Depression in Parkinson's disease: loss of dopamine and noradrenaline innervation in the limbic system

Morphometric changes of gray matter in Parkinson's disease with depression: a voxel-based morphometry study

The origin of the high rate of depression in idiopathic Parkinson's disease (PD) is unknown. We applied voxel-based morphometry (VBM), as a sensitive tool in detection of gray matter MR density alterations, to find differences in depressed and nondepressed PD patients. Patients with idiopathic PD were classified into depressed (DPD) and nondepressed (NDPD) groups based on the Montgomery-Asberg Depression Rating Scale (MADRS). Subsequently, a group comparisons were performed between depressed PD (n = 23), nondepressed PD (n = 27) and normal healthy controls (NC, n = 16). There was no difference in gray matter density comparing healthy controls to any PD groups. However, when NDPD and DPD cohorts were compared, density alteration of the bilateral orbitofrontal, bilateral rectal gyrus, and also the right superior temporal pole was detected in the depressed subgroup. Exploratory analyses revealed an inverse correlation of MADRS scores and severity of VBM alteration in these regions beside the right medial temporal gyrus, anterior and medial cingular gyrus, and parahippocampal gyrus. These results suggest that depression in PD is related to gray matter decrease in the bilateral orbitofrontal and right temporal regions as well as the limbic system.

Circuit-based framework for understanding neurotransmitter and risk gene interactions in schizophrenia

Many risk genes interact synergistically to produce schizophrenia and many neurotransmitter interactions have been implicated. We have developed a circuit-based framework for understanding gene and neurotransmitter interactions. NMDAR hypofunction has been implicated in schizophrenia because NMDAR antagonists reproduce symptoms of the disease. One action of antagonists is to reduce the excitation of fast-spiking interneurons, resulting in disinhibition of pyramidal cells. Overactive pyramidal cells, notably those in the hippocampus, can drive a hyperdopaminergic state that produces psychosis. Additional aspects of interneuron function can be understood in this framework, as follows. (i) In animal models, NMDAR antagonists reduce parvalbumin and GAD67, as found in schizophrenia. These changes produce further disinhibition and can be viewed as the aberrant response of a homeostatic system having a faulty activity sensor (the NMDAR). (ii) Disinhibition decreases the power of gamma oscillation and might thereby produce negative and cognitive symptoms. (iii) Nicotine enhances the output of interneurons, and might thereby contribute to its therapeutic effect in schizophrenia.

The assessment of depression in Parkinson's disease

BACKGROUND

Motor symptoms form the hallmark of Parkinson's Disease (PD), although features like depression are often present. Depression rating scales [e.g. Montgomery-Asberg Depression Rating Scale (MADRS)] used in PD measure affective, cognitive and somatic symptoms. An important clinical question is which items of the MADRS are likely to be influenced by PD symptoms.

METHODS

Depression was assessed in 43 PD patients who scored below the cut-off of the MADRS and who differed widely in motor severity.

RESULTS

Parkinson's Disease patients scored relatively highest on Concentration difficulties, Reduced sleep and Inner tension. Reduced sleep, Lassitude and Suicidal thoughts were associated with motor severity and specifically with Bradykinesia, Rigidity and Axial impairment, however not with Tremor. To avoid a possible influence on our results of coincidentally included PD patients with a depression, all associations between somatic MADRS items and motor severity were corrected for the influence of affective symptoms of depression. All associations remained significant.

DISCUSSION

In conclusion, the items Reduced sleep and Lassitude of the MADRS are likely to be influenced by motor symptoms. The high score on Concentration difficulties is suggested to be a reflection of cognitive dysfunction in PD. Thus, when assessing depression in PD, using a depression rating scale like the MADRS, adjusted cut-off scores are required.

Are locus coeruleus neurons involved in blinking?

To investigate the involvement of the noradrenergic locus coeruleus (LC) in the reflex blink circuit, c-Fos and neuronal tracer experiments were performed in the rat. LC neurons involved in reflex blink were localized by analyzing c-Fos protein expression after electrical stimulation of the supraorbital nerve. Subsequently, neuronal tracers were injected in two different nuclei which are part of the reflex blink circuit. Anterograde tracer experiments in the sensory trigeminal complex (STC) explored the trigemino-coerulear connection; retrograde tracer experiments in the latero-caudal portion of the superior colliculus (SC) established coerulear-collicular connections. The combination of retrograde tracer injections into the latero-caudal SC portion combined with electrical stimulation of the supraorbital nerve identified c-Fos positive LC neurons that project to the latero-caudal SC. Our results revealed the existence of a STC-LC-SC loop.

Management of non-motor symptoms in advanced Parkinson disease

Progress in pharmacology has markedly improved the treatment of early Parkinson's disease. The management of advanced Parkinson's symptoms, however, remains a challenge. These symptoms are divided into motor and non-motor symptoms. Non-motor symptoms may appear early or late in the disease and sometimes even before the onset of the first motor symptoms confirming the diagnosis. The spectrum of non-motor symptoms encompasses autonomic dysfunctions, sleep disorders, mood disorders, impulse control disorders, cognitive dysfunction, dementia, paranoia and hallucinations. They are often less appreciated than motor symptoms but are important sources of disability for many PD patients. This review describes these non-motor symptoms and their managements.

Variability in the clinical expression of Parkinson's disease

Parkinsonism is a clinical syndrome characterized by bradykinesia, hypo-/akinesia, muscular rigidity, and resting tremor, mainly caused by Parkinson's disease (PD). Symptoms of PD are due to a progressive loss of nigral neurons causing striatal dopaminergic denervation. However, nigral degeneration is only a part of the underlying synucleinopathy, and clinical symptoms go far beyond motor parkinsonism. Olfactory disturbances, fatigue, pain, autonomic dysfunction, sleep fragmentation, depression, and dementia with or without psychosis are frequently seen. The variability in the expression of these signs and symptoms, as discussed in this paper, might be explained by the specific topographical sequence of the pathology, depending on the extent and progression of the degenerative process at defined sites. Better insight in the clinicopathological correlations of this disease may help to further develop early diagnosis and adequate therapeutic strategies.

Dopamine receptor gene expression in human amygdaloid nuclei: elevated D4 receptor mRNA in major depression

Previous findings from this laboratory demonstrating changes in dopamine (DA) transporter and D2 receptors in the amygdaloid complex of subjects with major depression indicate that disruption of dopamine neurotransmission to the amygdala may contribute to behavioral symptoms associated with depression. Quantitative real-time RT-PCR was used to investigate the regional distribution of gene expression of DA receptors in the human amygdala. In addition, relative levels of mRNA of DA receptors in the basal amygdaloid nucleus were measured postmortem in subjects with major depression and normal control subjects. All five subtypes of DA receptor mRNA were detected in all amygdaloid subnuclei, although D1, D2, and D4 receptor mRNAs were more abundant than D3 and D5 mRNAs by an order of magnitude. The highest level of D1 mRNA was found in the central nucleus, whereas D2 mRNA was the most abundant in the basal nucleus. Levels of D4 mRNA were highest in the basal and central nuclei. In the basal nucleus, amounts of D4, but not D1 or D2, mRNAs were significantly higher in subjects with major depression as compared to control subjects. These findings demonstrate that the D1, D2 and D4 receptors are the major subtypes of DA receptors in the human amygdala. Elevated DA receptor gene expression in depressive subjects further implicates altered dopaminergic transmission in the amygdala in depression.

Idiopathic rapid-eye-movement sleep disorder: associations with antidepressants, psychiatric diagnoses, and other factors, in relation to age of onset

BACKGROUND

A retrospective, case-control chart review was performed to examine the relationship between the age of onset of idiopathic RBD and secondary associations.

METHODS

Forty-eight idiopathic RBD patients were divided into early-onset and late-onset groups, compared to each other, and to their respective non-RBD controls.

RESULTS

There were more females in the early-onset group as compared to their older counterparts (45% vs. 11%, p=0.007). Early-onset patients also had significantly more past and present psychiatric diagnoses [85% (both categories) vs. 46% and 36%, respectively, p<0.01 for both comparisons] and antidepressant use (80% vs. 46%, p=0.02) than the late-onset group. In comparison to non-RBD controls, early-onset patients again exhibited more psychiatric diagnoses (odds ratio=17.0 [3.5-83.4], equivalent for past and present diagnoses) and antidepressant use (odds ratio=12.0 [2.7-53.3]). Late-onset patients also had a higher frequency of past (odds ratio=7.2 [1.8-29.6]) and present (odds ratio=4.6 [1.1-19.3]) psychiatric diagnoses as compared to their non-RBD controls, but did not demonstrate a statistically significant difference in antidepressant use. There were otherwise no significant intergroup or intragroup differences with respect to the other assessed variables.

CONCLUSIONS

Although causality cannot be inferred, numerous implications can be entertained, particularly in the early-onset group, including direct or indirect correlations with medication use and/or psychopathology and the development of RBD. The relatively high number of females in the early-onset group suggests a unique clinical profile for a condition typically characterized as male-predominant.

NEUROPSYCHOLOGICAL EFFECTS AFTER CHRONIC SUBTHALAMIC STIMULATION AND THE TOPOGRAPHY OF THE NUCLEUS IN PARKINSON'S DISEASE

OBJECTIVE

The neuropsychological effects of chronic subthalamic nucleus (STN)-deep brain stimulation (DBS) as a treatment for Parkinson's disease are variable. Whether these side effects result from the target per se or current diffusion into neighboring structures is uncertain. In this study, the relationship between clinical outcomes and coordinates of active contact are analyzed and compared between patients with and without neuropsychological sequelae.

METHODS

Thirty-eight Parkinsonian patients who underwent bilateral STN-DBS were enrolled in this retrospective cohort study. They were followed for at least 12 months. During the follow-up period, they were divided into two groups for comparison; Group A included patients with neuropsychological side effects and Group B was composed of patients without neuropsychological side effects. The position of the active contact of the electrode was defined with postoperative magnetic resonance imaging scans according to the midcommissural line. Active contact coordinates and clinical outcomes were compared for the two groups.

RESULTS

Among the 38 Parkinsonian patients who underwent STN-DBS, eight patients who had neuropsychological side effects were assigned to Group A; the other 30 patients were assigned to Group B. In Groups A and B, the mean follow-up periods were 13.9 and 12.1 months, respectively, the Unified Parkinson's Disease Rating Scale motor score was improved by 53.4 and 45.2% (P = 0.24), respectively, and the levodopa equivalent daily dosage was decreased by 68.4 and 46.4% (P = 0.16), respectively. The mean coordinates of active contact in both Groups A and B were x = 10.1 and 10.5 mm, respectively, y = −2.8 and −3.9 mm, respectively, and z = −6.3 and −6.2 mm, respectively, relative to the midcommissural point. A significant difference was observed on the y axis (P = 0.01).

CONCLUSION

When taking spatial influence into consideration, the neuropsychological effects of chronic STN-DBS were related to a significant anteriorly located active contact within the ventral STN in this preliminary study. This might suggest the existence of topography of STN in patients with Parkinson's disease concerning limbic and associative circuits.

[Non-motor fluctuations in Parkinson's disease]

Nonmotor fluctuations (NMF) in Parkinson's disease are nonmotor symptoms that occur in coincidence with motor fluctuations or independently. Long under-assessed, NMF are now recognized as frequent and sometimes involving a greater degree of disability than motor fluctuations. They can be classified in three categories: dysautonomic, cognitive/psychiatric and sensory/pain. Recognition of these nonmotor fluctuations as part of Parkinson's disease has important implications. Some symptoms such as dyspnea, chest pain, or abdominal pains can mimic cardiac or gastrointestinal emergencies. The underlying pathogenic mechanisms of NMF are not well known. The dopaminergic system is probably involved via modulation of other systems (serotoninergic, adrenergic) since NMF usually respond to dopaminergic treatment. Subthalamic nucleus deep brain stimulation alleviates NMF-- particularly sensory, dysautonomic and cognitive fluctuations--while psychic fluctuations respond less consistently to this treatment. The development of new instruments that enable a comprehensive and precocious assessment of NMF is important for optimized management of advanced Parkinson's disease.

The premotor phase of Parkinson's disease

There is growing evidence that a variety of symptoms can precede the classical motor features of Parkinson's disease (PD). The period when these symptoms arise can be referred to as the premotor phase of the disease. Well-documented premotor symptoms in PD include constipation, loss of smell, sleep disturbances such as REM sleep behavior disorder (RBD), and mood disturbances like depression. Diagnostic and therapeutic implications linked to improved identification of these premotor features are discussed.

Thalamo-cortical dysfunction in cocaine abusers: implications in attention and perception

Cocaine affects sensory perception and attention, but little is known about the neural substrates underlying these effects in the human brain. We used functional magnetic resonance imaging (fMRI) and a sustained visuospatial attention task to assess if the visual attention network is dysfunctional in cocaine abusers (n=14) compared to age-, gender-, and education-matched controls (n=14). Compared with controls, cocaine abusers showed (1) hypo-activation of the thalamus, which may reflect noradrenergic and/or dopaminergic deficits; (2) hyper-activation in occipital and prefrontal cortices, which may reflect increased visual cortical processing to compensate for inefficient visual thalamic processing; and (3) larger deactivation of parietal and frontal regions possibly to support the larger hemodynamic supply to the hyper-activated brain regions. These findings provide evidence of abnormalities in thalamo-cortical responses in cocaine abusers that are likely to contribute to the impairments in sensory processing and in attention. The development of therapies that diminish these thalamo-cortical deficits could improve the treatment of cocaine addiction.

Lesions of dopaminergic neurons in the substantia nigra pars compacta and in the ventral tegmental area enhance depressive-like behavior in rats

Depression is the most common psychiatric complication in Parkinson's disease (PD). The pathophysiological events leading to PD-associated depression, however, remain largely unknown. The present study tested the differential implication of dopaminergic systems in depressive-like behavior in rats and its response to l-Dopa and the selective serotonin reuptake inhibitor citalopram. The learned helplessness model was used as a behavioral paradigm. Rats were lesioned in the substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) and assigned to subgroups with respect to the stereologically verified extent of the nigral and/or VTA degeneration. Both lesions increased depressive-like behavior in rats, which was reduced by both citalopram and l-Dopa treatment. We conclude that dopaminergic lesions of either the SNc or the VTA contribute to the manifestation of depressive-like behavior in rats. The effects of citalopram administration on depressive behavior induced by lesions of dopaminergic brain regions furthermore suggest an involvement of serotonergic pathways in dopaminergic cell loss-induced depression.

Meta-analysis of COMT val158met in panic disorder: ethnic heterogeneity and gender specificity

There is strong evidence for a genetic contribution to the pathogenesis of panic disorder, with the functional catechol-O-methyltransferase (COMT) val158met polymorphism having been suggested as a potential susceptibility factor. In the present study, a meta-analysis of six available case-control studies (557 patients with panic disorder and 763 healthy controls in total) on the role of the COMT val158met polymorphism in panic disorder was conducted in an attempt to reconcile previous conflicting results and to facilitate evaluation of the role of COMT gene variation in panic disorder. Overall, no significant association, but strong between-study heterogeneity, was discerned. Analysis of studies pooled by ancestry yielded a significant association of the COMT 158val allele with panic disorder in Caucasian samples and, conversely, a trend towards association of the COMT 158met allele with the disorder in Asian samples. Interestingly, stratification for gender as well as ethnicity revealed that association of the 158val allele in Caucasians and, reciprocally, the 158met allele in Asian samples was restricted to females. The present meta-analysis provides tentative support for the COMT val158met polymorphism as a possible risk factor for panic disorder, with differential effects in Caucasian and Asian populations, and suggests a female-specific effect. However, given the relatively small number of case-control studies presently available, several more association studies, preferably including a larger number of family-based studies, are warranted for conclusive evaluation of the COMT val158met polymorphism as a vulnerability factor in panic disorder.

Dopaminergic action beyond its effects on motor function: imaging studies

Along with motor programming, it is now thought that tonic release of dopamine in the striatum acts to focus and filter non-motor activities such as working memory, implicit learning, decision making, and planning. Additionally, thresholds to painful stimuli may well be dopamine dependant. Phasic (burst) release of dopamine in the basal ganglia and frontal areas is thought to play a role in alerting organisms to novel and potentially rewarding stimuli and in mediating contextual learning. Dopamine release also drives a craving for stimuli and facilitates their enjoyment. Functional imaging can help elucidate the role of dopamine in mediating non-motor activities. The integrity of dopamine terminal function can be measured with PET and SPECT in vivo in health and Parkinson's disease (PD) and this can be correlated with performance of executive tasks. In addition, these imaging modalities allow dopamine release in response to stimuli (both rewarding and unrewarding) to be detected, as reflected by changes in D2 receptor availability to radioligands. Finally, the functional effects of dopamine deficiency and its replacement can be monitored by studying patterns of brain activation, as evidenced by regional blood flow changes. In this review, some of the insights that imaging has given us concerning the role of dopamine in non-motor functions is presented.

Intervening in the neuropsychiatric features of Parkinson's disease

Although Parkinson's disease is considered a movement disorder, it has a wide range and high prevalence of affective, psychotic, cognitive, behavioral and sleep-related features. To treat such features, agents including antidepressants, anxiolytics, antipsychotics and cognition-enhancing agents are commonly prescribed, although the targeted syndromes are often incompletely understood and controlled studies demonstrating a treatment's efficacy and tolerability in Parkinson's disease patients are often lacking. Nevertheless, the available information does suggest the outlines of management methods, pending expanded research to identify optimal strategies specific to Parkinson's disease.

Management of the behavioral aspects of Parkinson's disease

Parkinson's disease is a progressive and debilitating movement disorder that is diagnosed by its motor signs. The behavioral manifestations of Parkinson's disease are prevalent and frequently complicate the course of the disease. These may be due to the illness itself or its treatment and are often more disabling than the motor symptoms. This review focuses on the management of the most common behavioral symptoms of Parkinson's disease, including depression, anxiety, psychosis, dementia, delirium, sleep disorders, fatigue, apathy, emotionalism and compulsive behaviors.

Imaging the norepinephrine transporter in humans with (S,S)-[11C]O-methyl reboxetine and PET: problems and progress

Results from human studies with the PET radiotracer (S,S)-[(11)C]O-methyl reboxetine ([(11)C](S,S)-MRB), a ligand targeting the norepinephrine transporter (NET), are reported. Quantification methods were determined from test/retest studies, and sensitivity to pharmacological blockade was tested with different doses of atomoxetine (ATX), a drug that binds to the NET with high affinity (K(i)=2-5 nM).

METHODS

Twenty-four male subjects were divided into different groups for serial 90-min PET studies with [(11)C](S,S)-MRB to assess reproducibility and the effect of blocking with different doses of ATX (25, 50 and 100 mg, po). Region-of-interest uptake data and arterial plasma input were analyzed for the distribution volume (DV). Images were normalized to a template, and average parametric images for each group were formed.

RESULTS

[(11)C](S,S)-MRB uptake was highest in the thalamus (THL) and the midbrain (MBR) [containing the locus coeruleus (LC)] and lowest for the caudate nucleus (CDT). The CDT, a region with low NET, showed the smallest change on ATX treatment and was used as a reference region for the DV ratio (DVR). The baseline average DVR was 1.48 for both the THL and MBR with lower values for other regions [cerebellum (CB), 1.09; cingulate gyrus (CNG) 1.07]. However, more accurate information about relative densities came from the blocking studies. MBR exhibited greater blocking than THL, indicating a transporter density approximately 40% greater than THL. No relationship was found between DVR change and plasma ATX level. Although the higher dose tended to induce a greater decrease than the lower dose for MBR (average decrease for 25 mg=24+/-7%; 100 mg=31+/-11%), these differences were not significant. The different blocking between MBR (average decrease=28+/-10%) and THL (average decrease=17+/-10%) given the same baseline DVR indicates that the CDT is not a good measure for non-NET binding in both regions. Threshold analysis of the difference between the average baseline DV image and the average blocked image showed the expected NET distribution with the MBR (LC) and hypothalamus>THL>CNG and CB, as well as a significant change in the supplementary motor area. DVR reproducibility for the different brain regions was approximately 10%, but intersubject variability was large.

CONCLUSIONS

The highest density of NETs was found in the MBR where the LC is located, followed by THL, whereas the lowest density was found in basal ganglia (lowest in CDT), consistent with the regional localization of NETs in the nonhuman primate brain. While all three doses of ATX were found to block most regions, no significant differences between doses were found for any region, although the average percent change across subjects of the MBR did correlate with ATX dose. The lack of a dose effect could reflect a low signal-to-noise ratio coupled with the possibility that a sufficient number of transporters were blocked at the lowest dose and further differences could not be detected. However, since the lowest (25 mg) dose is less than the therapeutic doses used in children for the treatment of attention-deficit/hyperactivity disorder ( approximately 1.0 mg/kg/day), this would suggest that there may be additional targets for ATX's therapeutic actions.

Striatal dopaminergic activity (FDOPA-PET) associated with cognitive items of a depression scale (MADRS) in Parkinson's disease

Motor symptoms form the hallmark of Parkinson's disease (PD), although other features such as depression are often present. Currently-used depression rating scales measure affective and somatic symptoms. These somatic symptoms of depression can also be core PD symptoms, suggesting an overlap of symptoms between depression and PD. Using in vivo radiotracer methods, striatal dopaminergic dysfunction is found in both PD and depression. This study investigates to what extent the overlapping symptoms of depression and PD are associated with the striatal dopaminergic dysfunction typical of PD. Symptoms of depression were assessed in 23 PD patients who did not have major depression according to the Montgomery-Asberg depression rating scale (MADRS; cut-off < 18) and according to a trained psychologist who interviewed all patients. The striatal dopaminergic activity of patients was assessed with FDOPA-PET. Dopaminergic activity of the putamen and caudate nucleus was associated with MADRS total score and specifically with the symptom 'Concentration difficulties'. These results suggest that the typical striatal dopaminergic dysfunction of PD can cause symptoms that can also be categorized as symptoms of depression. In particular, cognitive symptoms measured with a depression rating scale may be based on the dopaminergic dysfunction of the striatum in PD patients.

Cortical cholinergic denervation is associated with depressive symptoms in Parkinson's disease and parkinsonian dementia

AIM

To investigate the relationship between ratings of depressive symptoms and in vivo cortical acetylcholinesterase (AChE) activity in subjects with Parkinson's disease (PD) and parkinsonian dementia (PDem).

METHODS

Subjects (with PD, n = 18, including subjects with PDem, n = 6, and normal controls, n = 10) underwent [11C]methyl-4-piperidinyl propionate AChE positron emission tomography imaging and clinical assessment including the Cornell Scale for Depression in Dementia (CSDD).

RESULTS

Subjects with PD and PDem had higher scores on the CSDD compared with normal controls: 7.3 (5.4) and 2.8 (2.6), respectively (F = 6.9, p = 0.01). Pooled analysis demonstrated a significant inverse correlation between cortical AChE activity and CSDD scores: R = -0.5, p = 0.007. This correlation remained significant after controlling for Mini-Mental State Examination scores.

CONCLUSION

Depressive symptomatology is associated with cortical cholinergic denervation in PD that tends to be more prominent when dementia is present.

Imaging Non-Dopaminergic Function in Parkinson’s Disease

In Parkinson's disease (PD), there is degeneration of the cholinergic, noradrenergic, and serotonergic systems in addition to dopaminergic projections. Function of these non-dopaminergic systems can be imaged with positron emission tomography (PET) and single photon emission computed tomography (SPECT) and correlated with motor and nonmotor symptomatology. In addition, neuronal loss in PD is associated with microglial activation. The role of microglia in driving the disease process remains uncertain. This review presents and discusses current findings in these areas.

Aging of the rat mesostriatal system: Differences between the nigrostriatal and the mesolimbic compartments

The impairment of the mesostriatal dopaminergic system has been considered responsible for motor and affective disturbances associated with aging and a risk factor for Parkinson's disease. However, the basic mechanisms underlying this phenomenon are still unknown. Here we used biochemical, molecular and morphological techniques directed at detecting flaws in the dopamine synthesis route and signs of dopaminergic degeneration in the rat mesostriatal system during normal aging. We found two different age-related processes. One is characterized by a dopa decarboxylase decrease, and involves both the nigrostriatal and mesolimbic compartments, and is responsible for a moderate dopamine loss in the dorsal striatum, where other parameters of dopamine synthesis are not affected. The other is characterized by axonal degeneration with aggregation of phosphorylated forms of tyrosine hydroxylase (TH) and amyloid precursor protein in degenerate terminals, and alpha-synuclein in their original somata. This process is restricted to mesolimbic regions and is responsible for the decline of TH activity and l-dopa levels and the greater decrease in dopamine levels in this compartment. These findings suggest that both the nigrostriatal and the mesolimbic systems are vulnerable to aging, but in contrast to what occurs in Parkinson's disease, the mesolimbic system is more vulnerable to aging than the nigrostriatal one.

Dopaminergic function in depressed patients with affective flattening or with impulsivity: [18F]fluoro-L-dopa positron emission tomography study with voxel-based analysis

A decreased striatal presynaptic dopaminergic function has been reported in depressed patients with affective flattening and psychomotor retardation, using (18)F-fluorodopa positron emission tomography and regions-of-interest. The present study aimed to investigate regional ;[(18)F]dopa uptake in mesolimbic and mesocortical dopaminergic projections with the hypothesis that there should be a decrease in mesolimbic [(18)F]dopa uptake associated with affective flattening and psychomotor retardation. [(18)F]Dopa-positron emission tomography and anatomical magnetic resonance imaging datasets from 12 screened depressed patients with either marked affective flattening and psychomotor retardation (n=6) or with marked impulsivity (n=6), and from eight healthy subjects, were analyzed using a voxel-based approach. Regional differences in [(18)F]dopa uptake rate constant (K(i)) values between the healthy group and the two depression subgroups were compared using both statistical parametric mapping and cluster-based regions-of-interest. Patients with affective flattening and psychomotor retardation had [(18)F]dopa K(i) decreases in the left caudate, bilateral putamen and nucleus accumbens, left parahippocampus and dorsal brainstem. Impulsive depressives had [(18)F]dopa K(i) decreases in the anterior cingulate and hypothalamus, and an increase in the right parahippocampal gyrus. These findings support distinct regional dysfunctions of monoamines depending on the depressive symptomatology.

Does dopamine dysfunction drive depression?

OBJECTIVE

To examine the evidence that dopamine (DA) dysfunction contributes to melancholic depression.

METHOD

Database (EMBASE, PsychLit and MEDLINE) searches using relevant key words were conducted and citations were scrutinized.

RESULTS

In this paper, we assume that the definition of melancholia is contingent upon the presence of psychomotor disturbance (PMD). In melancholic depression PMD comprises both a cognitive and motor component and DA is found to be important in both. DA neurotransmission modulates cognition in particular in attention, adaptation and motivational processes and has a pivotal role in motor function.

CONCLUSION

DA is a credible aetiological candidate for the PMD in melancholic depression. However, melancholia needs first to be characterized both clinically and in terms of its pathophysiology. In this regard, illnesses such as bipolar depression and Parkinson's disease warrant consideration as they provide suitable models of both the cognitive and motor aspects of PMD, and hold the necessary markers to better define melancholia.

Prodromal non-motor symptoms of Parkinson's disease

The motor symptoms of Parkinson's disease (PD), bradykinesia, muscular rigidity, and tremor depend upon degeneration of the dopaminergic neurons in the substantia nigra pars compacta. Recent neuropathological studies show that the Lewy bodies, the intraneuronal landmark of PD, accumulate in several neuronal cell types in the brain. An ascending gradient of pathological involvement, from the medulla oblongata to neocortical areas has been reported. Thus the original view of PD as a disease characterized by selective damage of the dopaminergic neurons in the mesencephalon should be updated into the concept of a severe multisystemic neurodegenerative disorder. Additionally, the neuropathological alterations outside the substantia nigra are soundly correlated with the non-motor symptoms of PD. As a result of these findings, interest is growing in the identification of prodromal non-motor symptoms of PD. Indeed, data from the literature suggest that autonomic disturbances, olfactory dysfunctions, depression and sleep disorders (in particular REM-sleep behavior disorder) may represent prodromal non-motor symptoms of PD. Several tests are available to detect most of these symptoms. Thus, the identification of prodromal non-motor symptoms may contribute to the precocious diagnosis of PD, and might be useful in the future to test the efficacy of neuroprotective agents.

Antidepressant use in treatment of psychosis with comorbid depression in Parkinson's disease

The authors report an improvement in delusions and hallucinations after antidepressant treatment (Clomipramine) in a parkinsonian patient with psychosis and comorbid depression. Their findings, which support a previous case treated with Citalopram, highlight the possible effectiveness of antidepressant therapy on psychotic symptoms in parkinsonian patients.

Depression symptoms in movement disorders: Comparing Parkinson's disease, dystonia, and essential tremor

Depression is common in Parkinson's disease (PD) and affects 30 to 50% of all patients. In contrast to the wealth of research on depression in PD, little is known about the occurrence of depression in other movement disorders. The primary objective of the current study was to determine whether the high prevalence of depression symptoms seen in PD is also found in other movement disorders, by directly comparing rates of specific depression symptoms and depression severity across PD, dystonia, and essential tremor (ET). Three hundred and fifty-four patients with PD, 83 patients with dystonia, and 53 patients with ET completed the Beck Depression Inventory (BDI). We found no significant between-groups differences for depression severity, frequency, or endorsement of specific depression symptoms. Forty-eight percent of PD patients, 37.3% of dystonia patients, and 34% of ET patients were found to be at least mildly depressed (BDI score of 10 or higher). The most commonly endorsed symptoms were fatigability, difficulty with work, anhedonia, and sleep disturbance. Clinicians should be aware that depression is a frequent problem in dystonia and ET, in addition to PD, and inquire about depression symptoms in these patients so that they can be appropriately treated.

Acute effects of immediate and controlled-release levodopa on mood in Parkinson's disease: A double-blind study

Mood fluctuations related to levodopa (LD) dosing are well-known psychiatric complications of Parkinson's disease (PD). No formal studies explored how affective response to LD relates to the type of motor response to oral LD (stable or wearing-off) and to different pharmacokinetic profiles of oral LD. We used an intrasubject randomized double-blind crossover design to study 14 patients (7 stable, 7 wearing-off) who were monitored for motor status, mood, anxiety, and plasma LD levels 1 hour before and 6 hours after an oral dose of immediate-release (IR) and controlled-release LD formulations. Analysis of the dose-response curves showed a significant interaction between the type of motor response and the type of LD. Only the wearing-off patients had a significant mood elevation, and this effect was only significant following challenge with IR LD. Motor status strongly correlated with LD plasma levels and anxiety but not with mood ratings. Mood changes in PD patients are related to the patient's type of motor response to oral LD and also to the kinetic profile of the LD formulation used for dopaminergic replacement.

Depressivität und Depression bei der Parkinson-Erkrankung

Zusammenfassung: Ein erheblicher Anteil an Patienten mit einer idiopathischen Parkinson-Erkrankung (PD) entwickelt im Verlauf eine sekundäre Depression. Die Prävalenzraten schwanken erheblich, da die Diagnosestellung aufgrund von Symptomüberschneidungen zwischen neurologischer Grunderkrankung und Major Depression (MD) erschwert ist. Dies führt zu Problemen bei der therapeutischen Indikationsstellung sowie zu einer eingeschränkten Interpretierbarkeit neuropsychologischer und neurophysiologischer Studien. Ein weiterer Aspekt bezieht sich auf Gemeinsamkeiten und Unterschiede zwischen sekundärer und primärer Depression. Entgegen dem klinischen Eindruck einer PD-spezifischen Depression erbrachten psychometrische Verfahren zur Depressionsdiagnostik diesbezüglich bisher nur unbefriedigende Ergebnisse. Ziele dieses Überblicksartikels: 1. Charakterisierung depressiver Syndrome bei der PD, 2. Überblick über den Forschungsstand zur Neuropathologie und Neuropsychologie, 3. Gegenüberstellung klinisch- und/oder neuropsychologischer Gemeinsamkeiten/Unterschiede zwischen sekundärer und primärer MD und 4. Konsequenzen für Forschung und Differenzialdiagnostik.

Impaired recognition of facial expressions of anger in Parkinson's disease patients acutely withdrawn from dopamine replacement therapy

We have previously reported that acute dopaminergic blockade in healthy volunteers results in a transient disruption of the recognition of facial expressions of anger, whilst leaving intact the recognition of other facial expressions (including fear and disgust) and facial identity processing. Parkinson's disease (PD) is characterised by cell loss in dopaminergic neuronal populations, and hence we predicted that PD would be associated with impaired anger recognition. We reasoned that treatment with dopamine replacement therapy (DRT) could mask any deficit present in PD, and therefore studied facial expression recognition in a group of PD patients transiently withdrawn from DRT. Seventeen PD patients were compared to 21 age- and IQ-matched controls on the Ekman 60 task, which required the forced-choice labelling of 10 exemplars of each of six facial expressions (anger, disgust, fear, sadness, happiness, surprise). In line with our predictions, PD patients showed a selective impairment in the recognition of facial expressions of anger. This deficit was not related to the PD patients' performance on the Benton unfamiliar-face matching task, which was normal, nor was the deficit related to overall disease severity, or to depression symptoms. However, as predicted by simulation theories, impaired anger recognition in PD was related to reduced levels of the anger-linked temperament trait, exploratory excitability. The results extend our previous findings of a role for dopamine in the processing of facial expressions of anger, and demonstrate the power of adopting a phylogenetic, comparative perspective on emotions.

Non-motor symptoms in Parkinson's disease: an underdiagnosed problem

Parkinson's disease results from degeneration of the substantia nigra pars compacta and the consequent dysfunction of the dopaminergic nigrostriatal pathway. Serotonergic and noradrenergic pathways are also affected. However, It has been recognized that nondopaminergic and non-motor symptoms are sometimes present prior to diagnosis and these inevitably emerge with disease progression, impacting on morbidity, quality of life and mortality. The non-motor symptoms of Parkinson's disease continue to be poorly recognized and inadequately treated in contrast with motor symptoms, and a modern holistic approach to treatment of Parkinson's disease should therefore include recognition and assessment of non-motor symptoms. Certain aspects of the non-motor symptoms complex of Parkinson's disease can be improved with currently available treatments, but other features may be more refractory and require research into effective nondopaminergic drug therapies for the future.

Apathy and the basal ganglia

We should like to emphasize the following points: 1. Apathy is defined here as a quantified and observable behavioral syndrome consisting in a quantitative reduction of voluntary (or goal-directed) behaviors; 2. Therefore, apathy occurs when the systems that generate and control voluntary actions are altered; 3. These systems are mostly represented by the different subregions embedded in the Prefrontal cortex (PFC) and in the basal ganglia regions that are closely connected with the PFC; 4. In consequence, clinically, apathy is a prefrontal syndrome either due to direct lesions of the PFC or to lesions of basal ganglia areas that are closely related to the PFC; 5. Apathy is not a single entity but rather heterogeneous. Several different mechanisms may lead to apathy; Because there are several anatomical-functional prefrontal-basal ganglia circuits, the underlying mechanisms responsible for apathy may differ according to which prefrontal-basal ganglia circuit is affected; 6. In this context, apathy is the macroscopic results of the disruption of one or several elementary steps necessary for goal-directed behavior that are subserved by different prefrontal-basal ganglia circuits; 7. Intense apathy is related to caudate nucleus and GPi, disrupting associative and limbic pathways from/to the PFC; 8. in progressive supranuclear palsy (PSP) and focal lesions (caudate nuclei, GPi), apathy may be due to a loss of PFC activation; 9. In Parkinson's disease (PD), apathy may be due to a loss of signal focalization; 10. More globally, we propose that apathy may be explained by the impact of lesions or dysfunctions of the BG, because these lesions or dysfunctions lead to a loss of amplification of the relevant signal and/or to a loss of temporal and spatial focalization, both of which result in a diminished extraction of the relevant signal within the frontal cortex, thereby inhibiting the capacity of the frontal cortex to select, initiate, maintain and shift programs of action.

Future prospects in depression research

Major depression is a common, disabling, and often difficult-to-treat illness. Decades of research into the neurobiology and treatment of depression have greatly advanced our ability to manage this disorder. However, a number of challenges remain. A substantial number of depressed patients do not achieve full remission despite optimized treatment. For patients who do achieve resolution of symptoms, depression remains a highly recurrent illness, and repeated episodes are common. Finally, little is known about how depression might be prevented, especially in individuals at increased risk. In the face of these challenges, a number of exciting research efforts are currently under way and promise to greatly expand our knowledge of the etiology, pathophysiology, and treatment of depression. This review highlights these future prospects for depression research with a specific focus on lines of investigation likely to generate novel, more effective treatment options.

Quality of life and depression in Parkinson's disease

This paper reviews the literature on health-related quality of life (Hr-QoL) and depressive disorders, and the relationship between them, in patients with Parkinson's disease (PD). PD is associated with reduced Hr-QoL, including motor and non-motor physical consequences of the disease, emotional well-being and social functioning. While this effect is greater in advanced disease stages, there is no close relationship between disease duration and impact on quality of life, and the relationship between clinical rating scales and Hr-QoL scores is only moderate. On the other hand, presence and severity of depression in PD strongly correlates with Hr-QoL scores, and a number of studies have reported depression as the main determinant of poor HR-QoL scores. Despite being the main determinant of poor Hr-QoL and being recognized as an important problem by clinicians, until recently depression in PD has received relatively little attention in research studies. It is known that depression and anxiety occur more frequently in PD than in controls. Depression occurs in a bimodal pattern in PD, with increased rates at the onset and a later peak in advanced disease. Both anxiety and depression can also occur before the first motor symptoms of PD and predate the diagnosis of PD, indicating that these co-morbidities are manifestations of the underlying disease process of PD. Imaging studies have demonstrated abnormalities of dopaminergic, noradrenergic and serotonergic functioning with some correlation with severity of depression. The overall relationship between disease severity and rate of depression (except for off-period related depression) is poor, suggesting that nigrostriatal dysfunction alone is not sufficient to explain depressive symptoms in PD. Other factors are likely to contribute to occurrence and severity of depression in PD, either due to extrastriatal pathology or due to psychological and environmental factors leading to reactive depression. Thus, it is likely that depression in PD is multifactorial. The investigation of depression in PD is complicated by diagnostic difficulties in measuring and diagnosing depression in patients with PD due to the considerable overlap between symptoms of PD and depression. While a number of treatment approaches have been suggested, double-blind randomized controlled trials to demonstrate improvement of depression and overall Hr-QoL in PD are warranted.

Treatment of depression in Parkinson's disease

Depression is one of the most common nonmotor features observed in Parkinson's disease (PD), affecting approximately 40% of patients. Depression in Parkinson's disease (dPD) significantly affects quality of life of both patients and their families and has been shown to be more predictive of distress than motor disability. Depression frequently goes unrecognized in this population, however, in part because the diagnosis is often complicated by the overlap of psychiatric and PD symptoms. The etiology of dPD is unclear; dopaminergic, serotonergic, and noradrenergic systems may be implicated. Options for managing dPD include antidepressant medication; cognitive-behavioral therapy; behavioral lifestyle interventions such as exercise; and, in refractory cases, noninvasive brain stimulation (electroconvulsive therapy, transcranial magnetic stimulation). Randomized controlled trials are needed to evaluate the efficacy of interventional approaches for dPD; several trials are currently underway.

Imaging in Parkinson's disease: the role of monoamines in behavior

Positron emission tomography (PET) and single photon emission computed tomography (SPECT) can measure striatal dopamine (DA) terminal function in vivo as reflected by DA storage capacity and transporter binding. In Parkinson's disease (PD) posterior dorsal putamen DA terminals are initially targeted, the anterior putamen and head of caudate subsequently becoming affected. In contrast, dopaminergic function in pallidal, amygdala, and cingulate regions is upregulated in early PD and only later becomes reduced. Rigidity and bradykinesia in PD have been shown to correlate with loss of putamen dopaminergic function, whereas performance on executive and working memory tasks correlates with integrity of caudate dopaminergic terminals. 11C-RTI32 PET, a marker of noradrenergic and dopaminergic transporter binding, can be used to assess noradrenergic along with dopaminergic terminal function. Serotonergic transporter binding can be assessed with 11C-DASB PET and 123I-beta CIT SPECT, whereas HT1A binding can be measured with 11C-WAY100635 PET. With these modalities, the relationship between mood, noradrenergic and serotonergic function can be examined in PD. The functional effects of focal DA replacement on DA storage capacity and patterns of brain activation via implantation of fetal midbrain cells or glial derived neurotrophic factor (GDNF) infusion into putamen of PD patients has been examined with PET. Both approaches lead to consistently increased levels of putamen 18F-dopa uptake, and cell implantation can restore levels of frontal activation. Clinical outcome, however, has proved to be variable and off-medication dyskinesias are an unwanted side effect in transplanted cases. Dopamine release after pharmacological challenges or during behavioral tasks can be assessed indirectly by studying changes in receptor availability to PET radioligands. Stereotyped sequential movements are associated with striatal DA release, and this increases with more complex behaviors and the presence of financial incentives, which also increase frontal DA levels. Parkinson patients release less putamen DA than healthy control subjects during stereotyped finger movements. Interestingly, those PD patients who develop a dopa dependency syndrome, craving their medication, generate significantly greater levels of ventral striatal DA compared with similarly disabled patients without such a psychological dependency. In the future, functional imaging is likely to throw light on the roles of peptide transmission in regulating mood and behavior as non-peptide analogue ligands become available. Novel markers of amyloid plaque load will also help clarify the etiology of dementia in PD.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Late-life depression: a neuropsychiatric approach

Late-life depression refers to depressive syndromes defined in the American Psychiatric Association's Diagnostic and Statistical Manual and in the International Classification of Diseases that arise in adults older than 65 years of age. Late life depressive syndromes often arise in the context of medical and neurologic disorders. There is a high prevalence of depression in various neurodegenerative disorders such as Alzheimer's disease, Lewy body disease, Parkinson's disease, cerebrovascular disease and frontotemporal dementias. It has been well recognized that late life depression may itself be the presenting symptom of a latent neurodegenerative disorder. Therefore, an accurate diagnosis of late-onset depression may serve to identify a high-risk group that would benefit from initiation of therapies with the goal of delaying or possibly even preventing the onset of dementia.

Imaging in cell-based therapy for neurodegenerative diseases

Fetal cell transplantation for the treatment of Parkinson's and Huntington's diseases has been developed over the past two decades and is now in early clinical testing phase. Direct assessment of the graft's survival, integration into the host brain and impact on neuronal functions requires advanced in vivo neuroimaging techniques. Owing to its high sensitivity, positron emission tomography is today the most widely used tool to evaluate the viability and function of the transplanted tissue in the brain. Nuclear magnetic resonance techniques are opening new possibilities for imaging neurochemical events in the brain. The ultimate goal will be to use the combination of multiple imaging modalities for complete functional monitoring of the repair processes in the central nervous system.

Non-motor symptoms of Parkinson's disease: diagnosis and management

The clinical diagnosis of Parkinson's disease rests on the identification of the characteristics related to dopamine deficiency that are a consequence of degeneration of the substantia nigra pars compacta. However, non-dopaminergic and non-motor symptoms are sometimes present before diagnosis and almost inevitably emerge with disease progression. Indeed, non-motor symptoms dominate the clinical picture of advanced Parkinson's disease and contribute to severe disability, impaired quality of life, and shortened life expectancy. By contrast with the dopaminergic symptoms of the disease, for which treatment is available, non-motor symptoms are often poorly recognised and inadequately treated. However, attention is now being focused on the recognition and quantitation of non-motor symptoms, which will form the basis of improved treatments. Some non-motor symptoms, including depression, constipation, pain, genitourinary problems, and sleep disorders, can be improved with available treatments. Other non-motor symptoms can be more refractory and need the introduction of novel non-dopaminergic drugs. Inevitably, the development of treatments that can slow or prevent the progression of Parkinson's disease and its multicentric neurodegeneration provides the best hope of curing non-motor symptoms.

Disgust-specific impairment of facial expression recognition in Parkinson's disease

There is contradictory evidence regarding whether the impairments of the recognition of emotional facial expressions in Parkinson's disease are specific to certain emotions such as disgust and fear. Generally, neurological case reports on emotion-specific impairments have been suspected of being confounded with the factor of task difficulty. Using a refined assessment method in which the difficulty factors were controlled by means of mixed facial expressions and item response theory, we attempted to clarify whether Parkinson's disease disproportionately impaired the recognition of specific emotions. We studied 14 patients with Parkinson's disease and 39 healthy controls who were matched in terms of gender, age, years of education and intelligence quotient. Whereas the refined method revealed that the patients with Parkinson's disease displayed significantly lower scores in disgust recognition alone, conventional methods failed to detect this impairment. In addition, control measures including face recognition abilities did not statistically explain the impairment observed in the patients. The results indicate that Parkinson's disease can indeed selectively impair the recognition of facial expressions of disgust; this provides concrete evidence for emotion-specific impairments that sufficiently withstands criticisms regarding the difficulty artefacts. Furthermore, the results support the proposed role of the basal ganglia-insula system in disgust recognition. This study effectively demonstrates the benefits of refining neuropsychological assessment by taking advantage of the modern psychometric theory.

Perception of emotional speech in Parkinson's Disease

Nonmotor symptoms in Parkinson's disease (PD) involving cognition and emotionality have progressively received attention. The objective of the present study was to investigate recognition of emotional prosody in patients with PD (n = 14) in comparison to healthy control subjects (HC, n = 14). Event-related brain potentials (ERP) were recorded in a modified oddball paradigm under passive listening and active target detection instructions. Results showed a poorer performance of PD patients in classifying emotional prosody. ERP generated by emotional deviants (happy/sad) during passive listening revealed diminished amplitudes of the mismatch-related negativity for sad deviants, indicating an impairment of early preattentive processing of emotional prosody in PD.

Parkinson's disease: premotor clinico-pathological correlations

Parkinsonism is a clinical syndrome characterized by bradykinesia, hypo-/ akinesia, muscular rigidity, and resting tremor, mainly caused by Parkinson's disease (PD). Progressive loss of nigral neurons with Lewy bodies is considered an essential neuropathological feature. Recent studies, however, indicate that nigral degeneration is only a part of this synucleinopathy, and clinical symptoms go far beyond motor parkinsonism. Olfactory disturbances, autonomic dysfunction, pain, sleep fragmentation, depression, and dementia with or without psychosis are frequently seen. The variability in the expression of these signs and symptoms suggests multiple causes and/or pathogeneses within the present diagnostic disease entity. In this article, a recently proposed staging of PD-related brain pathology will be correlated with the various clinical expressions. It will be argued that the specific topographical sequence of the pathology, depending on the extent and progression of the degenerative process at defined sites, may explain the individually variable expression of this disease.

Minor depression and brain perfusion images in Parkinson's disease

Depression is common in individuals with Parkinson's disease. However, the pathophysiology of depression in Parkinson's disease remains obscure. Here we compared brain perfusion images of Parkinson's disease patients with and without depression to investigate correlations between depression and brain perfusion images in Parkinson's disease. We divided 40 consecutive patients with Parkinson's disease into two groups: patients with minor depression (n = 22) and patients without depression (n = 18). We then compared brain perfusion images between the two groups. As a result, hypoperfusion of the left superior and inferior frontal gyrus was demonstrated in depressed patients. These results were partially in agreement with previous studies on de novo and parkinsonian major depression. We could not conclude on whether pathophysiological mechanisms differed between de novo depression and depression with Parkinson's disease, and between major and minor depressions.