Depression and Parkinson's disease: possible role of serotonergic mechanisms

Depression and Parkinson's disease: a Chicken-Egg story

Parkinson's disease (PD) is a neurodegenerative disease, however, besides the motor symptoms, such as rest tremor, hypokinesia, postural instability and rigidity, PD patients have also non-motor symptoms, namely neuropsychiatric disorders. Apart from the required motor symptoms, psychopathological symptoms are very common and include mood disorders, anxiety disorders, hallucinations, psychosis, cognitive deterioration and dementia. The underlying pathophysiological process in PD is mainly due to the loss of dopaminergic neural cells and thereby causes the shortage of nigrostriatal dopamine content in them. In addition, it may involve other neurotransmitter systems such as the noradrenergic, serotonergic, cholinergic and noradrenergic systems as well. Depression can result from any unhealthy conditions making the diagnosis a challenging task. The manifestation of depression associated with or without PD is inadequate. The co-occurrence of depression and PD often leads to the conceptual discussion on whether depressive symptoms appear before or after PD develops. This paper will discuss the conceptual mechanism of PD and depression. Keep in mind both conditions belong to two separate entities but share some similar aspects in their pathophysiology.

Low plasma serotonin linked to higher nigral iron in Parkinson's disease

A growing body of evidence suggests nigral iron accumulation plays an important role in the pathophysiology of Parkinson's disease (PD), contributing to dopaminergic neuron loss in the substantia nigra pars compacta (SNc). Converging evidence suggests this accumulation might be related to, or increased by, serotonergic dysfunction, a common, often early feature of the disease. We investigated whether lower plasma serotonin in PD is associated with higher nigral iron. We obtained plasma samples from 97 PD patients and 89 controls and MRI scans from a sub-cohort (62 PD, 70 controls). We measured serotonin concentrations using ultra-high performance liquid chromatography and regional iron content using MRI-based quantitative susceptibility mapping. PD patients had lower plasma serotonin (p < 0.0001) and higher nigral iron content (SNc: p < 0.001) overall. Exclusively in PD, lower plasma serotonin was correlated with higher nigral iron (SNc: r(58) =  - 0.501, p < 0.001). This correlation was significant even in patients newly diagnosed (< 1 year) and stronger in the SNc than any other region examined. This study reveals an early, linear association between low serotonin and higher nigral iron in PD patients, which is absent in controls. This is consistent with a serotonin-iron relationship in the disease process, warranting further studies to determine its cause and directionality.

Antidepressant-Like Properties of Intrastriatal Botulinum Neurotoxin-A Injection in a Unilateral 6-OHDA Rat Model of Parkinson's Disease

Parkinson’s patients often suffer from depression and anxiety, for which there are no optimal treatments. Hemiparkinsonian (hemi-PD) rats were used to test whether intrastriatal Botulinum neurotoxin-A (BoNT-A) application could also have antidepressant-like properties in addition to the known improvement of motor performance. To quantify depression- and anxiety-like behavior, the forced swim test, tail suspension test, open field test, and elevated plus maze test were applied to hemi-PD rats injected with BoNT-A or vehicle. Furthermore, we correlated the results in the forced swim test, open field test, and elevated plus maze test with the rotational behavior induced by apomorphine and amphetamine. Hemi-PD rats did not show significant anxiety-like behavior as compared with Sham 6-OHDA- + Sham BoNT-A-injected as well as with non-injected rats. However, hemi-PD rats demonstrated increased depression-like behaviors compared with Sham- or non-injected rats; this was seen by increased struggling frequency and increased immobility frequency. Hemi-PD rats intrastriatally injected with BoNT-A exhibited reduced depression-like behavior compared with the respective vehicle-receiving hemi-PD animals. The significant effects of intrastriatally applied BoNT-A seen in the forced swim test are reminiscent of those found after various antidepressant drug therapies. Our data correspond with the efficacy of BoNT-A treatment of glabellar frown lines in treating patients with major depression and suggest that also intrastriatal injected BoNT-A may have some antidepressant-like effect on hemi-PD.

[Relationship between striatal 123I-FP-CIT uptake and cognitive functions in Parkinson's disease]

We studied whether ¹²³I-FP-CIT uptake in the striatum correlates with cognitive performance in patients with Parkinson's disease (PD). Sixty-nine patients with PD (24 men and 45 women, average age = 71.3 years, disease duration = 5.2 years) underwent ¹²³I-FP-CIT SPECT and neuropsychiatric measurements. Cognitive performance was assessed using the MMSE (Mini-mental state examination), TMT (Trail making test), MoCA-J (Japanese version of Montreal cognitive assessment), FAB (Frontal assessment battery), ACE-R (Addenbrooke's cognitive examination revised), BDI-II (Beck depression inventory-II), and RBMT (Rivermead behavioural memory test) in the ON state. The average specific binding ratio (SBR) and AI (Asymmetry index) of striatal ¹²³I-FP-CIT uptake were semi-quantitatively measured using DaTView software. Clinical data and SBR were compared. In addition, participants were divided into four groups according to the visibility of the striatum on ¹²³I-FP-CIT SPECT images, and results of the Eagle Wing (EW) group and the Egg shape (ES) group were compared. SBR was negatively correlated with age (P < 0.001), disease duration (P < 0.001), H-Y stage (P < 0.001), levodopa equivalent dose (P = 0.004), TMT-A (P = 0.001), and TMT-B (P < 0.001), and positively correlated with MMSE (P = 0.021) and FAB (P = 0.029), MoCA-J (P = 0.012)，RBMT (P = 0.021). Multiple regression analysis confirmed that age (P = 0.016) and FAB (P = 0.035) were independent predictors for SBR. Furthermore, in the ES group, Movement Disorder Society - Unified Parkinson's disease rating scale part III scores were significantly higher (P = 0.013) and the AI was lower (P < 0.001) than those in the EW group. Conversely, there were no differences in the findings of neuropsychiatric measures between the two groups. Our study results demonstrate that imaging with ¹²³I-FP-CIT SPECT is sensitive for detecting dopaminergic deficits associated with frontal lobe functions in patients with PD.

Depression et Maladie de Parkinson: étude d’une série de 135 parkinsoniens

Objective:

La fréquence de la dépression au cours de la maladie de Parkinson (MP) conduit à s’interroger sur les difficultés du diagnostic et sur les liens entre la dépression et l’histoire naturelle de la maladie.

Méthodes:

Une série consécutive de 135 sujets atteints d’une MPidiopathique a été examinée sur le plan psychiatrique (DSM-III-R, échelle de dépression de Goldberg), neurologique (en distinguant les signes “axiaux” des autres signes parkinsoniens), neuropsychologique ( et en particulier tests frontaux).

Résultats:

Plus de la moitié des sujets ont une dépression qui apparaît plus fréquente dans les formes akinétiques et les formes fluctuantes de la maladie. Les sujets déprimés n’ont pas de déficit cognitif plus marqué mais leurs scores aux tests frontaux sont plus élevés. En outre les signes axiaux de la maladie (instabilité posturale, rigidité axiale) sont plus marqués chez les parkinsoniens déprimés, suggérant un lien entre la dépression et les lésions non dopaminergiques de la maladie. Alors que le ralentissement, les troubles de l’appétit et du sommeil, la fatigue peuvent être observés même chez des parkinsoniens non dépressifs, la séparation de la population parkinsonienne en plusieurs groupes montre que certains symptômes ne sont jamais rencontrés chez les parkinsoniens non dépressifs: il en est ainsi apparu que “l’impression que la vie ne vaut pas la peine d’être vécue”, “la perte d’espoir pour l’avenir”, “l’impression de ne pas être à la hauteur, de ne rien faire de bien”, “la baisse d’énergie”, “la tristesse matinale” caractérisent la dépression parkinsonienne. La dépression parkinsonienne revêt deux grandes formes cliniques. La première est la plus riche en manifestations somatiques: troubles du sommeil, fatigue matinale; elle correspond aux dépressions les plus sévères avec une absence d’espoir pour l’avenir , une perte de confiance en soi. La seconde est pauvre en manifestations somatiques alors que l’apathie y est très fréquente ainsi que le ralentissement.

Conclusions:

Cette étude permet ainsi de préciser les symptômes de la dépression parkinsonienne qui doit être mieux reconnue pour être plus souvent traitée. Les liens entre la dépression et les signes axiaux de la maladie expliquent sans doute pourquoi la L-dopa et les agonistes dopaminergiques améliorent les signes moteurs de la dépression sans agir le plus souvent sur les manifestations dépressives.

An Investigation on the Clinical Features and Neurochemical Changes in Parkinson's Disease With Depression

Objective: To investigate the clinical features and neurochemical changes in Parkinson's disease with depression (PD-D). Methods: A total of 478 PD patients were divided into PD-D and PD patients without depression (PD-ND) groups according to the 24-item Hamilton Depression Rating Scale (HAMD) score. Demographic variables, motor and non-motor symptoms and activities of daily living were evaluated. The independent influencing factors of PD-D were investigated via binary logistic regression analysis. The levels of neurotransmitters in cerebrospinal fluid (CSF) were measured and their correlations with HAMD score were analyzed. Results: The proportion of PD-D was 59.0%, of which 76.95, 20.92, and 2.13% had mild, moderate, and severe depression, respectively. Anxiety/somatization was the most prevalent sub-factor of HAMD in PD-D. The scores of UPDRS III, postural instability/gait difficulty (PIGD) type and the scores of 14-item Hamilton Anxiety Scale (HAMA) and 14-item Chalder Fatigue Scale (FS) were independently associated with PD-D. The levels of dopamine (DA) and 5-hydroxytryptamine (5-HT) were all significantly reduced in PD-D group compared with those in PD-ND group. HAMD scores were negatively correlated with the DA levels in CSF. Conclusions: PD patients have a high proportion of depression, mainly of mild and moderate levels. The profile of depression in PD population is subtly different from that of the general population. Motor symptoms, PIGD type, anxiety and fatigue are the significant influencing factors of PD-D. Compared to 5-HT, DA may play a more important role in PD-D.

Depression in Parkinson's Disease: The Contribution from Animal Studies

Besides being better known for causing motor impairments, Parkinson's disease (PD) can also cause many nonmotor symptoms, like depression and anxiety, which can cause significant loss of life quality and may not respond to regular drugs treatment. In this review, we discuss the depression in PD, based on data from studies in humans and rodents. Depression frequency seems higher in PD patients than in general population, despite high variation in data due to diagnosis disparities. Development of depression in PD seems more likely to be caused by the nigrostriatal pathway degeneration than as a consequence of the awareness of disease prognostic, and it seems to be related to dopaminergic, noradrenergic, and serotoninergic synapses deficits. The dopaminergic role could be more significant, since it can modulate the release of the others, and its depletion is progressive, due to the degenerative feature of PD. Highly regarded in major depression, serotonin can be depleted in rats after nigrostriatal damage, but data from human patients are more conflicting. Animal studies can help in understanding the neurobiological mechanisms of depression in PD and the pursuit for more effective drugs for its treatment, but they lack the complexity of the disease progression, especially the nondopaminergic degeneration.

Chronic MPTP administration regimen in monkeys: a model of dopaminergic and non-dopaminergic cell loss in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder clinically characterized by cardinal motor deficits including bradykinesia, tremor, rigidity and postural instability. Over the past decades, it has become clear that PD symptoms extend far beyond motor signs to include cognitive, autonomic and psychiatric impairments, most likely resulting from cortical and subcortical lesions of non-dopaminergic systems. In addition to nigrostriatal dopaminergic degeneration, pathological examination of PD brains, indeed, reveals widespread distribution of intracytoplasmic inclusions (Lewy bodies) and death of non-dopaminergic neurons in the brainstem and thalamus. For that past three decades, the MPTP-treated monkey has been recognized as the gold standard PD model because it displays some of the key behavioral and pathophysiological changes seen in PD patients. However, a common criticism raised by some authors about this model, and other neurotoxin-based models of PD, is the lack of neuronal loss beyond the nigrostriatal dopaminergic system. In this review, we argue that this assumption is largely incorrect and solely based on data from monkeys intoxicated with acute administration of MPTP. Work achieved in our laboratory and others strongly suggest that long-term chronic administration of MPTP leads to brain pathology beyond the dopaminergic system that displays close similarities to that seen in PD patients. This review critically examines these data and suggests that the chronically MPTP-treated nonhuman primate model may be suitable to study the pathophysiology and therapeutics of some non-motor features of PD.

Neuropeptide Y and Calcitonin Gene-Related Peptide in Cerebrospinal Fluid in Parkinson's Disease with Comorbid Depression versus Patients with Major Depressive Disorder

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. The diagnosis of PD is based on movement dysfunctions. Many patients also suffer from comorbid depression in spite of adequate treatment with dopamine replacement, indicating that also other non-dopaminergic mechanisms are involved. Indeed, neuropeptides are critically implicated in the pathophysiology of major depressive disorder (MDD). To increase our understanding of the biochemical basis of depression in PD patients, we examined the levels of neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) in cerebrospinal fluid (CSF) from PD patients, with or without comorbid depression, and compared them to the levels in patients with MDD. We also compared the levels of NPY and CGRP with 5-hydroxyindoleacetic acid (5-HIAA), the major serotonin metabolite. Both NPY and CGRP were higher in PD patients with comorbid depression compared to MDD patients. No similar difference was found in 5-HIAA levels. Accordingly, there were no correlations between NPY and 5-HIAA or CGRP and 5-HIAA levels. The finding of higher NPY and CGRP CSF levels in PD patients with MDD raises the possibility that different pathophysiological processes may underlie depression in PD and MDD.

Serotonergic dysfunctions and abnormal iron metabolism: Relevant to mental fatigue of Parkinson disease

Fatigue is a very common non-motor symptom in Parkinson disease (PD) patients. It included physical fatigue and mental fatigue. The potential mechanisms of mental fatigue involving serotonergic dysfunction and abnormal iron metabolism are still unknown. Therefore, we evaluated the fatigue symptoms, classified PD patients into fatigue group and non-fatigue group, and detected the levels of serotonin, iron and related proteins in CSF and serum. In CSF, 5-HT level is significantly decreased and the levels of iron and transferrin are dramatically increased in fatigue group. In fatigue group, mental fatigue score is negatively correlated with 5-HT level in CSF, and positively correlated with the scores of depression and excessive daytime sleepiness, and disease duration, also, mental fatigue is positively correlated with the levels of iron and transferrin in CSF. Transferrin level is negatively correlated with 5-HT level in CSF. In serum, the levels of 5-HT and transferrin are markedly decreased in fatigue group; mental fatigue score exhibits a negative correlation with 5-HT level. Thus serotonin dysfunction in both central and peripheral systems may be correlated with mental fatigue through abnormal iron metabolism. Depression, excessive daytime sleepiness and disease duration were the risk factors for mental fatigue of PD.

Migraine is related to an increased risk of Parkinson’s disease: A population-based, propensity score-matched, longitudinal follow-up study

Background

The association between migraine and Parkinson’s disease (PD) remains controversial. The purpose of the present population-based, propensity score-matched follow-up study was to investigate whether migraineurs are at a higher risk of developing PD.

Methods

A total of 41,019 subjects aged between 40 and 90 years with at least two ambulatory visits with a diagnosis of migraine in 2001 were enrolled in the migraine group. A logistic regression model that included age, sex, pre-existing comorbidities and socioeconomic status as covariates was used to compute the propensity score. The non-migraine group consisted of 41,019 propensity score-matched, randomly sampled subjects without migraine. The PD-free survival rate were estimated using the Kaplan–Meier method. Stratified Cox proportional hazard regression was used to estimate the effect of migraine on the risk of developing PD.

Results

During follow-up, 148 subjects in the migraine group and 101 in the non-migraine group developed PD. Compared to the non-migraine group, the hazard ratio of PD for the migraine group was 1.64 (95% confidence interval: 1.25–2.14, p = 0.0004). The PD-free survival rate for the migraine group was significantly lower than that for the non-migraine group ( p = 0.0041).

Conclusions

This study showed an increased risk of developing PD in patients with migraine.

The longitudinal impact of depression on disability in Parkinson disease

OBJECTIVE

Depression in Parkinson disease (PD) is a common problem that worsens quality of life and causes disability. However, little is known about the longitudinal impact of depression on disability in PD. This study examined the association between disability and DSM-IV-TR depression status across six years.

METHODS

Longitudinal cohort study with assessments at study entry, year two, four, and six conducted in the Morris K. Udall Parkinson Disease Research Center. Recruitment totaled 137 adult men and women with idiopathic PD in which up to six years of data on demographic, motor, and non-motor variables was collected. Movement disorder specialists used the structured interview for DSM-IV-TR depressive disorders and the Northwestern Disability Scale to assess depression and disability. A generalized linear mixed model was fitted with Northwestern Disability Scale score as the dependent variable to determine the effect of baseline depression status on disability.

RESULTS

A total of 43 participants were depressed at baseline compared to 94 without depression. Depressed participants were more likely to be female, were less educated, were less likely to take dopamine agonists, and more likely to have motor fluctuations. Controlling for these variables, symptomatic depression predicted greater disability compared to both never depressed (p = 0.0133) and remitted depression (p = 0.0009). Disability associated with symptomatic depression at baseline was greater over the entire six-year period compared to participants with remitted depressive episodes or who were never depressed.

CONCLUSIONS

Persisting depression is associated with a long-term adverse impact on daily functioning in PD. Adequate treatment or spontaneous remission of depression improves ADL function.

Cerebrospinal fluid biochemical studies in patients with Parkinson's disease: toward a potential search for biomarkers for this disease

The blood-brain barrier supplies brain tissues with nutrients and filters certain compounds from the brain back to the bloodstream. In several neurodegenerative diseases, including Parkinson's disease (PD), there are disruptions of the blood-brain barrier. Cerebrospinal fluid (CSF) has been widely investigated in PD and in other parkinsonian syndromes with the aim of establishing useful biomarkers for an accurate differential diagnosis among these syndromes. This review article summarizes the studies reported on CSF levels of many potential biomarkers of PD. The most consistent findings are: (a) the possible role of CSF urate on the progression of the disease; (b) the possible relations of CSF total tau and phosphotau protein with the progression of PD and with the preservation of cognitive function in PD patients; (c) the possible value of CSF beta-amyloid 1-42 as a useful marker of further cognitive decline in PD patients, and (d) the potential usefulness of CSF neurofilament (NFL) protein levels in the differential diagnosis between PD and other parkinsonian syndromes. Future multicentric, longitudinal, prospective studies with long-term follow-up and neuropathological confirmation would be useful in establishing appropriate biomarkers for PD.

Serotonin impairment in CSF of PD patients, without an apparent clinical counterpart

In Parkinson's disease (PD), several studies have detected an impaired serotonin (5-HT) pathway, likely affecting both motor and non-motor domains. However, the precise impact of 5-HT impairment is far from established. Here, we have used a HPLC chromatographic method, in a homogenous cohort (n = 35) of non fluctuating, non dyskinetic PD patients, to assess the concentration of 5-HT and its metabolite 5-HIAA in peripheral cerebrospinal fluid (CSF) obtained from lumbar puncture (LP). LP was performed following three days of therapy withdrawal, in order to vanish the effects of prolonged released dopamine agonists (DA), and in absence of any serotonergic agent. The PD patient group showed a significantly reduced CSF level of both 5-HT and 5-HIAA compared to either age-matched control subjects (n = 18), or Alzheimer's disease patients (n = 20). However, no correlation emerged between 5-HT/5-HIAA concentrations and UPDRS-III (r = −0.12), disease duration (r = −0.1), age (r = −0.27) and MMSE (r = 0.11). Intriguingly, low CSF 5-HT levels did not differ for gender or for motor phenotype (in terms of non-tremor dominant subtype and tremor dominant subtype). Further, low CSF 5-HT levels did not correlate with the presence of depression, apathy or sleep disturbance. Our findings support the contention that 5-HT impairment is a cardinal feature of stable PD, probably representing a hallmark of diffuse Lewy bodies deposition in the brainstem. However, clinical relevance remains uncertain. Given these findings, an add-on therapy with serotonergic agents seems questionable in PD patients, or should be individually tailored, unless severe depression is present.

Anxiety and depression in Parkinson's disease

OPINION STATEMENT

Anxiety and depression, while very common problems in Parkinson's disease (PD), have not been subject to adequate treatment trials. While a handful of double blind placebo-controlled trials of depression have been published, only a small number of subjects have been enrolled in most of these. There have been no adequate treatment trials of anxiety. Thus, most practitioners base their treatments on what has been published in the general population and their own personal experience. The data suggest that depression is probably treatable in some cases, but there are no data to support any drug treatment of anxiety. Much of the rationale for treating these disorders is based primarily on side effect profiles rather than efficacy and is almost entirely based on anecdotal experience. Although we lack convincing data, we do believe in the pharmacologic treatment of depression and anxiety and choose medications based on side effect profiles, some of which may be useful. We favor the selective serotonin reuptake inhibitors (SSRIs) in general for both depression and anxiety because of their relative freedom from side effects but will often choose mirtazapine if insomnia or weight loss is a problem, clonazepam for anxiety without depression if an SSRI is insufficient or if REM sleep behavior disorder is a problem, or a tricyclic antidepressant if drooling is troubling and the patient is not demented. Alternatively, we use the serotonin and noradrenaline reuptake inhibitor venlafaxine in those who do not tolerate an SSRI. SSRIs cannot be used for anxiety on an as needed basis, whereas short-acting benzodiazepines may be useful for this purpose. Psychosocial treatments of both depression and anxiety have also been under-studied, with probable benefits and a benign adverse effect profile.

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.

Depression in Parkinson disease--epidemiology, mechanisms and management

Depression occurs in around 35% of patients with Parkinson disease (PD) and is often persistent. Symptoms of depression can be evident in individuals at the time of diagnosis and might develop in the premotor stage of the disease. The underlying mechanisms of depression in PD are not known in detail, but changes in brain structure, signaling by neurotransmitters, and levels of inflammatory and neurotrophic factors are all suggested to contribute to its development. Psychosocial factors and pain could also have roles in depression. Changes in dopaminergic, noradrenergic and serotonergic systems in patients with PD might help to explain the incidence of depression in these individuals. Antidepressants that have dual serotonergic and noradrenergic effects are the drugs of choice for treating depression in PD. However, antiparkinsonian drugs might have beneficial effects not only on the motor symptoms of disease, but also on a patient's mood. Deep brain stimulation can worsen depression in some patients, but a preliminary study has suggested that transcranial magnetic stimulation could improve symptoms of depression. This Review describes the frequency and course of depression in patients with PD. The mechanisms that underlie depression in this disease are also discussed, and the management strategies for these patients are highlighted.

Assessment methods and factors associated with depression in Parkinson's disease

Depression is a common problem experienced by patients with Parkinson's disease (PD). Identifying depression in PD is difficult and the determinants of depression in PD are complex and debatable. Here we review our recent studies which have (i) examined the validity of current depression rating scales in PD, (ii) introduced a self-reported and validated strategy to identify a lifetime history of depression in PD, and (iii) investigated genetic and non-genetic factors associated with depression in the context of PD. Our research showed PD-specific cut-off values suitable to use for the Hamilton Depression Scales (HAMD and HDI) and the Geriatric Depression Scale (GDS-15) when dichotomising patients with and without a current depression. Using the GDS-15 specific cut-off scores and a number of self-reported questions that screen for a lifetime history of depression, we developed a novel method to dichotomise PD patients according to current depression or a past history of depression. This method was applied in a large-scale study examining the factors associated with depression in PD. We clarified that the severity of PD is positively related to depression. We also showed that a number of other clinical factors including a longer duration of PD, a younger PD onset age, frequent falls, a history of anxiety disorder and memory problems were associated with depression in PD. In addition to these clinical factors, we observed associations between depression, and lower education levels, a history of smoking and a regular use of non-aspirin bases NSAIDs or analgesics. No associations were found between depression in PD and common genetic variations examined across the serotonin and dopamine transporter genes. Our studies provide a focus for future intervention strategies.

Factors associated with depression in Parkinson's disease

BACKGROUND

Depression is common in Parkinson's disease (PD) and contributes significantly to a reduced quality of life in PD patients. The determinants of depression in PD are complex and poorly understood. We investigated the factors associated with depression in PD.

METHODS

PD patients were recruited from Neurology clinics. A validated method was used to screen for a lifetime history of depression. 'Depressed' patients were identified by a score of >6 in the Geriatric Depression Scale (GDS-15) or by having had prescribed treatment for depression. 'Never depressed' patients were recognised by a score of <5 in the GDS-15 with no signs of a history of depression. A newly developed and validated questionnaire was used to collect other information.

RESULTS

Depression was identified in 66% of the 639 PD patients who met the inclusion criteria. Depression was associated with an increased severity of illness as evidenced by higher Unified PD Rating Scale scores and a higher Hoehn and Yahr stage. Other clinical factors associated with disease severity were also more frequently observed in depressed patients. Similar to findings in non-PD samples, depressed PD patients were more likely to have a lower education level, a history of smoking and to regularly use non-aspirin based NSAIDs or analgesics. Comorbidities such as anxiety, memory problems, hallucinations, sleep disturbances and postural hypotension were more common in depressed PD patients.

LIMITATIONS

To avoid patient exhaustion of over-surveying, some factors within the psychological domain were not examined.

CONCLUSION

Our results provide a focus for future intervention strategies.

Unilateral lesion of the nigrostriatal pathway decreases the response of fast-spiking interneurons in the medial prefrontal cortex to 5-HT1A receptor agonist and expression of the receptor in parvalbumin-positive neurons in the rat

5-Hydroxytryptamine(1A) (5-HT(1A)) receptors are expressed in the prefrontal cortical interneurons. Among these interneurons, calcium-binding protein parvalbumin (PV)-positive fast spiking (FS) interneurons play an important role in regulatory function of the prefrontal cortex. In the present study, the response of medial prefrontal cortex (mPFC) FS interneurons to the selective 5-HT(1A) receptor agonist 8-OH-DPAT and change in expression of 5-HT(1A) receptor on PV-positive neurons were examined in rats with 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra pars compacta (SNc) by using extracellular recording and double-labeling immunofluorescence histochemistry. Systemic administration of 8-OH-DPAT (1-243 μg/kg, i.v.) dose-dependently inhibited the mean firing rate of the FS interneurons in sham-operated and the lesioned rats, respectively. The cumulative doses producing inhibition in the lesioned rats (243 μg/kg) was significantly higher than that of sham-operated rats (27 μg/kg). Furthermore, the local application of 8-OH-DPAT (0.01 μg) in the mPFC inhibited the FS interneurons in sham-operated rats, while having no effect on firing rate of the FS interneurons in the lesioned rats. In contrast to sham-operated rats, the lesion of the SNc in rats did not cause the change of PV-positive neurons in the prelimbic prefrontal cortex, a subregion of the mPFC, whereas the lesion of the SNc markedly reduced in percentage of PV-positive neurons expressing 5-HT(1A) receptors. Our results indicate that degeneration of the nigrostriatal pathway results in the decreased response of FS interneurons in the mPFC to 5-HT(1A) receptor stimulation, which attributes to down-regulation of 5-HT(1A) receptor expression in these interneurons.

Biopterin levels in the cerebrospinal fluid of patients with PARK8 (I2020T)

PARK8 is the most common form of familial Parkinson's disease (PD). We measured biopterin and monoamine metabolite levels in the cerebrospinal fluids of 7 PARK8 patients (I2020T mutation in leucine-rich repeat kinase 2), 2 asymptomatic mutation carriers, and 21 sporadic PD patients. The biopterin levels in PARK8 patients were significantly higher than those in sporadic PD patients, although the symptoms were comparable in both groups, suggesting that PARK8 patients exhibit parkinsonian symptoms with higher biopterin levels than sporadic PD patients.

Tryptophan hydroxylase 2 aggregates through disulfide cross-linking upon oxidation: possible link to serotonin deficits and non-motor symptoms in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopamine neurons of the nigrostriatal system, resulting in severe motor disturbances. Although much less appreciated, non-motor symptoms are also very common in PD and many can be traced to serotonin neuronal deficits. Tryptophan hydroxylase (TPH) 2, the rate-limiting enzyme in the serotonin biosynthesis, is a phenotypic marker for serotonin neurons and is known to be extremely labile to oxidation. Therefore, the oxidative processes that prevail in PD could cause TPH2 misfolding and modify serotonin neuronal function much as is seen in dopamine neurons. Oxidation of TPH2 inhibits enzyme activity and leads to the formation of high molecular weight aggregates in a dithiothreitol-reversible manner. Cysteine-scanning mutagenesis shows that as long as a single cysteine residue (out of a total of 13 per monomer) remains in TPH2, it cross-links upon oxidation and only cysteine-less mutants are resistant to this effect. The effects of oxidants on TPH2 catalytic function and cross-linking are also observed in intact TPH2-expressing HEK293 cells. Oxidation shifts TPH2 from the soluble compartment into membrane fractions and large inclusion bodies. Sequential non-reducing/reducing 2-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting confirmed that TPH2 was one of a small number of cytosolic proteins that form disulfide-bonded aggregates. The propensity of TPH2 to misfold upon oxidation of its cysteine residues is responsible for its catalytic lability and may be related to loss of serotonin neuronal function in PD and the emergence of non-motor (psychiatric) symptoms.

Potential mechanisms underlying anxiety and depression in Parkinson's disease: consequences of l-DOPA treatment

Though the most recognizable symptoms of Parkinson's disease (PD) are motor-related, many patients also suffer from debilitating affective symptoms that deleteriously influence quality of life. Dopamine (DA) loss is likely involved in the onset of depression and anxiety in PD. However, these symptoms are not reliably improved by DA replacement therapy with l-3,4-dihydroxyphenylalanine (l-DOPA). In fact, preclinical and clinical evidence suggests that l-DOPA treatment may worsen affect. Though the neurobiological mechanisms remain unclear, recent research contends that l-DOPA further perturbs the function of the norepinephrine and serotonin systems, already affected by PD pathology, which have been intimately linked to the development and expression of anxiety and depression. As such, this review provides an overview of the clinical characteristics of affective disorders in PD, examines the utility of animal models for the study of anxiety and depression in PD, and finally, discusses potential mechanisms by which DA loss and subsequent l-DOPA therapy influence monoamine function and concomitant affective symptoms.

Cortical serotonin and norepinephrine denervation in parkinsonism: preferential loss of the beaded serotonin innervation

Parkinson's Disease (PD) is marked by prominent motor symptoms that reflect striatal dopamine insufficiency. However, non-motor symptoms, including depression, are common in PD. It has been suggested that these changes reflect pathological involvement of non-dopaminergic systems. We examined regional changes in serotonin (5-HT) and norepinephrine (NE) systems in mice treated with two different 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment paradigms, at survival times of 3 or 16 weeks after the last MPTP injection. MPTP caused a decrease in striatal dopamine concentration, the magnitude of which depended on the treatment regimen and survival interval after MPTP treatment. There was significant involvement of other subcortical areas receiving a dopamine innervation, but no consistent changes in 5-HT or NE levels in subcortical sites. In contrast, we observed an enduring decrease in 5-HT and NE concentrations in both the somatosensory cortex and medial prefrontal cortex (PFC). Immunohistochemical studies also revealed a decrease in the density of PFC NE and 5-HT axons. The decrease in the cortical serotonergic innervation preferentially involved the thick beaded but not smooth fine 5-HT axons. Similar changes in the 5-HT innervation of post-mortem samples of the PFC from idiopathic PD cases were seen. Our findings point to a major loss of the 5-HT and NE innervations of the cortex in MPTP-induced parkinsonism, and suggest that loss of the beaded cortical 5-HT innervation is associated with a predisposition to the development of depression in PD.

Unilateral lesion of the nigrostriatal pathway decreases the response of interneurons in medial prefrontal cortex to 5-HT 2A/2C receptor stimulation in the rat

The aim of the present study was to investigate changes in the firing rate and pattern of interneurons in the medial prefrontal cortex (mPFC), and effects of 5-HT(2A/2C) receptor agonist DOI and antagonist ritanserin, and the selective 5-HT(2C) receptor antagonist SB 242084 on the neuronal firing in rats with 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra pars compacta (SNc) by extracellular recording in vivo. The lesion of the SNc decreased the firing rate of the interneurons compared to sham-lesioned rats, and firing pattern of these interneurons changed toward a more burst-firing. Administration of DOI (20-320 microg/kg, i.v.) dose-dependently increased the firing rate of all interneurons examined in sham-lesioned and the 6-OHDA-lesioned rats. The excitation was significant at doses higher than 40 microg/kg and 320 microg/kg in sham-lesioned and the 6-OHDA-lesioned rats, respectively. This dose, which produced marked effect in the 6-OHDA-lesioned rats, was much higher than that of sham-lesioned rats. The local application of DOI (5 microg) in mPFC increased the firing rate of the interneurons in sham-lesioned rats, while having no effect on the firing rate in the 6-OHDA-lesioned rats. The excitatory effect of DOI in sham-lesioned and the 6-OHDA-lesioned rats was completely or partially reversed by ritanserin or SB 242084. The results of our study show that lesion of the SNc leads to a decrease in the firing rate of interneurons in mPFC and fire with a more burst pattern, and decreased response of the interneurons to DOI in rat.

Monoamines, BDNF, IL-6 and corticosterone in CSF in patients with Parkinson's disease and major depression

The biochemical basis of major depression (MD) in Parkinson's disease (PD) is largely unknown. To increase our understanding of MD in PD patients, the levels of monoamine metabolites (HVA, 5-HIAA and MHPG), BDNF, orexin-A, IL-6 and corticosterone were examined in cerebrospinal fluid. The analyses were performed in MD patients with (n = 11) and without (n = 12) PD at baseline and after 12 weeks' of treatment with the antidepressant citalopram, and in patients with solely PD (n = 14) at baseline and after 12 weeks. The major findings were that PD patients with MD had significantly lower baseline levels of MHPG, corticosterone and IL-6 when compared to patients with solely MD. In response to citalopram treatment, patients with solely MD exhibited an expected decrease in 5-HIAA and MHPG levels which was not found in PD patients with MD. Moreover, the levels of BDNF and IL-6 were lower in PD patients with MD compared with patients with solely MD after treatment with citalopram. Thus, the biochemical basis and the response to citalopram differ between PD patients with MD and patients with solely MD.

In vivo effects of activation and blockade of 5-HT(2A/2C) receptors in the firing activity of pyramidal neurons of medial prefrontal cortex in a rodent model of Parkinson's disease

In the present study, we examined changes in the firing rate and firing pattern of pyramidal neurons in medial prefrontal cortex (mPFC), and the effects of 5-HT(2A/2C) receptor agonist DOI and antagonist ritanserin on the neuronal firing in rats with 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra pars compacta by using extracellular recording. The unilateral lesion of the nigrostriatal pathway significantly increased the mean firing rate of pyramidal neurons compared to sham-operated rats, and the firing pattern of these neurons also changed significantly towards a more bursty one. Systemic administration of DOI (20-320 microg/kg, i.v.) increased the mean firing rate of pyramidal neurons in sham-operated and the lesioned rats. The excitation was significant only at doses higher than 160 microg/kg and 320 microg/kg in sham-operated and the lesioned rats, respectively. In addition, the local application of DOI, 5 microg, in mPFC inhibited the firing rate of pyramidal neurons in sham-operated rats, while having no effect on firing rate in the lesioned rats. After treatment with GABAA receptor antagonist picrotoxinin, the local application of DOI, at the same dose, increased the mean firing rate of the neurons in sham-operated rats; however, DOI did not alter the firing activity of the neurons in the lesioned rats. These results indicate that the lesion of the nigrostriatal pathway leads to hyperactivity of pyramidal neurons in mPFC, and the decreased response of pyramidal neurons to DOI, suggesting dysfunction of 5-HT2A and 5-HT2C receptors on pyramidal neurons and GABAergic interneurons in the 6-OHDA-lesioned rats.

The firing activity of pyramidal neurons in medial prefrontal cortex and their response to 5-hydroxytryptamine-1A receptor stimulation in a rat model of Parkinson's disease

The changes in the firing rate and firing pattern of pyramidal neurons in medial prefrontal cortex (mPFC) and the effects of selective 5-hydroxytryptamine-(1A) (5-HT(1A)) receptor agonist (R)-(+)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT) and antagonist N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-2-pyridylcyclohexane carboxamide maleate salt (WAY-100635) on the firing activity of the neurons were studied in sham-lesioned rats and rats with 6-hydroxydopamine lesions of the substantia nigra pars compacta (SNc). The lesion of the SNc increased the firing rate of pyramidal neurons significantly compared to sham-lesioned rats, and the firing pattern of these neurons also changed significantly towards a more burst-firing. The systemic administration of 8-OH-DPAT at doses in the range of 0.5-128 microg/kg showed an excitatory-inhibitory effect on the firing rate of pyramidal neurons in mPFC of sham-lesioned rats. At lower doses, 0.5-32 microg/kg, it evoked excitation of the neurons, and at a high dose, i.e. 128 microg/kg, inhibited the activity of the neurons. In contrast to sham-lesioned rats, 8-OH-DPAT, at the same doses, showed no excitatory effect in the lesioned rats although the inhibitory phase of the effect of 8-OH-DPAT on the firing rate of pyramidal neurons in mPFC was still present. Furthermore, the local application of 8-OH-DPAT, 5 microg, in mPFC inhibited the firing rate of pyramidal neurons in sham-lesioned rats, while having no effect on firing rate in the lesioned rats. The excitatory or inhibitory effects of 8-OH-DPAT were reversed by WAY-100635, indicating that these effects are mediated by 5-HT(1A) receptor. Altogether, these results indicate that the lesion of the SNc leads to hyperactivity of pyramidal neurons in mPFC and the abnormality of response of these neurons to 5-HT(1A) receptor stimulation, suggesting that mPFC may be involved in the pathophysiology of the psychiatric disturbance of Parkinson's disease.

Clinical correlates of depressive symptoms in familial Parkinson's disease

Depression is one of the most common nonmotor complications of Parkinson's disease (PD) and has a major impact on quality of life. Although several clinical factors have been associated with depression in PD, the relationship between depression and stage of illness as well as between depression and degree of disability remains controversial. We have collected clinical data on 1,378 PD cases from 632 families, using the Unified Parkinson's Disease Rating Scale (UPDRS) Parts II (activities of daily living) & III (motor), the Mini-Mental State Exam, the Geriatric Depression Scale (GDS), and the Blessed Functional Activity Scale (Blessed). Analyses were performed using the 840 individuals with verified PD and without evidence of cognitive decline. Logistic regression was used to identify study variables that individually and collectively best predicted the presence of depressive symptoms (GDS >or= 10). After correcting for multiple tests, depressive symptoms were significantly associated with Hoehn and Yahr stage and other clinical measures but not with any genetic variant (parkin, LRRK2, APOE). The Blessed score, education, presence of a first degree relative with signs of depression, and UPDRS Part II were found to best predict depressive symptomatology (R(2) = 0.33; P = 4 x 10(-48)). Contrary to several reports, the results from this large study indicate that stage of illness, motor impairment, and functional disability are strongly correlated with depressive symptoms.

Unilateral lesion of the nigrostriatal pathway induces an increase of neuronal firing of the midbrain raphe nuclei 5-HT neurons and a decrease of their response to 5-HT(1A) receptor stimulation in the rat

Several studies have shown that the 5-hydroxytryptamine (serotonin, 5-HT) system is severely affected after degeneration of nigrostriatal dopaminergic neurons. In the present study, we examined the changes in the firing rate and firing pattern of the dorsal and median raphe nuclei (DRN and MRN) 5-HT neurons, and the effect of the selective 5-HT(1A) receptor agonist (R)-(+)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT) and antagonist (N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-2-pyridylcyclohexane carboxamide maleate salt (WAY-100635) on the neuronal firing in rats with 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra pars compacta by using extracellular recording. The unilateral lesion of the nigrostriatal pathway significantly increased the mean firing rate of DRN and MRN 5-HT neurons compared with normal rats, and the firing pattern of these neurons also changed significantly towards a more bursty one. The lower dose of 8-OH-DPAT, 4 microg/kg (cumulative doses, i.v.), completely inhibited the firing activity of all DRN and MRN 5-HT neurons examined in normal and sham rats. In contrast to normal and sham rats, only the higher doses of 8-OH-DPAT, 128 and 64 microg/kg, completely inhibited the firing rate of DRN and MRN 5-HT neurons in 6-OHDA-lesioned rats, respectively. Furthermore, the local application of 8-OH-DPAT, 1.5 microg, in the DRN completely inhibited the firing rate of 5-HT neurons in normal and sham rats, while having no effect on firing rate in the lesioned rats. Altogether, these results indicate that lesion of the nigrostriatal pathway leads to hyperactivity of DRN and MRN 5-HT neurons, suggesting the implication of the DRN and MRN in the pathophysiology of Parkinson's disease, and the decreased response of these 5-HT neurons to 5-HT(1A) receptor stimulation, reflecting 5-HT(1A) receptor dysfunction in 6-OHDA-lesioned rats.

Circadian variation of core body temperature in Parkinson disease patients with depression: a potential biological marker for depression in Parkinson disease

BACKGROUND

The biological rhythm in comorbidity of depression and Parkinson disease (PD) is still unclear. For early diagnosis or clarification of the pathologic condition of comorbidity of depression and PD, the present study investigated the presence of circadian rhythm abnormalities in patients with depression.

METHODS

We measured the rectal temperature (RT) in 30 PD patients with or without depression during 48 consecutive hours using the maximum entropy method (MEM) and least-squares method (COSINOR). The presence of major or minor depression was evaluated by the Mini International Neuropsychiatric Interview based on the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders, and the Hamilton Depression Scale.

RESULTS

The RT rhythms of patients without depression predominately showed a circadian rhythm. However, 2 of 6 patients with depression showed an infradian rhythm using MEM. COSINOR revealed that PD patients with depression showed lower amplitudes of core body temperature (p = 0.012) and higher minimum RT (p = 0.031) relative to those of patients without depression.

CONCLUSION

PD patients with depression show an altered RT circadian rhythm. The results suggest that the characteristics of core body temperature could be potentially used as a biological marker for depression in PD.

The neuropathological basis for depression in Parkinson's disease

Depression is found in 30-40% of all patients with Parkinson's disease (PD), but its etiology is unclear. Using neuropathology as a signpost for neurotransmitter function, we investigated the prevalence of pathological features found at postmortem and sought to uncover differences between depressed (n=11) and non-depressed (n=9) elderly PD patients. The results indicate a higher prevalence of pathological features in depressed compared to non-depressed PD patients, particularly in catecholamine areas of the brain; the locus coeruleus (neuronal loss: odds ratio=7.2, p=08; gliosis: odds ratio=18.0, p=008); dorsal vagus nerve (gliosis: odds ratio=7.63, p<0.05), and substantia nigra pars compacta (gliosis: odds ratio=2.85, ns). However, neuropathological differences were absent in the dorsal raphe nuclei, amygdala, and cortical regions. Our evidence suggests that depression in PD is related more to catecholaminergic than serotonergic system dysfunction.

Loss of thalamic serotonin transporters in early drug-naïve Parkinson's disease patients is associated with tremor: an [(123)I]beta-CIT SPECT study

In vitro studies revealed serotonin transporter (5-HTT) decline in Parkinson’s disease (PD). Yet, few studies investigated thalamic 5-HTT in vivo and its effect on PD heterogeneity. We analyzed thalamic [¹²³I]β-CIT binding (mainly reflecting 5-HTT binding) in 32 drug-naïve PD patients and 13 controls with SPECT. Twenty-six patients were examined twice (17 months apart). Based on UPDRS scores, we identified subgroups of patients with moderate/severe tremor (PD_T) and without tremor (PD_WT) at the time of clinical diagnosis. Additionally, depressive symptoms were evaluated using the Beck Depression Inventory (BDI) at baseline. Mean thalamic specific to non-specific [¹²³I]β-CIT binding ratio was lower in patients when compared to controls, and further decreased during follow-up. At baseline, average thalamic ratio was significantly lower in the PD_T than in the PD_WT subgroup. No correlation was found between BDI scores and thalamic binding ratios. Our findings show decline of [¹²³I]β-CIT binding to thalamic 5-HTT in PD and its possible contribution to tremor onset.

Depression in Parkinson's disease: health risks, etiology, and treatment options

Depression is found in about 30%-40% of all patients with Parkinson's disease (PD), but only a small percentage (about 20%) receive treatment. As a consequence, many PD patients suffer with reduced health-related quality of life. To address quality of life in depressed PD patients, we reviewed the literature on the health correlates of depression in PD (eg, cognitive function), etiology of depression in PD, and treatment options (ie, antidepressants, electroconvulsive therapy, and psychotherapy). The current review is unique in its focus on psychosocial aspects, as well as neuropathological factors, of depression in PD. Overall, we conclude that neurochemical (eg, serotonin) and psychosocial factors (eg, coping style, self-esteem, and social support) contribute to the affective disturbances found in this neuropsychiatric population. Therefore, we recommend that a multidisciplinary (eg, pharmacotherapeutic, psychoeducational, and/or psychotherapeutic) approach to treatment be taken with depressed PD patients.

Long-term L-DOPA treatment causes indiscriminate increase in dopamine levels at the cost of serotonin synthesis in discrete brain regions of rats

(1) The treatment of choice for Parkinson's disease (PD) is 3,4-dihydroxyphenylalanine (L-DOPA) with peripheral decarboxylase inhibitor, but long-term therapy leads to motor and psychiatric complications. In the present study we investigated 5-hydroxytryptamine (5-HT) and dopamine concentrations in serotonergic and dopaminergic nuclei following chronic administration of L-DOPA to find whether the neurotransmitter synthesis in these brain areas are compensated. (2) Rats were administered L-DOPA (250 mg/kg) and carbidopa (25 mg/kg) daily for 59 and 60 days, and killed on the 60th day, respectively at 24 h and 30 min after the last dose. L-DOPA, norepinephrine, 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), dopamine, homovanillic acid (HVA), and 3,4-dihydroxyphenylacetic acid (DOPAC) were measured in striatum, nucleus raphe dorsalis (NRD), nucleus accumbens (NAc), substantia nigra, cerebellum, and cortex employing HPLC-electrochemical procedure. (3) Prolonged treatment of L-DOPA caused depression in the animals as revealed in a forced swim test. Serotonin content was significantly decreased in all brain regions studied 30 min after long-term L-DOPA, except in NAc. The cortex and striatum showed lowered levels of this indoleamine 24 h after 59 doses of L-DOPA. Dopamine, HVA, and DOPAC concentrations were significantly higher in all the regions studied after 30 min, and in the cerebellum after 24 h of L-DOPA. The levels of DOPAC were elevated in all the brain areas studied 24 h after prolonged L-DOPA treatment. (4) The present results suggest that long-term L-DOPA treatment results in significant loss of 5-HT in serotonergic and dopaminergic regions of the brain. Furthermore, while L-DOPA metabolism per se was uninfluenced, dopamine synthesis was severely impaired in all the regions. The imbalance of serotonin and dopamine formation may be the cause of overt cognitive, motor, and psychological functional aberrations seen in parkinsonian patients following prolonged L-DOPA treatment.

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.

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.

The serotonergic hypothesis for depression in Parkinson's disease: an experimental approach

The serotonergic hypothesis for depression in Parkinson's disease (PD) states that the reduced cerebral serotonergic activity that occurs in PD constitutes a biological risk factor for depression. The aim of our study was to assess the serotonergic hypothesis of depression in PD patients using an experimental approach. In a double-blind, randomized order, placebo-controlled crossover design, the response on the Profile of Mood States (POMS) questionnaire to acute tryptophan depletion (ATD) was studied in 15 PD nondepressed patients and 15 control subjects, without a prior personal or family history of depression. PD patients had lower (worse) baseline scores on the sadness, fatigue and vigor subscales of the POMS, in both ATD and the placebo condition, but not on the tension and anger subscales. There was however neither a significance between group effect, nor significance within-group effect due to ATD. We could find no evidence of a specific serotonergic vulnerability of PD patients for depression. Therefore, our results do not support the serotonergic hypothesis for depression in PD.

Functional investigations into the role of dopamine and serotonin in partial bilateral striatal 6-hydroxydopamine lesioned rats

In Parkinson's disease (PD), several neurotransmitter systems, such as the dopaminergic and serotonergic system, show signs of degeneration. This led to the suggestion that alterations in the serotonergic system play a role in the pathophysiology of PD. Partial bilateral dopaminergic lesions of the caudate putamen complex (CPu) of rats induced by 6-hydroxydopamine (6-OHDA) produce behavioral symptoms mimicking PD. In the present study, the role of serotonin and dopamine was investigated both behaviorally and neuroanatomically. In a reaction time task, motor initiation and motor performance were impaired in the lesioned animals compared to controls. The performance of rats treated with d-amphetamine or serotonergic ligands (DOI and ketanserin) in the reaction time task indicated that 5-HT and DA appear to be agonistically related in the CPu. The relation was the same in both control and 6-OHDA lesioned rats. 12 weeks after lesioning, motor initiation recovered, whereas motor performance did not. Parallel to the behavioral study, a second group of animals was lesioned and, at 3 days, 6 weeks and 12 weeks after lesioning, a subgroup was killed to obtain a qualitative indication of the degree of 6-OHDA lesion. Over the three time points, a substantial recovery of tyrosine hydroxylase staining in the CPu was visible. Taken together, since serotonergic ligands have the same effect as dopaminergic ligands on reaction time responding indicated that 5-HT and DA release are agonistically linked in control and 6-OHDA lesioned rats.

The effect of depression on motor function and disease severity of Parkinson's disease

OBJECTIVES

Approximately 40% of patients with Parkinson's disease (PD) experience symptoms of depression. Our aim was to evaluate the effect of depression on disease severity, motor function and other phenotypic characteristics of PD.

PATIENTS AND METHODS

We studied 32 PD patients with major depression (PD-D) according to the DSM-IV criteria and 32 PD patients with no depression (PD-C) matched for gender, age of onset and duration.

RESULTS

Major depression in PD patients was associated with increased disease severity, poorer motor function and worse performance in the activities of daily living as measured by UPDRS scores. Furthermore, there was an association of depression with the severity of bradykinesia and axial rigidity.

CONCLUSIONS

Depression in PD can have a profound negative impact on a patient's sense of wellbeing and motor functioning. Therefore, PD patients should be routinely and carefully screened for the presence of depression and appropriate management should be considered. Larger studies on the subject are warranted.

Conceptualization of depression in Parkinson's disease

AIMS

To discuss the current methodological and conceptual difficulties inherent in characterizing the emotional manifestations of neurodegenerative disease through critically reviewing depression as a manifestation of idiopathic Parkinson's disease (PD).

METHODS

Selective literature review of the neurobiological, psychological, and physical basis of depressive symptoms in PD from 1993-2003, with reference to key earlier articles.

CONCLUSIONS

There are difficulties in defining the syndromes of PD itself as well as depression in PD. The use of more conceptually reductionistic definitions of emotion and behavior in comprehensive longitudinal studies of the natural history of PD is recommended.

Taste responses in patients with Parkinson's disease

OBJECTIVE

Preclinical studies indicate that dopaminergic transmission in the basal ganglia may be involved in processing of both pleasant and unpleasant stimuli. Given this, the aim of the present study was to assess taste responses to sweet, bitter, sour, and salty substances in patients with Parkinson's disease (PD).

METHODS

Rated intensity and pleasantness of filter paper discs soaked in sucrose (10-60%), quinine (0.025-0.5%), citric acid (0.25-4.0%), or sodium chloride (1.25-20%) solutions was evaluated in 30 patients with PD and in 33 healthy controls. Paper discs soaked in deionised water served as control stimuli. In addition, reactivity to 100 ml samples of chocolate and vanilla milk was assessed in both groups. Taste detection thresholds were assessed by means of electrogustometry. Sociodemographic and neuropsychiatric data, including cigarette smoking, alcohol consumption, tea and coffee drinking, depressive symptoms, and cognitive functioning were collected.

RESULTS

In general, perceived intensity, pleasantness, and identification of the sucrose, quinine, citric acid, or sodium chloride samples did not differ between the PD patients and controls. Intensity ratings of the filter papers soaked in 0.025% quinine were significantly higher in the PD patients compared with the control group. No inter-group differences were found in taste responses to chocolate and vanilla milk. Electrogustometric thresholds were significantly (p = 0.001) more sensitive in the PD patients.

CONCLUSIONS

PD is not associated with any major alterations in responses to pleasant or unpleasant taste stimuli. Patients with PD may present enhanced taste acuity in terms of electrogustometric threshold.