型标准。4周跑台运动干预后,PD大鼠A2AR及D...     

6-羟基多巴胺诱发帕金森病大鼠模型的制作和评价

目的 向大鼠中脑黑质区注入6-羟基多巴胺(6-OHDA)建立帕金森病(PD)大鼠模型,并从行为学(ethology)及组织病理、生化角度对该模型进行评价.方法 将6-OHDA立体定向微量注入大鼠右侧中脑黑质(SN)区,观察阿朴吗啡(APO)诱发的大鼠旋转行为及黑质细胞形态学变化,测定脑组织液中儿茶酚胺类物质含量及黑质酪氨酸羟化酶的免疫活性.结果 120只大鼠中经APO诱导后有67只(占55.8%)持续转向健侧(旋转圈数＞7r/min),帕金森病大鼠模型复制成功.PD鼠注射侧黑质区多巴胺能神经元数量较对侧明显减少,体积缩小,结构欠清晰.注射侧脑组织液中多巴胺(DA)、3,4-二羟基苯酸(DOPAC)、高香草酸(HVA)、5-羟色胺(5-HT)含量均低于对侧,注射侧黑质致密部酪氨酸羟化酶(TH)免疫阳性细胞较健侧明显减少.连续观察10个月,PD模型大鼠的异常旋转行为无自发性恢复.结论 用6-OHDA选择性损毁大鼠黑质多巴胺能神经元,可造成与PD患者相似的基本病理变化,建立起可靠而稳定的PD大鼠模型.     

运动干预通过减缓纹状体多巴胺丢失改善帕金森病模型大鼠行为功能的研究

目的:探讨跑台运动干预对帕金森病(Parkinson’s disease,PD)模型大鼠行为功能、纹状体多巴胺(dopamine,DA)含量的影响。方法:健康雄性SD大鼠,随机分为假手术安静组(Control组)、假手术运动组(Control+Ex组)、6-OHDA安静组(PD组)、6-OHDA运动组(PD+Ex组)。依据实验设计要求,PD和PD+Ex组右脑内侧前脑束(MFB)注射6-羟基多巴胺(6-OHDA)建立偏侧PD大鼠模型,假手术组于相同位点注射等量生理盐水。在造模后的第7天颈部皮下注射阿朴吗啡(APO)进行旋转行为测试,评价PD模型的可靠性,不符合PD模型标准的大鼠剔除。运动组术后1周开始进行跑台训练,运动方案为11 m/min,30 min/day,5 days/week,共4周。采用旷场试验评价PD模型大鼠的自主活动能力;微透析-高效液相色谱电化学联用技术检测纹状体DA浓度;免疫组织化学检测纹状体酪氨酸羟化酶(TH)阳性纤维的表达。结果:PD和PD+Ex组移动距离较Control组显著降低(P<0.01);PD+Ex组第3、4周移动距离较PD组显著增加(P<0.01)。PD和PD+Ex组纹状体DA含量较Control组显著降低(P<0.01);但PD+Ex组第3、4周纹状体DA浓度较PD组显著升高(P<0.01)。结论:PD模型大鼠总移动距离与纹状体DA浓度之间存在高度正相关,且二者均随6-OHDA药物及运动干预持续时间延长出现"时序性"变化特征。运动干预通过减缓纹状体DA丢失改善PD模型大鼠自主行为功能,推测其机制可能与运动的神经保护作用减轻了6-OHDA神经毒素对DA能神经元的毒性损伤、促进其存活有关。     

Mdivi-1对帕金森病大鼠多巴胺能神经元损伤的保护作用研究

目的 研究线粒体分裂引发帕金森病（Parkinson’s disease,PD）大鼠模型中多巴胺能神经元损伤作用及线粒体分裂抑制剂1（mitochondrial division inhibitor 1,Mdivi-1）对神经元损伤的保护作用机制。方法 将大鼠随机分成对照组(生理盐水组)、模型组、美多巴组和Mdivi-1组,采用6-羟基多巴胺(6-hydroxydopamine,6-OHDA)注射大鼠单侧纹状体的方法建立PD动物模型,利用阿朴吗啡（apomorphine,APO）引起的大鼠旋转实验和转棒实验来观察行为学变化。利用免疫组化方法评估酪氨酸羟化酶（tyrosine hydroxylasez,TH）在中脑黑质中阳性细胞比例以及纹状体中TH阳性纤维数量,采用ELISA法检测大鼠黑质和纹状体中超氧化物歧化酶（superoxide dismutase,SOD）、谷胱甘肽过氧化物酶（glutathione peroxidase,GSH-Px）、还原型谷胱甘肽（glutathione,GSH）、过氧化氢酶（catalase,CAT）、丙二醛（malondialdehyde,MDA）、一氧化氮（nitric oxide,NO）及一氧化氮合酶（nitric oxide synthase,NOS）的含量。结果与对照组相比,PD模型组大鼠在APO诱发第3周和6周后旋转圈数均显著增加,同时转棒上停留时间均显著缩短;大脑黑质TH阳性细胞数和纹状体中TH阳性纤维数目显著减少;组织内SOD、GSH Px、CAT的活性显著降低,而NOS 活性显著升高,MDA和NO含量升高,而GSH含量则降低。美多巴及Mdivi-1处理3周和6周后均可显著改善PD大鼠的相关行为学症状,并增加黑质TH阳性细胞数和纹状体中TH阳性纤维数目,同时增加组织内SOD,GSH-Px,CAT,GSH含量,降低NOS 活性,减少MDA和NO含量。结论 Mdivi-1对6-OHDA诱导PD大鼠的多巴胺能神经元损伤具有保护作用,其机制可能与其抗氧化能力有关。     

光遗传操控D2-MSNs揭示跑台训练改善帕金森病小鼠运动行为障碍的可能机制

目的:采用光遗传学技术揭示纹状体表达多巴胺Ⅱ型受体的中等多棘神经元(D₂-MSNs)在改善帕金森病(PD)小鼠运动行为障碍中的作用。方法:雄性D₂-Cre转基因小鼠,随机分成假手术安静组(Control组)、帕金森病组(PD组)、帕金森病运动组(PD+Ex组)和帕金森病光刺激组(PD+Laser组),最终每组样本量为6只。PD+Laser组小鼠纹状体注射包装抑制性光敏感蛋白病毒(rAAV-Ef1α-DIO-eNpHR3.0-EYFP-WPRE-pA),并采用全细胞膜片钳技术记录纹状体D₂-MSNs对注入电流的反应,在激光共聚焦显微镜下鉴定病毒转染情况。采用右侧纹状体两点注射6羟基多巴胺(6-OHDA)药物建立偏侧PD小鼠模型,采用阿扑吗啡(APO)诱导旋转试验和纹状体酪氨酸羟化酶(TH)表达评价PD模型可靠性。PD+Ex组小鼠跑台运动干预方案为18 m/min,40 min/d,5 d/w,4 w。采用旷场实验通过运动总距离、平均运动速度和活动模式占比等参数评价各组小鼠自主活动能力,旷场实验中PD+Laser组光刺激方案...     

帕金森病模型大鼠脑D2受体与血流灌注的对比研究

目的 对偏侧帕金森病（ＰＤ）模型大鼠脑多巴胺（ＤＡ）Ｄ２受体改变与脑血流灌注进行对比研究。方法 立体定位脑黑质、腹侧被盖区、以６－羟基多巴胺定向损毁制作偏侧ＰＤ大白鼠模型，通过阿朴吗啡诱发其向健侧旋转的转数筛选模型，并用高效液相－电化学检测器（ＨＰＬＣ－ＥＣＤ）检测ＰＤ模型及对照组大鼠脑纹状体ＤＡ含量；彩用＾１２５Ｉ－左旋－３－碘－２－羟基－６－甲氧基－Ｎ（１－乙基－２－吡咯烷）甲基）苯酰胺（ＩＢ     

TH基因修饰的永生化神经干细胞移植对帕金森病大鼠行为和多巴胺代谢的影响

 目的 评价脑内移植酪氨酸羟化酶(tyrosine hydroxylase, TH)基因修饰的温度敏感型永生化神经干细胞(immortalized neural stem cells, iNSCs)的生物学稳定性和安全性,探讨TH基因表达对帕金森病(Parkinson's disease, PD)大鼠旋转行为和多巴胺代谢的影响. 方法 6-羟基多巴胺(6-OHDA)制备PD模型大鼠73只,随机分为3组.治疗组(36只,TG)脑内纹状体移植体外转染稳定表达TH基因的iNSCs株(RMN-TH),对照组(27只,CG)同部位植入未转染TH基因的RMN细胞株,余10只为模型组(MG).分别比较细胞移植后不同时间点实验大鼠肿瘤发生、排斥反应和阿扑吗啡(APO)诱导旋转行为、免疫组织化学染色观察TH表达;高效液相色谱电化学方法检测多巴胺(dopamine, DA)及其代谢产物3、4-二羟苯乙酸(DOPAC)和高香草酸(HVA)水平. 结果移植细胞在受体大鼠纹状体内存活均超过6个月,并广泛迁移、稳定表达TH,而未诱发肿瘤和排斥反应.RMN-TH TG组的APO诱导旋转行为得到明显改善,移植后第8周与CG组、MG组比较,旋转圈数分别下降64.17%和61.54%(P＜0.01);TG组大鼠移植侧纹状体内TH表达显著高于健侧(P=0.0029)、CG组移植侧和MG组(P=0.0031).TG组纹状体DA及其代谢产物水平明显高于CG组和MG组(P=0.0027).与MG组比较,CG组大鼠旋转行为、TH表达,以及DA,DOPAC和HVA水平均无统计学差异.结论 TH基因修饰的iNSCs细胞株RMN-TH可以在PD大鼠纹状体内长时间安全存活并稳定表达TH,显著增加内源性DA及其代谢产物水平,有效改善模型大鼠PD症状.     

雌激素对PD模型大鼠黑质纹状体通路的保护作用及其机制探讨

目的研究雌激素（Estrogen）对6-羟基多巴（6-OHDA）制备的去卵巢（OVX）帕金森病（PD）模型大鼠黑质纹状体通路的保护作用及其可能机制。方法应用6-OHDA两点注射单侧损毁内侧前脑束（MFB）制备OVXPD模型大鼠,侧脑室给予17-β雌二醇（17-βestradiol,1μg/5μl）,观察大鼠旋转行为、黑质酪氨酸羟化酶（TH）基因表达、黑质铁染色阳性细胞数量和纹状体内多巴胺（DA）及其代谢产物含量的变化。结果雌激素用药组可明显减少阿朴吗啡诱导的PD模型大鼠单侧旋转行为（P〈0.01）。在损毁侧黑质,雌激素用药组TH基因的表达较PD模型组明显增加（P〈0.01）;纹状体DA及其代谢产物亦较PD模型组显著升高（P〈0.01）。黑质铁染色阳性细胞数量较PD模型组明显减少（P〈0.01）。结论雌激素对PD模型大鼠黑质DA能神经元有明显的保护作用,其作用机制可能与降低铁负载有关。     

Striatal adenosine A(2A) receptor-mediated positron emission tomographic imaging in 6-hydroxydopamine-lesioned rats using [(18)F]-MRS5425

Introduction

A_2A receptors are expressed in the basal ganglia, specifically in striatopallidal GABAergic neurons in the striatum (caudate–putamen). This brain region undergoes degeneration of presynaptic dopamine projections and depletion of dopamine in Parkinson's disease. We developed an ¹⁸F-labeled A_2A analog radiotracer ([¹⁸F]-MRS5425) for A_2A receptor imaging using positron emission tomography (PET). We hypothesized that this tracer could image A_2A receptor changes in the rat model for Parkinson's disease, which is created following unilateral injection of the monoaminergic toxin 6-hydroxydopamine (6-OHDA) into the substantia nigra.

Methods

[¹⁸F]-MRS5425 was injected intravenously in anesthetized rats, and PET imaging data were collected. Image-derived percentage injected doses per gram (%ID/g) in regions of interest was measured in the striatum of normal rats and in rats unilaterally lesioned with 6-OHDA after intravenous administration of saline (baseline), D₂ agonist quinpirole (1.0 mg/kg) or D₂ antagonist raclopride (6.0 mg/kg).

Results

Baseline %ID/g reached a maximum at 90 s and maintained plateau for 3.5 min, and then declined slowly thereafter. In 6-OHDA-lesioned rats, %ID/g was significantly higher in the lesioned side compared to the intact side, and the baseline total %ID/g (data from both hemispheres were combined) was significantly higher compared to quinpirole stimulation starting from 4.5 min until the end of acquisition at 30 min. Raclopride did not produce any change in uptake compared to baseline or between the hemispheres.

Conclusion

Thus, increase of A_2A receptor-mediated uptake of radioactive MRS5425 could be a superior molecular target for Parkinson's imaging.     

Manganese-enhanced MRI in a rat model of Parkinson's disease

PURPOSE: To measure intra- and inter-hemispheric connectivity within the basal ganglia (BG) nuclei in healthy and in unilateral 6-hydroxydopamine (6-OHDA) Parkinson disease rat model in order to test the BG interhemispheric connectivity hypothesis. MATERIAL AND METHODS: The manganese-enhanced MRI (MEMRI) method with direct injection of manganese chloride into the entopeduncular (EP), substantia nigra (SN), and the Habenula nuclei in unilateral 6-OHDA (N = 22) and sham-operated (N = 16) rat groups was used. MEMRI measurements were applied before, 3, 24, and 48 hours post-manganese injection. Signal enhancements in T1-weighted images were compared between groups. RESULTS: Manganese injection into the EP nucleus resulted with bihemispheric signal enhancements in the habenular complex (Hab) at both groups with stronger enhancements in the 6-OHDA group. It also exhibited lower sensorimotor cortex signal enhancement in the 6-OHDA rat group. SN manganese injection caused enhanced anteroventral thalamic and habenular nuclei signals in the 6-OHDA rat group. Manganese habenula injection revealed enhanced interpeduncular (IP) and raphe nuclei signals of the 6-OHDA rat group. CONCLUSION: Modulations in the effective intra- and interhemispheric BG connectivity in unilateral 6-OHDA Parkinson's disease (PD) rat model support the BG interhemispheric connectivity hypothesis and suggest a linkage between the dopaminergic and serotonergic systems in PD, in line with clinical symptoms.     

6-羟基多巴脑内注射建立帕金森病大鼠模型的实验研究

目的 探讨6-羟基多巴脑内注射建立稳定的帕金森病大鼠模型的方法.方法 将6-羟基多巴立体定向注入大鼠右侧前脑内侧束和中脑被盖腹侧区,观察大鼠的行为变化和中脑黑质区的形态学变化.结果 注药后2周,动物经阿扑吗啡诱导即出现向健侧的旋转行为,注射效果稳定.在长达3个月的观察中,动物的旋转行为稳定,无明显的差异.形态学显示,毁损侧的黑质致密部和中脑被盖腰侧区的酪氨酸羟化酶阳性神经元的数量明显减少.结论 通过6-羟基多巴脑内注射的方法可以建立起稳定、有效的帕金森病大鼠模型.     

Administration of rotenone enhanced voluntary alcohol drinking behavior in C57BL/6J mice

Rotenone, a commonly used lipophic pesticide, is a high-affinity mitochondrial complex I inhibitor. The aim of this project is to study the causal relationship between changes of brain monoamine levels and drinking behavior in rotenone-treated mice. In the first experiment, we investigated the effects of acute exposure to rotenone (20 mg/kg, p.o.) on the 8-h time limited-access alcohol drinking behavior and brain monoamine levels in C57BL/6J mice at 0, 2, 8 and 24 h. Dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5HIAA) levels in the nucleus accumbens (ACC), caudate-putamen (C/P) and lateral hypothalamus (LH) of rotenone-treated mice were decreased at 2 and/or 8 h. Rotenone-exposed mice showed a suppression of voluntary alcohol intake at 4 and 8 h, but total daily alcohol intake did not differ significantly between the two groups. The effects of chronic exposure to rotenone (1, 5, 10 and 20 mg/kg, p.o. for 30 days) on the alcohol drinking behavior and monoamine levels of rotenone-exposed mice (10 mg/kg, p.o.) were investigated in the second experiment. The mice treated with rotenone showed increases in alcohol drinking behavior. Levels of DA and 5-HT in the ACC and C/P of chronic rotenone-treated mice were decreased, while the ratios of DOPAC to DA in the ACC and C/P and of 5HIAA to 5-HT in the ACC, C/P and DRN were increased significantly. Tyrosine hydroxylase immunoreactivity of chronic rotenone-treated mice (10 mg/kg, p.o.) slightly were decreased in both the striatum and the substantia nigra. Ethanol and acetaldehyde metabolism was not significantly different between mice treated with rotenone (10 mg/kg, p.o.) and controls. It was suggested that rotenone-treated mice had increased alcohol drinking behavior associated with increases in the DA turnover ratios of ACC and striatum to compensate for the neural degeneration.     

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.     

酪氨酸对心理应激大鼠中枢多巴胺含量及其更新率的影响

目的 探讨酪氨酸(Tyr)干预对心理应激大鼠中枢多巴胺(DA)含量及其更新率的影响.方法 40只SD大鼠按数字表法随机分为5组:对照组、心理应激组和3个剂量Tyr干预组(分别经饲料每天给予Tyr 250、500、1000 mg/kg),每组8只.建立大鼠Communication Box心理应激模型,采用高效液相色谱-电化学(HPLC-ECD)法测定各组大鼠前额皮质(mPFC)、伏隔核(Nac)和中脑腹侧被盖区(VTA)的DA与3,4-二羟基苯乙酸(DOPAC)含量.结果 与对照组mPFC、Nac、VTA区的DA含量[(0.36±0.15)、(3.47±0.52)、(1.35±0.31)μg/g]相比,心理应激组相应区的DA含量[(0.08±0.05)、(1.88±0.27)、(1.01±0.26)μg/g]降低(P＜0.05),DOPAC/DA升高(P＜0.01).与心理应激组相比,Tyr 500 mg/kg干预组和1000 mg/kg干预组mPFC、Nac、VTA区的DA含量增加(P＜0.05),mPFC、VTA区的DOPAC/DA降低(P＜0.05).结论 心理应激导致大鼠mPFC、Nac、VTA区的DA含量下降和DA更新率升高;Tyr干预能提高心理应激大鼠VTA-Nac-mPFC脑区的DA含量,降低DA更新率.     

Dependence of cardiac 11C-meta-hydroxyephedrine retention on norepinephrine transporter density.

The norepinephrine analog (11)C-meta-hydroxyephedrine (HED) is used with PET to map the regional distribution of cardiac sympathetic neurons. HED is rapidly transported into sympathetic neurons by the norepinephrine transporter (NET) and stored in vesicles. Although much is known about the neuronal mechanisms of HED uptake and retention, there is little information about the functional relationship between HED retention and cardiac sympathetic nerve density. The goal of this study was to characterize the dependence of HED retention on nerve density in rats with graded levels of cardiac denervation induced chemically with the neurotoxin 6-hydroxydopamine (6-OHDA). METHODS: Thirty male Sprague-Dawley rats were divided into 6 groups, and each group was administered a different dose of 6-OHDA: 0 (controls), 7, 11, 15, 22, and 100 mg/kg intraperitoneally. One day after 6-OHDA injection, HED (3.7-8.3 MBq) was injected intravenously into each animal and HED concentrations in heart and blood at 30 min after injection were determined. Heart tissues were frozen and later processed by tissue homogenization and differential centrifugation into a membrane preparation for in vitro measurement of cardiac NET density. A saturation binding assay using (3)H-mazindol as the radioligand was used to measure NET density (maximum number of binding sites [B(max)], fmol/mg protein) for each heart. RESULTS: In control animals, NET B(max) was 388 +/- 23 fmol/mg protein and HED heart uptake (HU) at 30 min was 2.89% +/- 0.35 %ID/g (%ID/g is percentage injected dose per gram tissue). The highest 6-OHDA dose of 100 mg/kg caused severe cardiac denervation, decreasing both NET B(max) and HED HU to 8% of their control values. Comparing values for all doses of 6-OHDA, HED retention had a strong linear correlation with NET density: HU = 0.0077B(max) -0.028, r(2) = 0.95. CONCLUSION: HED retention is linearly dependent on NET density in rat hearts that have been chemically denervated with 6-OHDA, suggesting that HED retention is a good surrogate measure of NET density in the rat heart. This finding is discussed in relation to clinical observations of the dependence of HED retention on cardiac nerve density in human subjects using PET.