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Supplemental Digital Content is available in the text., Rationale: Endothelial cells (ECs) are highly glycolytic and generate the majority of their energy via the breakdown of glucose to lactate. At the same time, a main role of ECs is to allow the transport of glucose to the surrounding tissues. GLUT1 (glucose transporter isoform 1/Slc2a1) is highly expressed in ECs of the central nervous system (CNS) and is often implicated in blood-brain barrier (BBB) dysfunction, but whether and how GLUT1 controls EC metabolism and function is poorly understood. Objective: We evaluated the role of GLUT1 in endothelial metabolism and function during postnatal CNS development as well as at the adult BBB. Methods and Results: Inhibition of GLUT1 decreases EC glucose uptake and glycolysis, leading to energy depletion and the activation of the cellular energy sensor AMPK (AMP-activated protein kinase), and decreases EC proliferation without affecting migration. Deletion of GLUT1 from the developing postnatal retinal endothelium reduces retinal EC proliferation and lowers vascular outgrowth, without affecting the number of tip cells. In contrast, in the brain, we observed a lower number of tip cells in addition to reduced brain EC proliferation, indicating that within the CNS, organotypic differences in EC metabolism exist. Interestingly, when ECs become quiescent, endothelial glycolysis is repressed, and GLUT1 expression increases in a Notch-dependent fashion. GLUT1 deletion from quiescent adult ECs leads to severe seizures, accompanied by neuronal loss and CNS inflammation. Strikingly, this does not coincide with BBB leakiness, altered expression of genes crucial for BBB barrier functioning nor reduced vascular function. Instead, we found a selective activation of inflammatory and extracellular matrix related gene sets. Conclusions: GLUT1 is the main glucose transporter in ECs and becomes uncoupled from glycolysis during quiescence in a Notch-dependent manner. It is crucial for developmental CNS angiogenesis and adult CNS homeostasis but does not affect BBB barrier function.

We investigated the glucose metabolism in an adeno-associated viral vector based alpha-synuclein rat model for Parkinson's disease (PD) using longitudinal 18F-FDG PET imaging, which resulted in an improved characterization of this animal model. We generated a PD specific pattern (PDSP) based on a multivariate classification approach to differentiate between a PD and control group at a late disease stage, where the neurodegeneration is considered nearly complete. In particular, we applied a principal component analysis prior to classification by a support vector machine (SVM). Moreover, by using a SVM for regression to predict corresponding motor scores, a PD motor pattern (PDMP) was derived as well. The PDSP mainly corresponds to the PDMP and overlaps to a large extent with the human pattern. We were able to quantify disease expression at previous time points by projecting onto the PDSP and PDMP. While a univariate analysis indicated metabolic changes which did not persist through time, both PDSP and PDMP were able to differentiate significantly (p-value

Currently TAR DNA binding protein 43 (TDP-43) pathology, underlying Amyotrophic Lateral Sclerosis (ALS), remains poorly understood which hinders both clinical diagnosis and drug discovery efforts. To better comprehend the disease pathophysiology, positron emission tomography (PET) and multi-parametric magnetic resonance imaging (mp-MRI) provide a non-invasive mode to investigate molecular, structural, and neurochemical abnormalities in vivo. For the first time, we report the findings of a longitudinal PET-MR study in the TDP-43A315T ALS mouse model, investigating disease-related changes in the mouse brain. 2-deoxy-2-[18F]fluoro-D-glucose [18F]FDG PET showed significantly lowered glucose metabolism in the motor and somatosensory cortices of TDP-43A315T mice whereas metabolism was elevated in the region covering the bilateral substantia nigra, reticular and amygdaloid nucleus between 3 and 7 months of age, as compared to non-transgenic controls. MR spectroscopy data showed significant changes in glutamate + glutamine (Glx) and choline levels in the motor cortex and hindbrain of TDP-43A315T mice compared to controls. Cerebral blood flow (CBF) measurements, using an arterial spin labelling approach, showed no significant age- or group-dependent changes in brain perfusion. Diffusion MRI indices demonstrated transient changes in different motor areas of the brain in TDP-43A315T mice around 14 months of age. Cytoplasmic TDP-43 proteinaceous inclusions were observed in the brains of symptomatic, 18-month-old mice, but not in non-symptomatic transgenic or wild-type mice. Our results reveal that disease- and age-related functional and neurochemical alterations, together with limited structural changes, occur in specific brain regions of transgenic TDP-43A315T mice, as compared to their healthy counterparts. Altogether these findings shed new light on TDP-43A315T disease pathogenesis and may prove useful for clinical management of ALS. ispartof: Neuroimage-Clinical vol:27 ispartof: location:Netherlands status: published

Many Huntington disease (HD) mutation carriers already have cognitive and psychiatric symptoms in the premanifest (premotor) phase of the disease (pre-HD), but the molecular underpinnings of these symptoms are not well understood. Previous work has shown reduced availability of the cerebral type 1 cannabinoid receptor (CB1R) in manifest HD. Here, we investigated whether CB1R binding is related to cognitive and psychiatric symptoms in pre-HD mutation carriers. Methods: CB1R binding was measured with 18F-MK-9470 (N-[(2S,3S)-3-(3-cyanophenyl)-4-(4-ethoxyphenyl)butan-2-yl]-2-methyl-2-(5-methylpyridin-2-yl)oxypropanamide) PET in 15 pre-HD subjects (8 men, 7 women; age, 39.3 ± 9.9 y), 15 gene-negative controls from HD families (9 men, 6 women; age, 37.0 ± 10.6 y), and 12 community controls (6 men and 6 women; age, 39.9 ± 15.1 y). All subjects also underwent extensive assessment of motor and cognitive function, as well as a behavioral test battery including the Problem Behavior Assessment for HD (PBA-HD), and MRI. Parametric binding images of 18F-MK-9470 were corrected for partial-volume effect. Results: There was no difference in CB1R binding, gray matter volume, cognitive function, or psychiatric scores between gene-negative controls from HD families and community controls, which were therefore pooled to one control group. Compared with controls, pre-HD subjects showed striatal atrophy, a decrease in CB1R binding in the prefrontal cortex, and higher PBA-HD scores on depression, apathy, and irritability (range, P = 0.01-0.005). The PBA-HD scores inversely correlated with CB1R binding in prefrontal regions and cingulate cortex in pre-HD (range: r = -0.64 to -0.72; P = 0.01-0.008). Conclusion: The association between behavioral symptoms and reduced prefrontal CB1R levels may provide new insight into the molecular basis of neuropsychiatric symptoms in pre-HD and suggest new therapeutic avenues.

In a longitudinal rat model of alcohol consumption, we showed that exposure to alcohol decreased the concentration of glutamate in the prefrontal cortex, whereas a normalization occurred during abstinence. 18F-FPEB PET scans revealed that pre-exposure mGluR5 availability in the nucleus accumbens was associated with future alcohol preference. Finally, alcohol exposure induced a decrease in mGluR5 availability in the bilateral hippocampus and amygdala compared with baseline, and in the hippocampus and striatum compared with saccharin (Figure). ispartof: ADDICTION BIOLOGY vol:24 issue:4 pages:696-706 ispartof: location:United States status: published

INTRODUCTION: A possible target for stroke management is modulation of neuroinflammation. Evidence suggests that food components may exert anti-inflammatory properties and thus may reduce stroke-induced brain damage.AIM: To investigate the efficacy of a diet, containing anti-inflammatory ingredients, as treatment for focal ischemic brain damage induced by photothrombotic stroke in the somatosensory cortex of rats.RESULTS: Brain lesions were surrounded by strong astrogliosis on both day 7 and day 21 after stroke and were accompanied by a trend toward globally decreased glucose metabolism on day 7. The investigational diet applied 2 weeks before the ischemia did not affect astrocyte activation on day 7, but reduced it at day 21. The investigational diet applied immediately after the ischemia, increased astrocyte activation on day 7 and completely reversed this effect on day 21. Moreover, postischemic intervention increased glucose metabolism in somatosensory cortex ipsilateral to the lesion on day 7.CONCLUSION: This study reveals potentially beneficial effects of a diet containing elevated amounts of anti-inflammatory nutrients on the recovery from ischemic brain damage. Therefore, dietary intervention can be considered as an adjuvant therapy for recovery from this brain pathology.

OBJECTIVE: We investigated changes in the endocannabinoid system and glucose metabolism during temporal lobe epileptogenesis. METHODS: Because it is rarely possible to study epileptogenesis in humans, we applied the electrical amygdala kindling model in nonhuman primates to image longitudinal changes in type 1 cannabinoid receptor (CB1R) binding and cerebral glucose metabolism. Two rhesus monkeys received [18 F]-MK-9470 and fluorodeoxyglucose-positron emission tomography ([18 F]-FDG -PET) scans in each of the 4 kindling stages to quantify relative changes over time of CB1R binding and cerebral glucose metabolism in vivo. We constructed z-score images relative to a control group (n = 8), and considered only those changes measured in both kindled animals by calculating the binary conjunction image per kindling stage. RESULTS: The seizure-onset zone exhibited an increased CB1R binding and a decreased glucose metabolism, which both aggravated gradually in extent and intensity throughout kindling. The ipsilateral thalamus and insula showed hypometabolism that coincided with an increase and a decrease in CB1R binding, respectively. These changes also became gradually more severe throughout kindling and overlapped with ictal perfusion changes during the final stage of amygdala kindling, with hyperperfusion in the ipsilateral thalamus and hypoperfusion in the ipsilateral insula. SIGNIFICANCE: The observed changes in CB1R binding may reflect a combination of a protective mechanism of neurons against seizure activity that becomes stronger over time to combat more severe seizures, and on the other hand, a process of epileptogenesis that facilitates seizure activity and generalization, depending on the cell type involved in those specific regions. This study provides unique evidence that the CB1R is dynamically and progressively involved from the start of mesial temporal lobe epileptogenesis. ispartof: Epilepsia vol:59 issue:5 pages:959-970 ispartof: location:United States status: published

Cocaine addiction is a disorder that still lacks diagnostic biomarkers or effective pharmacotherapy. We present findings in a rat model of cocaine self-administration that was followed-up longitudinally using the metabotropic glutamate receptor 5 (mGluR5) tracer 18F-FPEB positron emission tomography (PET), proton magnetic resonance spectroscopy (1H-MRS) and behavioral tests. Methods: Forty-two Wistar rats were scanned with 18F-FPEB PET and 1H-MRS before and after sucrose or IV cocaine self-administration, during withdrawal and relapse. All animals performed a rodent Iowa Gambling Task (rIGT) at baseline to evaluate decision-making. Baseline values were used in a mixed model to assess associations with later cocaine use and follow-up measurements were compared to the values before drug exposure. Results: Pre-exposure rIGT scores were significantly related to both cocaine and sucrose use during the drug-exposure phase. However, only cocaine self-administration induced a decrease in 18F-FPEB binding. This decrease was most pronounced in the bilateral hippocampus, where mGluR5 availability correlated with the amount of cocaine used during relapse. Compared to the sucrose group, a larger decrease was observed in the hippocampo-prefrontal cortex pathway. Pre-exposure glutamate and glycine concentrations in the prefrontal cortex were significantly associated with cocaine use during the drug-exposure phase. Moreover, prefrontal glutamate exhibited a distinct, reversible decrease when animals had access to cocaine, but not sucrose. Conclusion: Baseline values of prefrontal glutamate and glycine are associated with future cocaine use. Furthermore, baseline rIGT scores are associated with both sucrose and cocaine. Finally, we found that both glutamate concentration and mGluR5 availability decrease during exposure to cocaine. ispartof: Journal of Nuclear Medicine vol:59 issue:6 pages:952-959 ispartof: location:United States status: published

Metabotropic glutamate receptors (mGluRs) have been proposed as promising therapeutic targets to correct the dysregulated glutamate signaling, associated with neurodegenerative pathologies. Of all mGluR subtypes, especially mGluR5 acts as a modulator of glutamate-induced excitotoxicity. To study the behavior of mGluR5 following localized excitotoxicity, we utilised a pharmacological model that portrays exacerbated neuronal glutamate release, mediated by the endogenous excitotoxin quinolinic acid (QA). Using longitudinal positron emission tomography (PET) with [18F]FPEB, we investigated cerebral changes in mGluR5 following striatal QA-lesioning. Behavioral tests were executed to monitor motor and cognitive performance. Decreased mGluR5 binding potential (BPND) was found in the affected striatum and globus pallidus of QA-lesioned rats at week 3, and further decreased at week 7, as compared to sham-injected controls. mGluR5 availability in the ipsilateral nucleus accumbens was significantly decreased at 7 weeks post-injection. QA rats performed significantly worse on motor coordination and balance compared to control rats. Correlation analysis indicated a positive correlation between striatal mGluR5 BPND and rotarod performance whereas print width of the unaffected forepaws showed a positive relation with mGluR5 BPND in the contralateral motor cortex. Together, our results suggest decreased mGluR5 availability to be related to excitotoxin-induced neurodegeneration and symptomatology although late stage effects do indicate possible cortical mGluR5-mediated effects on motor behavior.

Rat models based on viral vector-mediated overexpression of α-synuclein are regarded as highly valuable models that closely mimic cardinal features of human Parkinson's disease (PD) such as L-DOPA-dependent motor impairment, dopaminergic neurodegeneration and α-synuclein inclusions. To date, the downstream effects of dopaminergic cell loss on brain glucose metabolism, including the neuroinflammation component, have not been phenotyped in detail for this model. Cerebral glucose metabolism was monitored throughout different stages of the disease using in vivo 2-[18F]-fluoro-2-deoxy- d -glucose ([18F]FDG) positron emission tomography (PET) and was combined with in vitro [18F]DPA-714 autoradiography to assess concomitant inflammation. Rats were unilaterally injected with recombinant adeno-associated viral vector serotype 2/7 (rAAV2/7) encoding either A53T α-synuclein or eGFP. Brain [18F]FDG microPET was performed at baseline, 1, 2, 3, 4, 6, and 9 weeks post-surgery, in combination with behavioral tests. As a second experiment, [18F]DPA-714 autoradiography was executed across the same timeline. Voxel-based analysis of relative [18F]FDG uptake showed a dynamic pattern of PD-related metabolic changes throughout the disease progression (weeks 2–9). Glucose hypermetabolism covering a large bilateral area reaching from the insular, motor- and somatosensory cortex to the striatum was observed at week 2. At week 4, hypermetabolism presented in a cluster covering the ipsilateral nigra-thalamic region, whereas hypometabolism was noted in the ipsilateral striatum at week 6. Elevated [18F]FDG uptake was seen in a cluster extending across the contralateral striatum, motor- and somatosensory cortex at week 9. Increased [18F]FDG in the region of the substantia nigra was associated with increased [18F]DPA-714 binding, and correlated significantly with motor symptoms. These findings point to disease-associated metabolic and neuroinflammatory changes taking place in the primary area of dopaminergic neurodegeneration but also closely interconnected motor and somatosensory brain regions.

PURPOSE: The endocannabinoid system plays a regulatory role in a number of physiological functions, including motor control but also mood, emotion, and cognition. A number of preclinical studies in Parkinson's disease (PD) models demonstrated that modulating the type 1 cannabinoid receptor (CB1R) may improve motor symptoms and components of cognitive processing. However, the relation between CB1R, cognitive decline and behavioral symptoms has not been investigated in PD patients so far. The aim of this study was to examine whether CB1R availability is associated with measures of cognitive and behavioral function in PD patients. METHODS: Thirty-eight PD patients and ten age- and gender-matched controls underwent a [18F]MK-9470 PET scan to assess CB1R availability, as well as volumetric MR imaging. Neuropsychological symptoms were evaluated using an extensive cognitive and behavioral battery covering the five cognitive domains, depression, anxiety, apathy, and psychiatric complications, and were correlated to CB1R availability using vowel-wise regression analysis (P 4.0). Also, PD patients with more severe visuospatial dysfunction showed decreased CB1R availability in the precuneus, midcingulate, supplementary motor cortex, inferior orbitofrontal gyrus and thalamus (Tpeak-level = 5.5). These correlations were not related to cortical gray matter atrophy. No relationship was found between CB1R availability and mood or behavioral symptom scores. CONCLUSIONS: Decreased CB1R availability in the prefrontal and midcingulate cortex in PD patients is strongly correlated with disturbances in executive functioning, episodic memory, and visuospatial functioning. Further investigation of regional CB1R expression in groups of PD patients with mild cognitive impairment or dementia is warranted in order to further investigate the role of CB1R expression in different levels of cognitive impairment in PD. This article is part of the Topical Collection on Neurology ispartof: European Journal Of Nuclear Medicine And Molecular Imaging vol:46 issue:11 pages:2348-2357 ispartof: location:Germany status: published

We investigated the glucose metabolism in an adeno-associated viral vector based alpha-synuclein rat model for Parkinson’s disease (PD) using longitudinal 18F-FDG PET imaging, which resulted in an improved characterization of this animal model. We generated a PD specific pattern (PDSP) based on a multivariate classification approach to differentiate between a PD and control group at a late disease stage, where the neurodegeneration is considered nearly complete. In particular, we applied a principal component analysis prior to classification by a support vector machine (SVM). Moreover, by using a SVM for regression to predict corresponding motor scores, a PD motor pattern (PDMP) was derived as well. The PDSP mainly corresponds to the PDMP and overlaps to a large extent with the human pattern. We were able to quantify disease expression at previous time points by projecting onto the PDSP and PDMP. While a univariate analysis indicated metabolic changes which did not persist through time, both PDSP and PDMP were able to differentiate significantly (p-value

(18)F-FPEB is a promising PET tracer for studying the metabotropic glutamate subtype 5 receptor (mGluR5) expression in neuropsychiatric disorders. To assess the potential of (18)F-FPEB for longitudinal mGluR5 evaluation in patient studies, we evaluated the long-term test-retest reproducibility using various kinetic models in the human brain. Nine healthy volunteers underwent consecutive scans separated by a 6-month period. Dynamic PET was combined with arterial sampling and radiometabolite analysis. Total distribution volume (V(T)) and nondisplaceable binding potential (BP(ND)) were derived from a two-tissue compartment model without constraints (2TCM) and with constraining the K(1)/k(2) ratio to the value of either cerebellum (2TCM-CBL) or pons (2TCM-PONS). The effect of fitting different functions to the tracer parent fractions and reducing scan duration were assessed. Regional absolute test-retest variability (aTRV), coefficient of repeatability (CR) and intraclass correlation coefficient (ICC) were computed. The 2TCM-CBL showed best fits. The mean 6-month aTRV of V(T) ranged from 8 to 13% (CR 0.6 for all kinetic models. BPND from 2TCM-CBL with a sigmoid fit for the parent fractions showed the best reproducibility, with aTRV ≤ 7% (CR 0.9 in most regions. Reducing the scan duration from 90 to 60 min did not affect reproducibility. These results demonstrate for the first time that (18)F-FPEB brain PET has good long-term reproducibility, therefore validating its use to monitor mGluR5 expression in longitudinal clinical studies. We suggest a 2TCM-CBL with fitting a sigmoid function to the parent fractions to be optimal for this tracer.

Many Huntington disease (HD) mutation carriers already have cognitive and psychiatric symptoms in the premanifest (premotor) phase of the disease (pre-HD), but the molecular underpinnings of these symptoms are not well understood. Previous work has shown reduced availability of the cerebral type 1 cannabinoid receptor (CB

In a longitudinal rat model of alcohol consumption, we showed that exposure to alcohol decreased the concentration of glutamate in the prefrontal cortex, whereas a normalization occurred during abstinence. 18F-FPEB PET scans revealed that pre-exposure mGluR5 availability in the nucleus accumbens was associated with future alcohol preference. Finally, alcohol exposure induced a decrease in mGluR5 availability in the bilateral hippocampus and amygdala compared with baseline, and in the hippocampus and striatum compared with saccharin (Figure).To study the role of the glutamatergic system in alcohol abuse disorders, we conducted a longitudinal study of alcohol exposure in rats. Rats were followed with

Several lines of evidence point to alterations in glutamatergic signaling in Parkinson's disease (PD) and levodopa-induced dyskinesia (LID), involving the metabotropic glutamate receptor type 5 (mGluR5). Using small-animal positron emission tomography (PET) with [18F]FPEB and proton magnetic resonance spectroscopy, we investigated cerebral changes in the mGluR5 and glutamate/glutamine availability invivo in PD rats and following onset of LIDs. In parallel, behavioral tests were performed. Comparing PD to control rats, mGluR5 binding potential was decreased in a cluster comprising the bilateral caudate-putamen (CP), ipsilateral motor cortex and somatosensory cortex, and the contralateral somatosensory cortex and parietal association cortex, with the most pronounced reduction in the ipsilateral CP. mGluR5 binding potentials were not significantly altered upon levodopa (L-DOPA) treatment. However, following L-DOPA, an increase in relative mGluR5 uptake was present in the contralateral motor cortex and somatosensory cortex. Glutamate and glutamine concentrations did not differ between control and untreated PD rats or between hemispheres. Though, glutamine levels were higher in the contralateral CP of saline- and L-DOPA-treated rats as compared to the ipsilateral side. Relative mGluR5 uptake in the CP of levodopa-treated rats was also found positively correlated with abnormal involuntary movement scores. Conclusively, mGluR5 availability and glutamine concentrations in the CP are involved in PD, whereas mGluR5 availability in cortical regions may be involved in LID pathology.

Molecular imaging is indispensable for determining the fate and persistence of engrafted stem cells. Standard strategies for transgene induction involve the use of viral vectors prone to silencing and insertional mutagenesis or the use of nonhuman genes. Methods: We used zinc finger nucleases to induce stable expression of human imaging reporter genes into the safe-harbor locus adeno-associated virus integration site 1 in human embryonic stem cells. Plasmids were generated carrying reporter genes for fluorescence, bioluminescence imaging, and human PET reporter genes. Results: In vitro assays confirmed their functionality, and embryonic stem cells retained differentiation capacity. Teratoma formation assays were performed, and tumors were imaged over time with PET and bioluminescence imaging. Conclusion: This study demonstrates the application of genome editing for targeted integration of human imaging reporter genes in human embryonic stem cells for long-term molecular imaging.

Involvement of the type 1 cannabinoid receptor (CB1R) in the effects of alcohol on the brain is supported by animal experiments, but howin vivoCB1R levels are altered in alcoholic patients is still unclear. To assess the short-time effects of a binge drinking episode on CB1R availability, 20 healthy social drinkers underwent [18F]MK-9470-positron emission tomography (PET) at baseline and after intravenous ethanol administration (ALC ACU). Moreover, 26 alcoholic patients underwent sequential CB1R PET after chronic heavy drinking (ALC CHR) and after 1 month of abstinence (ALC ABST). Seventeen healthy subjects served as controls.Compared with baseline, ALC ACU resulted in a global increase of CB1R availability (+15.8%). In contrast, a global decreased CB1R availability was found in ALC CHR patients (−16.1%) compared with controls, which remained unaltered after abstinence (−17.0%). Voxel-based analysis showed that ALC CHR patients had reduced CB1R availability, especially in the cerebellum and parieto-occipital cortex. After abstinence, reduced CB1R availability extended also to other areas such as the ventral striatum and mesotemporal lobe.In conclusion, whereas the acute alcohol effect is an increase in CB1R availability, chronic heavy drinking leads to reduced CB1R availability that is not reversible after 1 month of abstinence. Longer follow-up is required to differentiate whether this is a compensatory effect of repeated endocannabinoid overstimulation or an enduring trait-like feature. An enhanced CB1R signaling may offer a new therapeutic direction for treatment of the negative affective state produced by alcohol withdrawal and abstinence, which is critical for the maintenance of alcohol addiction.

Several lines of evidence strongly implicate a dysfunctional endocannabinoid system (ECS) in eating disorders. Using [18F]MK-9470 and small animal positron emission tomography (PET), we investigated for the first time cerebral changes in type 1 cannabinoid (CB1) receptor binding in vivo in the activity-based rat model of anorexia (ABA), in comparison to distinct motor- and food-related control conditions and in relation to gender and behavioural variables. In total, experiments were conducted on 80 Wistar rats (23 male and 57 female). Male rats were assigned to the cross-sectional conditions: ABA (n = 12) and CONTROL (n = 11), whereas female rats were divided between two settings: (1) a cross-sectional design using ABA (n = 13), CONTROL (n = 9), and two extra control conditions for each of the variables manipulated in ABA, i.e. DIET (n = 8) and WHEEL (n = 9), and (2) a longitudinal one using ABA (n = 10) and CONTROL (n = 8) studied at baseline, during the model and upon recovery. The ABA group was subjected to food restriction in the presence of a running wheel, the DIET group to food restriction without wheel, the WHEEL group to a normal diet with wheel and CONTROL animals had a normal diet and no running wheel. Parametric CB1 receptor images of each group were spatially normalized to Paxinos space and analysed voxel-wise. In the ABA model, absolute [18F]MK-9470 binding was significantly increased in all cortical and subcortical brain areas as compared to control conditions (male +67 %; female >51 %, all p cluster

(18)F-FPEB is a promising PET tracer for studying the metabotropic glutamate subtype 5 receptor (mGluR5) expression in neuropsychiatric disorders. To assess the potential of (18)F-FPEB for longitudinal mGluR5 evaluation in patient studies, we evaluated the long-term test-retest reproducibility using various kinetic models in the human brain. Nine healthy volunteers underwent consecutive scans separated by a 6-month period. Dynamic PET was combined with arterial sampling and radiometabolite analysis. Total distribution volume (V(T)) and nondisplaceable binding potential (BP(ND)) were derived from a two-tissue compartment model without constraints (2TCM) and with constraining the K(1)/k(2) ratio to the value of either cerebellum (2TCM-CBL) or pons (2TCM-PONS). The effect of fitting different functions to the tracer parent fractions and reducing scan duration were assessed. Regional absolute test-retest variability (aTRV), coefficient of repeatability (CR) and intraclass correlation coefficient (ICC) were computed. The 2TCM-CBL showed best fits. The mean 6-month aTRV of V(T) ranged from 8 to 13% (CR 0.6 for all kinetic models. BPND from 2TCM-CBL with a sigmoid fit for the parent fractions showed the best reproducibility, with aTRV ≤ 7% (CR 0.9 in most regions. Reducing the scan duration from 90 to 60 min did not affect reproducibility. These results demonstrate for the first time that (18)F-FPEB brain PET has good long-term reproducibility, therefore validating its use to monitor mGluR5 expression in longitudinal clinical studies. We suggest a 2TCM-CBL with fitting a sigmoid function to the parent fractions to be optimal for this tracer.

We have characterized both acute and long-term vascular and metabolic effects of unilateral common carotid artery occlusion in mice by in vivo magnetic resonance imaging and positron emission tomography. This common carotid artery occlusion model induces chronic cerebral hypoperfusion and is therefore relevant to both preclinical stroke studies, where it serves as a control condition for a commonly used mouse model of ischemic stroke, and neurodegeneration, as chronic hypoperfusion is causative to cognitive decline. By using perfusion magnetic resonance imaging, we demonstrate that under isoflurane anesthesia, cerebral perfusion levels recover gradually over one month. This recovery is paralleled by an increase in lumen diameter and altered tortuosity of the contralateral internal carotid artery at one year post-ligation as derived from magnetic resonance angiography data. Under urethane/α-chloralose anesthesia, no acute perfusion differences are observed, but the vascular response capacity to hypercapnia is found to be compromised. These hemispheric perfusion alterations are confirmed by water [15O]-H2O positron emission tomography. Glucose metabolism ([18F]-FDG positron emission tomography) or white matter organization (diffusion-weighted magnetic resonance imaging) did not show any significant alterations. In conclusion, permanent unilateral common carotid artery occlusion results in acute and long-term vascular remodeling, which may have immediate consequences for animal models of stroke but also vascular dementia.

In order to study the molecular pathways of Parkinson's disease (PD) and to develop novel therapeutic strategies, scientific investigators rely on animal models. The identification of PD-associated genes has led to the development of genetic PD models. Most transgenic α-SYN mouse models develop gradual α-SYN pathology but fail to display clear dopaminergic cell loss and dopamine-dependent behavioral deficits. This hurdle was overcome by direct targeting of the substantia nigra with viral vectors overexpressing PD-associated genes. Local gene delivery using viral vectors provides an attractive way to express transgenes in the central nervous system. Specific brain regions can be targeted (e.g. the substantia nigra), expression can be induced in the adult setting and high expression levels can be achieved. Further, different vector systems based on various viruses can be used. The protocol outlines all crucial steps to perform a viral vector injection in the substantia nigra of the rat to develop a viral vector-based alpha-synuclein animal model for Parkinson's disease.

PURPOSE: [(18)F]MK-9470 is an inverse agonist for the type 1 cannabinoid (CB1) receptor allowing its use in PET imaging. We characterized the kinetics of [(18)F]MK-9470 and evaluated its ability to quantify CB1 receptor availability in the rat brain. METHODS: Dynamic small-animal PET scans with [(18)F]MK-9470 were performed in Wistar rats on a FOCUS-220 system for up to 10 h. Both plasma and perfused brain homogenates were analysed using HPLC to quantify radiometabolites. Displacement and blocking experiments were done using cold MK-9470 and another inverse agonist, SR141716A. The distribution volume (V (T)) of [(18)F]MK-9470 was used as a quantitative measure and compared to the use of brain uptake, expressed as SUV, a simplified method of quantification. RESULTS: The percentage of intact [(18)F]MK-9470 in arterial plasma samples was 80 ± 23 % at 10 min, 38 ± 30 % at 40 min and 13 ± 14 % at 210 min. A polar radiometabolite fraction was detected in plasma and brain tissue. The brain radiometabolite concentration was uniform across the whole brain. Displacement and pretreatment studies showed that 56 % of the tracer binding was specific and reversible. V (T) values obtained with a one-tissue compartment model plus constrained radiometabolite input had good identifiability (≤10 %). Ignoring the radiometabolite contribution using a one-tissue compartment model alone, i.e. without constrained radiometabolite input, overestimated the [(18)F]MK-9470 V (T), but was correlated. A correlation between [(18)F]MK-9470 V (T) and SUV in the brain was also found (R (2) = 0.26-0.33; p ≤ 0.03). CONCLUSION: While the presence of a brain-penetrating radiometabolite fraction complicates the quantification of [(18)F]MK-9470 in the rat brain, its tracer kinetics can be modelled using a one-tissue compartment model with and without constrained radiometabolite input. ispartof: European journal of nuclear medicine and molecular imaging vol:39 issue:9 pages:1467-1477 ispartof: location:Germany status: published

Several lines of evidence suggest a functional interaction between central nicotinic and endocannabinoid systems. Furthermore, type 1 cannabinoid receptor (CB1R) antagonism is evaluated as antismoking therapy, and nicotine usage can be an important confound in positron emission tomography (PET) imaging studies of the CB1R. We evaluated CB1R binding in the rat brain using the PET radioligand [(18)F]MK-9470 after chronic administration of nicotine. Twelve female Wistar rats were scanned at baseline and after chronic administration of either nicotine (1 mg/kg; 2 weeks daily intraperitoneal (IP)) or saline as control. In vivo micro-PET images of CB1R binding were anatomically standardized and analyzed by voxel-based statistical parametric mapping and a predefined volume-of-interest approach. We did not observe changes in [(18)F]MK-9470 binding (p (height) < 0.001 level; uncorrected) on a group basis in either condition. Only at a less stringent threshold of p (height) < 0.005 (uncorrected) was a modest increase observed in tracer binding in the cerebellum for nicotine (peak voxel value + 6.8%, p (cluster) = 0.002 corrected). In conclusion, chronic IP administration of nicotine does not produce major cerebral changes in CB1R binding of [(18)F]MK-9470 in the rat. These results also suggest that chronic nicotine usage is unlikely to interfere with human PET imaging using this radioligand. ispartof: Journal of Molecular Neuroscience vol:42 issue:2 pages:162-167 ispartof: location:United States status: published

Type 1 cannabinoid (CB1) receptors are expressed in high concentrations in the central nervous system, including the basal ganglia, and could have direct or indirect effects on motor behavior through modulation of dopaminergic, glutamatergic and GABA-ergic neurotransmission. Using the CB1 receptor radioligand [(18)F]MK-9470 and small-animal PET, we investigated for the first time in vivo cerebral changes in [(18)F]MK-9470 binding in the 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease (PD), parallel to dopamine transporter (DAT) imaging, tyrosine hydroxylase (TH) staining, and behavioral measurements. In the 6-OHDA model, relative [(18)F]MK-9470 PET binding decreased in the contralateral cerebellum (-9%, p

Functional neuroimaging is widely used to unravel changes in brain functioning in psychiatric disorders. In the current study, we review single-photon emission tomography (SPECT), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies in anorexia nervosa (AN), a difficult-to-treat eating disorder with the highest mortality rate among psychiatric disorders. We discuss the role of the parietal cortex, anterior and subgenual cingulate cortex, frontal cortex and temporal lobe in light of the cardinal symptoms of AN. The insights of the current review may ultimately lead to the development of new treatments.

There is substantial evidence that the endocannabinoid system and in particular the type 1 cannabinoid receptor (CB1R) is involved in epilepsy. We evaluated the in vivo effect of chronic administration of the anti-epileptic drugs valproate (VPA) and levetiracetam (LEV) on rat brain CB1 receptors using the positron emission tomography (PET) tracer [F-18]MK-9470. Six Wistar rats were treated with VPA (200 mg/kg) or LEV (50 mg/kg) IP daily for 2 weeks. Dynamic imaging after intravenous injection of 18 MBq [F-18]MK-9470 was performed on a FOCUS 220 microPET at baseline and after chronic treatment. Six animals were used as controls and were injected with saline, using the same protocol. Parametric images based on standardized uptake values (SUV) were generated and were spatially normalized to Paxinos space. These CB1R images were analyzed using a predefined volume of interest (VOI)-based analysis. Differences in SUV values between chronic and baseline scans in each condition (saline, VPA and LEV treatment) were calculated in each VOI. Direct binding affinity of the drugs at CB1R was assessed by competitive binding assay in Chinese hamster ovarian cells expressing human MR. Chronic injections of saline did not produce significant changes in global [F-18]MK-9470 binding (p = 0.43), nor in tracer binding in individual VOIs. We found a significant increase in global cerebral [F-18]MK-9470 binding after chronic VPA administration compared to sham treated animals (+32.5%, p < 0.001), as well as in tracer binding in all individual VOI. After chronic administration of LEV, there was no significant change in global cerebral CB1R binding (+6.9%, p = 0.81), nor in tracer binding in individual VOIs. As VPA does not exhibit high affinity for CB1R (displacement of [H-3]-SR141716A 1.3 +/- 14.0%), such upregulation is most likely caused by an indirect effect on the endocannabinoid system. This increase in CB1R tracer binding and possibly signaling may represent a supplementary and new mechanism of VPA, but not LEV, since activation of CB1Rs has been shown to decrease excitability and excitotoxicity on-demand. (C) 2008 Elsevier Ltd. All rights reserved.

The endocannabinoid system (ECS) is implicated as a regulator of homeostasis of several cerebral functions and is a novel target for drug treatment of neuropyschiatric disorders. So far, the cerebral cannabinoid-type 1 receptor (CB1R) has only been studied using in vitro, animal model, electrophysiological and post-mortem data. We have used positron emission tomography (PET) using a high-affinity, subtype-selective radioligand, [(18)F]MK-9470, to assess the in vivo cerebral CB1R distribution and its variation with healthy aging and gender. Fifty healthy volunteers (25 M/25 F, 18-69 years) underwent [(18)F]MK-9470 PET. Parametric [(18)F]MK-9470 binding maps were constructed, corrected for partial volume effects and analyzed using statistical parametric mapping in a combined categorical (gender) and covariate (age) design. We found that [(18)F]MK-9470 binding to CB1R increased with aging but only in women (p(FWE)

Summary Objective Amygdala kindling is a widely used animal model for studying mesial temporal lobe epileptogenesis. In the macaque monkey, electrical amygdala kindling develops slowly and provides an opportunity for investigating ictal perfusion changes during epileptogenesis. Methods Two rhesus monkeys were electrically kindled through chronically implanted electrodes in the right amygdala over a period of 16 and 17 months. Ictal perfusion single photon emission computed tomography (SPECT) imaging was performed during each of the four predefined clinical stages. Results Afterdischarge duration increased slowly over 477 days for monkey K and 515 days for monkey S (18 ± 8 s in stage I; 52 ± 13 s in stage IV). During this time, the animals progressed through four clinical stages ranging from interrupting ongoing behavior to bilateral convulsions. Ictal SPECT perfusion imaging showed well-localized but widely distributed regions of hyperperfusion and hypoperfusion, in both cortical and subcortical structures, at every seizure stage. A large portion of the ictal network was involved in the early stages of epileptogenesis and subsequently expanded over time as seizure severity evolved. Significance Our data indicate that the different mesial temporal lobe seizure types occur within a common network affecting several parts of the brain, and that seizure severity may be determined by seizure-induced epileptogenesis within a bihemispheric network that is implicated from the start of the process.

PURPOSE: [(18)F]DPA-714 is a radiotracer with high affinity for TSPO. We have characterized the kinetics of [(18)F]DPA-714 in rat brain and evaluated its ability to quantify TSPO expression with PET using a neuroinflammation model induced by unilateral intracerebral injection of lipopolysaccharide (LPS). METHODS: Dynamic small-animal PET scans with [(18)F]DPA-714 were performed in Wistar rats on a FOCUS-220 system for up to 3h. Both plasma and perfused brain homogenates were analysed using HPLC to quantify radiometabolites. Full kinetic modelling of [(18)F]DPA-714 brain uptake was performed using a metabolite-corrected arterial plasma input function. Binding potential (BPND) calculated as the distribution volume ratio minus one (DVR-1) between affected and healthy brain tissue was used as the outcome measure and evaluated against reference tissue models. RESULTS: The percentage of intact [(18)F]DPA-714 in arterial plasma samples was 92 ± 4% at 10min, 75 ± 8% at 40min and 52 ± 6% at 180min. The radiometabolite fraction in brain was negligible ( CONCLUSION: Quantification of [(18)F]DPA-714 binding to TSPO with full kinetic modelling is feasible using a 2T model. SRTM and MRTM can be suggested as reasonable substitutes with the contralateral striatum as the reference region and a scan duration of at least 90min. However, selection of the reference region depends on the disease model used.

The endocannabinoid system (ECS) is a ubiquitous modulatory neurotransmission system in the brain. It consists of a family of naturally occurring lipids, the endocannabinoids, of transport and degradation proteins, and of cannabinoid receptors. Experimental evidence points towards an important role of the type 1 cannabinoid (CB1) receptor in the pathogenesis of Huntington’s disease (HD) in multiple disease domains, including motor, cognitive, and behavioral aspects. Also, the type 2 cannabinoid (CB2) receptor is part of an endogenous mechanism of defense that is involved in neuroinflammation. In this chapter, we provide an overview of the role of the ECS in the pathophysiology of HD. We focus on molecular imaging using PET for visualization and quantitative assessment of CB1 and CB2 receptors.

UNLABELLED: The metabotropic glutamate receptor 5 (mGluR5) is a high-interest target for PET imaging because it plays a role in several pathologies, including addiction, schizophrenia, and fragile X syndrome. METHODS: We studied the pharmacokinetics of (18)F-FPEB (3-(18)F-fluoro-5-(2-pyridinylethynyl)benzonitrile), a selective PET radioligand for mGluR5, and used it to quantify mGluR5 in rat brain. Quantification was performed using both arterial sampling in combination with compartment models and simplified reference methods. The simplified reference tissue model (SRTM), Ichise's original multi-linear reference tissue model (MRTMO), and Logan noninvasive were tested as reference models with nondisplaceable binding (BPND) as outcome parameter. Additionally, test-retest scans were obtained in 6 animals. RESULTS: (18)F-FPEB uptake in rat brain was consistent with its known distribution. No radiometabolites were present in the brain, and binding was specific as shown in blocking experiments, which also confirmed the cerebellum as a viable reference region. A 2-tissue-compartment model was used to determine BPND for the striatum (11.7 ± 1.5), nucleus accumbens (10.6 ± 2.0), hippocampus (9.0 ± 1.2), cortex (7.2 ± 1.0), and thalamus (4.0 ± 0.9). Reference methods were able to estimate these values with small bias (

High-resolution anatomical image data in preclinical brain PET and SPECT studies is often not available, and inter-modality spatial normalization to an MRI brain template is frequently performed. However, this procedure can be challenging for tracers where substantial anatomical structures present limited tracer uptake. Therefore, we constructed and validated strain- and tracer-specific rat brain templates in Paxinos space to allow intra-modal registration. PET [18F]FDG, [11C]flumazenil, [11C]MeDAS, [11C] PK11195 and [11C]raclopride, and SPECT [99mTc]HMPAO brain scans were acquired from healthy male rats. Tracer-specific templates were constructed by averaging the scans, and by spatial normalization to a widely used MRI-based template. The added value of tracer-specific templates was evaluated by quantification of the residual error between original and realigned voxels after random misalignments of the data set. Additionally, the impact of strain differences, disease uptake patterns (focal and diffuse lesion), and the effect of image and template size on the registration errors were explored. Mean registration errors were 0.70±0.32mm for [18F] FDG ( n = 25), 0.23±0.10mm for [11C]flumazenil ( n = 13), 0.88±0.20 mm for [11C]MeDAS (n = 15), 0.64±0.28mm for [11C] PK11195 (n = 19), 0.34±0.15mm for [11C] raclopride ( n = 6), and 0.40±0.13mm for [99mTc]HMPAO ( n = 15). These values were smallest with tracer-specific templates, when compared to the use of [18F]FDG as reference template (p&0.001). Additionally, registration errors were smallest with strain-specific templates (p&0.05), and when images and templates had the same size (p≤0.001). Moreover, highest registration errors were found for the focal lesion group (p&0.005) and the diffuse lesion group (p = n . s.). In the voxel-based analysis, the reported coordinates of the focal lesion model are consistent with the stereotaxic injection procedure. The use of PET/SPECT strain- and tracer-specific templates allows accurate registration of functional rat brain data, independent of disease specific uptake patterns and with registration error below spatial resolution of the cameras. The templates and the SAMIT package will be freely available for the research community.

OBJECTIVE: The goal of this study was to measure functional and structural aspects of local neuroinflammation induced by intracerebral injection of lipopolysaccharide (LPS) in rats using TSPO microPET imaging with [(18)F]DPA-714, magnetic resonance imaging (MRI), in vitro autoradiography and immunohistochemistry (IHC) in order to characterize a small animal model for screening of new PET tracers targeting neuroinflammation. METHODS: Rats were injected stereotactically with LPS (50 μg) in the right striatum and with saline in the left striatum. [(18)F]DPA-714 microPET, MRI, in vitro autoradiography and IHC studies were performed at different time points after LPS injection for 1 month. RESULTS: Analysis of the microPET data demonstrated high uptake of the tracer in the LPS injected site with an affected-to-non-affected side-binding potential ratio (BPright-to-left) of 3.0 at 3 days after LPS injection. This BP ratio decreased gradually over time to 0.9 at 30 days after LPS injection. In vitro autoradiography ([(18)F]DPA-714) and IHC (CD68, GFAP and TSPO) confirmed local neuroinflammation in this model. Dynamic contrast enhanced (DCE) MRI demonstrated BBB breakdown near the LPS injection site at day 1, which gradually resolved over time and was absent at 1 month after LPS injection. CONCLUSION: The LPS model is useful for first screening of newly developed tracers because of the easy design and the robust, unilateral inflammatory reaction allowing the use of the contralateral region as control. Additionally, this model can be used to test and follow up the benefits of anti-inflammatory therapies by non-invasive imaging.

Purpose: Several lines of evidence imply early alterations in endocannabinoid and phosphodiesterase10A (PDE10A) signaling in Huntington disease (HD). Using [18F]MK-9470 and [18F]JNJ42259152small-animal PET, we investigated for the first time cerebral changes in type 1 cannabinoid (CB1)receptor binding and PDE10A levels in vivo in pre-, early- and late symptomatic HD (R6/2) mice, inrelation to glucose metabolism ([18F]FDG PET), brain morphology (MRI) and motor function. Methods:Ten R6/2 and 16 wild-type (WT) mice were investigated at 3 different time points between the age of 4and 13 weeks. Parametric CB1 receptor and PDE10A images were anatomically standardized toPaxinos space and analyzed voxel-wise. Volumetric microMRI imaging was performed to assess HDpathology. Results: In R6/2 mice, CB1 receptor binding was decreased in comparison to WT in acluster comprising the bilateral caudate-putamen, globus pallidus and thalamic nucleus at week 5 (-8.1±2.6%; p=1.7.10-5). Longitudinal follow-up showed further progressive decline compared to controlsin a cluster comprising the bilateral hippocampus, caudate-putamen, globus pallidus, superiorcolliculus, thalamic nucleus and cerebellum (late vs. presymptomatic age: -13.7±3.1% for R6/2 and+1.5±4.0% for WT; p=1.9.10-5). In R6/2 mice, PDE10A binding potential also decreased over time, toreach significance at early and late symptomatic HD (late vs. presymptomatic age: -79.1±1.9% forR6/2 and +2.1±2.7% for WT; p=1.5.10-4). The observed changes in CB1 receptor and PDE10A bindingwere correlated to anomalies exhibited by R6/2 animals in motor function, while no correlation wasfound with MRI-based striatal volume. Conclusion: Our findings point to early regional dysfunctions inendocannabinoid and PDE10A signaling, involving the caudate-putamen and lateral globus pallidus,that may play a role in the progression of the disease in R6/2 animals. PET quantification of in vivoCB1 and/or PDE10A binding may thus be useful early biomarkers for HD. Our results also provideevidence of subtle motor deficits at earlier stages than previously described.

The endocannabinoid system (ECS) is a ubiquitous modulatory system in the brain that is responsible for one of the major forms of retrograde neurotransmission feedback. It consists of a family of naturally occurring lipids, the endocannabinoids, of transport and degradation proteins, and of cannabinoid receptors. Genetic, pharmacological, and ex vivo preclinical studies point toward a role of the type 1 cannabinoid receptor in the pathogenesis of several neuropsychiatric diseases. The type 2 cannabinoid receptor is part of an endogenous mechanism of defense in neuroinflammatory conditions. However, the function of the ECS has remained difficult to assess in vivo. In this perspective, molecular imaging using positron emission tomography and single-photon emission computed tomography is a novel route for visualization and quantitative assessment of this system. This review focuses on our current possibilities for molecular imaging of cannabinoid receptors.

Next to genetical testing and behavioural observations, neuroimaging studies are increasingly performed on primates and rodents to model a variety of human diseases and traits. Animal models of brain disease are available for all major neurodegenerative diseases, epilepsy, stroke, but also psychiatric diseases such as anorexia nervosa, obesity, depression and anxiety [1].