Muscarinic M2 and M4 receptors in anterior cingulate cortex: relation to neuropsychiatric symptoms in dementia with Lewy bodies

Differences in the treatment needs of patients with dementia with Lewy bodies and their caregivers and differences in their physicians' awareness of those treatment needs according to the clinical department visited by the patients: a subanalysis of an observational survey study

BACKGROUND

We investigated whether the treatment needs of patients with dementia with Lewy bodies (DLB) and their caregivers, along with their attending physicians' perception of those treatment needs, differ according to the clinical department visited by the patients.

METHODS

This was a subanalysis of a multicenter, cross-sectional, observational survey study. Data from the main study were classified according to the clinical department visited by the patient: psychiatric group (P-group), geriatric internal medicine group (G-group), and neurology group (N-group). The treatment needs of patients and caregivers were defined as "the symptom that causes them the most distress", and the frequency of each answer was tabulated.

RESULTS

This subanalysis included 134, 65, and 49 patient-caregiver pairs in the P-, G-, and N-groups, respectively. Statistically significant differences in patient background characteristics such as patient age; initial symptom domains; use of cholinesterase inhibitors, levodopa, antipsychotics, and Yokukansan; and total scores of the Mini-Mental State Examination, Neuropsychiatric Inventory-12, and Movement Disorder Society-Unified Parkinson's Disease Rating Scale Parts II and III were shown among the three subgroups. While there were no differences in patients' treatment needs among the subgroups, residual analysis showed that in the N-group, parkinsonism was more of a problem than other symptom domains (p = 0.001). There were significant differences in caregivers' treatment needs among the three subgroups (p < 0.001). The patient-physician concordance rates for the symptom domains that caused patients the most distress were: P-group, 42.9% (kappa coefficient [κ] = 0.264); G-group, 33.3% (κ = 0.135), and N-group, 67.6% (κ = 0.484). The caregiver-physician concordance rates for the symptom domains that caused the caregivers the most distress were: P-group, 54.8% (κ = 0.351), G-group, 50.0% (κ = 0.244), and N-group, 47.4% (κ = 0.170).

CONCLUSION

This subanalysis revealed differences in the treatment needs of patients with DLB and their caregivers according to the clinical department they attended. There might be a lack of awareness of those treatment needs by the attending physicians, regardless of their specialty.

TRIAL REGISTRATION

UMIN Clinical Trials Registry UMIN000041844.

Noradrenergic and cholinergic systems take centre stage in neuropsychiatric diseases of ageing

Noradrenergic and cholinergic systems are among the most vulnerable brain systems in neuropsychiatric diseases of ageing, including Alzheimer's disease, Parkinson's disease, Lewy body dementia, and progressive supranuclear palsy. As these systems fail, they contribute directly to many of the characteristic cognitive and psychiatric symptoms. However, their contribution to symptoms is not sufficiently understood, and pharmacological interventions targeting noradrenergic and cholinergic systems have met with mixed success. Part of the challenge is the complex neurobiology of these systems, operating across multiple timescales, and with non-linear changes across the adult lifespan and disease course. We address these challenges in a detailed review of the noradrenergic and cholinergic systems, outlining their roles in cognition and behaviour, and how they influence neuropsychiatric symptoms in disease. By bridging across levels of analysis, we highlight opportunities for improving drug therapies and for pursuing personalised medicine strategies.

Cholinergic Antagonists and Behavioral Disturbances in Neurodegenerative Diseases

Cholinergic antagonists interfere with synaptic transmission in the central nervous system and are involved in pathological processes in patients with neurocognitive disorders (NCD), such as behavioral and psychological symptoms of dementia (BPSD). In this commentary, we will briefly review the current knowledge on the impact of cholinergic burden on BPSD in persons with NCD, including the main pathophysiological mechanisms. Given the lack of clear consensus regarding symptomatic management of BPSD, special attention must be paid to this preventable, iatrogenic condition in patients with NCD, and de-prescription of cholinergic antagonists should be considered in patients with BPSD.

Dopaminergic connectivity reconfiguration in the dementia with Lewy bodies continuum

INTRODUCTION

The impairment of nigrostriatal dopaminergic network is a core feature of dementia with Lewy bodies (DLB). The involvement and reconfiguration of extranigrostriatal dopaminergic circuitries in the DLB continuum is still theme of debate. We aim to investigate in vivo the dynamic changes of local and long-distance dopaminergic networks across DLB continuum.

METHODS

Forty-nine patients (including 29 with dementia and 20 prodromal cases) and fifty-two controls entered the study. Each subject underwent a standardized clinical and neurological examination and performed Brain SPECT to measuring brain dopamine transporter (DAT) density. Spatially normalized images underwent the occipital-adjusted specific binding to obtain parametric data. The ANCOVA was applied to assess ¹²³I-FP-CIT differences between pDLB, overt-DLB and CG, considering age, gender, and motor impairment as variables of no interest. Between-nodes correlation analysis measured molecular connectivity within the ventral and dorsal dopaminergic networks.

RESULTS

Prodromal DLB and DLB patients showed comparable nigrostriatal deficits in basal ganglia regions compared with CG. Molecular connectivity analyses revealed extensive connectivity losses, more in ventral than in dorsal dopaminergic network in DLB dementia. Conversely, the prodromal group showed increased connectivity compared to CG, mostly putamen-thalamus-cortical and striatal-cortical connectivity.

CONCLUSIONS

This study indicates a comparable basal ganglia deficit in nigrostriatal projections in DLB continuum and supports a different reorganization of extra-striatal dopaminergic connectivity in the prodromal phases of DLB. The shift from an increased to a decreased bilateral putamen-thalamus-cortex connectivity might be a hallmark of transition from prodromal to dementia DLB stages.

Tailoring the therapeutic interventions for behavioral and psychological symptoms of dementia

INTRODUCTION

Behavioral and psychological symptoms of dementia (BPSD) are symptoms of non-cognitive nature, which frequently develop during the course and different stages of dementia. The diagnosis of BPSD is complex due to symptom variety, and relies on detailed clinical evaluation and medical history. Accurate assessment of BPSD is crucial in order to tailor therapeutic intervention (non-pharmacological and pharmacological) for each individual and monitor patient response to therapy.

AREAS COVERED

This review encompasses the epidemiology, classification, assessment and etiology of BPSD, as well as their impact on caregiver distress, and gives an overview of current and emerging non-pharmacological and pharmacological therapeutic options, as well as potential BPSD biomarkers, in order to provide a framework for improving BPSD diagnosis and developing novel, targeted and specific therapeutic strategies for BPSD.

EXPERT OPINION

Due to the large heterogeneity of BPSD and of the fact that drugs available only alleviate symptoms, finding an adequate treatment is very challenging and often involves a polytherapeutic approach. Non-pharmacologic interventions have shown promising results in improving BPSD, however further research is needed to confirm their beneficial effects. Thus, the modification of pre-existancing as well as the development of novel pharmacologic and non-pharmacologic solutions should be considered for BPSD therapy.

Clinical Effectiveness of Muscarinic Receptor-Targeted Interventions in Neuropsychiatric Disorders: A Systematic Review

BACKGROUND

For decades, treatment of mood disorders, psychoses, anxiety and dementia have been confounded by limited efficacy and high rates of treatment resistance. Preclinical and clinical evidence have highlighted disruption of cholinergic signalling in several neuropsychiatric conditions and examined intervention strategies including acetylcholinesterase inhibitors and nicotinic receptor-targeted intervention. However, the effectiveness of these approaches is often curtailed by on-target side effects. Post mortem studies implicate muscarinic receptor dysregulation in neuropsychiatric pathophysiology; therefore, we conducted a systematic review and meta-analysis to investigate the therapeutic efficacy and safety of muscarinic receptor-targeted interventions in adults with neuropsychiatric disorders.

METHODS

PubMed, EMBASE, PsycINFO, EBSCO and Web of Science were searched using relevant keywords from database inception to 7 August 2022. Randomised, double-blind, placebo-controlled studies were included if they investigated the effect of muscarinic receptor-targeted intervention in adults with a diagnosis of a neuropsychiatric disorder and were published in English. A narrative synthesis approach was adopted to describe the findings. Wherever three or more studies with a similar intervention were available, effect sizes were calculated, and a meta-analysis was performed. Cochrane risk-of-bias-2 tool was utilised to assess the risk of bias, and sensitivity analyses were performed to identify publication bias. Certainty analysis (high, moderate, low and/or very low) was conducted using GRADE criteria.

RESULTS

Overall, 33 studies met the inclusion criteria and 5 were included in the meta-analysis. Despite a limited pool with several different interventions, we found therapeutic efficacy of xanomeline (M₁/M₄ agonist) in primary psychotic disorders plus behavioural and psychological symptoms of dementia. Scopolamine showed a significant antidepressant effect in a combined cohort of major depressive and bipolar disorders in the short-term outcome measure, but no effect following cessation of treatment. Results from bias assessments suggest "very low" certainty in the antidepressant effect of scopolamine. Critical limitations of the current literature included low power, high heterogeneity in the patient population and a lack of active comparators.

CONCLUSION

While the results are not definitive, findings on muscarinic receptor-targeted interventions in several mental disorders are promising in terms of efficacy and safety, specifically in treating schizophrenia, mood disorders, and behavioural and psychiatric symptoms of Alzheimer's disease. However, orthosteric muscarinic receptor-targeted interventions are associated with a range of peripheral adverse effects that are thought to be mediated via M₂/M₃ receptors. The orthosteric binding site of muscarinic acetylcholine receptors is remarkably conserved, posing a challenge for subtype-selective interventions; nonetheless allosteric ligands with biased signalling pathways are now in development. We conclude that adequately powered prospective studies with subtype-selective interventions are required to determine the clinical effectiveness of muscarinic-receptor targeted interventions for the treatment of neuropsychiatric disorders.

Functional Brain Connectivity Patterns Associated with Visual Hallucinations in Dementia with Lewy Bodies

BACKGROUND

The presence of recurrent, complex visual hallucinations (VH) is among the core clinical features of dementia with Lewy bodies (DLB). It has been proposed that VH arise from a disrupted organization of functional brain networks. However, studies are still limited, especially investigating the resting-state functional brain features underpinning VH in patients with dementia.

OBJECTIVE

The aim of the present pilot study was to investigate whether there were any alterations in functional connectivity associated with VH in DLB.

METHODS

Seed-based analyses and independent component analysis (ICA) of resting-state fMRI scans were carried out to explore differences in functional connectivity between DLB patients with and without VH.

RESULTS

Seed-based analyses reported decreased connectivity of the lateral geniculate nucleus, the superior parietal lobule and the putamen with the medial frontal gyrus in DLB patients with VH. Visual areas showed a pattern of both decreased and increased functional connectivity. ICA revealed between-group differences in the default mode network (DMN).

CONCLUSION

Functional connectivity analyses suggest dysfunctional top-down and bottom-up processes and DMN-related alterations in DLB patients with VH. This impairment might foster the generation of false visual images that are misinterpreted, ultimately resulting in VH.

Cholinergic muscarinic M1/M4 receptor networks in dementia with Lewy bodies

Cholinergic dysfunction is central in dementia with Lewy bodies, possibly contributing to the cognitive and psychiatric phenotypes of this condition. We investigated baseline muscarinic M₁/M₄ receptor spatial covariance patterns in dementia with Lewy bodies and their association with changes in cognition and neuropsychiatric symptoms after 12 weeks of treatment with the cholinesterase inhibitor donepezil. Thirty-eight participants (14 cholinesterase inhibitor naive patients, 24 healthy older individuals) underwent ¹²³I-iodo-quinuclidinyl-benzilate (M₁/M₄ receptor assessment) and ^99mTc-exametazime (perfusion) single-photon emission computed tomography scanning. We implemented voxel principal components analysis, producing a series of images representing patterns of inter-correlated voxels across individuals. Linear regression analyses derived specific M₁/M₄ and perfusion spatial covariance patterns associated with patients. A discreet M₁/M₄ pattern that distinguished patients from controls (W_1,19.7 = 16.7, P = 0.001), showed relative decreased binding in right lateral temporal and insula, as well as relative preserved/increased binding in frontal, precuneus, lingual and cuneal regions, implicating nodes within attention and dorsal visual networks. We then derived from patients an M₁/M₄ pattern that correlated with a positive change in mini-mental state examination (r = 0.52, P = 0.05), showing relative preserved/increased uptake in prefrontal, temporal pole and anterior cingulate, elements of attention-related networks. We also generated from patients an M₁/M₄ pattern that correlated with a positive change in neuropsychiatric inventory score (r = 0.77, P = 0.002), revealing relative preserved/increased uptake within a bilateral temporal-precuneal-striatal system. Although in a small sample and therefore tentative, we posit that optimal response of donepezil on cognitive and neuropsychiatric signs in patients with dementia with Lewy bodies were associated with a maintenance of muscarinic M₁/M₄ receptor expression within attentional/executive and ventral visual network hubs, respectively.

Visual hallucinations in neurological and ophthalmological disease: pathophysiology and management

Visual hallucinations are common in older people and are especially associated with ophthalmological and neurological disorders, including dementia and Parkinson's disease. Uncertainties remain whether there is a single underlying mechanism for visual hallucinations or they have different disease-dependent causes. However, irrespective of mechanism, visual hallucinations are difficult to treat. The National Institute for Health Research (NIHR) funded a research programme to investigate visual hallucinations in the key and high burden areas of eye disease, dementia and Parkinson's disease, culminating in a workshop to develop a unified framework for their clinical management. Here we summarise the evidence base, current practice and consensus guidelines that emerged from the workshop.Irrespective of clinical condition, case ascertainment strategies are required to overcome reporting stigma. Once hallucinations are identified, physical, cognitive and ophthalmological health should be reviewed, with education and self-help techniques provided. Not all hallucinations require intervention but for those that are clinically significant, current evidence supports pharmacological modification of cholinergic, GABAergic, serotonergic or dopaminergic systems, or reduction of cortical excitability. A broad treatment perspective is needed, including carer support. Despite their frequency and clinical significance, there is a paucity of randomised, placebo-controlled clinical trial evidence where the primary outcome is an improvement in visual hallucinations. Key areas for future research include the development of valid and reliable assessment tools for use in mechanistic studies and clinical trials, transdiagnostic studies of shared and distinct mechanisms and when and how to treat visual hallucinations.

Cholinergic muscarinic M1 and M4 receptors as therapeutic targets for cognitive, behavioural, and psychological symptoms in psychiatric and neurological disorders

Cholinergic dysfunction is involved in a range of neurological and psychiatric disorders, including schizophrenia, dementia and Lewy body disease (LBD), leading to widespread use of cholinergic therapies. However, such drugs have focused on increasing the availability of acetylcholine (ACh) generally, with relatively little work done on the muscarinic system and specific muscarinic receptor subtypes. In this review, we provide an overview of the major cholinergic pathways and cholinergic muscarinic receptors in the human brain and evidence for their dysfunction in several neurological and psychiatric disorders. We discuss how the selectivity of cholinergic system dysfunction suggests that targeted cholinergic therapeutics to the muscarinic receptor subtypes will be vital in treating several disorders associated with cognitive dysfunction and behavioural and psychological symptoms.

Structural insights into the subtype-selective antagonist binding to the M2 muscarinic receptor

Human muscarinic receptor, M₂ is one of the five subtypes of muscarinic receptors belonging to the family of G protein-coupled receptors. Muscarinic receptors are targets for multiple neurodegenerative diseases. The challenge has been designing subtype selective ligands against one of the five muscarinic receptors. We report high resolution structures of a thermostabilized mutant M₂ receptor bound to a subtype selective antagonist AF-DX 384 and a non-selective antagonist NMS. The thermostabilizing mutation S110R in M₂ was predicted using a theoretical strategy previously developed in our group. Comparison of the crystal structures and pharmacological properties of the M₂ receptor shows that the Arg in the S110R mutant mimics the stabilizing role of the sodium cation, that is known to allosterically stabilize inactive state(s) of class A GPCRs. Molecular Dynamics simulations reveal that tightening of the ligand-residue contacts in M₂ receptor compared to M₃ receptor leads to subtype selectivity of AF-DX 384.

Functional connectivity in dementia with Lewy bodies: A within- and between-network analysis

Dementia with Lewy bodies (DLB) is a common form of dementia and is characterized by cognitive fluctuations, visual hallucinations, and Parkinsonism. The phenotypic expression of the disease may, in part, relate to alterations in functional connectivity within and between brain networks. This resting-state study sought to clarify this in DLB, how networks differed from Alzheimer's disease (AD), and whether they were related to clinical symptoms in DLB. Resting-state networks were estimated using independent component analysis. We investigated functional connectivity changes in 31 DLB patients compared to 31 healthy controls and a disease comparator group of 29 AD patients using dual regression and FSLNets. Within-network connectivity was generally decreased in DLB compared to controls, mainly in motor, temporal, and frontal networks. Between-network connectivity was mainly intact; only the connection between a frontal and a temporal network showed increased connectivity in DLB. Differences between AD and DLB were subtle and we did not find any significant correlations with the severity of clinical symptoms in DLB. This study emphasizes the importance of reduced connectivity within motor, frontal, and temporal networks in DLB with relative sparing of the default mode network. The lack of significant correlations between connectivity measures and clinical scores indicates that the observed reduced connectivity within these networks might be related to the presence, but not to the severity of motor and cognitive impairment in DLB patients. Furthermore, our results suggest that AD and DLB may show more similarities than differences in patients with mild disease.

Reduction of the Anticholinergic Burden Makes It Possible to Decrease Behavioral and Psychological Symptoms of Dementia

OBJECTIVE

The aim of this study was to evaluate the impact of a reduction of the anticholinergic burden (AB) on the frequency and severity of behavioral and psychological symptoms of dementia (BPSD) and their repercussions on the care team (occupational disruptiveness).

METHODS

In this prospective, single-center study in an acute care unit for Alzheimer disease (AD) and related disorders, 125 elderly subjects (mean age: 84.4 years) with dementia presented with BPSD. The reduction of the AB was evaluated by the Anticholinergic Cognitive Burden Scale. BPSD were evaluated with the Neuropsychiatric Inventory-Nursing Home Version (NPI-NH). The effect of the reduction of the AB on the BPSD was studied using logistic regression adjusting for the variables of the comprehensive geriatric assessment.

RESULTS

Seventy-one subjects (56.8%) presenting with probable AD, 32 (25.6%) mixed dementia (AD and vascular), 17 (13.6%) vascular dementia, and 5 (4.0%) Lewy body dementia were included. Reducing the AB by at least 20% enabled a significant decrease in the frequency × severity scores of the NPI-NH (adjusted odds ratio: 3.5; 95% confidence interval: 1.6-7.9) and of the occupational disruptiveness score (adjusted odds ratio: 9.9; 95% confidence interval: 3.6-27.3).

CONCLUSION

AB reduction in elderly subjects with dementia makes is possible to reduce BPSD and caregiver burden. Recourse to treatments involving an AB must be avoided as much as possible in these patients, and preferential use of nonpharmacologic treatment management plans is encouraged.

Biomarker investigations related to pathophysiological pathways in schizophrenia and psychosis

Post-mortem brain investigations of schizophrenia have generated swathes of data in the last few decades implicating candidate genes and protein. However, the relation of these findings to peripheral biomarker indicators and symptomatology remain to be elucidated. While biomarkers for disease do not have to be involved with underlying pathophysiology and may be largely indicative of diagnosis or prognosis, the ideal may be a biomarker that is involved in underlying disease processes and which is therefore more likely to change with progression of the illness as well as potentially being more responsive to treatment. One of the main difficulties in conducting biomarker investigations for major psychiatric disorders is the relative inconsistency in clinical diagnoses between disorders such as bipolar and schizophrenia. This has led some researchers to investigate biomarkers associated with core symptoms of these disorders, such as psychosis. The aim of this review is to evaluate the contribution of post-mortem brain investigations to elucidating the pathophysiology pathways involved in schizophrenia and psychosis, with an emphasis on major neurotransmitter systems that have been implicated. This data will then be compared to functional neuroimaging findings as well as findings from blood based gene expression investigations in schizophrenia in order to highlight the relative overlap in pathological processes between these different modalities used to elucidate pathogenesis of schizophrenia. In addition we will cover some recent and exciting findings demonstrating microRNA (miRNA) dysregulation in both the blood and the brain in patients with schizophrenia. These changes are pertinent to the topic due to their known role in post-transcriptional modification of gene expression with the potential to contribute or underlie gene expression changes observed in schizophrenia. Finally, we will discuss how post-mortem studies may aid future biomarker investigations.

Randomized controlled trial of mibampator for behavioral and psychological symptoms of dementia: comments on the trial and thoughts for future studies

Behavioral and psychological symptoms of dementia (BPSD) frequently arise in people with Alzheimer's disease (AD) and other dementias. They cause significant distress and confer risk to the person and others, in addition to presenting a complex clinical challenge for treatment (Ballard et al., 2009b). There is good evidence for the value of first-line management strategies such as psychological interventions and treatment of concurrent medical conditions, particularly pain, which are known to be effective (Ballard et al., 2009b). However, there are limited pharmacological treatment options for severe aggression, which causes significant risk, and for other severe BPSD which do not respond to first-line approaches. The only pharmacological intervention with an adequate evidence base is the prescription of atypical antipsychotics, where 18 placebo-controlled trials have evaluated the effect of treatment over 6–12 weeks. The literature indicates modest but significant benefits in the treatment of aggression and psychosis with risperidone and aripiprazole (Cohen's d standardized effect size of 0.2), uncertain benefits with olanzapine, and no benefits with quetiapine (Ballard and Howard, 2006; Schneider et al., 2006a; Ballard et al., 2009b; Corbett et al., 2012). Unfortunately, the benefits of longer term prescribing are more limited (Schneider et al., 2006b; Ballard et al., 2008) and there have been increasing concerns regarding the potential for serious adverse outcomes, including accelerated cognitive decline, stroke, and death (Schneider et al., 2006b; Ballard et al., 2009a). There is therefore an urgent imperative to identify more effective pharmacological treatments for severe BPSD which have a better safety profile, particularly for long-term treatment and prophylaxis. Despite this urgency, there has been very little effort toward developing or evaluating potential novel therapies for the treatment of key symptoms such as aggression, psychosis, restlessness, and apathy.

Electroencephalographic dipole source modeling of frontal intermittent rhythmic delta activity

BACKGROUND

Frontal intermittent rhythmic delta activity (FIRDA) on electroencephalography (EEG) consists of a run of rhythmic delta waves with frontal predominance. Although FIRDA is a relatively common abnormal EEG finding, the underlying mechanisms that produce FIRDA remain unclear. The aim of this study was to investigate the cortical source of FIRDA using dipole source modeling.

METHODS

We selected EEG epochs, including typical FIRDAs, from EEG recordings obtained using 25 scalp electrodes on 5 subjects. We averaged these epochs by arranging the negative peaks of the delta waves at the Fp electrodes and estimated dipoles for nine averaged waveforms.

RESULTS

Averaged waveforms were explained by a single-dipole model in seven FIRDAs and by a two-dipole model in the remaining two FIRDAs with high reliability. Estimated dipoles had a radial orientation with respect to the frontal pole and were located in the medial frontal region. The anterior cingulate cortex was the most common dipole location.

CONCLUSIONS

This is the first study to approach the fundamental FIRDA mechanism by dipole source modeling and to clarify that FIRDA may be generated from the medial frontal region, particularly from the anterior cingulate cortex.

Behavioral and psychological symptoms of dementia

Behavioral and psychological symptoms of dementia (BPSD), also known as neuropsychiatric symptoms, represent a heterogeneous group of non-cognitive symptoms and behaviors occurring in subjects with dementia. BPSD constitute a major component of the dementia syndrome irrespective of its subtype. They are as clinically relevant as cognitive symptoms as they strongly correlate with the degree of functional and cognitive impairment. BPSD include agitation, aberrant motor behavior, anxiety, elation, irritability, depression, apathy, disinhibition, delusions, hallucinations, and sleep or appetite changes. It is estimated that BPSD affect up to 90% of all dementia subjects over the course of their illness, and is independently associated with poor outcomes, including distress among patients and caregivers, long-term hospitalization, misuse of medication, and increased health care costs. Although these symptoms can be present individually it is more common that various psychopathological features co-occur simultaneously in the same patient. Thus, categorization of BPSD in clusters taking into account their natural course, prognosis, and treatment response may be useful in the clinical practice. The pathogenesis of BPSD has not been clearly delineated but it is probably the result of a complex interplay of psychological, social, and biological factors. Recent studies have emphasized the role of neurochemical, neuropathological, and genetic factors underlying the clinical manifestations of BPSD. A high degree of clinical expertise is crucial to appropriately recognize and manage the neuropsychiatric symptoms in a patient with dementia. Combination of non-pharmacological and careful use of pharmacological interventions is the recommended therapeutic for managing BPSD. Given the modest efficacy of current strategies, there is an urgent need to identify novel pharmacological targets and develop new non-pharmacological approaches to improve the adverse outcomes associated with BPSD.

Cerebral correlates of psychotic syndromes in neurodegenerative diseases

Psychosis has been recognized as a common feature in neurodegenerative diseases and a core feature of dementia that worsens most clinical courses. It includes hallucinations, delusions including paranoia, aggressive behaviour, apathy and other psychotic phenomena that occur in a wide range of degenerative disorders including Alzheimer's disease, synucleinopathies (Parkinson's disease, dementia with Lewy bodies), Huntington's disease, frontotemporal degenerations, motoneuron and prion diseases. Many of these psychiatric manifestations may be early expressions of cognitive impairment, but often there is a dissociation between psychotic/behavioural symptoms and the rather linear decline in cognitive function, suggesting independent pathophysiological mechanisms. Strictly neuropathological explanations are likely to be insufficient to explain them, and a large group of heterogeneous factors (environmental, neurochemical changes, genetic factors, etc.) may influence their pathogenesis. Clinico-pathological evaluation of behavioural and psychotic symptoms (PS) in the setting of neurodegenerative and dementing disorders presents a significant challenge for modern neurosciences. Recognition and understanding of these manifestations may lead to the development of more effective preventive and therapeutic options that can serve to delay long-term progression of these devastating disorders and improve the patients' quality of life. A better understanding of the pathophysiology and distinctive pathological features underlying the development of PS in neurodegenerative diseases may provide important insights into psychotic processes in general.

Characterization of a new muscarinic toxin from the venom of the Brazilian coral snake Micrurus lemniscatus in rat hippocampus

AIMS

We have isolated a new muscarinic protein (MT-Mlα) from the venom of the Brazilian coral snake Micrurus lemniscatus.

MAIN METHODS

This small protein, which had a molecular mass of 7,048Da, shared high sequence homology with three-finger proteins that act on cholinergic receptors. The first 12 amino acid residues of the N-terminal sequence were determined to be: Leu-Ile-Cys-Phe-Ile-Cys-Phe-Ser-Pro-Thr-Ala-His.

KEY FINDINGS

The MT-Mlα was able to displace the [(3)H]QNB binding in the hippocampus of rats. The binding curve in competition experiments with MT-Mlα was indicative of two types of [(3)H]QNB-binding site with pK(i) values of 9.08±0.67 and 6.17±0.19, n=4, suggesting that various muscarinic acetylcholine receptor (mAChR) subtypes may be the target proteins of MT-Mlα. The MT-Mlα and the M(1) antagonist pirenzepine caused a dose-dependent block on total [(3)H]inositol phosphate accumulation induced by carbachol. The IC(50) values for MT-Mlα and pirenzepine were, respectively, 33.1 and 2.26 nM. Taken together, these studies indicate that the MT-Mlα has antagonist effect on mAChRs in rat hippocampus.

SIGNIFICANCE

The results of the present study show, for the first time, that mAChRs function is drastically affected by MT-Mlα since it not only has affinity for mAChRs but also has the ability to inhibit mAChRs.

Localisation of pre- and postsynaptic cholinergic markers in the human brain

The cholinergic neurotransmission in the central nervous system plays an important role in modulating cognitive processes such as learning, memory, arousal and sleep as well as in modulating locomotor activity. Dysfunction of the central cholinergic system is involved in numerous neuropsychiatric diseases. This review will provide a synopsis on the regional localisation of cholinergic and cholinoceptive structures within the adult human brain. On the cholinergic site data based on the distribution of choline acetyltransferase-immunoreactive structures are in the focus, complemented by data from acetylcholinesterase and vesicular acetylcholine transporter studies. On the cholinoceptive site, the distribution and localisation of receptors that transduce the acetylcholine message, i.e. the muscarinic and the nicotinic acetylcholine receptors is summarized. In addition to these data obtained on post mortem brain an overview of markers which allow for the in vivo monitoring of the cholinergic system in the brain is given. The detailed knowledge on the distribution and localisation of cholinergic markers in human brain will provide further information on the cholinergic circuits of neurotransmission - a prerequisite for the interpretation of in vivo imaging data and the development of selective diagnostic and therapeutic compounds.

Visuospatial deficits predict rate of cognitive decline in autopsy-verified dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is often characterized by pronounced impairment in visuospatial skills, attention, and executive functions. However, the strength of the phenotypic expression of DLB varies and may be weaker in patients with extensive concomitant Alzheimer's disease (AD). To determine whether strength of the DLB clinical phenotype impacts cognitive decline, visuospatial and language tests were retrospectively used to predict 2-year rate of global cognitive decline in 22 autopsy-confirmed DLB patients (21 with concomitant AD) and 44 autopsy-confirmed "pure" AD patients. Generalized estimating equations (GEE) revealed a significant interaction such that poor baseline performances on tests of visuospatial skills were strongly associated with a rapid rate of cognitive decline in DLB but not AD (p < .001). No effect of confrontation naming was found. DLB patients with poor visuospatial skills had fewer neurofibrillary tangles and were more likely to experience visual hallucinations than those with better visuospatial skills. These results suggest that the severity of visuospatial deficits in DLB may identify those facing a particularly malignant disease course and may designate individuals whose clinical syndrome is impacted more by Lewy body formation than AD pathology.

Muscarinic receptor binding activity of polyoxygenated flavones from Melicope subunifoliolata

The bark extract of Melicope subunifoliolata (Stapf) T.G. Hartley showed competitive muscarinic receptor binding activity. Six polymethoxyflavones [melibentin (1); melisimplexin (3); 3,3',4',5,7-pentamethoxyflavone (4); meliternatin (5); 3,5,8-trimethoxy-3',4',6,7-bismethylenedioxyflavone (6); and isokanugin (7)] and one furanocoumarin [5-methoxy-8-geranyloxypsoralen (2)] were isolated from the bark extract. Compounds 2 and 6 were isolated for the first time from M. subunifoliolata. The methoxyflavones (compounds 1, 3, 4, 5, 6, and 7) show moderate inhibition in a muscarinic receptor binding assay, while the furanocoumarin (compound 2) is inactive. The potency of the methoxyflavones to inhibit [(3)H]NMS-muscarinic receptor binding is influenced by the position and number of methoxy substitution. The results suggest these compounds are probably muscarinic modulators, agonists or partial agonists/antagonists.

Psychosis in Alzheimer's Disease: Prevalence, Clinical Characteristics, Symptom Co-Morbidity, and Aetiology

Alzheimer's disease was identified almost a century ago. Cognitive morbidity (deterioration in memory, attention, language, and executive functioning) was regarded as a sufficient index for the description and diagnosis of Alzheimer's disease. Within the cognitive discourse, the importance of neuropsychiatric and neurobehavioural referents was often eschewed. Recent research studies attest to the profound impact of the non-cognitive symptoms on the quality of life of both patient and caregiver. The purpose of this article is to review studies on psychosis in Alzheimer's disease, examine its prevalence, and discuss its manifestation with reference to the association between neuropathology and psychotic disturbances. The importance of clarifying the validity of the construct ‘psychosis in Alzheimer's disease’, the specificity of symptoms, and the phenomenology of subtypes with their distinct clinical and biological associations is addressed.

New approaches to understanding hallucinations in Parkinson's disease: phenomenology and possible origins

The authors review current literature on hallucinations in Parkinson's disease (PD). Recent neuropathological studies showed that hallucinations occur in synucleinopathies and are a significant predictor of Lewy Body depositions. Therefore, hallucinations are a hallmark of PD and of dementia with Lewy Bodies. Visual hallucinations are mostly complex and kinematic; preserved or disturbed insight on the nature of hallucinations is a major prognostic factor, although eventually all hallucinators will present with reduced insight. Current theories on the origin of hallucinations point to visual dysfunction, dream overflow and cognitive impairment, yet objection can be raised on each one of the putative models of hallucinations. Understanding of the origin of hallucinations is required in order to develop treatments: all treatment evaluations were focused in general on psychosis, and only clozapine obtained positive evidence-based ratings on efficacy. However, it is likely that cholinesterase inhibitors, antipsychotics and anti-5-hydroxytryptamine(3) agents and drugs acting on sleep regulation will have different and perhaps opposite effects on different types of hallucinations, whether they are accompanied by disturbed insight, sleep disorders or other psychotic features. Further studies will try to separate phenomenology and responses to treatment and will investigate the relevance of concomitant sleep disorders and abnormality of frontoparietal networks involved in the attention process.

Imidacloprid induces neurobehavioral deficits and increases expression of glial fibrillary acidic protein in the motor cortex and hippocampus in offspring rats following in utero exposure

Imidacloprid, a neonicotinoid, is one of the fastest growing insecticides in use worldwide because of its selectivity for insects. The potential for neurotoxicity following in utero exposure to imidacloprid is not known. Timed pregnant Sprague-Dawley rats (300-350 g) on d 9 of gestation were treated with a single intraperitoneal injection (i.p.) of imidacloprid (337 mg/kg, 0.75 x LD50, in corn oil). Control rats were treated with corn oil. On postnatal day (PND) 30, all male and female offspring were evaluated for (a) acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activity, (b) ligand binding for nicotinic acetylcholine receptors (nAChR) and muscarinic acetylcholine receptors (m2 mAChR), (c) sensorimotor performance (inclined plane, beam-walking, and forepaw grip), and (d) pathological alterations in the brain (using cresyl violet and glial fibrillary acidic protein [GFAP] immunostaining). The offspring of treated mothers exhibited significant sensorimotor impairments at PND 30 during behavioral assessments. These changes were associated with increased AChE activity in the midbrain, cortex and brainstem (125-145% increase) and in plasma (125% increase). Ligand binding densities for [3H]cytosine for alpha4beta2 type nAchR did not show any significant change, whereas [3H]AFDX 384, a ligand for m2mAChR, was significantly increased in the cortex of offspring (120-155% increase) of imidacloprid-treated mothers. Histopathological evaluation using cresyl violet staining did not show any alteration in surviving neurons in various brain regions. On the other hand, there was a rise in GFAP immunostaining in motor cortex layer III, CA1, CA3, and the dentate gyrus subfield of the hippocampus of offspring of imidacloprid-treated mothers. The results indicate that gestational exposure to a single large, nonlethal, dose of imidacloprid produces significant neurobehavioral deficits and an increased expression of GFAP in several brain regions of the offspring on PND 30, corresponding to a human early adolescent age. These changes may have long-term adverse health effects in the offspring.

A comparison of cerebral glucose metabolism in Parkinson's disease, Parkinson's disease dementia and dementia with Lewy bodies

Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) share many similar aspects, and making a clinical diagnosis of one disorder over the other relies heavily on an arbitrary criterion, so-called 1-year rule. This study was designed to search for any difference of metabolic patterns in these two disorders using F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) images. We enrolled 16 patients with PD, 13 patients with PDD, and seven patients with DLB. FDG PET was performed, and images were reconstructed by iterative reconstruction using the computed tomography (CT) images, and were normalized to a standard template. Statistical comparison between groups were performed on a voxel-by-voxel basis using t-statistics (two-sample t-test). Compared with the patients with PD, both PDD and DLB patients showed similar patterns of decreased metabolism in bilateral inferior and medial frontal lobes, and right parietal lobe (P(uncorrected) < 0.001). In a direct comparison, DLB patients had significant metabolic decrease (p(uncorrected) < 0.005) in the anterior cingulate compared with those with PDD. These findings support the concept that PDD and DLB have similar underlying neurobiological characteristics, and that they can be regarded as a spectrum of Lewy body disorders.

Treatment of delusions in dementia with Lewy bodies - response to pharmacotherapy

BACKGROUND

Delusions are clinically important symptoms in dementia with Lewy bodies (DLB). The purpose of this review is to examine the level of evidence for treatment of delusions in DLB.

METHODS

To achieve this objective Medline was searched. Studies were included in the review if they were prospective, separated delusions from hallucinations and were tested in patients with DLB.

RESULTS

The review yielded a total of six studies. Although all studies showed effectiveness, only one study using rivastigmine had an adequate patient sample size and used a randomized controlled design.

CONCLUSION

Further studies are required before a definitive conclusion can be reached about effective treatments.

Relationship between age and subtypes of psychotic symptoms in Parkinson's disease

OBJECTIVE

Psychotic symptoms (PS) in Parkinson's disease (PD) usually develop as a side effect of the dopaminergic therapy and consist of hallucinations and delusions. We observed that PD patients who developed delusions tend to be younger than those with hallucinations and we aimed to investigate the validity of this observation.

METHODS

The medical records of 127 PD patients with PS were reviewed and 76 patients who were on treatment with dopamine agonists with or without levodopa at the time of developing PS were included. Patients were stratified into 3 groups according to the subtypes of PS: patients with solely hallucinations (n = 46), solely delusions (n = 18), and both types (n = 12). The groups were compared with respect to the age-at-onset of PD and PS, duration of PD, Activities of Daily Living (ADL) and motor subscale scores of Unified PD Rating Scale (UPDRS), and levodopa equivalent dose of the dopaminergic agents administered at the time of PS onset.

RESULTS

The mean age-at onset of PD and PS was significantly younger (p = 0.0001) in patients with delusions (49 and 55.9 years) than those with hallucinations (61.9 and 68.9 years). The same parameters were also significantly different (p = 0.002 and p = 0.001, respectively) between the groups of patients with concurrent delusions and hallucinations (51.7 and 57.2 years) and those with only hallucinations. ADL and motor subscale scores were higher in patients with hallucinations (p = 0.016 and p = 0.013) compared with those noted in patients with delusions despite similar disease duration. The mean levodopa equivalent doses of the dopaminergic agents administered at the time of onset of PS did not differ between the groups.

CONCLUSION

This study supported an association of delusions with younger onset of both PD and psychosis as compared with hallucinations. However, additional factors related to this association remain to be elucidated.

The neurobiology of neuropsychiatric syndromes in dementia

PURPOSE OF REVIEW

Neuropsychiatric disturbances in dementia are prevalent, and research is uncovering their neurobiological correlates.

RECENT FINDINGS

Late-onset depression appears to be associated with Alzheimer's disease pathology at autopsy, and lifetime depression episodes may worsen Alzheimer's disease pathology in the hippocampus. Vascular disease and elevated homocysteine increase risk for both late-onset depression and Alzheimer's disease and may partly mediate their relationship. Monoamine changes are robust finding in Alzheimer's disease and may account for many observed depression symptoms. Risk of psychosis of Alzheimer's disease appears to be increased by several genes also implicated in schizophrenia (e.g., catechol-O-methyltransferase, neuregulin-1). Psychosis in dementia with Lewy bodies appears to be related to cholinergic deficits. Alzheimer's disease is associated with changes in the circadian sleep-wake cycles, including decreased night-time melatonin. Sleep apnea may be related to apolipoprotein E genotype and impact cognition in Alzheimer's disease. Rapid eye movement sleep behavior disorder is intricately related to synucleinopathies, such as dementia with Lewy bodies, but synuclein changes may not totally explain this relationship.

SUMMARY

Neuropsychiatric disturbances are a core feature of dementia and worsen many clinical outcomes. Among the most validated syndromes are depression, psychosis, and sleep disturbance of Alzheimer's disease. Neuropathology, neuroimaging, and genetic studies increasingly provide insight into the origins of these psychiatric symptoms in dementia.

In vivo SPECT imaging of muscarinic acetylcholine receptors using (R,R) 123I-QNB in dementia with Lewy bodies and Parkinson's disease dementia

INTRODUCTION

Alterations in cholinergic function have been reported to be associated with dementia. The aim of this study was to investigate differences in the distribution of muscarinic acetylcholine receptors (mAChRs) using (R,R) 123I-iodo-quinuclidinyl-benzilate (QNB) and single photon emission computed tomography (SPECT) in dementia with Lewy bodies (DLB), Parkinson's disease dementia (PDD) and age-matched controls. 123I-QNB binding was also compared to the corresponding cerebral perfusion changes in the same subjects.

METHODS

63 subjects (24 controls, 14 DLB, 25 PDD) underwent 123I-QNB and perfusion 99mTc-exametazine SPECT scanning. Image analysis, using statistical parametric mapping (SPM99), involved spatial normalisation of each image to a customised template, followed by smoothing and intensity normalisation of each image to its corresponding mean whole brain uptake. Group effects and correlations were assessed using two sample t tests and linear regression respectively.

RESULTS

Relative to controls, significant elevation of 123I-QNB binding was apparent in the right occipital lobe in DLB and right and left occipital lobes in PDD (height threshold p<or=0.001 uncorrected). PDD also showed significant loss in uptake in frontal regions and temporal lobes bilaterally that was not present in DLB. These patterns appeared to be independent of any corresponding rCBF changes.

CONCLUSION

Significant elevation of mAChRs in the occipital lobe was associated with DLB and PDD. This may relate to the visual disturbances that are prevalent in these disorders. Further studies are required in order to establish the role of mAChRs in visual function.

Muscarinic receptor subtypes in neuronal and non-neuronal cholinergic function

1 Muscarinic M1-M5 receptors mediate the metabotropic actions of acetylcholine in the nervous system. A growing body of data indicate they also mediate autocrine functions of the molecule. The availability of novel and selective muscarinic agonists and antagonists, as well as in vivo gene disruption techniques, has clarified the roles of muscarinic receptors in mediating both functions of acetylcholine. 2 Selective M1 agonists or mixed M1 agonists/M2 antagonists may provide an approach to the treatment of cognitive disorders, while M3 antagonism, or mixed M2/M3 antagonists, are approved for the treatment of contractility disorders including overactive bladder and chronic obstructive pulmonary disease. Preclinical data suggest that selective agonism of the M4 receptor will provide novel anti-nociceptive agents, while therapeutics-based upon agonism or antagonism of the muscarinic M5 receptor have yet to be reported. 3 The autocrine functions of muscarinic receptors broadly fall into two areas - control of cell growth or proliferation and mediation of the release of chemical mediators from epithelial cells, ultimately causing muscle relaxation. The former particularly are involved in embryological development, oncogenesis, keratinocyte function and immune responsiveness. The latter regulate contractility of smooth muscle in the vasculature, airways and urinary bladder. 4 Most attention has focused on muscarinic M1 or M3 receptors which mediate lymphocyte immunoresponsiveness, cell migration and release of smooth muscle relaxant factors. Muscarinic M4 receptors are implicated in the regulation of keratinocyte adhesion and M2 receptors in stem cell proliferation and development. Little data are available concerning the M5 receptor, partly due to the difficulties in defining the subtype pharmacologically. 5 The autocrine functions of acetylcholine, like those in the nervous system, involve activation of several muscarinic receptor subtypes. Consequently, the role of these subtypes in autocrine, as well neuronal cholinergic systems, significantly expands their importance in physiology and pathophysiology.