Stratifying drug treatment of cognitive impairments after traumatic brain injury using neuroimaging.

Cognitive impairment is common following traumatic brain injury. Dopaminergic drugs can enhance cognition after traumatic brain injury, but individual responses are highly variable. This may be due to variability in dopaminergic damage between patients. We investigate whether measuring dopamine transporter levels using 123I-ioflupane single-photon emission computed tomography (SPECT) predicts response to methylphenidate, a stimulant with dopaminergic effects. Forty patients with moderate-severe traumatic brain injury and cognitive impairments completed a randomized, double-blind, placebo-controlled, crossover study. 123I-ioflupane SPECT, MRI and neuropsychological testing were performed. Patients received 0.3 mg/kg of methylphenidate or placebo twice a day in 2-week blocks. Subjects received neuropsychological assessment after each block and completed daily home cognitive testing during the trial. The primary outcome measure was change in choice reaction time produced by methylphenidate and its relationship to stratification of patients into groups with normal and low dopamine transporter binding in the caudate. Overall, traumatic brain injury patients showed slow information processing speed. Patients with low caudate dopamine transporter binding showed improvement in response times with methylphenidate compared to placebo [median change = -16 ms; 95% confidence interval (CI): -28 to -3 ms; P = 0.02]. This represents a 27% improvement in the slowing produced by traumatic brain injury. Patients with normal dopamine transporter binding did not improve. Daily home-based choice reaction time results supported this: the low dopamine transporter group improved (median change -19 ms; 95% CI: -23 to -7 ms; P = 0.002) with no change in the normal dopamine transporter group (P = 0.50). The low dopamine transporter group also improved on self-reported and caregiver apathy assessments (P = 0.03 and P = 0.02, respectively). Both groups reported improvements in fatigue (P = 0.03 and P = 0.007). The cognitive effects of methylphenidate after traumatic brain injury were only seen in patients with low caudate dopamine transporter levels. This shows that identifying patients with a hypodopaminergic state after traumatic brain injury can help stratify the choice of cognitive enhancing therapy.

Improving the Sequence Coverage of Integral Membrane Proteins during Hydrogen/Deuterium Exchange Mass Spectrometry Experiments.

Insight into the structure-function relationship of membrane proteins is important to understand basic cell function and inform drug development, as these are common targets for drugs. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is an established technique for the study of protein conformational dynamics and has shown compatibility with membrane proteins. However, the digestion and mass analysis of peptides from membrane proteins can be challenging, severely limiting the HDX-MS experiment. Here we compare the digestion of four integral membrane proteins-Cl-/H+ exchange transporter (ClC-ec1), leucine transporter (LeuT), dopamine transporter (DAT), and serotonin transporter (SERT)-by the use of porcine pepsin and three alternative aspartic proteases either in-solution or immobilized on-column in an optimized HDX-MS-compatible workflow. Pepsin was the most favorable for the digestion of ClC-ec1 and LeuT, providing coverage of 82.2 and 33.2% of the respective protein sequence; however, the alternative proteases surpassed pepsin for the digestion of DAT and SERT. By also screening quench solution additives, we observe that the denaturant urea was beneficial, resulting in improved sequence coverage of all membrane proteins, in contrast to guanidine hydrochloride. Furthermore, significant improvements in sequence coverage were achieved by tailoring the chromatography to handle hydrophobic peptides. Overall, we demonstrate that the susceptibility of membrane proteins to proteolytic digestion during HDX-MS is highly protein-specific. Our results highlight the importance of having multiple proteases and different quench buffer additives in the HDX-MS toolbox and the need to carefully screen a range of digestion conditions to successfully optimize the HDX-MS analysis of integral membrane proteins.

Effects of sleep disruption on stress, nigrostriatal markers, and behavior in a chronic/progressive MPTP male mouse model of parkinsonism.

Sleep complaints are an early clinical symptom of neurodegenerative disorders. Patients with Parkinson's disease (PD) experience sleep disruption (SD). The objective of this study was to determine if preexisting, chronic SD leads to a greater loss of tyrosine hydroxylase (TH) within the striatum and the substantia nigra following chronic/progressive exposure with the neurotoxin, 1-methyl-2-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Male mice underwent chronic SD for 4 weeks, then injected with vehicle (VEH) or increasing doses of MPTP for 4 weeks. There was a significant decrease in the plasma corticosterone levels in the MPTP group, an increase in the SD group, and a return to the VEH levels in the SD+MPTP group. Protein expression levels for TH in the striatum (terminals) and substantia nigra pars compacta (dopamine [DA] cell counts) revealed up to a 78% and 38% decrease, respectively, in the MPTP and SD+MPTP groups compared to their relevant VEH and SD groups. DA transporter protein expression increased in the striatum in the MPTP versus VEH group and in the SN/midbrain between the SD+MPTP and the VEH group. There was a main effect of MPTP on various gait measures (e.g., braking) relative to the SD or VEH groups. In the SD+MPTP group, there were no differences compared to the VEH group. Thus, SD, prior to administration of MPTP, has effects on serum corticosterone and gait but more importantly does not potentiate greater loss of TH within the nigrostriatal pathway compared to the MPTP group, suggesting that in PD patients with SD, there is no exacerbation of the DA cell loss.

Patterns of dopamine transporter imaging in subtypes of multiple system atrophy.

OBJECTIVES: To investigate the differences in the pattern of striatal (caudate and putamen) dopamine transporter (DAT) loss in a multiple system atrophy (MSA) cohort, based on the clinical variants parkinsonian subtype (MSA-P) and cerebellar subtype (MSA-C) via (11)C-N-2-carbomethoxy-3-(4-fluorophenyl)-tropane (11 C-CFT) positron emission tomography (PET) imaging. MATERIALS AND METHODS: One hundred and six subjects (forty-one patients with probable MSA-P; forty patients with probable MSA-C; twenty-five healthy controls) underwent 11 C-CFT PET. Subregional 11 C-CFT uptake of bilateral caudate, anterior putamen, and posterior putamen was calculated respectively to measure the striatal dopaminergic function. RESULTS: Significant decrease in DAT binding in striatum was revealed in patients with MSA-C and MSA-P compared to normal controls (all regions, MSA-C vs controls, P < .0001; MSA-P vs controls, P < .0001). DAT reduction was more pronounced in MSA-P patients than that in MSA-C patients (all regions, P < .0001). Eleven of forty MSA-C patients displayed no DAT loss, whereas striatal DAT loss was evident in all MSA-P patients. MSA-P subtype showed a more obvious anteroposterior gradient of DAT loss and more asymmetric dopaminergic dysfunction compared to MSA-C patients. CONCLUSION: The subtypes of MSA studied here show significantly different spatial/anatomic patterns of striatonigral degeneration which may provide insights into their disease pathophysiology. Specifically, MSA-P patients exhibit an uneven and much greater pronounced loss of dopamine innervation, while a relatively uniform pattern is revealed in patients with the MSA-C. Furthermore, the typical reduction in DAT 11 C-CFT binding in striatum is not present in all MSA-C patients, with a minority of cases showing normal DAT binding.

Differential Internalization Rates and Postendocytic Sorting of the Norepinephrine and Dopamine Transporters Are Controlled by Structural Elements in the N Termini.

The norepinephrine transporter (NET) mediates reuptake of synaptically released norepinephrine in central and peripheral noradrenergic neurons. The molecular processes governing availability of NET in the plasma membrane are poorly understood. Here we use the fluorescent cocaine analogue JHC 1-64, as well as several other approaches, to investigate the trafficking itinerary of NET in live noradrenergic neurons. Confocal imaging revealed extensive constitutive internalization of JHC 1-64-labeled NET in the neuronal somata, proximal extensions and presynaptic boutons. Phorbol 12-myristate 13-acetate increased intracellular accumulation of JHC 1-64-labeled NET and caused a parallel reduction in uptake capacity. Internalized NET strongly colocalized with the "long loop" recycling marker Rab11, whereas less overlap was seen with the "short loop" recycling marker Rab4 and the late endosomal marker Rab7. Moreover, mitigating Rab11 function by overexpression of dominant negative Rab11 impaired NET function. Sorting of NET to the Rab11 recycling compartment was further supported by confocal imaging and reversible biotinylation experiments in transfected differentiated CATH.a cells. In contrast to NET, the dopamine transporter displayed markedly less constitutive internalization and limited sorting to the Rab11 recycling compartment in the differentiated CATH.a cells. Exchange of domains between the two homologous transporters revealed that this difference was determined by non-conserved structural elements in the intracellular N terminus. We conclude that NET displays a distinct trafficking itinerary characterized by continuous shuffling between the plasma membrane and the Rab11 recycling compartment and that the functional integrity of the Rab11 compartment is critical for maintaining proper presynaptic NET function.

Precise Evaluation of Striatal Oxidative Stress Corrected for Severity of Dopaminergic Neuronal Degeneration in Patients with Parkinson's Disease: A Study with 62Cu-ATSM PET and 123I-FP-CIT SPECT.

BACKGROUND: This study sought to precisely evaluate striatal oxidative stress and its relationship with the disease severity in Parkinson's disease (PD) using double brain imaging, 62Cu-diacetyl-bis (N4-methylthiosemicarbazone) (62Cu-ATSM) PET and 123I-FP-CIT SPECT. METHODS: Nine PD patients were studied with brain 62Cu-ATSM PET for oxidative stress and 123I-FP-CIT SPECT for the density of striatal dopamine transporter. Standardized uptake values (SUVs) were obtained from the delayed phase of dynamic 62Cu-ATSM PET, and striatum-to-cerebellum SUV ratio (SUVR) was calculated. To correct the effect of neuronal loss in the striatum, 62Cu-ATSM SUVR was corrected for striatal specific binding ratio (SBR) values of 123I-FP-CIT (SUVR/SBR). RESULTS: 62Cu-ATSM SUVR without correction was not significantly correlated with disease severity estimated by the Unified Parkinson's Disease Rating Scale (UPDRS) scores or 123I-FP-CIT SBR. In contrast, the SUVR/SBR showed significant correlations with the UPDRS total and motor scores, and 123I-FP-CIT SBR. CONCLUSION: Oxidative stress in the remaining striatal dopaminergic neurons estimated by SUVR/SBR was increased with disease severity in PD patients, suggesting that oxidative stress based on mitochondrial dysfunction contributes to promoting dopaminergic neuronal degeneration in PD. 62Cu-ATSM PET with 123I-FP-CIT SPECT correction would be a promising tool to evaluate dopaminergic neuronal oxidative stress in PD.

Optimized Acquisition Time for Dopamine Transporter Imaging.

Excess acquisition counts were often obtained by the current image acquisition of 30 minutes after 123I-ioflupane administration in a dopamine transporter study. The purpose of this study was to calculate the minimum acquisition time while retaining sufficient image quality, which could be adjusted for individual characteristics. Fifty patients who underwent dopamine transporter imaging were included in this retrospective study. The brain count density, determined by a striatum phantom, was compared to the participant's characteristics. The individual characteristics were divided into five categories of gender, age, height, weight, and body mass index. The values of 40 counts / voxel (brain count density) were set as the image quality criteria by the striatum phantom study. Weight was the characteristic that most correlated with brain count density in the 50 patients (correlation coefficient: -0.728). The acquisition time for the 50 patients was calculated as 23.4±2.6 minutes using the following formula: 0.332×W+5.42 minutes (W kg (individual weight)). A shorter acquisition time with sufficient image quality can be achieved by adjusting for individual patient weight.

Optimization of Reformatting Angle Using Orbitomeatal Base Line in Dopamine Transporter Scintigraphy.

Recently, dopamine transporter (DaT) scintigraphy, which contributes to the early diagnosis of Parkinson's disease and Lewy body dementia, has been widely spread. It has been revealed that analytical results can be affected by the image-reformatting angle, and a horizontal section is recommended for the anterior commissure-posterior commissure (AC-PC) line according to the clinical guidelines for ioflupane. However, it is difficult to identify AC-PC line visually, as there is no remarkable accumulation in the cerebral parenchyma in DaT scintigraphy with poor contrast resolution. The objective of this study was to establish and optimize an adjustment method for the image-reformatting angle by using orbitomeatal base line (OM line). Evaluations were made on items such as comparison of image reformatting angles by an analyst, comparison of measurement angles of OM line, the angle formed by the intersection of OM line and AC-PC line, and the change in specific biding ratio (SBR) according to the difference in the image-reformatting angle. Consequently, the difference in analytical results among technicians became smaller, and consistent results were obtained by adjusting the image-reformatting angle.

Examination of a Method to Determine the Reference Region for Calculating the Specific Binding Ratio in Dopamine Transporter Imaging.

The specific binding ratio (SBR) was first reported by Tossici-Bolt et al. for quantitative indicators for dopamine transporter (DAT) imaging. It is defined as the ratio of the specific binding concentration of the striatum to the non-specific binding concentration of the whole brain other than the striatum. The non-specific binding concentration is calculated based on the region of interest (ROI), which is set 20 mm inside the outer contour, defined by a threshold technique. Tossici-Bolt et al. used a 50% threshold, but sometimes we couldn't define the ROI of non-specific binding concentration (reference region) and calculate SBR appropriately with a 50% threshold. Therefore, we sought a new method for determining the reference region when calculating SBR. We used data from 20 patients who had undergone DAT imaging in our hospital, to calculate the non-specific binding concentration by the following methods, the threshold to define a reference region was fixed at some specific values (the fixing method) and reference region was visually optimized by an examiner at every examination (the visual optimization method). First, we assessed the reference region of each method visually, and afterward, we quantitatively compared SBR calculated based on each method. In the visual assessment, the scores of the fixing method at 30% and visual optimization method were higher than the scores of the fixing method at other values, with or without scatter correction. In the quantitative assessment, the SBR obtained by visual optimization of the reference region, based on consensus of three radiological technologists, was used as a baseline (the standard method). The values of SBR showed good agreement between the standard method and both the fixing method at 30% and the visual optimization method, with or without scatter correction. Therefore, the fixing method at 30% and the visual optimization method were equally suitable for determining the reference region.

Ctr9, a Protein in the Transcription Complex Paf1, Regulates Dopamine Transporter Activity at the Plasma Membrane.

Dopamine (DA) is a major regulator of sensorimotor and cognitive functions. The DA transporter (DAT) is the key protein that regulates the spatial and temporal activity of DA release into the synaptic cleft via the rapid reuptake of DA into presynaptic termini. Several lines of evidence have suggested that transporter-interacting proteins may play a role in DAT function and regulation. Here, we identified the tetratricopeptide repeat domain-containing protein Ctr9 as a novel DAT binding partner using a yeast two-hybrid system. We showed that Ctr9 is expressed in dopaminergic neurons and forms a stable complex with DAT in vivo via GST pulldown and co-immunoprecipitation assays. In mammalian cells co-expressing both proteins, Ctr9 partially colocalizes with DAT at the plasma membrane. This interaction between DAT and Ctr9 results in a dramatic enhancement of DAT-mediated DA uptake due to an increased number of DAT transporters at the plasma membrane. We determined that the binding of Ctr9 to DAT requires residues YKF in the first half of the DAT C terminus. In addition, we characterized Ctr9, providing new insight into this protein. Using three-dimensional modeling, we identified three novel tetratricopeptide repeat domains in the Ctr9 sequence, and based on deletion mutation experiments, we demonstrated the role of the SH2 domain of Ctr9 in nuclear localization. Our results demonstrate that Ctr9 localization is not restricted to the nucleus, as previously described for the transcription complex Paf1. Taken together, our data provide evidence that Ctr9 modulates DAT function by regulating its trafficking.

Predictors of normal and abnormal outcome in clinical brain dopamine transporter imaging.

Brain dopamine transporter (DAT) imaging with [(123)I]FP-CIT SPECT can be used to evaluate the integrity of the mesostriatal dopaminergic system in patients with clinically uncertain parkinsonism. To evaluate whether scanning a patient is clinically necessary, it is vital to understand possible factors that affect the scanning result. Therefore, we investigated an unselected sample of 538 consecutively scanned patients from a 6-year period, and the demographic data and indications for DAT SPECT were recorded. After scanning, the patients were divided into groups according to the scanning outcome. Multivariate binary logistic regression analyses were performed to investigate whether the pre-imaging variables had independent associations with the outcome of the scan. Three hundred and three (56.3 %) patients had abnormal scans showing a dopaminergic deficit. The independent factors associated with abnormal scans were older age (p = 0.002), asymmetry of motor symptoms (p = 0.005) and shorter symptom duration (p < 0.001). Re-evaluation of the previously established Parkinson's disease diagnosis was associated with a higher probability of an abnormal scan (74.4 % abnormal, p = 0.004), whereas the possibility of medication-induced parkinsonism was associated with a higher probability of a normal scan (35.4 %, p = 0.036). The probability of an abnormal outcome in clinical brain DAT imaging increases with known risk factors of neurodegenerative parkinsonism. However, a long duration of uncertain motor symptoms and suspicion of medication-induced parkinsonism are associated with a higher probability of a normal outcome. The findings reflect epidemiological factors in parkinsonism together with referral biases that may be used to improve the clinical use of DAT imaging.

24-Hour Ambulatory Blood Pressure Monitoring in SWEDDs Patients With Parkinsonism.

BACKGROUND: Patients diagnosed with Parkinson's disease (PD) on clinics who subsequently turn out to have normal dopamine transporter images have been referred to as scans without evidence of dopaminergic deficits (SWEDDs) patients. Cardiovascular autonomic dysfunction has frequently been reported in PD. In this study, we determined the similarities and differences in cardiac autonomic dysfunction between SWEDDs and PD patients. This study investigated whether 24-hour ambulatory blood pressure monitoring (24-hour ABPM) can help identify possible cases with SWEDDs. METHODS: We enrolled 28 SWEDDs patients, 46 patients with PD, and 30 healthy controls. To evaluate cardiac autonomic function, 24-hour ABPM was performed on all subjects. Cardiac metaiodobenzylguanidine (MIBG) scintigraphy was performed on the SWEDDs and PD subjects. RESULTS: The percentage nocturnal decline in blood pressure differed significantly among SWEDDs patients, PD patients, and controls (p<0.05). In addition to the abnormal nocturnal BP, regulation (nondipping and reverse dipping) was significantly higher in SWEDDs and PD subjects than in the control subjects (p<0.05). There was no significant correlation between the % nocturnal blood pressure reduction and parameters of cardiac MIBG uptake ratio. However, orthostatic hypotension was significant correlated with the nocturnal blood pressure dip (%), nocturnal blood pressure patterns, and the cardiac MIBG uptake ratio (early and late) in combined SWEDDs and PD subjects. CONCLUSIONS: Pathologic nocturnal blood pressure regulation and nocturnal hypertension, known characteristics of PD, are also present in SWEDDs. Moreover, cardiac sympathetic denervation should not be attributed to cardiac autonomic dysfunction in SWEDDs patients. As with PD patients, the SWEDDs patients studied here tended to have cardiac autonomic dysfunction.

Dopamine, vesicular transporters, and dopamine receptor expression in rat major salivary glands.

The localization of dopamine stores and the expression and localization of dopamine (DAT) and vesicular monoamine transporters (VMAT) type-1 and -2 and of dopamine D1-like and D2-like receptor subtypes were investigated in rat submandibular, sublingual, and parotid salivary glands by HPLC with electrochemical detection, as well as immunochemical and immunohistochemical techniques. Male Wistar rats of 2 mo of age were used. The highest dopamine levels were measured in the parotid gland, followed by the submandibular and sublingual glands. Western blot analysis revealed DAT, VMAT-1, VMAT-2, and dopamine receptors immunoreactivity in membrane preparations obtained from the three glands investigated. Immunostaining for dopamine and transporters was developed within striated ducts. Salivary glands processed for dopamine receptors immunohistochemistry developed an immunoreaction primarily in striated and excretory ducts. In the submandibular gland, acinar cells displayed strong immunoreactivity for the D2 receptor, while cells of the convoluted granular tubules were negative for both D1-like and D2-like receptors. Parotid glands acinar cells displayed the highest immunoreactivity for both D1 and D2 receptors compared with other salivary glands. The above localization of dopamine and dopaminergic markers investigated did not correspond closely with neuron-specific enolase (NSE) localization. This indicates that at least in part, catecholamine stores and dopaminergic markers are independent from glandular innervation. These findings suggest that rat major salivary glands express a dopaminergic system probably involved in salivary secretion. The stronger immunoreactivity for dopamine transporters and receptors in striated duct cells suggests that the dopaminergic system could regulate not only quality, but also volume and ionic concentration of saliva.

Uric acid relates to dopamine transporter availability in Parkinson's disease.

BACKGROUND: Diagnosing Parkinson's disease (PD) and tracking its progression may require the combination of reliable biomarkers. Among them, both serum uric acid (UA) and dopamine transporter (DaT) binding deserve more investigations. AIMS OF THE STUDY: We aimed to investigate the relationship between serum UA levels and DaT availability in newly diagnosed, drug-naïve PD patients, by means of semiquantitative [(123) I]FP-CIT-SPECT. METHODS: We recruited 52 newly diagnosed, drug-naïve PD patients, and performed serum UA dosage and [(123) I]FP-CIT-SPECT. RESULTS: Pearson's correlation analysis showed that UA levels were significantly higher in patients with higher averaged, ipsilateral and contralateral DaT binding in caudate, putamen, and striatum. CONCLUSIONS: We showed, for the first time, by regional semiquantitative analysis of DaT binding in PD patients that UA levels significantly correlates with the severity of dopaminergic impairment in caudate, putamen, and striatum. This study broadens our knowledge on the importance of UA as a biomarker of PD.

Cognitive performances and DAT imaging in early Parkinson's disease with mild cognitive impairment: a preliminary study.

OBJECTIVES: Mild cognitive impairment (MCI) is a common feature in Parkinson's disease (PD). We performed an exploratory study to investigate dopaminergic nigrostriatal innervation and its cognitive correlates in early untreated PD patients with MCI as compared to cognitively intact patients. PATIENTS AND METHODS: A consecutive series of 34-de-novo, drug-naïve patients with PD were enrolled. They underwent [123-I] FP-CIT SPECT and comprehensive neuropsychological battery. MCI was identified in 15 of 34 patients with PD. RESULTS: The two groups did not show any statistically significant difference in age, sex, disease duration, education, lateralization, and H&Y and Hospital Anxiety and Depression Scale scores. Logistic regression analysis showed that UPDRS-III was weakly associated with MCI (P = 0.034). Partial correlation analysis controlling for UPDRS-III and age suggested that in PD patients with MCI reduced V3″ values in the more affected caudate were correlated with reduced performances in frontal assessment battery, Trail Making Test: part B minus Part A and copy task of the Rey-Osterrieth complex figure test. Reduced V3″ values in the more and less affected putamen were significantly related with reduced performance in frontal assessment battery and in copy task of Rey-Osterrieth complex figure test, respectively. No correlation was found between neuropsychological scores and DAT availability in PD patients without MCI. CONCLUSIONS: Although preliminary, our results suggest that striatal dopamine depletion may contribute to some cognitive deficit in early never treated PD patients with MCI.

[Comparison of Quantitative Value of Dopamine Transporter Scintigraphy Calculated from Different Analytical Software].

In the dopamine transporter scintigraphy there are two quantitative analysis softwares, DaTView and DaTQUANT. The quantitative value of both software has to be treated independently because there is a difference between them in the point of how to set the region of interest on the striatum and the background, calculation formula of quantitation. And also DaTQUANT has a capability of performing anatomical standardization which DaTView does not have. The aim of this study was to evaluate the accuracy of registration on DaTQUANT using a phantom, and to evaluate the correlation between the quantitative values between DaTView and DaTQUANT using clinical data. As a result, the accuracy of registration was acceptable. Regardless of the degree of accumulation in the striatum, there was a high correlation to each analysis software (r>0.85).

[Assessment of Inspection Technology of Dopamine Transporter Imaging with ¹²³I-Ioflupane].

Imaging start time of single-photon emission computed tomography (SPECT) scan is recommended between 3 hours and 6 hours after injection of ¹²³I-ioflupane in Ioflupane clinical practice guidelines. But image includes the effect of physiological actions of the human body and the attenuation at 13.27 hours physical half-life of ¹²³I. Therefore, we evaluated the effect of the image by the elapsed time of imaging start time. Optimal cut-off frequency of Butterworth filter were examined phantom by normalized mean square error. Count was reduced by 23.1% in 5 hours, but cut-off frequency of Butterworth filter was 0.11 cycle/pixel in 0-5 hours from phantom data. Ten subjects (age 55-85 years) were injected with ¹²³I-ioflupane of 110-199 MBq into the vein only once. And we examined the specific binding ratio (SBR) in inspection of injection after 5. 5 hours and 3 hours. Decrease of counts value increased the coefficient of variance (CV) between 3 hours and 5.5 hours after injection, but the improvement of statistical noise by pre-processing filter reduced the CV. No significant difference in the result of SBR was found between 3 hours and 5. 5 hours after injection. Our results suggest that imaging start time of SPECT scan is recommended between 3 hours and 5.5 hours after injection of ¹²³I-ioflupane.

Flow cytometry analysis of synaptosomes from post-mortem human brain reveals changes specific to Lewy body and Alzheimer's disease.

Synaptic dysfunction is thought to have an important role in the pathophysiology of neurodegenerative diseases, such as Alzheimer's disease (AD) and Lewy body disease (LBD). To improve our understanding of synaptic alterations in health and disease, we investigated synaptosomes prepared from post-mortem human cerebral cortex, putamen (PT), and two regions of the caudate nucleus, dorso-lateral (DL) and ventro-medial (VM), regions commonly affected in AD and LBD. We observed that the fraction of synaptosomal particles with reactivity for dopamine transporter (DAT) was significantly reduced in the PT and VM caudate of patients with neuropathological diagnosis of LBD. As expected, these differences also were reflected in direct measurements of dopamine (DA) and its metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), in caudate and PT of LBD patients. The fraction of synaptosomal particles positive for amyloid ß (Aß) was significantly increased in frontal cortical samples of patients with the neuropathological diagnosis of severe AD, and was positively correlated with disease progression. We also prepared synaptosomes from the striatum of mice with severe loss of DA neurons (Slc6a3-DTR mice) and wild-type littermate controls. We observed markedly reduced levels of DAT-positive synaptosomes in Slc6a3-DTR mice following exposure to diphtheria toxin (DT). Striatal levels of DA and DOPAC in Slc6a3-DTR mice also were reduced significantly following DT exposure. We conclude that flow cytometric analysis of synaptosomes prepared from human or mouse brain provides an opportunity to study expression of pathology-associated proteins and also the specific loss of dopaminergic nerve terminals. Hence, we believe it is a valid method to detect pathological changes at the level of the synapse in LBD as well as AD.

Differences of various region-of-interest methods for measuring dopamine transporter availability using 99mTc-TRODAT-1 SPECT.

This study was to investigate whether various region-of-interest (ROI) methods for measuring dopamine transporter (DAT) availabilities by single photon emission computed tomography (SPECT) are statistically different, whether results of medical research are thereby influenced, and causes of these differences. Eighty-four healthy adults with (99m)Tc-TRODAT-1 SPECT and magnetic resonance imaging (MRI) scans were included. Six major analysis approaches were compared: (1) ROI drawn on the coregistered MRI; (2) ROIs drawn on the SPECT images; (3) standard ROI templates; (4) threshold-ROIs; (5) atlas-based mappings with coregistered MRI; and (6) atlas-based mappings with SPECT images. Using the atlas-based approaches we assessed the influence of striatum ROIs by slice-wise and voxel-wise comparisons. In (5) and (6), three partial-volume correction (PVC) methods were also explored. The results showed that DAT availabilities obtained from different methods were closely related but quite different and leaded to significant differences in determining the declines of DAT availability per decade (range: 5.95-11.99%). Use of 3D whole-striatum or more transverse slices could avoid biases in measuring the striatal DAT declines per decade. Atlas-based methods with PVC may be the preferable methods for medical research.

Validation of parametric methods for [¹¹C]PE2I positron emission tomography.

OBJECTIVES: The radioligand [(11)C]PE2I is highly selective for dopamine transporter (DAT) and can be used in vivo for investigation of changes in DAT concentration, progression of disease and validation of treatment using positron emission tomography (PET). DAT is an important protein for regulation of central dopamine concentration and DAT deficiency has been associated with several neurodegenerative and neuropsychiatric disorders. Accurate parametric images are a prerequisite for clinical application of [(11)C]PE2I. The purpose of this study was to evaluate different methods for producing [(11)C]PE2I parametric images, showing binding potential (BPND) and relative delivery (R1) at the voxel level, using clinical data as well as simulations. METHODS: Investigations were made in twelve subjects either with social anxiety disorder (n=6) or parkinsonian syndrome (n=6), each receiving an 80 min dynamic PET scan. All subjects underwent a T1-weighted MRI scan which was co-registered to the PET images and used for definition of regions of interest using a probabilistic template (PVElab). Two basis function implementations (receptor parametric mapping: RPM, RPM2) of the simplified reference tissue model (SRTM) and three multilinear reference tissue models (MRTMo, MRTM and MRTM2) were used for computation of parametric BPND and R1 images. In addition, reference Logan and standard uptake value ratio (SUVr) were investigated. Evaluations of BPND and R1 images were performed using linear regression to compare the parametric methods to region-based analyses with SRTM and cerebellar gray matter as reference region. Accuracy and precision of each method were assessed by simulations. RESULTS: Correlation and slope of linear regression between parametric and region-based BPND and R1 values in both striatum and extra-striatal regions were optimal for RPM (R(2)=0.99 for both BPND and R1; slopes 0.99 and 0.98 for BPND and R1, respectively, in striatum). In addition, accuracy and precision were best for RPM and RPM2. CONCLUSION: The basis function methods provided more robust estimations of the parameters compared to the other models and performed best in simulations. RPM, a basis function implementation of SRTM, is the preferred method for voxel level analysis of [(11)C]PE2I PET studies.