Monoamine transporter availability in Parkinson’s disease patients with or without depression

Antidepressants and type 2 diabetes: highways to knowns and unknowns

Type 2 diabetes (T2D) is a metabolic disease caused by the development of insulin resistance (IR), relative insulin deficiency, and hyperglycemia. Hyperglycemia-induced neurochemical dysregulation activates the progression of depression in T2D patients. Therefore, management of depression by antidepressant agents improves glucose homeostasis and insulin sensitivity. However, prolong use of antidepressant drugs may increase the risk for the development of T2D. However, there is strong controversy concerning the use of antidepressant drugs in T2D. Therefore, this review try to elucidate the potential effects of antidepressant drugs in T2D regarding their detrimental and beneficial effects.

The Role of α-Synuclein in the Regulation of Serotonin System: Physiological and Pathological Features

In patients affected by Parkinson's disease (PD), up to 50% of them experience cognitive changes, and psychiatric disturbances, such as anxiety and depression, often precede the onset of motor symptoms and have a negative impact on their quality of life. Pathologically, PD is characterized by the loss of dopamine (DA) neurons in the substantia nigra pars compacta (SNc) and the presence of intracellular inclusions, called Lewy bodies and Lewy neurites, composed mostly of α-synuclein (α-Syn). Much of PD research has focused on the role of α-Syn aggregates in the degeneration of SNc DA neurons due to the impact of striatal DA deficits on classical motor phenotypes. However, abundant Lewy pathology is also found in other brain regions including the midbrain raphe nuclei, which may contribute to non-motor symptoms. Indeed, dysfunction of the serotonergic (5-HT) system, which regulates mood and emotional pathways, occurs during the premotor phase of PD. However, little is known about the functional consequences of α-Syn inclusions in this neuronal population other than DA neurons. Here, we provide an overview of the current knowledge of α-Syn and its role in regulating the 5-HT function in health and disease. Understanding the relative contributions to α-Syn-linked alterations in the 5-HT system may provide a basis for identifying PD patients at risk for developing depression and could lead to a more targeted therapeutic approach.

Depression in Patients with Parkinson's Disease: Current Understanding of its Neurobiology and Implications for Treatment

Depression is one of the most frequent and burdensome non-motor symptoms in Parkinson’s disease (PD), across all stages. Even when its severity is mild, PD depression has a great impact on quality of life for these patients and their caregivers. Accordingly, accurate diagnosis, supported by validated scales, identification of risk factors, and recognition of motor and non-motor symptoms comorbid to depression are critical to understanding the neurobiology of depression, which in turn determines the effectiveness of dopaminergic drugs, antidepressants and non-pharmacological interventions. Recent advances using in vivo functional and structural imaging demonstrate that PD depression is underpinned by dysfunction of limbic networks and monoaminergic systems, depending on the stage of PD and its associated symptoms, including apathy, anxiety, rapid eye movement sleep behavior disorder (RBD), cognitive impairment and dementia. In particular, the evolution of serotonergic, noradrenergic, and dopaminergic dysfunction and abnormalities of limbic circuits across time, involving the anterior cingulate and orbitofrontal cortices, amygdala, thalamus and ventral striatum, help to delineate the variable expression of depression in patients with prodromal, early and advanced PD. Evidence is accumulating to support the use of dual serotonin and noradrenaline reuptake inhibitors (desipramine, nortriptyline, venlafaxine) in patients with PD and moderate to severe depression, while selective serotonin reuptake inhibitors, repetitive transcranial magnetic stimulation and cognitive behavioral therapy may also be considered. In all patients, recent findings advocate that optimization of dopamine replacement therapy and evaluation of deep brain stimulation of the subthalamic nucleus to improve motor symptoms represents an important first step, in addition to physical activity. Overall, this review indicates that increasing understanding of neurobiological changes help to implement a roadmap of tailored interventions for patients with PD and depression, depending on the stage and comorbid symptoms underlying PD subtypes and their prognosis.

Data-driven identification of diagnostically useful extrastriatal signal in dopamine transporter SPECT using explainable AI

This study used explainable artificial intelligence for data-driven identification of extrastriatal brain regions that can contribute to the interpretation of dopamine transporter SPECT with ¹²³I-FP-CIT in parkinsonian syndromes. A total of 1306 ¹²³I-FP-CIT-SPECT were included retrospectively. Binary classification as ‘reduced’ or ‘normal’ striatal ¹²³I-FP-CIT uptake by an experienced reader served as standard-of-truth. A custom-made 3-dimensional convolutional neural network (CNN) was trained for classification of the SPECT images with 1006 randomly selected images in three different settings: “full image”, “striatum only” (3-dimensional region covering the striata cropped from the full image), “without striatum” (full image with striatal region removed). The remaining 300 SPECT images were used to test the CNN classification performance. Layer-wise relevance propagation (LRP) was used for voxelwise quantification of the relevance for the CNN-based classification in this test set. Overall accuracy of CNN-based classification was 97.0%, 95.7%, and 69.3% in the “full image”, “striatum only”, and “without striatum” setting. Prominent contributions in the LRP-based relevance maps beyond the striatal signal were detected in insula, amygdala, ventromedial prefrontal cortex, thalamus, anterior temporal cortex, superior frontal lobe, and pons, suggesting that ¹²³I-FP-CIT uptake in these brain regions provides clinically useful information for the differentiation of neurodegenerative and non-neurodegenerative parkinsonian syndromes.

Dopamine Transporter Imaging, Current Status of a Potential Biomarker: A Comprehensive Review

A major goal of current clinical research in Parkinson's disease (PD) is the validation and standardization of biomarkers enabling early diagnosis, predicting outcomes, understanding PD pathophysiology, and demonstrating target engagement in clinical trials. Molecular imaging with specific dopamine-related tracers offers a practical indirect imaging biomarker of PD, serving as a powerful tool to assess the status of presynaptic nigrostriatal terminals. In this review we provide an update on the dopamine transporter (DAT) imaging in PD and translate recent findings to potentially valuable clinical practice applications. The role of DAT imaging as diagnostic, preclinical and predictive biomarker is discussed, especially in view of recent evidence questioning the incontrovertible correlation between striatal DAT binding and nigral cell or axon counts.

Clinical and Striatal Dopamine Transporter Predictors of Mild Behavioral Impairment in Drug-Naive Parkinson Disease

PURPOSE

Neuropsychiatric symptoms are important and frequent nonmotor features in Parkinson disease (PD). We explored mild behavioral impairment (MBI) in drug-naive patients with PD and its clinical and dopamine transporter (DAT) correlates.

METHODS

We recruited 275 drug-naive patients with PD who had undergone Unified Parkinson's Disease Rating Scale, a neuropsychological battery, Neuropsychiatric Inventory, and N-(3-[F]fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) PET within 6 months. Patients with PD were divided into groups without MBI (PD-MBI-, n = 186) and with MBI (PD-MBI+, n = 89) according to the Neuropsychiatric Inventory. We performed comparative analysis of DAT availability, cognitive function, and motor deficits between the groups.

RESULTS

Mild behavioral impairment was found in 32.4% of PD patients at the time of diagnosis, and affective dysregulation and decreased motivation were the 2 most common neuropsychiatric domains. Dopamine transporter availability in the anterior caudate (odds ratio, 0.60; P = 0.016) and anterior putamen (odds ratio, 0.58; P = 0.008) was associated with the development of MBI in PD. PD-MBI+ group had a lower z-score in memory-related tests and Stroop color reading test than PD-MBI- group. PD-MBI+ group had a higher Unified Parkinson's Disease Rating Scale motor score after controlling for DAT availability in the posterior putamen than PD-MBI- group (P = 0.007).

CONCLUSIONS

This study suggests that early behavioral impairment is associated with more pathological involvement in the anterior striatum, memory and frontal dysfunction, and motor deficits, which could be regarded as a different phenotype in PD.

Management of psychiatric disorders in Parkinson's disease : Neurotherapeutics - Movement Disorders Therapeutics

Affective disorders (depression and anxiety), psychosis, impulse control disorders, and apathy are common and sometimes disabling psychiatric conditions in Parkinson disease (PD). Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their high frequency, there remains incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically co- or multimorbid, and there is great intra- and interindividual variability in presentation [1]. The neuropathophysiological changes that occur in PD, as well as the association between PD treatment and particular psychiatric disorders, suggest a neurobiological contribution to many psychiatric symptoms. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated, and although psychotropic medication use is common, randomized controlled trials demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors, and most importantly, establishing efficacious and well-tolerated treatment strategies.

Clinical implications of early caudate dysfunction in Parkinson's disease

OBJECTIVE

Although not typical of Parkinson's disease (PD), caudate dopaminergic dysfunction can occur in early stages of the disease. However, its frequency and longitudinal implications in large cohorts of recently diagnosed patients remain to be established. We investigated the occurrence of caudate dopaminergic dysfunction in the very early phases of PD (<2 years from diagnosis) using ¹²³I-FP-CIT single photon emission CT and determined whether it was associated with the presence or subsequent development of cognitive impairment, depression, sleep and gait problems.

METHODS

Patients with PD and healthy controls were identified from the Parkinson's Progression Markers Initiative (PPMI) database. We defined a clinically significant caudate dysfunction as ¹²³I-FP-CIT binding <-2 SDs compared with the controls' mean and categorised three groups accordingly (no reduction, unilateral reduction, bilateral reduction). All statistical analyses were adjusted for mean putamen binding.

RESULTS

At baseline, 51.6% of 397 patients had normal caudate dopamine transporter binding, 26.0% had unilateral caudate involvement, 22.4% had bilaterally impaired caudate.Compared with those with a baseline normal caudate function, at the4-year follow-up patients with a baseline bilateral caudate involvement showed a higher frequency of cognitive impairment (p<0.001) and depression (p<0.001), and worse cognitive (p<0.001), depression (<0.05) and gait (<0.001) ratings. Significant caudate involvement was observed in 83.9% of the population after 4 years (unilateral 22.5%, bilateral 61.4%).

CONCLUSIONS

Early significant caudate dopaminergic denervation was found in half of the cases in the PPMI series. Baseline bilateral caudate involvement was associated with increased risk of developing cognitive impairment, depression and gait problems over the next 4 years.

The Neuropsychiatry of Parkinson Disease: A Perfect Storm

Affective disorders, cognitive decline, and psychosis have long been recognized as common in Parkinson disease (PD), and other psychiatric disorders include impulse control disorders, anxiety symptoms, disorders of sleep and wakefulness, and apathy. Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their frequent occurrence, there is incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically multimorbid, and there is great intra- and interindividual variability in presentation. The hallmark neuropathophysiological changes that occur in PD, plus the association between exposure to dopaminergic medications and certain psychiatric disorders, suggest a neurobiological basis for many psychiatric symptoms, although psychological factors are involved as well. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated and although psychotropic medication use is common, controlled studies demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors and establishing efficacious and well-tolerated treatment strategies.

"Depressed" caudate and ventral striatum dopamine transporter availability in de novo Depressed Parkinson's disease

Depression can occur before the onset of motor symptoms in Parkinson's disease (PD) patients. The pathophysiology of depression in PD involves various brain regions and relevant functional circuits. This study investigated whether there exist distinctive patterns of presynaptic monoamine transporter densities in the basal ganglia depending on the degree of depression in patients with PD. A total of 123 early and drug-naïve PD patients were enrolled. Their affective status was evaluated by the Montgomery-Asberg Depression Rating Scale (MADRS), and subjects were subgrouped into one of the following three groups according to their MADRS scores: no depression, mild depression, and moderate-to-severe depression. All patients underwent positron emission tomography (PET) using ¹⁸F-N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane. The PET images were normalized, and differences in the regional standardized uptake value ratios (SUVRs) for each side of the caudate, putamen, globus pallidus, thalamus, and ventral striatum were analyzed and compared between the three groups. A trend analysis was performed across the groups to discern any associations between SUVR values of the basal ganglia and depression severity. The SUVR values of the caudate, anterior caudate nuclei, and ventral striatum declined as MADRS increased. The SUVR values of the striatum showed an inverse dose-dependent trend of antero- and ventroposterior gradient across the groups. This result indirectly revealed the involvement of the associative and limbic circuitry of the brain that are modulated by monoamines in early PD with depression. This might suggest an in vivo causal relationship between the ventral striatum, caudate and depression.

Assessment of Striatal Dopamine Transporter Binding in Individuals With Major Depressive Disorder: In Vivo Positron Emission Tomography and Postmortem Evidence

IMPORTANCE

Major depressive disorder (MDD) might involve dopamine (DA) reductions. The DA transporter (DAT) regulates DA clearance and neurotransmission and is sensitive to DA levels, with preclinical studies (including those involving inescapable stressors) showing that DAT density decreases when DA signaling is reduced. Despite preclinical data, evidence of reduced DAT in MDD is inconclusive.

OBJECTIVE

Using a highly selective DAT positron emission tomography (PET) tracer ([11C] altropane), DAT availability was probed in individuals with MDD who were not taking medication. Levels of DAT expression were also evaluated in postmortem tissues from donors with MDD who died by suicide.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional PET study was conducted at McLean Hospital (Belmont, Massachusetts) and Massachusetts General Hospital (Boston) and enrolled consecutive individuals with MDD who were not taking medication and demographically matched healthy controls between January 2012 and March 2014. Brain tissues were obtained from the Douglas-Bell Canada Brain Bank. For the PET component, 25 individuals with current MDD who were not taking medication and 23 healthy controls recruited from McLean Hospital were included (all provided usable data). For the postmortem component, 15 individuals with depression and 14 healthy controls were considered.

INTERVENTION

PET scan.

MAIN OUTCOMES AND MEASURES

Striatal and midbrain DAT binding potential was assessed. For the postmortem component, tyrosine hydroxylase and DAT levels were evaluated using Western blots.

RESULTS

Compared with 23 healthy controls (13 women [56.5%]; mean [SD] age, 26.49 [7.26] years), 25 individuals with MDD (19 women [76.0%]; mean [SD] age, 26.52 [5.92] years) showed significantly lower in vivo DAT availability in the bilateral putamen and ventral tegmental area (Cohen d range, -0.62 to -0.71), and both reductions were exacerbated with increasing numbers of depressive episodes. Unlike healthy controls, the MDD group failed to show an age-associated reduction in striatal DAT availability, with young individuals with MDD being indistinguishable from older healthy controls. Moreover, DAT availability in the ventral tegmental area was lowest in individuals with MDD who reported feeling trapped in stressful circumstances. Lower DAT levels (and tyrosine hydroxylase) in the putamen of MDD compared with healthy controls were replicated in postmortem analyses (Cohen d range, -0.92 to -1.15).

CONCLUSIONS AND RELEVANCE

Major depressive disorder, particularly with recurring episodes, is characterized by decreased striatal DAT expression, which might reflect a compensatory downregulation due to low DA signaling within mesolimbic pathways.

Progressive loss of raphe nuclei serotonin transporter in early Parkinson's disease: A longitudinal 123I-FP-CIT SPECT study

BACKGROUND

Serotonergic raphe nuclei dysfunction has been documented in Parkinson's disease, both in pathological and neuroimaging studies, and has been associated with scores of tremor and non-motor symptoms. However, no in vivo longitudinal investigations have been conducted to assess the rate of decline of raphe serotonin transporter availability in the early stages of the disease.

OBJECTIVE

To measure the rate of decline of raphe serotonin transporter availability over a two-year interval in patients with recently diagnosed disease and its association with non-motor symptoms over time.

METHODS

Baseline and two-year follow-up ¹²³ioflupane-fluoropropyl-carbomethoxy-3-beta-4-iodo-phenyltropane (¹²³I-FP-CIT) SPECT scans of 173 early Parkinson's disease patients enrolled in the Parkinson's Progressive Markers Initiative were analysed and non-motor symptoms scores recorded.

RESULTS

A 16.6 ± 20.9% (mean ± SD) reduction in raphe serotonin transporter availability was found from baseline to two-year follow-up in the entire cohort. No differences in progression were found between tremor dominant and postural instability/gait difficulty phenotypes. At follow-up 34.1% of patients showed a moderate-to-severe reduction of raphe serotonin transporter availability with respect to the controls' mean. We did not find any significant correlation between raphe serotonin transporter availability and scores of depression, excessive daytime sleepiness and REM sleep behaviour disorder.

CONCLUSION

¹²³I-FP-CIT SPECT was able to measure longitudinal reductions in raphe serotonin transporter availability in the early phases of Parkinson's disease. About four years after diagnosis, raphe serotonin transporter availability was significantly reduced in more than one third of the population, but does not appear to be correlated to non-motor symptoms at this stage.

Exercise as a therapeutic intervention for motor and non-motor symptoms in Parkinson's disease: Evidence from rodent models

Parkinson's disease (PD) is characterised by degeneration of dopaminergic neurons of the nigrostriatal pathway, which leads to the cardinal motor symptoms of the disease - tremor, rigidity and postural instability. A number of non-motor symptoms are also associated with PD, including cognitive impairment, mood disturbances and dysfunction of gastrointestinal and autonomic systems. Current therapies provide symptomatic relief but do not halt the disease process, so there is an urgent need for preventative strategies. Lifestyle interventions such as aerobic exercise have shown potential to lower the risk of developing PD and to alleviate both motor and non-motor symptoms. However, there is a lack of large-scale randomised clinical trials that have employed exercise in PD patients. This review will focus on the evidence from studies on rodent models of PD, for employing exercise as an intervention for both motor and non-motor symptoms.

The presence of depression in de novo Parkinson's disease reflects poor motor compensation

Depression frequently accompanies Parkinson's disease and often precedes the onset of motor symptoms. This study aimed to evaluate the impact of depression on motor compensation in patients with de novo Parkinson's disease. This retrospective cohort study analyzed data from 474 non-demented patients with de novo Parkinson's disease (mean age, 64.6±9.8 years; 242 men) who underwent both dopamine transporter PET scan and depression assessment using the Beck Depression Inventory at baseline. Patients were classified into tertiles by Beck Depression Inventory score. At baseline, high-tertile group (Beck Depression Inventory score ≥15, n = 157) showed more severe motor deficits and lower cognitive function than low-tertile group (Beck Depression Inventory score ≤7, n = 158, P = 0.034 and P = 0.008, respectively). Greater motor deficits in high-tertile group than low-tertile group remained significant after controlling for dopamine transporter binding in the posterior putamen, as well as other confounding variables. During follow-up of a median duration of 47 months, high-tertile group received higher levodopa-equivalent doses for symptom control than did low-tertile group after controlling for age, gender, and initial motor deficit severity. These results demonstrate that depression in de novo Parkinson's disease is associated with motor deficit severity at baseline and dose of PD medications during follow-up, suggesting that the presence of depression in de novo Parkinson's disease represents poor motor compensation.

Depression, anxiety, and apathy in Parkinson's disease: insights from neuroimaging studies

Depression, anxiety and apathy are common mood disturbances in Parkinson's disease (PD) but their pathophysiology is unclear. Advanced neuroimaging has been increasingly used to unravel neural substrates linked to these disturbances. A systematic review is provided of neuroimaging findings in depression, anxiety and apathy in PD. A PubMed, MEDLINE and EMBASE search of peer‐reviewed original research articles on these mood disturbances in PD identified 38 studies on depression, eight on anxiety and 14 on apathy in PD. Most of the imaging studies used either position emission tomography or single‐photon emission computed tomography techniques. These studies generally suggest increased neural activity in the prefrontal regions and decreased functional connectivity between the prefrontal−limbic networks in depressed patients. Functional imaging studies revealed an inverse correlation between dopaminergic density in the caudate and putamen with the severity of anxiety in PD. There was no consistent correlation between dopaminergic density of thalamus and anxiety. Studies demonstrated both positive and inverse correlations between apathy and metabolism or activity in the striatum, amygdalar, prefrontal, temporal and parietal regions. The clinical variability of study subjects and differences in image pre‐processing and analytical strategies may contribute to discrepant findings in these studies. Both nigrostriatal and extra‐nigrostriatal pathways (in particular the frontal region and its connecting areas) are affected in mood disorders in PD. Identifying the relative contributions of these neural pathways in PD patients with overlapping motor and mood symptoms could provide new pathophysiological clues for the development of better therapeutic targets for affected patients.

Imaging the Etiology of Apathy, Anxiety, and Depression in Parkinson's Disease: Implication for Treatment

Apathy, depression, and anxiety are among the most important non-motor signs of Parkinson's disease (PD). This may be encountered at early stages of illness and represent a major source of burden. Understanding their pathophysiology is a major prerequisite for efficient therapeutic strategies. Anatomical and metabolic imaging studies have enabled a breakthrough by demonstrating that widespread abnormalities within the limbic circuits notably the orbitofrontal and anterior cingulate cortices, amygdala, thalamus, and ventral striatum are involved in the pathophysiology of depression, anxiety, and apathy in PD. Functional imaging has further shown that mesolimbic dopaminergic but also serotonergic lesions play a major role in the mechanisms of these three neuropsychiatric manifestations, which has direct therapeutic implications.

Nonmotor Effects of Conventional and Transdermal Dopaminergic Therapies in Parkinson's Disease

Nonmotor symptoms (NMS) are an integral component of Parkinson's disease (PD). Because the burden and range of NMS are key determinants of quality of life for patients and caregivers, their management is a crucial issue in clinical practice. Although a range of NMS have a dopaminergic pathophysiological basis, this fact is underrecognized, and thus, they are often regarded as dopamine unresponsive symptoms. However, substantial evidence indicates that many NMS respond to oral and transdermal dopaminergic therapies. In contrast, certain NMS are exacerbated or even precipitated by dopaminergic drugs and these unwanted effects may be seriously dangerous. Therefore, a dopaminergic strategy for NMS should be based on a consideration of the benefits vs the risks in individual patients with PD.

Imaging the Nonmotor Symptoms in Parkinson's Disease

Parkinson's disease is acknowledged to be a multisystem syndrome, manifesting as a result of multineuropeptide dysfunction, including dopaminergic, cholinergic, serotonergic, and noradrenergic deficits. This multisystem disorder ultimately leads to the presentation of a range of nonmotor symptoms, now appreciated to be an integral part of the disease-specific spectrum of symptoms, often preceding the diagnosis of motor Parkinson's disease. In this chapter, we review the dopaminergic and nondopaminergic basis of these symptoms by exploring the neuroimaging evidence based on several techniques including positron emission tomography, single-photon emission computed tomography molecular imaging, magnetic resonance imaging, functional magnetic resonance imaging, and diffusion tensor imaging. We discuss the role of these neuroimaging techniques in elucidating the underlying pathophysiology of NMS in Parkinson's disease.

Polymorphisms of COMT (c.649G>A), MAO-A (c.1460C>T), NET (c.1287G>A) Genes and the Level of Catecholamines, Serotonin in Patients with Parkinson's Disease

The purpose of this study was to determine the concentration of plasma norepinephrine (NE), epinephrine (E), and serotonin (5-HT) in two collections, after a 30-min supine (I) and 5-min upright position (II), and polymorphisms of genes, COMT (c.649G>A), MAO-A (c.1460C>T), and NET (c.1287G>A), in patients with Parkinson's disease (PD) and other degenerative parkinsonism and controls. The study was performed in 49 PD patients, 19 parkinsonism patients, and 48 controls. The level of NE, E, and 5-HT was determined by HPLC/EC. PCR-RFLP was conducted to analyze the COMT, MAO-A, and NET polymorphisms. Genotypes of COMT, MAO-A, and NET genes occurred with different frequencies in patients with movement disorders and controls. NET AA occurred 4.8 times more frequently in patients with parkinsonism than in PD (p < 0.05). COMT AA genotype was associated with increased E levels [E (I) p < 0.01, E (II) p < 0.05] in PD compared to controls. Patients with parkinsonism with MAO-A TT genotype have a significantly higher level of 5-HT [5-HT (II), p < 0.05] compared to controls. Moreover, PD patients with NET GA genotype have the lowest level of NE (p < 0.05) compared to controls. It appears that COMT, MAO-A, and NET polymorphisms and levels of NE, E, and 5-HT are involved in pathogenesis of PD.

The relationship between the dopaminergic system and depressive symptoms in cervical dystonia

PURPOSE

Cervical dystonia (CD) is associated with tremor/jerks (50%) and psychiatric complaints (17-70%). The dopaminergic system has been implicated in the pathophysiology of CD in animal and imaging studies. Dopamine may be related to the motor as well as non-motor symptoms of CD. CD is associated with reduced striatal dopamine D_2/3 (D2/3) receptor and increased dopamine transporter (DAT) binding. There are differences in the dopamine system between CD patients with and without jerks/tremor and psychiatric symptoms.

METHODS

Patients with CD and healthy controls underwent neurological and psychiatric examinations. Striatal DAT and D2/3 receptor binding were assessed using [¹²³I]FP-CIT and [¹²³I]IBZM SPECT, respectively. The ratio of specific striatal to non-specific binding (binding potential; BP_ND) was the outcome measure.

RESULTS

Twenty-seven patients with CD and 15 matched controls were included. Nineteen percent of patients fulfilled the criteria for a depression. Striatal DAT BP_ND was significantly lower in depressed versus non-depressed CD patients. Higher DAT BP_ND correlated significantly with higher scores on the Unified Myoclonus Rating Scale (UMRS). The striatal D2/3 receptor BP_ND in CD patients showed a trend towards lower binding compared to controls. The D2/3 BP_ND was significantly lower in depressed versus non-depressed CD patients. A significant correlation between DAT and D2/3R BP_ND was found in both in patients and controls.

CONCLUSIONS

Alterations of striatal DAT and D2/3 receptor binding in CD patients are related mainly to depression. DAT BP_ND correlates significantly with scores on the UMRS, suggesting a role for dopamine in the pathophysiology of tremor/jerks in CD.

Presynaptic dopaminergic terminal imaging and non-motor symptoms assessment of Parkinson's disease: evidence for dopaminergic basis?

Parkinson's disease (PD) is now considered to be a multisystemic disorder consequent on multineuropeptide dysfunction including dopaminergic, serotonergic, cholinergic, and noradrenergic systems. This multipeptide dysfunction leads to expression of a range of non-motor symptoms now known to be integral to the concept of PD and preceding the diagnosis of motor PD. Some non-motor symptoms in PD may have a dopaminergic basis and in this review, we investigate the evidence for this based on imaging techniques using dopamine-based radioligands. To discuss non-motor symptoms we follow the classification as outlined by the validated PD non-motor symptoms scale.

Test-retest reproducibility of extrastriatal binding with 123I-FP-CIT SPECT in healthy male subjects

¹²³I-labeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (¹²³I-FP-CIT) is used to assess striatal dopamine transporter (DAT) expression, but it can also quantify extrastriatal serotonin transporter (SERT) expressions. While FP-CIT uptake in extrastriatal regions has been quantified, no information exists on the reproducibility of the ¹²³I-FP-CIT specific uptake ratio (SUR) in extrastriatal regions. We investigated test-retest reproducibility of ¹²³I-FP-CIT binding in the striatum, the midbrain, and cortical regions in eight healthy male subjects. All subjects underwent two ¹²³I-FP-CIT SPECT scans, and SUR was calculated using the cerebellum as the reference. We found good test-retest reproducibility of ¹²³I-FP-CIT SUR in the midbrain, and in the lateral frontal/temporal cortex and combined cortical regions. The overall variability and intraclass correlation of SUR were, respectively, 4.9-7.8% and 0.90-0.96 in striatal regions, 8.6% and 0.79 in the midbrain, and 3.6-9.1% and 0.84-0.95 in the lateral frontal/temporal cortex and combined cortical regions. Our results provide evidence that ¹²³I-FP-CIT SPECT is a valid technique for analyzing striatal DAT, as well as extrastriatal SERT in areas such as the SERT-enriched midbrain. In addition, our data suggest that ¹²³I-FP-CIT could be used for analyzing SERT in regions with relatively low SERT expression (e.g., temporal or frontal cortices).

Changes in neural circuitry associated with depression at pre-clinical, pre-motor and early motor phases of Parkinson's disease

Although Parkinson's Disease (PD) is mostly considered a motor disorder, it can present at early stages as a non-motor pathology. Among the non-motor clinical manifestations, depression shows a high prevalence and can be one of the first clinical signs to appear, even a decade before the onset of motor symptoms. Here, we review the evidence of early dysfunction in neural circuitry associated with depression in the context of PD, focusing on pre-clinical, pre-motor and early motor phases of the disease. In the pre-clinical phase, structural and functional changes in the substantia nigra, basal ganglia and limbic structures are already observed. Some of these changes are linked to motor compensation mechanisms while others correspond to pathological processes common to PD and depression and thus could underlie the appearance of depressive symptoms during the pre-motor phase. Studies of the early motor phase (less than five years post diagnosis) reveal an association between the extent of damage in different monoaminergic systems and the appearance of emotional disorders. We propose that the limbic loop of the basal ganglia and the lateral habenula play key roles in the early genesis of depression in PD. Alterations in the neural circuitry linked with emotional control might be sensitive markers of the ongoing neurodegenerative process and thus may serve to facilitate an early diagnosis of this disease. To take advantage of this, we need to improve the clinical criteria and develop biomarkers to identify depression, which could be used to determine individuals at risk to develop PD.

Different patterns of 5-HT receptor and transporter dysfunction in neuropsychiatric disorders--a comparative analysis of in vivo imaging findings

Impairment of serotonin receptor and transporter function is increasingly recognized to play a major role in the pathophysiology of neuropsychiatric diseases including anxiety disorder (AD), major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ). We conducted a PubMed search, which provided a total of 136 in vivo studies with PET and SPECT, in which 5-HT synthesis, 5-HT transporter binding, 5-HT1 receptor binding or 5-HT2 receptor binding in patients with the primary diagnosis of acute AD, MDD, BD or SZ was compared to healthy individuals. A retrospective analysis revealed that AD, MDD, BD and SZ differed as to affected brain region(s), affected synaptic constituent(s) and extent as well as direction of dysfunction in terms of either sensitization or desensitization of transporter and receptor binding sites.

Trait Impulsivity and Anhedonia: Two Gateways for the Development of Impulse Control Disorders in Parkinson's Disease?

Apathy and impulsivity are two major comorbid syndromes of Parkinson's disease (PD) that may represent two extremes of a behavioral spectrum modulated by dopamine-dependent processes. PD is characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta to which are attributed the cardinal motor symptoms of the disorder. Dopamine replacement therapy (DRT), used widely to treat these motor symptoms, is often associated with deficits in hedonic processing and motivation, including apathy and depression, as well as impulse control disorders (ICDs). ICDs comprise pathological gambling, hypersexuality, compulsive shopping, binge eating, compulsive overuse of dopaminergic medication, and punding. More frequently observed in males with early onset PD, ICDs are associated not only with comorbid affective symptoms, such as depression and anxiety, but also with behavioral traits, such as novelty seeking and impulsivity, as well as with personal or familial history of alcohol use. This constellation of associated risk factors highlights the importance of inter-individual differences in the vulnerability to develop comorbid psychiatric disorders in PD patients. Additionally, withdrawal from DRT in patients with ICDs frequently unmasks a severe apathetic state, suggesting that apathy and ICDs may be caused by overlapping neurobiological mechanisms within the cortico-striato-thalamo-cortical networks. We suggest that altered hedonic and impulse control processes represent distinct prodromal substrates for the development of these psychiatric symptoms, the etiopathogenic mechanisms of which remain unknown. Specifically, we argue that deficits in hedonic and motivational states and impulse control are mediated by overlapping, yet dissociable, neural mechanisms that differentially interact with DRT to promote the emergence of ICDs in vulnerable individuals. Thus, we provide a novel heuristic framework for basic and clinical research to better define and treat comorbid ICDs in PD.

The Role of the Serotonergic System in REM Sleep Behavior Disorder

STUDY OBJECTIVES

REM sleep behavior disorder (RBD) can be induced by antidepressants, especially serotonin reuptake inhibitors (SSRI), thus a role of the serotonergic system in the pathogenesis of RBD has been proposed. However, the serotonergic system integrity in idiopathic RBD (iRBD) is still unknown. We aimed to study brain stem serotonergic system integrity, by means of (123)I-FP-CIT-SPECT, in a group of iRBD patients as compared to normal subjects.

DESIGN

Single-center, prospective observational study.

SETTING

University hospital.

PATIENTS OR PARTICIPANTS

Twenty iRBD outpatients and 23 age-matched normal controls.

MEASUREMENTS AND RESULTS

The diagnosis of RBD was determined clinically and confirmed by means of overnight, laboratory-based video-polysomnography. Both iRBD patients and normal subjects underwent (123)I-FP-CIT-SPECT as a marker of dopamine transporter (DAT) at basal ganglia level and of serotonin transporter (SERT) at brainstem and thalamus levels. (123)I-FP-CIT-SPECT images were analyzed and compared between iRBD patients and controls by means of both region of interest analysis at basal ganglia, midbrain, pons and thalamus levels, and voxel-based analysis, taking into account age and the use of SSRI as confounding factors. No difference in (123)I-FP-CIT-SPECT specific to nondisplaceable binding ratios (SBR) values was found between iRBD and normal subjects at brainstem and thalamus levels while iRBD patients showed lower SBR values in all basal ganglia nuclei (P < 0.0001) compared to controls.

CONCLUSIONS

These results suggest that the serotonergic system is not directly involved in RBD pathogenesis while confirming nigro-striatal dopaminergic deafferentation in iRBD.

Comparison of somatostatin receptor agonist and antagonist for peptide receptor radionuclide therapy: a pilot study

Preclinical and clinical studies have indicated that somatostatin receptor (sst)-expressing tumors demonstrate higher uptake of radiolabeled sst antagonists than of sst agonists. In 4 consecutive patients with advanced neuroendocrine tumors, we evaluated whether treatment with (177)Lu-labeled sst antagonists is feasible.

METHODS

After injection of approximately 1 GBq of (177)Lu-DOTA-[Cpa-c(DCys-Aph(Hor)-DAph(Cbm)-Lys-Thr-Cys)-DTyr-NH2] ((177)Lu-DOTA-JR11) and (177)Lu-DOTATATE, 3-dimensional voxel dosimetry analysis based on SPECT/CT was performed. A higher tumor-to-organ dose ratio for (177)Lu-DOTA-JR11 than for (177)Lu-DOTATATE was the prerequisite for treatment with (177)Lu-DOTA-JR11.

RESULTS

Reversible minor adverse effects of (177)Lu-DOTA-JR11 were observed. (177)Lu-DOTA-JR11 showed a 1.7-10.6 times higher tumor dose than (177)Lu-DOTATATE. At the same time, the tumor-to-kidney and tumor-to-bone marrow dose ratio was 1.1-7.2 times higher. All 4 patients were treated with (177)Lu-DOTA-JR11, resulting in partial remission in 2 patients, stable disease in 1 patient, and mixed response in the other patient.

CONCLUSION

Treatment of neuroendocrine tumors with radiolabeled sst antagonists is clinically feasible and may have a significant impact on peptide receptor radionuclide therapy.

Extrastriatal binding of [¹²³I]FP-CIT in the thalamus and pons: gender and age dependencies assessed in a European multicentre database of healthy controls

PURPOSE

Apart from binding to the dopamine transporter (DAT), [(123)I]FP-CIT shows moderate affinity for the serotonin transporter (SERT), allowing imaging of both monoamine transporters in a single imaging session in different brain areas. The aim of this study was to systematically evaluate extrastriatal binding (predominantly due to SERT) and its age and gender dependencies in a large cohort of healthy controls.

METHODS

SPECT data from 103 healthy controls with well-defined criteria of normality acquired at 13 different imaging centres were analysed for extrastriatal binding using volumes of interest analysis for the thalamus and the pons. Data were examined for gender and age effects as well as for potential influence of striatal DAT radiotracer binding.

RESULTS

Thalamic binding was significantly higher than pons binding. Partial correlations showed an influence of putaminal DAT binding on measured binding in the thalamus but not on the pons. Data showed high interindividual variation in extrastriatal binding. Significant gender effects with 31 % higher binding in women than in men were observed in the thalamus, but not in the pons. An age dependency with a decline per decade (±standard error) of 8.2 ± 1.3 % for the thalamus and 6.8 ± 2.9 % for the pons was shown.

CONCLUSION

The potential to evaluate extrastriatal predominant SERT binding in addition to the striatal DAT in a single imaging session was shown using a large database of [(123)I]FP-CIT scans in healthy controls. For both the thalamus and the pons, an age-related decline in radiotracer binding was observed. Gender effects were demonstrated for binding in the thalamus only. As a potential clinical application, the data could be used as a reference to estimate SERT occupancy in addition to nigrostriatal integrity when using [(123)I]FP-CIT for DAT imaging in patients treated with selective serotonin reuptake inhibitors.

Depressive symptoms in Parkinson's disease are related to reduced [123I]FP-CIT binding in the caudate nucleus

BACKGROUND

Depression is a common neuropsychiatric symptom in Parkinson's disease (PD). In previous research, PD-related depression was associated with striatal dopaminergic deficits, presumably due to degeneration of brainstem dopaminergic projections. Segregated areas of the striatum are crucially involved in various parallelly arranged cortical-striatal-thalamocortical circuits and serve functions in, among others, motor control or emotion. This suggests regional specificity of dopaminergic deficits in the striatum in motor and depressive symptoms in PD.

METHODS

In this cross-sectional retrospective study, we correlated severity scores of depressive and motor symptoms in 100 non-demented PD patients (median Hoehn & Yahr stage: 2) with dopamine loss in specific regions of the striatum as measured by [(123)I]FP-CIT SPECT tracer binding to the dopamine transporter (DaT).

RESULTS

Depressive symptoms were related to lower DaT binding in the right caudate nucleus, while motor symptoms were associated with decreased DaT binding in the right putamen. This double dissociation was most pronounced in early-stage PD patients.

CONCLUSIONS

These results suggest that depressive symptoms in PD are associated with dopamine loss in the caudate nucleus, possibly related to degeneration of dopaminergic projections from the ventral tegmental area, while motor symptoms are associated with low dopamine signalling to the putamen and loss of nigrostriatal projections. This is consistent with the neuroanatomy of partially segregated cortical-striatal-thalamocortical circuits and supports the role of dysfunctional associative and motivational circuits in PD-related depression.

Neuroimaging of depression in Parkinson's disease: a review

BACKGROUND

Depression is the most common psychiatric manifestation in patients with Parkinson's disease (PD). In addition, depressive symptoms may be considered to be a prodromal manifestation of PD. In recent years, the association between PD and depression has been the focus of neuroimaging studies using functional and structural techniques.

METHODS

The aim of this study was to review the main neuroimaging studies assessing the comorbidity between depression and PD. Literature searches were conducted to find the major neuroimaging studies that consider primarily the comorbidity between depression and PD using the indices Web of Science and Lilacs.

RESULTS

In total, 296 papers were identified, and 18 of these studies were selected for the current review. The principal neuroimaging technique used was SPECT. The structural neuroimaging studies that have evaluated the impact of current or previous bouts of depression on the neurodegenerative process of PD are scarce and inclusive. The instruments that were used to evaluate depression differed among the studies. Several brain regions appear to be involved in depression, particularly the limbic system and the basal ganglia. In addition, the serotonergic, dopaminergic, and noradrenergic systems also appear to be associated with depressive symptoms in PD.

CONCLUSION

Several brain regions and neurotransmitter systems are involved in depression in PD; however, the variety of criteria used to evaluate depressive symptoms precludes more specific conclusions.

Depression and impulse control disorders in Parkinson's disease: two sides of the same coin?

Depression and impulse control disorders (ICD) are two common neuropsychiatric features in Parkinson's disease (PD). Studies have revealed that both phenomena are associated with aberrations in ventral striatal dopamine signaling and concomitant dysfunction of the reward-related (limbic) cortico-striatal-thalamocortical (CSTC) circuit. Depression in PD seems associated with decreased activity in the limbic CSTC circuit, whereas ICD seem associated with increased limbic CSTC circuit activity, usually after commencing dopamine replacement therapy (DRT). Not all DRT using PD patients, however, develop symptoms of ICD, suggesting an additional underlying neurobiological susceptibility. Furthermore, the symptoms of depression and ICD frequently coincide even though they are related to seemingly contrasting limbic CSTC circuit activation states. The aim of this review is to provide an overview of the currently available literature on the neurobiology of PD-related depression and ICD and discusses possible susceptibility factors. Finally, we propose a neurobiological model that identifies ventral striatal dopaminergic denervation as a common underlying neurobiological substrate of depression and ICD and subsequent dysfunction of reward and motivation-related brain areas.

Mild affective symptoms in de novo Parkinson's disease patients: relationship with dopaminergic dysfunction

BACKGROUND AND PURPOSE

The investigation of the relationship between affective symptoms and dopamine transporter (DAT) density provided conflicting data in both Parkinson's disease (PD) and non-PD patients. However, the potential interference of psychoactive as well as anti-parkinsonian drugs on DAT density should be taken into account.

OBJECTIVE

To investigate the relationship between affective symptoms and pre-synaptic dopaminergic function in de novo PD patients.

METHODS

Forty-four de novo PD consecutive outpatients were recruited, and the severity of anxious symptoms was evaluated with the Hamilton Anxiety Rating Scale (HAM-A), the severity of depressive symptoms with the Hamilton Depression Scale (HAM-D) and the Beck Depression Inventory (BDI). Six patients had a formal diagnosis of depression. All patients performed (123) I-FP-CIT SPECT, and semi-quantitative striatal indices were calculated.

RESULTS

Disease severity, as measured by Unified Parkinson's Disease Rating Scale (UPDRSIII), was inversely correlated with bilateral striatal indices. Bilateral striatal uptake was significantly positively correlated with HAM-D (r.329; r.423, respectively, right and left), BDI (r.377; r.360, respectively, right and left) and HAM-A (r.338; r.340, respectively, right and left). After controlling for age, disease duration and severity, and Mini Mental State Examination (MMSE), no significant reduction in r-values was observed (P < 0.05).

CONCLUSION

Our data support the existence of a relationship between depressive and anxious symptoms and the striatal (123) I-FP-CIT uptake. The finding of an increased DAT density associated with mild affective symptoms could be due to the lack of compensatory mechanisms usually present in early PD, and/or it might have a pathogenic role in affective symptoms by reducing the dopaminergic tone in the synaptic cleft.

Dopaminergic dysfunction and psychiatric symptoms in movement disorders: a 123I-FP-CIT SPECT study

PURPOSE

Psychiatric symptoms frequently occur in patients with movement disorders. They are not a mere reaction to chronic disability, but most likely due to a combination of psychosocial factors and biochemical dysfunction underlying the movement disorder. We assessed dopamine transporter (DAT) availability by means of (123)I-FP-CIT SPECT, and motor and psychiatric features in patients with Parkinson's disease, primary dystonia and essential tremor, exploring the association between SPECT findings and symptom severity.

METHODS

Enrolled in the study were 21 patients with Parkinson's disease, 14 patients with primary dystonia and 15 patients with essential tremor. The severity of depression symptoms was assessed using the Hamilton depression rating scale, anxiety levels using the Hamilton anxiety rating scale and hedonic tone impairment using the Snaith-Hamilton pleasure scale. Specific (123)I-FP-CIT binding in the caudate and putamen was calculated based on ROI analysis. The control group included 17 healthy subjects.

RESULTS

As expected, DAT availability was significantly decreased in patients with Parkinson's disease, whereas in essential tremor and dystonia patients it did not differ from that observed in the control group. In Parkinson's disease patients, an inverse correlation between severity of depression symptoms and DAT availability in the left caudate was found (r = -0.63, p = 0.002). In essential tremor patients, levels of anxiety symptoms were inversely correlated with DAT availability in the left caudate (r = -0.69, p = 0.004). In dystonia patients, the severities of both anxiety and depression symptoms were inversely associated with DAT availability in the left putamen (r = -0.71, p = 0.004, and r = -0.75, p = 0.002, respectively). There were no correlations between psychometric scores and (123)I-FP-CIT uptake ratios in healthy subjects.

CONCLUSION

We found association between presynaptic dopaminergic function and affective symptoms in different movement disorders. Interestingly, the inverse correlation was present in each group of patients, supporting the fascinating perspective that common subcortical substrates may be involved in both anxiety and depression dimensions and movement disorders.

[Imaging non motor signs in Parkinson's disease]

Parkinson's disease is mainly considered as a motor disorder defined by a motor triad. However, various non-motor manifestations may be encountered in Parkinson's disease, including hyposmia, pain, fatigue, sleep disorders, cognitive and behavioral disorders. The pathophysiology of these signs is complex, not univocal and remains poorly understood. Functional imaging techniques either by positron emission tomography, single photon emission tomography or functional magnetic resonance imaging provide an invaluable opportunity to better understand the pathophysiology of these signs. In this paper, we present a review of the recent advances provided by functional imaging in this area.

Is depression in Parkinson's disease (PD) a specific entity?

BACKGROUND

Clinical lore and research have suggested for a long time that depression and PD are closely related. We examined the validity of depression associated with PD (dPD) as a specific subtype of depression according to face validity, descriptive validity, construct validity and predictive validity.

METHODS

The English literature was reviewed after searching the MEDLINE database up to June 2010.

RESULTS

There appears to be three possible subtypes of comorbid depression: 1) patients who would have been depressed even if they had no PD (nonspecific-casual comorbid dPD), 2) patients who would have been depressed if they had had another disabling medical illness (nonspecific-reactive comorbid dPD) 3) those for which depression is directly related to the underlying pathophysiology of PD (specific comorbid dPD). These latter patients may more often present with particular clinical characteristics (descriptive validity): absence of history of depression or only within 5 years prior to onset of PD, absence of guilty thoughts and self-blame, absence of suicidal behavior, right-sided onset. However, dPD is only partly responsive to dopamine replacement and cannot be solely explained by dopamine deficiency. Other neurotransmitter systems are affected in PD and are involved in the pathophysiology of dPD. Their relative involvement however may differ from that in idiopathic depression (i.e.: lesser involvement of serotonergic systems).

LIMITATIONS

Therapeutic data are limited to few controlled trials.

CONCLUSIONS

Further research may allow differential diagnosis between dPD subtypes (i.e.: those who do and do not result from the underlying pathophysiological process of PD) and help inform treatment choice.

Psychosis in Parkinson's disease without dementia: common and comorbid with other non-motor symptoms

Psychosis in Parkinson's disease (PD) is common and associated with a range of negative outcomes. Dementia and psychosis are highly correlated in PD, but the frequency and correlates of psychosis in patients without cognitive impairment are not well understood. One hundred and ninety-one non-demented PD patients at two movement disorders centers participated in a study of neuropsychiatric complications in PD and completed a detailed neurological and neuropsychiatric assessment, including the rater-administered Parkinson Psychosis Rating Scale for hallucinations, delusions, and minor symptoms of psychosis (illusions and misidentification of persons). Psychotic symptoms were present in 21.5% of the sample. Visual hallucinations were most common (13.6%), followed by auditory hallucinations (6.8%), illusions or misidentification of people (7.3%), and paranoid ideation (4.7%). Visual hallucinations and illusions or misidentification of people were the most common comorbid symptoms (3.1%). Depression (P = 0.01) and rapid eye movement behavior disorder symptoms (P = 0.03) were associated with psychosis in a multivariable model. The odds of experiencing psychotic symptoms were approximately five times higher in patients with comorbid disorders of depression and sleep-wakefulness. Even in patients without global cognitive impairment, psychosis in PD is common and most highly correlated with other non-motor symptoms. Screening for psychosis should occur at all stages of PD as part of a broad non-motor assessment. In addition, these findings suggest a common neural substrate for disturbances of perception, mood, sleep-wakefulness, and incipient cognitive decline in PD.

Assessing the optimal time point for the measurement of extrastriatal serotonin transporter binding with 123I-FP-CIT SPECT in healthy, male subjects

(123)I-N-ω-fluoropropyl-2β-carboxymethoxy-3β-(4-iodophenyl)nortropane ((123)I-FP-CIT) is commonly used to assess the dopamine transporter in the striatum. However, recent studies suggest that this tracer may be used also to assess binding to monoamine transporters in the midbrain or diencephalon, which may reflect predominantly serotonin transporter (SERT) binding. However, it is still unclear at what time point after injection SPECT should be performed for optimal assessment of SERT with(123)I-FP-CIT. Therefore, we examined the time course of extrastriatal (123)I-FP-CIT binding.

METHODS

Nineteen healthy, male subjects were included, and SPECT images were acquired up to 3 h after (123)I-FP-CIT injection. Region-of-interest analysis was performed, and specific-to-nonspecific binding ratios were calculated.

RESULTS

Specific-to-nonspecific (123)I-FP-CIT binding ratios in the midbrain and diencephalon were significantly higher 2 h after injection than 1 h after injection and remained stable between 2 and 3 h after injection.

CONCLUSION

The optimal time frame for assessing (123)I-FP-CIT binding to extrastriatal SERT is between 2 and 3 h after injection of the tracer.

Stress, depression and Parkinson's disease

In this review, we focus on the relationship among Parkinson's disease (PD), stress and depression. Parkinson's disease patients have a high risk of developing depression, and it is possible that stress contributes to the development of both pathologies. Stress dysfunction may have a role in the etiology of preclinical non-motor symptoms of PD (such as depression) and, later in the course of the disease, may worsen motor symptoms. However, relatively few studies have examined stress or depression and the injured nigrostriatal system. This review discusses the effects of stress on neurodegeneration and depression, and their association with the symptoms and progression of PD.

Depression in mild dementia: associations with diagnosis, APOE genotype and clinical features

BACKGROUND

Depression is common in dementia, with important clinical implications. Few studies of depression in dementia with Lewy bodies are available, and the results are inconsistent.

OBJECTIVE

To examine the frequency of depression and its characteristics and correlates, in people with mild dementia.

METHODS

All referrals for patients with a first time diagnosis of dementia to geriatric and older psychiatry outpatient clinics in the counties of Rogaland and Hordaland in Western Norway from March 2005 to March 2007 were screened for the study. Participants and their caregivers underwent a comprehensive and standardised diagnostic and assessment procedure. The depression subitem of the neuropsychiatric inventory (NPId) and Montgomery and Åsberg depression rating scale (MADRS) were used to estimate depression. Cut-off scores for any depression were 0/1 (NPId) and 6/7 (MADRS), and for clinically significant depression 3/4 and 14/15, respectively.

RESULTS

Two hundered and twenty-three subjects with dementia participated, of whom 59 and 50% showed symptoms of depression assessed by NPI or MADRS, respectively, and 25 and 16% had clinically significant depression as measured by NPI and MADRS, respectively. Depression was more frequent in dementia with Lewy bodies (DLB) than in Alzheimer's disease (AD; p < 0.05). APOE genotype was available in 153 patients, and in AD, but not in DLB, a general linear model showed that the presence of APOEε4 allele was significantly associated with depression (F = 4.14; p = 0.045).

CONCLUSION

Depression is common even in mild dementia, and more common and severe in DLB compared to AD. Future studies should explore the longitudinal course of depression in DLB, and the neural underpinnings of depression in DLB.

Serotonin-dependent depression in Parkinson's disease: a role for the subthalamic nucleus?

Depression is the most common neuropsychiatric co-morbidity in Parkinson's disease (PD). The underlying mechanism of depression in PD is complex and likely involves biological, psychosocial and therapeutic factors. The biological mechanism may involve changes in monoamine systems, in particular the serotonergic (5-hydroxytryptamine, 5-HT) system. It is well established that the 5-HT system is markedly affected in the Parkinsonian brain, with evidence including pathological loss of markers of 5-HT axons as well as cell bodies in the dorsal and median raphe nuclei of the midbrain. However, it remains unresolved whether alterations to the 5-HT system alone are sufficient to confer vulnerability to depression. Here we propose low 5-HT combined with altered network activity within the basal ganglia as critically involved in depression in PD. The latter hypothesis is derived from a number of recent findings that highlight the close interaction between the basal ganglia and the 5-HT system, not only in motor but also limbic functions. These findings include evidence that clinical depression is a side effect of deep brain stimulation (DBS) of the subthalamic nucleus (STN), a treatment option in advanced PD. Further, it has recently been demonstrated that STN DBS in animal models inhibits 5-HT neurotransmission, and that this change may underpin depressive-like side effects. This review provides an overview of 5-HT alterations in PD and a discussion of how these changes might combine with altered basal ganglia network activity to increase depression vulnerability.

Parkinson's disease: the quintessential neuropsychiatric disorder

Although diagnosed by characteristic motor features, Parkinson's disease may be preceded, and is frequently accompanied by, a wide range of cognitive and neuropsychiatric features. In addition to the most commonly studied disorders of dementia, depression, and psychosis, other relatively common and clinically significant psychiatric complications include impulse control disorders, anxiety symptoms, disorders of sleep and wakefulness, and apathy. These problems may be underrecognized and are frequently undertreated. The emergent focus on nonmotor aspects of Parkinson's disease over the past quarter of a century is highlighted by a nonlinear increase in the number of articles published devoted to this topic. Although the development of newer antidepressants, atypical antipsychotics, and cholinesterase inhibitors in recent years has had a positive benefit on the management of these troublesome and distressing symptoms, responses are frequently suboptimal, and this remains an area of major unmet therapeutic need.