Dopamine dysregulation syndrome, addiction and behavioral changes in Parkinson's disease

When benefitting a patient increases the risk for harm for third persons - the case of treating pedophilic Parkinsonian patients with deep brain stimulation

This paper investigates the question whether it is ethically justified to treat Parkinsonian patients with known or suspected pedophilia with deep brain stimulation - given increasing evidence that this treatment might cause impulse control disorders, disinhibition, and hypersexuality. This specific question is not as exotic as it looks at a first glance. First, the same issue is raised for all other types of sexual orientation or behavior which imply a high risk for harming other persons, e.g. sexual sadism. Second, there are also several (psychotropic) drugs as well as legal and illegal leisure drugs which bear severe risks for other persons. We show that Beauchamp and Childress' biomedical ethics fails to derive a veto against medical interventions which produce risks for third persons by making the patients dangerous to others. Therefore, our case discussion reveals a blind spot of the ethics of principles. Although the first intuition might be to forbid the application of deep brain stimulation to pedophilic patients, we argue against such a simple way out, since in some patients the reduction of dopaminergic drugs allowed by deep brain stimulation of the nucleus subthalamicus improves impulsive control disorders, including hypersexuality. Therefore, we propose a strategy consisting of three steps: (1) risk assessment, (2) shared decision-making, and (3) risk management and safeguards.

Perimenopause Amelioration of a TCM Recipe Composed of Radix Astragali, Radix Angelicae Sinensis, and Folium Epimedii: An In Vivo Study on Natural Aging Rat Model

Traditional Chinese medicine (TCM) has been extensively applied as preferable herbal remedy for menopausal symptoms. In the present work, the potential of a TCM recipe named RRF, composed of Radix Astragali, Radix Angelicae Sinensis, and Folium Epimedii, was investigated on a natural aging rat model. After administration of RRF (141, 282, and 564 mg/kg/d), the circulated estradiol (E2) level increased accompanied by a reduction of serum follicle stimulating hormone (FSH). But no significant impact on serum lutenizing hormone (LH) level was observed. As a result of the E2-FSH-LH adjustment, the histomorphology degenerations of ovary, uterus, and vagina of the 11.5-month female rats were alleviated. And lumbar vertebrae trabecular microstructure was also restored under RRF exposure by means of increasing the trabecular area and area rate. Moreover, levels of hypothalamic dopamine (DA) and norepinephrine (NE) rallied significantly after RRF treatment. Results from our studies suggest that RRF possesses a positive regulation on the estrogen imbalance and neurotransmitter disorder, thereby restoring reproductive organ degeneration and skeleton deterioration. The above-mentioned benefits of RRF on the menopause syndromes recommend RRF as a potential candidate for the treatment of perimenopausal syndrome.

Demography, diagnostics, and medication in dementia with Lewy bodies and Parkinson's disease with dementia: data from the Swedish Dementia Quality Registry (SveDem)

INTRODUCTION

Whether dementia with Lewy bodies (DLB) and Parkinson's disease with dementia (PDD) should be considered as one entity or two distinct conditions is a matter of controversy. The aim of this study was to compare the characteristics of DLB and PDD patients using data from the Swedish Dementia Quality Registry (SveDem).

METHODS

SveDem is a national Web-based quality registry initiated to improve the quality of diagnostic workup, treatment, and care of patients with dementia across Sweden. Patients with newly diagnosed dementia of various types were registered in SveDem during the years 2007-2011. The current cross-sectional report is based on DLB (n = 487) and PDD (n = 297) patients. Demographic characteristics, diagnostic workup, Mini-Mental State Examination (MMSE) score, and medications were compared between DLB and PDD groups.

RESULTS

No gender differences were observed between the two study groups (P = 0.706). PDD patients were significantly younger than DLB patients at the time of diagnosis (74.8 versus 76.8 years, respectively; P < 0.001). A significantly higher prevalence of patients with MMSE score ≤24 were found in the PDD group (75.2% versus 67.6%; P = 0.030). The mean number of performed diagnostic modalities was significantly higher in the DLB group (4.9 ± 1.7) than in the PDD group (4.1 ± 1.6; P < 0.001). DLB patients were more likely than PDD patients to be treated with cholinesterase inhibitors (odds ratio = 2.5, 95% confidence interval = 1.8-3.5), whereas the use of memantine, antidepressants, and antipsychotics did not differ between the groups.

CONCLUSION

This study demonstrates several differences in the dementia work-up between DLB and PDD. The onset of dementia was significantly earlier in PDD, while treatment with cholinesterase inhibitors was more common in DLB patients. Severe cognitive impairment (MMSE score ≤24) was more frequent in the PDD group, whereas more diagnostic tests were used to confirm a DLB diagnosis. Some similarities also were found, such as gender distribution and use of memantine, antidepressants, and antipsychotics drugs. Further follow-up cost-effectiveness studies are needed to provide more evidence for workup and treatment guidelines of DLB and PDD.

The brain basis of musicophilia: evidence from frontotemporal lobar degeneration

Musicophilia, or abnormal craving for music, is a poorly understood phenomenon that has been associated in particular with focal degeneration of the temporal lobes. Here we addressed the brain basis of musicophilia using voxel-based morphometry (VBM) on MR volumetric brain images in a retrospectively ascertained cohort of patients meeting clinical consensus criteria for frontotemporal lobar degeneration: of 37 cases ascertained, 12 had musicophilia, and 25 did not exhibit the phenomenon. The syndrome of semantic dementia was relatively over-represented among the musicophilic subgroup. A VBM analysis revealed significantly increased regional gray matter volume in left posterior hippocampus in the musicophilic subgroup relative to the non-musicophilic group (p < 0.05 corrected for regional comparisons); at a relaxed significance threshold (p < 0.001 uncorrected across the brain volume) musicophilia was associated with additional relative sparing of regional gray matter in other temporal lobe and prefrontal areas and atrophy of gray matter in posterior parietal and orbitofrontal areas. The present findings suggest a candidate brain substrate for musicophilia as a signature of distributed network damage that may reflect a shift of hedonic processing toward more abstract (non-social) stimuli, with some specificity for particular neurodegenerative pathologies.

Impulse control disorders in Parkinson's disease: a psychosocial perspective

Parkinson's disease (PD) is a progressive neurodegenerative disease primarily characterised by motor symptoms. However, another feature of PD which is receiving increasing attention is the phenomenon of impulse control disorders (ICDs), such as pathological gambling. To date, research into ICDs in PD has centred on a biomedical model of cause, related to the effects of dopamine replacement therapy. However, there are several areas of discrepancy in the current biomedical account of ICDs in PD. In addition, we argue that social and psychological factors also need to be considered to achieve a more complete understanding of the phenomenon. We present a novel conceptual model which combines biomedical and psychosocial factors in the genesis of ICDs in PD and use the model to identify a number of potential treatment intervention points and to highlight important outstanding questions concerning the inter-relationship between psychosocial and biomedical factors in the genesis of ICDs in PD.

Motivational properties of D2 and D3 dopamine receptors agonists and cocaine, but not with D1 dopamine receptors agonist and L-dopa, in bilateral 6-OHDA-lesioned rat

Dopamine dysregulation syndrome in Parkinson's disease (PD) has been attributed to dopamine replacement therapy (DRT). We hypothesize that DRT can induce a potential rewarding effect in an animal model of PD. Using the conditioned place preference (CPP) paradigm, we investigated the motivational effects of L-dopa, dopamine receptor agonists (DRAs), and cocaine in rat with a bilateral 6-OHDA lesion of the nigrostriatal dopaminergic pathway. In 6-OHDA animals, D1 receptors agonist (SKF81297) revealed significantly a conditioned place aversion (CPA) at 3 mg/kg and 9 mg/kg doses. D2 receptors agonist (bromocriptine) induced both CPP and CPA at 1 mg/kg and 10 mg/kg doses respectively. D3 receptors agonist (PD128907) induced a CPP only at 1 mg/kg, comparable to that of cocaine. Sham animals revealed biphasic CPP curves, with significant dose effect, for the intermediate dose of the 3 DRAs. However, L-dopa induced no significant effect while cocaine induced CPP in both lesioned and sham animals. In conclusion, this study confirms the predominant roles of D2R class, and most specifically D3R subtypes, in rewarding properties of DRT.

Biological sources of inflexibility in brain and behavior with aging and neurodegenerative diseases

Almost unequivocally, aging and neurodegeneration lead to deficits in neural information processing. These declines are marked by increased neural noise that is associated with increased variability or inconsistency in behavioral patterns. While it is often viewed that these problems arise from dysregulation of dopamine (DA), a monoamine modulator, glutamate (GLU), an excitatory amino acid that interacts with DA, also plays a role in determining the level of neural noise. We review literature demonstrating that neural noise is highest at both high and low levels of DA and GLU, allowing their interaction to form a many-to-one solution map for neural noise modulation. With aging and neurodegeneration, the range over which DA and GLU can be modulated is decreased leading to inflexibility in brain activity and behavior. As the capacity to modulate neural noise is restricted, the ability to shift noise from one brain region to another is reduced, leading to greater uniformity in signal-to-noise ratios across the entire brain. A negative consequence at the level of behavior is inflexibility that reduces the ability to: (1) switch from one behavior to another; and (2) stabilize a behavioral pattern against external perturbations. In this paper, we develop a theoretical framework where inflexibility across brain and behavior, rather than inconsistency and variability is the more important problem in aging and neurodegeneration. This theoretical framework of inflexibility in aging and neurodegeneration leads to the hypotheses that: (1) dysfunction in either or both of the DA and GLU systems restricts the ability to modulate neural noise; and (2) levels of neural noise and variability in brain activation will be dedifferentiated and more evenly distributed across the brain; and (3) changes in neural noise and behavioral variability in response to different task demands and changes in the environment will be reduced.

Management of sexual dysfunction in Parkinson's disease

Nonmotor symptoms, among them sexual dysfunction, are common and underrecognized in patients with Parkinson disease; they play a major role in the deterioration of quality of life of patients and their partners. Loss of desire and dissatisfaction with their sexual life is encountered in both genders. Hypersexuality (HS), erectile dysfunction and problems with ejaculation are found in male patients, and loss of lubrication and involuntary urination during sex are found in female patients. Tremor, hypomimia, muscle rigidity, bradykinesia, 'clumsiness' in fine motor control, dyskinesias, hypersalivation and sweating may interfere with sexual function. Optimal dopaminergic treatment should facilitate sexual encounters of the couple. Appropriate counselling diminishes some of the problems (reluctance to engage in sex, problems with ejaculation, lubrication and urinary incontinence). Treatment of erectile dysfunction with sildenafil and apomorphine is evidence based. HS or compulsive sexual behaviour are side effects of dopaminergic therapy, particularly by dopaminergic agonists, and should be treated primarily by diminishing their dose. Neurologists should actively investigate sexual dysfunction in their Parkinsonian patients and offer treatment, optimally within a multidisciplinary team, where a dedicated professional would deal with sexual counselling.

Compulsive use of dopamine replacement therapy: a model for stimulant drug addiction?

The compulsive use of dopamine replacement therapy (DRT) or dopamine dysregulation syndrome (DDS) is one of the behavioural disturbances reported in some patients with Parkinson's disease (PD) and other disorders who are receiving DRT. We draw this phenomenon to the attention of the addiction field as a topic deserving of more systematic study. We outline: the clinical features, epidemiology and clinical correlates of the disorder; the unresolved issues in its definition and diagnosis; and its potential relevance to neurobiological models of psychostimulant addiction. We argue that compulsive DRT use may provide a useful model for drug addiction, while advancing our understanding of the neurobiology of addiction and improving the management of PD patients with the disorder.

Characterization of 3,4-methylenedioxymethamphetamine (MDMA) enantiomers in vitro and in the MPTP-lesioned primate: R-MDMA reduces severity of dyskinesia, whereas S-MDMA extends duration of ON-time

l-3,4-dihydroxyphenylalanine (l-DOPA) is the most effective treatment for Parkinson's disease, but long-term l-DOPA administration is marred by the emergence of motor complications, namely, dyskinesia and a shortening of antiparkinsonian benefit (wearing-OFF). 3,4-methylenedioxymethamphetamine (MDMA) is unique in that it exerts antidyskinetic effects and may enhance antiparkinsonian actions of l-DOPA. MDMA is composed of two enantiomers with different pharmacological profiles; here, we describe a novel enantiospecific synthesis of the two enantiomers and expand on the previous characterization of their pharmacology. R-MDMA (rectus-MDMA) is relatively selective for 5-HT(2A) receptors, whereas S-MDMA (sinister-MDMA) inhibits both serotonin (SERT) and dopamine transporters (DAT; SERT/DAT ratio of 10 to 1). R- or S-MDMA (1, 3, and 10 mg/kg, s.c.) was administered in combination with l-DOPA (15 mg/kg, s.c.) to six female common marmosets (Callithrix jacchus) rendered parkinsonian by MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) administration. Motor disability, including parkinsonism and dyskinesia, and duration of antiparkinsonian benefit (ON-time) were evaluated. After the administration of R-MDMA (3 and 10 mg/kg), the severity of peak-dose dyskinesia was decreased (by 33 and 46%, respectively; p < 0.05); although total ON-time was unchanged (approximately 220 min), the duration of ON-time with disabling dyskinesia was decreased by 90 min when compared to l-DOPA alone (69% reduction; p < 0.05). S-MDMA (1 mg/kg) increased the total ON-time by 88 min compared to l-DOPA alone (34% increase; p < 0.05), though dyskinesia were exacerbated. These data suggest that racemic MDMA exerts simultaneous effects, reducing dyskinesia and extending ON-time, by 5-HT(2A) antagonism and SERT-selective mixed monoamine uptake inhibition, which arise from its R and S enantiomers, respectively.

Impulsive behavior and associated clinical variables in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a degenerative brain disorder accompanied by the loss of dopaminergic neurons and the presence of motor and non-motor symptoms.

OBJECTIVE

We performed a cross-sectional, questionnaire-based analysis of impulsive behavior in our PD clinic population to assess prevalence and associated characteristics.

RESULTS

We found a higher prevalence of impulsive behavior (29.7%) than previously reported, and found multiple, concurrent impulsive behaviors in 26% of subjects reporting impulsive behavior.

CONCLUSIONS

Our findings contribute to the growing awareness of impulsive behavior in PD, and support the need for longitudinal studies to assess changes in impulsive behaviors in Parkinson's patients.

Impulse control and related disorders in Parkinson's disease patients treated with bilateral subthalamic nucleus stimulation: a review

Recently, impulse control and related disorders including punding and the dopamine dysregulation syndrome (DDS) have been increasingly recognized in treated patients with Parkinson's disease (PD). Especially the impulse control disorders (ICD) such as pathological gambling, hypersexuality, compulsive eating and buying may have dramatic repercussions on family, personal and professional life. Drug replacement therapy (DRT) is believed to play an important role in the onset of these behavioral disturbances. Although deep brain stimulation (DBS) of the subthalamic nucleus (STN) might be a therapeutic option for those patients with DRT-related behavior, it may also induce ICD. So far, little is known about the relationship between STN DBS and impulse control and related disorders. Our aim was to review the current knowledge on this relationship in PD patients. The available studies showed that stimulation of the STN is associated with both favorable and negative outcome in terms of impulse control and related disorders. Preoperative disorders may resolve or improve after STN DBS, but these can also worsen or show no change at all. Moreover, STN DBS can also reveal or even induce ICD. Possible explanations for this variability are proposed and suggestions for clinical management are given.

Impulse control disorders in patients with Parkinson's disease receiving dopamine replacement therapy: evidence and implications for the addictions field

AIMS

To describe the prevalence, phenomenology and correlates of 'impulse control disorders' (ICDs) in patients with Parkinson's disease (PD) treated with dopamine replacement therapy (DRT); to assess the strength of the evidence that DRT plays a contributory causal role in these disorders; and to highlight the implications of these disorders for research in the addiction field.

METHODS

PubMed and Web of Science databases were searched and the reference lists of papers examined.

RESULTS

The prevalence of ICDs in Parkinson's patients using DRT varied between 3.5% and 13.6%, depending on the severity and range of disorders assessed. PD patients with ICDs were: generally younger; had an earlier onset of PD; had a personal or family history of substance abuse or an ICD; and were more likely to be treated with dopamine receptor agonists (DA agonists) than levodopa (l-dopa). There is reasonable evidence that dopaminergic medications play a causal role in ICDs in that they occur at a higher rate in an otherwise low-risk population of adults, begin after initiation of DA agonist therapy and cease upon its discontinuation. A causal relationship is biologically plausible, but the role of other factors (such as concurrent mood disorders) remain to be clarified by better-controlled studies.

CONCLUSIONS

Impulse control disorders among patients with Parkinson's disease receiving dopamine replacement therapy may provide a unique opportunity for addiction researchers to study the neurobiology of impulsive forms of behaviour (such as problem gambling) that appear to be caused, in part, by the therapeutic use of dopamine receptor agonists.

Impulse control disorders and punding in Parkinson's disease: the need for a structured interview

INTRODUCTION

Impulse control disorders (ICD) including hypersexuality, compulsive gambling, buying, eating, shopping and dopaminergic medication use, have been reported to occur frequently in Parkinson's disease (PD). Punding (complex, repetitive, excessive, non-goal oriented behaviours) have also been described. As patients may not report such behaviours to their neurologist, ICD and punding appear to be under-recognised in clinical practice.

METHOD

We Prospectively screened 216 consecutive patients (102 men, age 77±5 years) with idiopathic PD. Patients and their caregivers were encouraged to complete a questionnaire with six questions on symptoms related to ICD and punding. In addition, we obtained a random sample matched by age and sex of 216 patients with idiopathic PD, and retrospective analysis of symptoms related to ICD and punding who had been referred spontaneously.

RESULTS

Only 20 cases (9.26%) of 216 patients with PD who answered the questionnaire prospectively presented ICD and / or punding, some involving more than one type of repetitive behaviour and reward-seeking: 7 hypersexuality (3.24%), 2 pathological gambling (0.93%), 4 compulsive buying (1.85%), 2 compulsive eating (0.93%), 8 punding (3.70%) and 1 abuse of medication (0.46%).Of the retrospective sample of 216 patients age- and gender-matched, only 5 patients (2,31%) had spontaneously mentioned these symptoms: 2 hypersexuality (0.93%), 2 pathological gambling (0.93%) and 1 punding (0.46%).

CONCLUSIONS

Patients with PD do not spontaneously admit the presence of ICD or punding and these behaviours appear to be under-recognised in clinical practice. A screening questionnaire is needed to ensure their detection.

From the cell to the clinic: a comparative review of the partial D₂/D₃receptor agonist and α2-adrenoceptor antagonist, piribedil, in the treatment of Parkinson's disease

Though L-3,4-dihydroxyphenylalanine (L-DOPA) is universally employed for alleviation of motor dysfunction in Parkinson's disease (PD), it is poorly-effective against co-morbid symptoms like cognitive impairment and depression. Further, it elicits dyskinesia, its pharmacokinetics are highly variable, and efficacy wanes upon long-term administration. Accordingly, "dopaminergic agonists" are increasingly employed both as adjuncts to L-DOPA and as monotherapy. While all recognize dopamine D(2) receptors, they display contrasting patterns of interaction with other classes of monoaminergic receptor. For example, pramipexole and ropinirole are high efficacy agonists at D(2) and D(3) receptors, while pergolide recognizes D(1), D(2) and D(3) receptors and a broad suite of serotonergic receptors. Interestingly, several antiparkinson drugs display modest efficacy at D(2) receptors. Of these, piribedil displays the unique cellular signature of: 1), signal-specific partial agonist actions at dopamine D(2)and D(3) receptors; 2), antagonist properties at α(2)-adrenoceptors and 3), minimal interaction with serotonergic receptors. Dopamine-deprived striatal D(2) receptors are supersensitive in PD, so partial agonism is sufficient for relief of motor dysfunction while limiting undesirable effects due to "over-dosage" of "normosensitive" D(2) receptors elsewhere. Further, α(2)-adrenoceptor antagonism reinforces adrenergic, dopaminergic and cholinergic transmission to favourably influence motor function, cognition, mood and the integrity of dopaminergic neurones. In reviewing the above issues, the present paper focuses on the distinctive cellular, preclinical and therapeutic profile of piribedil, comparisons to pramipexole, ropinirole and pergolide, and the core triad of symptoms that characterises PD-motor dysfunction, depressed mood and cognitive impairment. The article concludes by highlighting perspectives for clarifying the mechanisms of action of piribedil and other antiparkinson agents, and for optimizing their clinical exploitation.