Abnormal dopamine uptake sites in postmortem striatum from patients with Tourette's syndrome

G-quadruplex formation at human DAT1 gene promoter: Effect of cytosine methylation

The dopamine transporter gene (DAT1), a recognized genetic risk factor for attention deficit hyperactivity disorder (ADHD) is principally responsible for the regulation of dopamine synaptic levels and serves as a key target in many psychostimulants drugs. DAT1 gene methylation has been considered an epigenetic marker in ADHD. The identification of G-rich sequence motifs potential to form G-quadruplexes is correlated with functionally important genomic regions. Herein, biophysical and biochemical techniques are employed to investigate the structural polymorphism along with the effect of cytosine methylation on a 26-nt G-rich sequence present in the promoter region of the DAT1 gene. The gel electrophoresis, circular dichroism spectroscopy, and UV-thermal melting data are well correlated and conclude the formation of a parallel (bimolecular), as well as antiparallel (tetramolecular) G-quadruplex in Na⁺ solution. Interestingly, the existence of uni-, bi-, tri-, and tetramolecular quadruplex structures in K⁺ solution exhibited only the parallel type G-quadruplex. The results demonstrate that in presence of either cation (Na⁺ or K⁺) the cytosine methylation reserved the structural topologies unaltered. However, methylation lowers the thermal stability of G-quadruplexes and the duplex structures, as well. These findings provide insights to understand the regulatory mechanisms underlying the formation of the G-quadruplex structure induced by DNA methylation.

Molecular Landscape of Tourette's Disorder

Tourette's disorder (TD) is a highly heritable childhood-onset neurodevelopmental disorder and is caused by a complex interplay of multiple genetic and environmental factors. Yet, the molecular mechanisms underlying the disorder remain largely elusive. In this study, we used the available omics data to compile a list of TD candidate genes, and we subsequently conducted tissue/cell type specificity and functional enrichment analyses of this list. Using genomic data, we also investigated genetic sharing between TD and blood and cerebrospinal fluid (CSF) metabolite levels. Lastly, we built a molecular landscape of TD through integrating the results from these analyses with an extensive literature search to identify the interactions between the TD candidate genes/proteins and metabolites. We found evidence for an enriched expression of the TD candidate genes in four brain regions and the pituitary. The functional enrichment analyses implicated two pathways ('cAMP-mediated signaling' and 'Endocannabinoid Neuronal Synapse Pathway') and multiple biological functions related to brain development and synaptic transmission in TD etiology. Furthermore, we found genetic sharing between TD and the blood and CSF levels of 39 metabolites. The landscape of TD not only provides insights into the (altered) molecular processes that underlie the disease but, through the identification of potential drug targets (such as FLT3, NAALAD2, CX3CL1-CX3CR1, OPRM1, and HRH2), it also yields clues for developing novel TD treatments.

Randomized Controlled Trial of Probiotic PS128 in Children with Tourette Syndrome

Tourette syndrome results from a complex interaction between social–environmental factors, multiple genetic abnormalities, and neurotransmitter disturbances. This study is a double-blinded, randomized controlled trial using probiotics Lactobacillus plantarum PS128 as an intervention to examine if probiotics improve symptoms of children with Tourette syndrome. This study enrolled children aged 5 to 18 years old who fulfilled DSM-V diagnostic criteria for Tourette syndrome. Patients were assessed before initiating the trial, at one month, and at two months after randomization. The primary outcome was evaluated by Yale Global Tic Severity Scale (YGTSS), and the secondary outcome studied the possible comorbidities in these children. The results revealed no significant difference in improvement in YGTSS between the control group and the PS128 group. As for secondary endpoints, an analysis of Conners’ Continuous Performance Test (CPT) showed improvement in commission and detectability in the PS128 group. In conclusion, although probiotics may not have tic-reducing effects in children with Tourette syndrome, it may have benefits on comorbidities such as attention deficit and hyperactivity disorder (ADHD). Further studies are needed to clarify the effects of probiotics on the comorbidities of Tourette syndrome children.

The Recurrence of Motor Tics Mediated by Oral Prednisolone Use in Autistic Children: A Case Report

OBJECTIVES

This study aimed to report motor tics worsening by prednisolone acute treatment, despite the use of aripiprazole and clonidine. It was also aimed to discuss the mechanisms involved in neuropsychiatric adverse effects with the use of corticosteroids.

METHODS

It was reported a 7-year-old boy patient with a history of autism spectrum disorder and motor tics. He has remitted motor tics with an association between aripiprazole and clonidine. However, was registered motor tics' recurrence with acute use of prednisolone.

CONCLUSIONS

The neuropsychiatric adverse effects mediated by corticosteroid use are low explored, mainly in pediatric clinical practice. The prednisolone prescription is widespread in childhood and, considering some vulnerable conditions to this type of adverse effects, is imperative.

Gilles de la Tourette Syndrome-A Disorder of Action-Perception Integration

Gilles de la Tourette syndrome is a multifaceted and complex neuropsychiatric disorder. Given that tics as motor phenomena are the defining and cardinal feature of Tourette syndrome, it has long been conceptualized as a motor/movement disorder. However, considering premonitory urges preceding tics, hypersensitivity to external stimuli and abnormalities in sensorimotor integration perceptual processes also seem to be relevant in the pathophysiology of Tourette syndrome. In addition, tic expression depends on attention and tics can, at least partly and transiently, be controlled, so that cognitive processes need to be considered as well. Against this background, explanatory concepts should encompass not only the motor phenomenon tic but also perceptual and cognitive processes. Representing a comprehensive theory of the processing of perceptions and actions paying particular attention to their interdependency and the role of cognitive control, the Theory of Event Coding seems to be a suitable conceptual framework for the understanding of Tourette syndrome. In fact, recent data suggests that addressing the relation between actions (i.e., tics) and perceptions (i.e., sensory phenomena like premonitory urges) in the context of event coding allows to gaining relevant insights into perception-action coding in Tourette syndrome indicating that perception action binding is abnormally strong in this disorder.

Application of 18-fluorodeoxyglucose as an indicator of symptom severity in a rat model of tic disorder following treatment with traditional Chinese medicine

Quantitative evaluation of tic disorders (TDs) is challenging as there are few objective indicators that can be used for the assessment of treatment outcomes. 18F-Fluorodeoxyglucose (FDG) is a radioactive tracer that is able to cross the blood-brain barrier and can be detected by positron emission tomography/CT (PET/CT). In the present study, it was hypothesized that FDG PET/CT scan can be applied to reflect the severity of tic symptoms in a rat TD model, where signals detected in the brain striatum can be used to evaluate the efficacy of tic treatment with traditional Chinese medicine (TCM). A rat model of TD was established by treatment with iminodipropionitrile. Rats were divided into the following four groups (n=10 each): i) Control; ii) TCM; iii) haloperidol; and iv) model only. Observations of stereotypic behavior in rats were subsequently scored and micro-PET/CT was used to evaluate the rate of FDG uptake. Stereotypy scores were found to be significantly higher (P<0.05) in the TD rat model (P<0.05) compared with those in control rats. Both stereotypy scores (P<0.05) and standardized FDG uptake values (SUV; P<0.05) were revealed to be significantly reduced in the TD model rats after treatment with TCM or haloperidol. SUV correlated positively with stereotypy score (R=0.926; P<0.05) and the SUV scores were found to be significantly different among control group, TCM group, haloperidol group and model only group (P<0.05). These data suggest that the application of FDG in the striatum can be used to evaluate the effectiveness of TCM treatment for TDs.

Non-invasive Brain Stimulation for the Treatment of Gilles de la Tourette Syndrome

Gilles de la Tourette Syndrome is a multifaceted neuropsychiatric disorder typically commencing in childhood and characterized by motor and phonic tics. Its pathophysiology is still incompletely understood. However, there is convincing evidence that structural and functional abnormalities in the basal ganglia, in cortico-striato-thalamo-cortical circuits, and some cortical areas including medial frontal regions and the prefrontal cortex as well as hyperactivity of the dopaminergic system are key findings. Conventional therapeutic approaches in addition to counseling comprise behavioral treatment, particularly habit reversal therapy, oral pharmacotherapy (antipsychotic medication, alpha-2-agonists) and botulinum toxin injections. In treatment-refractory Tourette syndrome, deep brain stimulation, particularly of the internal segment of the globus pallidus, is an option for a small minority of patients. Based on pathophysiological considerations, non-invasive brain stimulation might be a suitable alternative. Repetitive transcranial magnetic stimulation appears particularly attractive. It can lead to longer-lasting alterations of excitability and connectivity in cortical networks and inter-connected regions including the basal ganglia through the induction of neural plasticity. Stimulation of the primary motor and premotor cortex has so far not been shown to be clinically effective. Some studies, though, suggest that the supplementary motor area or the temporo-parietal junction might be more appropriate targets. In this manuscript, we will review the evidence for the usefulness of repetitive transcranial magnetic stimulation and transcranial electric stimulation as treatment options in Tourette syndrome. Based on pathophysiological considerations we will discuss the rational for other approaches of non-invasive brain stimulation including state informed repetitive transcranial magnetic stimulation.

The opiate system inGilles de la Tourettesyndrome: diverse effects of naltrexone treatment

The main symptoms ofGilles de la Tourettesyndrome (GTS) are motor and vocal tics, but there are also several psychiatric disturbances such as obsessive compulsive symptoms (OCD) and mutilations. The etiology and pathophysiology of this basal ganglia disorder are unknown. Though many patients benefit from therapy with dopamine antagonists, the effect is often insufficient. Therapeutic efficacy of the opiate antagonist naltrexone has been described in recent years. Ten patients (three f, seven m) with GTS were invesitgated in a seven-week, open dose-response trial, using naltrexone in doses ranging from 12.5 mg to 200 mg/day. The severity of the GTS symptoms were rated with the Yale Global Tic Severity Scale (YGTSS) and theTourette SyndromeGlobal Scale (TSGS); OCD was estimated by the Maudsley Obsessive Compulsive Inventory (MOCI). The course of tics and psychopathology was assessed by three self-report scales, and two scales rated by clinicians (Clinical Global Impression, CGI; Brief Psychiatric Rating Scale, BPRS). Only two patients showed improvement of the GTS. In four patients, no effect was observed, whereas the other four patients exhibited deterioration. One patient finished the complete trial, three patients dropped out because of lack of improvement, and four because of deterioration of the symptoms. Considering the mean values, no improvement of GTS could therefore be observed, and because of the unpredictable effect, the study was stopped after ten patients. Nevertheless, the effects were quite controversial. The opiate system seems to be affected only in some of the GTS patients in a clinically relevant manner, and opiate antogonists can either improve or provoke GTS symptoms. Pathophysiologically different subgroups of GTS may contribute to the controversal results.

The Pathophysiology of Tics; An Evolving Story

Background:

Tics, defined as quick, rapid, sudden, recurrent, non-rhythmic motor movements or vocalizations are required components of Tourette Syndrome (TS) - a complex disorder characterized by the presence of fluctuating, chronic motor and vocal tics, and the presence of co-existing neuropsychological problems. Despite many advances, the underlying pathophysiology of tics/TS remains unknown.

Objective:

To address a variety of controversies surrounding the pathophysiology of TS. More specifically: 1) the configuration of circuits likely involved; 2) the role of inhibitory influences on motor control; 3) the classification of tics as either goal-directed or habitual behaviors; 4) the potential anatomical site of origin, e.g. cortex, striatum, thalamus, cerebellum, or other(s); and 5) the role of specific neurotransmitters (dopamine, glutamate, GABA, and others) as possible mechanisms (Abstract figure).

Methods:

Existing evidence from current clinical, basic science, and animal model studies are reviewed to provide: 1) an expanded understanding of individual components and the complex integration of the Cortico-Basal Ganglia-Thalamo-Cortical (CBGTC) circuit - the pathway involved with motor control; and 2) scientific data directly addressing each of the aforementioned controversies regarding pathways, inhibition, classification, anatomy, and neurotransmitters.

Conclusion:

Until a definitive pathophysiological mechanism is identified, one functional approach is to consider that a disruption anywhere within CBGTC circuitry, or a brain region inputting to the motor circuit, can lead to an aberrant message arriving at the primary motor cortex and enabling a tic. Pharmacologic modulation may be therapeutically beneficial, even though it might not be directed toward the primary abnormality.

Dopamine transporter gene expression within the nucleus accumbens plays important role in the acquisition and reinstatement of ethanol-seeking behavior in mice

Alcoholism and alcohol use disorders are chronically relapsing conditions which is a major problem in treating alcohol addiction. In a previous study we showed that the dopamine transporter (DAT) is implicated in voluntary intake and preference. However, its role in modulating ethanol-associated contextual memory remains largely unknown. In this study we have investigated the role of DAT in ethanol-induced conditioned place preference (EtOH-CPP) acquisition and reinstatement in adult male C57BL/6 mice. For this purpose, we used both loss- and gain-of-function approaches to test the effects of central DAT manipulation on EtOH-CPP. We developed a lentiviral-mediated gene transfer approach to examine whether DAT knockdown (shDAT) or overexpression in the nucleus accumbens (Nacc) is enough to impair EtOH-CPP acquisition and reinstatement. In the first experiment, results showed that DAT knockdown blocked, whereas DAT overexpression, exacerbated the acquisition of EtOH-CPP. In the second experiment and after the EtOH-CPP expression, the mice were subjected to a 14-day extinction trials before drug-induced EtOH-CPP reinstatement was induced by a priming injection of 1 g/kg EtOH. Results indicated that reinstatement of EtOH-CPP was considerably decreased after accumbal shDAT injection. However, DAT overexpression significantly increased EtOH-CPP reinstatement. Finally, and following DAT mRNA quantification using RT-PCR, Pearson's correlation showed a strong positive relationship between accumbal DAT mRNA and EtOH-CPP acquisition and reinstatement. These results suggest that DAT expression in the Nacc is involved in the acquisition and retrieval of EtOH contextual memory and that blockade of this transporter can decrease the rewarding properties of EtOH.

Regulatory effects of Ningdong granule on dopaminergic and serotonergic neurotransmission in a rat model of Tourette syndrome assessed by PET

Dysfunctions in dopamine (DA) and serotonin (5‑HT) metabolism have been widely implicated in Tourette syndrome (TS); however, the exact nature of these dysfunctions remains unclear. The objective of the present study was to investigate the variation in DA and 5‑HT metabolism in a rat model of TS, and to evaluate the therapeutic effect of Ningdong granule (NDG), a traditional Chinese medicine (TCM) preparation used specifically for the treatment of TS. Rats were treated with 3,3'‑iminodipropionitrile for 7 days to induce the model of TS, and were then intragastrically administered NDG each day. After 8 weeks of treatment, micro‑positron emission tomography was used to measure the binding of DA D2 receptors (D2Rs), DA transporters (DATs), 5‑HT2A receptors (5‑HT2ARs) and 5‑HT transporters (SERTs) in brain regions of interest. The results indicated that NDG could significantly reduce the typical characteristics of TS in the rat model. Decreased D2R binding and increased DAT binding were detected in the striatum compared with the binding activities in untreated rats. The density of 5‑HT2AR was also significantly increased in the striatum following NDG treatment; however, SERT levels were decreased in certain brain regions, including the striatum, cortex, nucleus accumbens and amygdala. Taken together, the current results demonstrated that NDG may be effective in treating patients with TS.

Merging the Pathophysiology and Pharmacotherapy of Tics

Background

Anatomically, cortical-basal ganglia-thalamo-cortical (CBGTC) circuits have an essential role in the expression of tics. At the biochemical level, the proper conveyance of messages through these circuits requires several functionally integrated neurotransmitter systems. In this manuscript, evidence supporting proposed pathophysiological abnormalities, both anatomical and chemical is reviewed. In addition, the results of standard and emerging tic-suppressing therapies affecting nine separate neurotransmitter systems are discussed. The goal of this review is to integrate our current understanding of the pathophysiology of Tourette syndrome (TS) with present and proposed pharmacotherapies for tic suppression.

Methods

For this manuscript, literature searches were conducted for both current basic science and clinical information in PubMed, Google-Scholar, and other scholarly journals to September 2018.

Results

The precise primary site of abnormality for tics remains undetermined. Although many pathophysiologic hypotheses favor a specific abnormality of the cortex, striatum, or globus pallidus, others recognize essential influences from regions such as the thalamus, cerebellum, brainstem, and ventral striatum. Some prefer an alteration within direct and indirect pathways, whereas others believe this fails to recognize the multiple interactions within and between CBGTC circuits. Although research and clinical evidence supports involvement of the dopaminergic system, additional data emphasizes the potential roles for several other neurotransmitter systems.

Discussion

A greater understanding of the primary neurochemical defect in TS would be extremely valuable for the development of new tic-suppressing therapies. Nevertheless, recognizing the varied and complex interactions that exist in a multi-neurotransmitter system, successful therapy may not require direct targeting of the primary abnormality.

Dopaminergic Disturbances in Tourette Syndrome: An Integrative Account

Tourette syndrome (TS) is thought to involve dopaminergic disturbances, but the nature of those disturbances remains controversial. Existing hypotheses suggest that TS involves 1) supersensitive dopamine receptors, 2) overactive dopamine transporters that cause low tonic but high phasic dopamine, 3) presynaptic dysfunction in dopamine neurons, or 4) dopaminergic hyperinnervation. We review evidence that contradicts the first two hypotheses; we also note that the last two hypotheses have traditionally been considered too narrowly, explaining only small subsets of findings. We review all studies that have used positron emission tomography and single-photon emission computerized tomography to investigate the dopaminergic system in TS. The seemingly diverse findings from those studies have typically been interpreted as pointing to distinct mechanisms, as evidenced by the various hypotheses concerning the nature of dopaminergic disturbances in TS. We show, however, that the hyperinnervation hypothesis provides a simple, parsimonious explanation for all such seemingly diverse findings. Dopaminergic hyperinnervation likely causes increased tonic and phasic dopamine. We have previously shown, using a computational model of the role of dopamine in basal ganglia, that increased tonic dopamine and increased phasic dopamine likely increase the propensities to express and learn tics, respectively. There is therefore a plausible mechanistic link between dopaminergic hyperinnervation and TS via increased tonic and phasic dopamine. To further bolster this argument, we review evidence showing that all medications that are effective for TS reduce signaling by tonic dopamine, phasic dopamine, or both.

Striatal dopaminergic alterations in Tourette's syndrome: a meta-analysis based on 16 PET and SPECT neuroimaging studies

Despite intense research, the underlying mechanisms and the etiology of Tourette's syndrome (TS) remain unknown. Data from molecular imaging studies targeting the dopamine system in Tourette patients are inconclusive. For a better understanding of the striatal dopamine function in adult dopamine-antagonist-free patients we performed a systematic review in August 2017 identifying 49 PET and SPECT studies on the topic of TS. A total of 8 studies appraised the dopamine transporter (DAT) with 111 Tourette patients and 93 healthy controls, and could be included in a meta-analytic approach. We found a significantly increased striatal DAT binding in Tourette patients (Hedges' g = 0.49; 95% CI: (0.01-0.98)), although this effect did not remain significant after correcting for age differences between cohorts. A second meta-analysis was performed for the striatal dopamine receptor including 8 studies with a total of 72 Tourette patients and 71 controls. This analysis revealed a nonsignificant trend toward lower dopamine 2/3 receptor binding in striatum of Tourette patients. Other analyses regarding study population characteristics in both the DAT and receptor meta-analysis did not show any meaningful results. Our results indicate that dopaminergic alterations in TS are likely and thereby this data would be in line with the current pathophysiological hypotheses of a dysfunction in the dopamine system, e.g., the hypothesis of tonic-phasic dysfunction. However, these analyses suffer from low effect sizes probably due to the heterogeneity of TS and highlight the need for further large-scaled neuroimaging studies.

Olfactory functioning in adults with Tourette syndrome

Tourette syndrome is a chronic tic disorder characterized by motor and vocal tics. Comorbidities such as attention deficit hyperactivity disorder and obsessive compulsive disorder can be found. The overlap between neuroanatomical regions and neurotransmitter systems in the olfactory system and the pathophysiology of Tourette syndrome let us hypothesize altered olfactory performance in Tourette syndrome. The main objective of this study was to systematically assess olfactory functioning in subjects with Tourette syndrome and to compare it to healthy controls. We assessed 28 adults with Tourette syndrome (age 33.1±9.4 years, disease duration 23.7±9.7 years) and 28 healthy controls (age 32.9±9.0 years) matched in regard to age, sex, education and smoking habits. The “Sniffin Sticks” test battery was applied to assess odor threshold, discrimination, and identification. Additionally, the combined score of the odor threshold test, the odor discrimination test and the odor identification test of the “Sniffin Sticks” test battery was calculated. Although it was not the primary aim of this study, we assessed whether tics and comorbidity could contribute to olfactory alterations in adults with Tourette syndrome. Therefore, clinical scores were used to assess severity of tics and co-morbidity such as attention deficit hyperactivity disorder, obsessive compulsive disorder, anxiety and depression in subjects with Tourette syndrome. Pathology of the nasal cavities was excluded with rhinoendoscopy. Independent sample t-tests were applied to compare performance in olfactory tests. In the case of statistically significant differences (critical p-value: 0.05), multiple linear regression analysis was carried out to explore whether tic severity, social impairment, co-morbidity or medical treatment had an impact on the differences found. Descriptive values are reported as mean ± standard deviation. Tourette syndrome subjects showed lower combined scores (Tourette syndrome subjects 31.9 ± 5.1 versus healthy controls 35.0 ± 3.1; p = 0.007), odor identification scores (Tourette syndrome subjects 12.4 ± 2.0 versus healthy controls 13.7 ± 1.4; p = 0.008) and odor discrimination scores (Tourette syndrome subjects 12.1 ± 2.1 versus healthy controls 13.2 ± 1.6; p = 0.041) in comparison to healthy subjects, while there was no difference in odor threshold (Tourette syndrome subjects 7.3 ± 2.7 versus healthy controls 8.1 ± 2.2; p = 0.22). Seven out of 28 Tourette syndrome subjects (25%) scored in the range of the age- and sex-dependent combined score for hyposmia, while two of 28 healthy controls (7%) had a similar low combined score. None of the participants were found to have functional anosmia. Multiple linear regression analyses suggest that social impairment may a predictor for low combined score and odor identification score in Tourette syndrome subjects (p = 0.003). Compared to healthy controls, altered olfaction in adults with Tourette syndrome was found in this study. Normal odor threshold level but lower scores at tasks involving supra-threshold odor concentrations point towards a central-nervous alteration in the processing of olfactory information in Tourette syndrome.

Haloperidol ameliorates androgen-induced behavioral deficits in developing male rats

The purpose of present study was to infer the potential effects of testosterone increase in some male-based childhood-onset neuropsychiatric disorders, such as Tourette syndrome. Thus, the influence of early postnatal androgen exposure upon the neurobehaviors and its possible neural basis were investigated in the study. Male pup rats received consecutive 14-day testosterone propionate (TP) subcutaneous injection from postnatal day (PND) 7. The TP treatment produced the hyperactive motor behavior and grooming behavior as well as the increased levels of dopamine, tyrosine hydroxylase and dopamine transporter in the mesodopaminergic system and the elevated levels of serotonin in the nucleus accumbens, without affecting the levels of glutamate, γ-aminobutyric acid, norepinephrine and histamine in the caudate putamen and nucleus accumbens of PND21 and PND49 rats. Dopamine D2 receptor antagonist haloperidol was administered to the early postnatal TP-exposed PND21 and PND49 male rats 30 min prior to open field test. Haloperidol significantly ameliorated the motor behavioral and grooming behavioral defects induced by early postnatal TP exposure. The results demonstrated that early postnatal androgen exposure significantly disturbed the brain activity of developing male rats via enhancing the mesodopaminergic activity. It was suggested that abnormal increments of testosterone levels during the early postnatal development might be a potential risk factor for the incidence of some male-based childhood-onset neuropsychiatric disorders by affecting the mesodopaminergic system.

Evidence for enhanced multi-component behaviour in Tourette syndrome - an EEG study

Evidence suggests that Tourette syndrome is characterized by an increase in dopamine transmission and structural as well as functional changes in fronto-striatal circuits that might lead to enhanced multi-component behaviour integration. Behavioural and neurophysiological data regarding multi-component behaviour was collected from 15 patients with Tourette syndrome (mean age = 30.40 ± 11.10) and 15 healthy controls (27.07 ± 5.44), using the stop-change task. In this task, participants are asked to sometimes withhold responses to a Go stimulus (stop cue) and change hands to respond to an alternative Go stimulus (change cue). Different onset asynchronies between stop and change cues were implemented (0 and 300 ms) in order to vary task difficulty. Tourette patients responded more accurately than healthy controls when there was no delay between stop and change stimulus, while there was no difference in the 300 ms delay condition. This performance advantage was reflected in a smaller P3 event related potential. Enhanced multi-component behaviour in Tourette syndrome is likely based on an enhanced ability to integrate information from multiple sources and translate it into an appropriate response sequence. This may be a consequence of chronic tic control in these patients, or a known fronto-striatal networks hyperconnectivity in Tourette syndrome.

Gilles de la Tourette syndrome is associated with hypermethylation of the dopamine D2 receptor gene

Several lines of evidence support a "dopaminergic hypothesis" in the pathophysiology of Gilles de la Tourette syndrome (TS). The aim of this study was to investigate for the first time epigenetic changes in DNA methylation in different dopamine genes in adult patients with TS. We included 51 well characterized adult patients with TS (41 males, 10 females, mean age = 35 ± 12.6 years, range, 18-71 years) and compared results with data from a group of 51 sex- and age-matched healthy controls. Bisulfite sequencing was used to measure peripheral DNA methylation of the dopamine transporter (DAT), the dopamine D2 receptor (DRD2), and the catechol-O-methyltransferase (COMT) genes. Compared to healthy controls, patients with TS showed significantly elevated methylation level of the DRD2 gene that positively correlated with tic severity. In contrast, DAT methylation was lower in more severely affected patients. Our results provide evidence for a role of altered epigenetic regulation of dopaminergic genes in the pathophysiology of TS. While DRD2 hypermethylation seems to be directly related to the neurobiology of TS that may lead to dopaminergic dysfunction resulting in enhanced thalamo-cortical movement-stimulating activity, DAT hypomethylation might reflect a secondary mechanism in order to compensate for increased dopaminergic signal transduction due to DRD2 hypermethylation. In addition, it can be speculated that spontaneous fluctuations of tics may be caused by short-term alterations of methylation levels of dopaminergic genes resulting in dynamic changes of tonic/phasic dopaminergic signaling in the striatum and thalamo-cortical output pathways.

Using Behavioral Interventions to Decrease Coprolalia in a Student with Tourette's Syndrome and Autism: A Case Study

The purpose of this study was to investigate the behavioral techniques that would be most effective in decreasing coprolalia for a student diagnosed with autism and Tourette's syndrome. The study involved a young female who was enrolled in a public school special education classroom for children with behavior and communication disorders. Four behavior-management strategies were used: (a) time-out, (b) differential reinforcement of other behavior, (c) differential reinforcement of other behavior paired with differential reinforcement of alternative behavior, and (d) intermittent differential reinforcement of alternative behavior. All interventions showed a reduction in the number of profane words used by the subject. The least effective behavior strategy was the independent implementation of time-out. The fewest occurrences of coprolalia occurred during the use of intermittent differential reinforcement of alternative behavior.

Fluorine-18 Radiolabeled PET Tracers for Imaging Monoamine Transporters: Dopamine, Serotonin, and Norepinephrine

This review focuses on the development of fluorine-18 radiolabeled PET tracers for imaging the dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET). All successful DAT PET tracers reported to date are members of the 3β-phenyl tropane class and are synthesized from cocaine. Currently available carbon-11 SERT PET tracers come from both the diphenylsulfide and 3β-phenyl nortropane class, but so far only the nortropanes have found success with fluorine-18 derivatives. NET imaging has so far employed carbon-11 and fluorine-18 derivatives of reboxetine but due to defluorination of the fluorine-18 derivatives further research is still necessary.

Animal Models of Tourette Syndrome-From Proliferation to Standardization

Tourette syndrome (TS) is a childhood onset disorder characterized by motor and vocal tics and associated with multiple comorbid symptoms. Over the last decade, the accumulation of findings from TS patients and the emergence of new technologies have led to the development of novel animal models with high construct validity. In addition, animal models which were previously associated with other disorders were recently attributed to TS. The proliferation of TS animal models has accelerated TS research and provided a better understanding of the mechanism underlying the disorder. This newfound success generates novel challenges, since the conclusions that can be drawn from TS animal model studies are constrained by the considerable variation across models. Typically, each animal model examines a specific subset of deficits and centers on one field of research (physiology/genetics/pharmacology/etc.). Moreover, different studies do not use a standard lexicon to characterize different properties of the model. These factors hinder the evaluation of individual model validity as well as the comparison across models, leading to a formation of a fuzzy, segregated landscape of TS pathophysiology. Here, we call for a standardization process in the study of TS animal models as the next logical step. We believe that a generation of standard examination criteria will improve the utility of these models and enable their consolidation into a general framework. This should lead to a better understanding of these models and their relationship to TS, thereby improving the research of the mechanism underlying this disorder and aiding the development of new treatments.

Tourette Syndrome: Bridging the Gap between Genetics and Biology

Tourette syndrome is a childhood neuropsychiatric disorder, which presents with disruptive motor and vocal tics. The disease also has a high comorbidity with obsessive-compulsive disorder and attention deficit hyperactivity disorder, which may further increase the distress experienced by patients. Current treatments act with varying efficacies in alleviating symptoms, as the underlying biology of the disease is not fully understood to provide precise therapeutic targets. Moreover, the genetic complexity of the disorder presents a substantial challenge to the identification of genetic alterations that contribute to the Tourette's phenotype. Nevertheless, genetic studies have suggested involvement of dopaminergic, serotonergic, glutamatergic, and histaminergic pathways in the pathophysiology of at least some cases. In addition, genetic overlaps with other neuropsychiatric disorders may point toward a shared biology. The findings that are emerging from genetic studies will allow researchers to piece together the underlying components of the disease, in the hopes that a deeper understanding of Tourette's can lead to improved treatments for those affected by it.

Abnormal neuronal activity in Tourette syndrome and its modulation using deep brain stimulation

Tourette syndrome (TS) is a common childhood-onset disorder characterized by motor and vocal tics that are typically accompanied by a multitude of comorbid symptoms. Pharmacological treatment options are limited, which has led to the exploration of deep brain stimulation (DBS) as a possible treatment for severe cases. Multiple lines of evidence have linked TS with abnormalities in the motor and limbic cortico-basal ganglia (CBG) pathways. Neurophysiological data have only recently started to slowly accumulate from multiple sources: noninvasive imaging and electrophysiological techniques, invasive electrophysiological recordings in TS patients undergoing DBS implantation surgery, and animal models of the disorder. These converging sources point to system-level physiological changes throughout the CBG pathway, including both general altered baseline neuronal activity patterns and specific tic-related activity. DBS has been applied to different regions along the motor and limbic pathways, primarily to the globus pallidus internus, thalamic nuclei, and nucleus accumbens. In line with the findings that also draw on the more abundant application of DBS to Parkinson's disease, this stimulation is assumed to result in changes in the neuronal firing patterns and the passage of information through the stimulated nuclei. We present an overview of recent experimental findings on abnormal neuronal activity associated with TS and the changes in this activity following DBS. These findings are then discussed in the context of current models of CBG function in the normal state, during TS, and finally in the wider context of DBS in CBG-related disorders.

PET Neuroimaging: Insights on Dystonia and Tourette Syndrome and Potential Applications

Primary dystonia (pD) is a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both. Gilles de la Tourette syndrome (GTS) is a childhood-onset neuropsychiatric developmental disorder characterized by motor and phonic tics, which could progress to behavioral changes. GTS and obsessive-compulsive disorders are often seen in comorbidity, also suggesting that a possible overlap in the pathophysiological bases of these two conditions. PET techniques are of considerable value in detecting functional and molecular abnormalities in vivo, according to the adopted radioligands. For example, PET is the unique technique that allows in vivo investigation of neurotransmitter systems, providing evidence of changes in GTS or pD. For example, presynaptic and post-synaptic dopaminergic studies with PET have shown alterations compatible with dysfunction or loss of D2-receptors bearing neurons, increased synaptic dopamine levels, or both. Measures of cerebral glucose metabolism with (18)F-fluorodeoxyglucose PET ((18)F-FDG PET) are very sensitive in showing brain functional alterations as well. (18)F-FDG PET data have shown metabolic changes within the cortico-striato-pallido-thalamo-cortical and cerebello-thalamo-cortical networks, revealing possible involvement of brain circuits not limited to basal ganglia in pD and GTS. The aim of this work is to overview PET consistent neuroimaging literature on pD and GTS that has provided functional and molecular knowledge of the underlying neural dysfunction. Furthermore, we suggest potential applications of these techniques in monitoring treatments.

Rapid Presentation of Emotional Expressions Reveals New Emotional Impairments in Tourette's Syndrome

OBJECTIVE

Based on a variety of empirical evidence obtained within the theoretical framework of embodiment theory, we considered it likely that motor disorders in Tourette's syndrome (TS) would have emotional consequences for TS patients. However, previous research using emotional facial categorization tasks suggests that these consequences are limited to TS patients with obsessive-compulsive behaviors (OCB).

METHOD

These studies used long stimulus presentations which allowed the participants to categorize the different emotional facial expressions (EFEs) on the basis of a perceptual analysis that might potentially hide a lack of emotional feeling for certain emotions. In order to reduce this perceptual bias, we used a rapid visual presentation procedure.

RESULTS

Using this new experimental method, we revealed different and surprising impairments on several EFEs in TS patients compared to matched healthy control participants. Moreover, a spatial frequency analysis of the visual signal processed by the patients suggests that these impairments may be located at a cortical level.

CONCLUSION

The current study indicates that the rapid visual presentation paradigm makes it possible to identify various potential emotional disorders that were not revealed by the standard visual presentation procedures previously reported in the literature. Moreover, the spatial frequency analysis performed in our study suggests that emotional deficit in TS might lie at the level of temporal cortical areas dedicated to the processing of HSF visual information.

Genetic susceptibility and neurotransmitters in Tourette syndrome

Family studies have consistently shown that Tourette syndrome (TS) is a familial disorder and twin studies have clearly indicated a genetic contribution in the etiology of TS. Whereas early segregation studies of TS suggested a single-gene autosomal dominant disorder, later studies have pointed to more complex models including additive and multifactorial inheritance and likely interaction with genetic factors. While the exact cellular and molecular base of TS is as yet elusive, neuroanatomical and neurophysiological studies have pointed to the involvement of cortico-striato-thalamocortical circuits and abnormalities in dopamine, glutamate, gamma-aminobutyric acid, and serotonin neurotransmitter systems, with the most consistent evidence being available for involvement of dopamine-related abnormalities, that is, a reduction in tonic extracellular dopamine levels along with hyperresponsive spike-dependent dopamine release, following stimulation. Genetic and gene expression findings are very much supportive of involvement of these neurotransmitter systems. Moreover, intriguingly, genetic work on a two-generation pedigree has opened new research pointing to a role for histamine, a so far rather neglected neurotransmitter, with the potential of the development of new treatment options. Future studies should be aimed at directly linking neurotransmitter-related genetic and gene expression findings to imaging studies (imaging genetics), which enables a better understanding of the pathways and mechanisms through which the dynamic interplay of genes, brain, and environment shapes the TS phenotype.

Emerging treatment strategies in Tourette syndrome: what's in the pipeline?

Tourette syndrome (TS) is a neurodevelopmental disorder characterized by multiple motor/phonic tics and a wide spectrum of behavioral problems (e.g., complex tic-like symptoms, attention deficit hyperactivity disorder, and obsessive-compulsive disorder). TS can be a challenging condition even for the specialists, because of the complexity of the clinical picture and the potential adverse effects of the most commonly prescribed medications. Expert opinions and consensus guidelines on the assessment and treatment of tic disorders have recently been published in Europe and Canada. All pharmacological treatment options are mere symptomatic treatments that alleviate, but do not cure, the tics. We still lack evidence of their effects on the natural long-term course and on the prognosis of TS and how these treatments may influence the natural course of brain development. The most commonly prescribed drugs are dopamine antagonists, such as typical (e.g., haloperidol, pimozide) and atypical neuroleptics (e.g., risperidone, aripiprazole), and α-2-adrenoreceptor agonists (e.g., clonidine). However, several studies have investigated the efficacy and tolerability of alternative pharmacological agents that may be efficacious, including the newest atypical antipsychotic agents (e.g., paliperidone, sertindole), tetrabenazine, drugs that modulate acetylcholine (e.g., nicotine) and GABA (e.g., baclofen, levetiracetam), tetrahydrocannabinol, botulinum toxin injections, anticonvulsant drugs (e.g., topiramate, carbamazepine), naloxone, lithium, norepinephrine, steroid 5α reductase, and other neuroactive agents (buspirone, metoclopramide, phytostigmine, and spiradoline mesylate). As regards nonpharmacological interventions, some of the more recent treatments that have been studied include electroconvulsive therapy and repetitive transcranial magnetic stimulation. This review focuses primarily on the efficacy and safety of these emerging treatment strategies in TS.

Effects of ningdong granule on DA, DRD2, and HVA in a rat model of Tourette's syndrome

OBJECTIVE

Ningdong granule is a traditional Chinese medicine preparation for the treatment of Tourette's syndrome.

METHODS

Sixty-four rats were randomly assigned to a control group and three experimental groups, respectively. Rat models of Tourette's syndrome were established via intraperitoneal injection of apomorphine (Apo). The rats in the experimental groups were subsequently intragastrically injected with haloperidol at 10 mg/kg (haloperidol group), ningdong granule at 370 mg/kg (NDG group), and normal saline (0.9%) at 10 mL/kg (Apo group), respectively. Rat behaviors were observed and recorded on a daily basis. After 12 w, all rats were sacrificed, and sera and striatal tissues were harvested. Homovanillic acid levels in sera, as well as dopamine and dopamine D2 receptor mRNA expression in the striatum, were measured to determine possible mechanisms of Ningdong granule on the dopamine system in a rat model ofTourette's syndrome.

RESULTS

Following intervention, stereotype actions of the Tourette's syndrome rats were significantly inhibited in the haloperidol and NDG groups, respectively (P < 0.01). Homovanillic levels were significantly greater in the haloperidol and NDG groups, respectively (P < 0.05). In addition, dopamine levels were significantly less in the NDG group (P < 0.01), and DRD2 mRNA expression was significantly reduced in the haloperidol and NDG groups, respectively (P < 0.05).

CONCLUSION

Results demonstrated that Ning-dong granule effectively inhibited stereotype actions and Tourette's syndrome symptoms by promoting dopamine metabolism, reducing dopamine levels in the striatum, increasing homovanillic acid content in sera, and reducing mRNA expression of DRD2 in the striatum.

Reward circuitry dysfunction in psychiatric and neurodevelopmental disorders and genetic syndromes: animal models and clinical findings

This review summarizes evidence of dysregulated reward circuitry function in a range of neurodevelopmental and psychiatric disorders and genetic syndromes. First, the contribution of identifying a core mechanistic process across disparate disorders to disease classification is discussed, followed by a review of the neurobiology of reward circuitry. We next consider preclinical animal models and clinical evidence of reward-pathway dysfunction in a range of disorders, including psychiatric disorders (i.e., substance-use disorders, affective disorders, eating disorders, and obsessive compulsive disorders), neurodevelopmental disorders (i.e., schizophrenia, attention-deficit/hyperactivity disorder, autism spectrum disorders, Tourette's syndrome, conduct disorder/oppositional defiant disorder), and genetic syndromes (i.e., Fragile X syndrome, Prader-Willi syndrome, Williams syndrome, Angelman syndrome, and Rett syndrome). We also provide brief overviews of effective psychopharmacologic agents that have an effect on the dopamine system in these disorders. This review concludes with methodological considerations for future research designed to more clearly probe reward-circuitry dysfunction, with the ultimate goal of improved intervention strategies.

Pharmacological treatment of tic disorders and Tourette Syndrome

The present review gives an overview of current pharmacological treatment options of tic disorders and Tourette Syndrome (TS). After a short summary on phenomenology, clinical course and comorbid conditions we review indications for pharmacological treatment in detail. Unfortunately, standardized and large enough drug trials in TS patients fulfilling evidence based medicine standards are still scarce. Treatment decisions are often guided by individual needs and personal experience of treating clinicians. The present recommendations for pharmacological tic treatment are therefore based on both scientific evidence and expert opinion. As first-line treatment of tics risperidone (best evidence level for atypical antipsychotics) or tiapride (largest clinical experience in Europe and low rate of adverse reactions) are recommended. Aripiprazole (still limited but promising data with low risk for adverse reactions) and pimozide (best evidence of the typical antipsychotics) are agents of second choice. In TS patients with comorbid attention deficit hyperactivity disorder (ADHD) atomoxetine, stimulants or clonidine should be considered, or, if tics are severe, a combination of stimulants and risperidone. When mild to moderate tics are associated with obsessive-compulsive symptoms, depression or anxiety sulpiride monotherapy can be helpful. In more severe cases the combination of risperidone and a selective serotonin reuptake inhibitor should be given. In summary, further studies, particularly randomized, double-blind, placebo-controlled trials including larger and/or more homogenous patient groups over longer periods are urgently needed to enhance the scientific basis for drug treatment in tic disorders. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Abnormal repetitive behaviours: shared phenomenology and pathophysiology

BACKGROUND

Self-injurious behaviour (SIB) is a devastating problem observed in individuals with various neurodevelopmental disorders, including specific genetic syndromes as well as idiopathic intellectual and developmental disability. Although an increased prevalence of SIB has been documented in specific genetic mutations, little is known about the neurobiological basis of SIB. This makes vulnerability assessment and pharmacological treatment incredibly challenging.

METHOD

Here we review evidence that SIB and other repetitive, invariant behaviours, such as stereotypy, compulsions and tics, share many phenotypic similarities, are often co-morbidly expressed and have common inducing conditions. This argues for shared or overlapping pathophysiology. As much more is known about the neurobiology of these related disorders, this should make the neurobiology of SIB a more tractable problem.

RESULTS

Stereotypy, compulsions and tics are diagnostic for disorders that have received focused neurobiological investigation (autism, obsessive compulsive disorder, Tourette syndrome, respectively). In addition, animal models of these repetitive behaviours have been well characterised. Collectively, these studies have found that cortical basal ganglia circuitry dysfunction mediates repetitive behaviour. Moreover, these studies provide more detailed information and potentially testable hypotheses about specific aspects of the circuitry that may be operative in SIB.

CONCLUSIONS

We can use available information from clinical and animal models to make more precise hypotheses regarding the particular pathophysiology driving SIB. The results of testing such hypotheses should generate pharmacological strategies that may prove efficacious in reducing SIB.

Neurobiology of tourette syndrome: current status and need for further investigation

Tourette syndrome (TS) is a common, chronic neuropsychiatric disorder characterized by the presence of fluctuating motor and phonic tics. The typical age of onset is ∼5-7 years, and the majority of children improve by their late teens or early adulthood. Affected individuals are at increased risk for the development of various comorbid conditions, such as obsessive-compulsive disorder, attention deficit hyperactivity disorder, school problems, depression, and anxiety. There is no cure for tics, and symptomatic therapy includes behavioral and pharmacological approaches. Evidence supports TS being an inherited disorder; however, the precise genetic abnormality remains unknown. Pathologic involvement of cortico-striatal-thalamo-cortical (CSTC) pathways is supported by neurophysiological, brain imaging, and postmortem studies, but results are often confounded by small numbers, age differences, severity of symptoms, comorbidity, use of pharmacotherapy, and other factors. The primary site of abnormality remains controversial. Although numerous neurotransmitters participate in the transmission of messages through CSTC circuits, a dopaminergic dysfunction is considered a leading candidate. Several animal models have been used to study behaviors similar to tics as well as to pursue potential pathophysiological deficits. TS is a complex disorder with features overlapping a variety of scientific fields. Despite description of this syndrome in the late 19th century, there remain numerous unanswered neurobiological questions.

Tourette syndrome and other tic disorders

Tic disorders, including Tourette syndrome, are an intriguing group of paroxysmal movement abnormalities that begin in childhood, have a fluctuating course, are capable of causing psychosocial and physical problems, and often improve by early adulthood. These disorders are frequently associated with a variety of comorbid problems whose negative effects may exceed those of tics. Therapy is strictly symptomatic and usually includes educational, behavioral, and a variety of pharmacological therapies. Although there is strong evidence supporting an inherited basis, the precise genetic abnormality remains unknown. A proposed poststreptococcal autoimmune etiology remains controversial. Pathophysiologically, tics appear to arise from an alteration within cortico-striatal-thalamo-cortical circuits, but the definitive site is unknown. Evidence supports an abnormality of synaptic neurotransmission, likely involving the dopaminergic system.

Embodying Emotional Disorders: New Hypotheses about Possible Emotional Consequences of Motor Disorders in Parkinson's Disease and Tourette's Syndrome

Parkinson's disease (PD) and Tourette's syndrome (TS) lead to important motor disorders among patients such as possible facial amimia in PD and tics in Tourette's syndrome. Under the grounded cognition framework that shows the importance of motor embodiment in emotional feeling (Niedenthal, 2007), both types of pathology with motor symptoms should be sufficient to induce potential impairments for these patients when recognizing emotional facial expressions (EFE). In this opinion paper, we describe a theoretical framework that assumes potential emotional disorders in Parkinson's disease and Tourette's syndrome based on motor disorders characterizing these two pathologies. We also review different methodological barriers in previous experimental designs that could enable the identification of emotional facial expressions despite emotional disorders in PD and TS.

European clinical guidelines for Tourette syndrome and other tic disorders. Part II: pharmacological treatment

To develop a European guideline on pharmacologic treatment of Tourette syndrome (TS) the available literature was thoroughly screened and extensively discussed by a working group of the European Society for the Study of Tourette syndrome (ESSTS). Although there are many more studies on pharmacotherapy of TS than on behavioral treatment options, only a limited number of studies meets rigorous quality criteria. Therefore, we have devised a two-stage approach. First, we present the highest level of evidence by reporting the findings of existing Cochrane reviews in this field. Subsequently, we provide the first comprehensive overview of all reports on pharmacological treatment options for TS through a MEDLINE, PubMed, and EMBASE search for all studies that document the effect of pharmacological treatment of TS and other tic disorders between 1970 and November 2010. We present a summary of the current consensus on pharmacological treatment options for TS in Europe to guide the clinician in daily practice. This summary is, however, rather a status quo of a clinically helpful but merely low evidence guideline, mainly driven by expert experience and opinion, since rigorous experimental studies are scarce.

Open-label study comparing the efficacy and tolerability of aripiprazole and haloperidol in the treatment of pediatric tic disorders

Due to its unique pharmacodynamic properties of dopamine partial agonist activity, and its association with few and mild side effects, aripiprazole is a candidate atypical antipsychotic for patients with tic disorders. This open-label study compared the efficacy and tolerability of aripiprazole with haloperidol, a typical antipsychotic widely used to treat patients with tic disorders. Forty-eight children and adolescents with tic disorders were recruited from the outpatient clinic at South Korea and treated with aripiprazole (initial dose, 5.0 mg/d; maximum dose 20 mg/d) or haloperidol (initial dose, 0.75 mg/d; maximum dose, 4.5 mg/d) for 8 weeks. Treatment efficacy was measured using the yale global tic severity scale (YGTSS), and tolerability was measured using the extrapyramidal symptom rating scale (ESRS) and an adverse effects checklist. Total tic scores as measured by the YGTSS decreased over time in both groups (p < 0.001) without any significant differences between groups. ESRS scores were significantly higher in the haloperidol group during the 4 weeks after commencement of medication (p < 0.05). These results indicate that aripiprazole may be a promising drug in the treatment of children and adolescents with tic disorders. Further controlled studies are needed to determine the efficacy and tolerability of aripiprazole in these patients.

Tourette syndrome in children: an updated review

Tourette syndrome (TS) is a common neuropsychiatric disorder in children characterized by multiple motor and vocal tics that fluctuate in severity and lasting for at least 1 year. Boys are more commonly affected than girls. Symptoms usually begin with simple motor or vocal tics which then evolve into more complex motor and vocal tics over time. Premonitory sensory urges are common in children over the age of 8 years, and these urges help distinguish tics from symptoms of other movement disorders. Common comorbidities of TS include attention deficit hyperactivity disorder, obsessive-compulsive disorder and learning difficulties. Several genes have been assessed as candidate genes for TS; environmental factors such as stress and streptococcal infections might also contribute to its etiology. The pathophysiology of TS mainly involves dysfunction of basal ganglia-related circuits and hyperactive dopaminergic innervations. A thorough history assessment and neurological examination are important for the correct diagnosis and differentiation from other movement disorders. Treatment for TS should focus on improving the patient's social functioning, minimizing the impairment from cormobid disorders, and controlling tics, if they are severe. Commonly used medications for TS include a2-adrenergic agonists and atypical neuroleptics. Habit reversal therapy is an effective option for TS, and repetitive transcranial magnetic stimulation may be a promising approach for severe cases.

Synthesis, fluorine-18 radiolabeling, and biological evaluation of N-((E)-4-fluorobut-2-en-1-yl)-2beta-carbomethoxy-3beta-(4'-halophenyl)nortropanes: candidate radioligands for in vivo imaging of the brain dopamine transporter with positron emission tomography

The N-(E)-fluorobutenyl-3beta-(para-halo-phenyl)nortropanes 9-12 were synthesized as ligands of the dopamine transporter (DAT) for use as (18)F-labeled positron emission tomography (PET) imaging agents. In vitro competition binding assays demonstrated that compounds 9-12 have a high affinity for the DAT and are selective for the DAT compared to the serotonin and norepinephrine transporters. MicroPET imaging with [(18)F]9-[(18)F]11 in anesthetized cynomolgus monkeys showed high uptake in the putamen with lesser uptake in the caudate, but significant washout of the radiotracer was only observed for [(18)F]9. PET imaging with [(18)F]9 in an awake rhesus monkey showed high and nearly equal uptake in both the putamen and caudate with peak uptake achieved after 20 min followed by a leveling-off for about 10 min and then a steady washout and attainment of a quasi-equilibrium. During the time period 40-80 min postinjection of [(18)F]9, the ratio of uptake in the putamen and caudate vs cerebellum uptake was > or = 4.

fMRI tracks reductions in repetitive behaviors in autism: two case studies

Autism is characterized by abnormal prefrontal brain activation during cognitive control, a potential biomarker of repetitive behaviors. In this proof-of-principle study, functional magnetic resonance imaging (fMRI) was used to examine brain activity during an oddball task in two high-functioning males with autism before and after 12 weeks of treatment with citalopram, a selective serotonin reuptake inhibitor. One participant showed marked reductions in repetitive behaviors whereas the other showed mild worsening. Brain activation in relevant prefrontal regions increased in only the participant whose repetitive behavior symptoms improved. These findings suggest that fMRI may elucidate potential mechanisms of action of targeted autism interventions.

Functional neuroimaging in Tourette syndrome

Functional neuroimaging of neuropsychiatric disorders is a complex discipline requiring skills in medical science, philosophy, and technical physics. This review first examines the broad categories of functional imaging studies that have been utilized in this area, comparing the strengths and weaknesses of each approach. This review then looks at much of the available literature on functional imaging in Tourette syndrome (TS) and provides a synthesis of data. The review will also examine the different methodologies employed and will suggest which methodologies are most likely to lead to elucidation of the pathophysiology of TS and related conditions.