Adrenergic receptors in Alzheimer's disease brain: selective increases in the cerebella of aggressive patients

Brexpiprazole: A new option in treating agitation in Alzheimer's dementia-Insights from transgenic mouse models

AIM

Brexpiprazole is the first FDA-approved treatment for agitation associated with dementia due to Alzheimer's disease. Agitation in Alzheimer's dementia (AAD) occurs in high prevalence and is a great burden for patients and caregivers. Efficacy, safety, and tolerability of brexpiprazole were demonstrated in the AAD clinical trials. To demonstrate the agitation-ameliorating effect of brexpiprazole in animals, we evaluated brexpiprazole in two AAD mouse models.

METHODS

The resident-intruder test was conducted in 5- to 6-month-old Tg2576 mice, given vehicle or brexpiprazole (0.01 or 0.03 mg/kg) orally 1 h before the test. Locomotor activity was measured in 6-month-old APPSL-Tg mice given vehicle or brexpiprazole (0.01 or 0.03 mg/kg) orally the evening before the start of locomotor measurement for 3 days.

RESULTS

In the resident-intruder test, Tg2576 mice showed significantly higher attack number and shorter latency to first attack compared to non-Tg mice. In the Tg mice, brexpiprazole treatment (0.03 mg/kg) significantly delayed the latency to first attack and showed a trend toward a decrease in attack number. APPSL-Tg mice (≧6 months old) showed significantly higher locomotion during dark period Phase II (Zeitgeber time [ZT] 16-20) and Phase III (ZT20-24) compared to non-Tg mice, correlating with the clinical observations of late afternoon agitation in Alzheimer's disease. Brexpiprazole treatment (0.01 and 0.03 mg/kg) significantly decreased hyperlocomotion during the Phase III in APPSL-Tg mice.

CONCLUSION

The suppression of attack behavior and the reduction of nocturnal hyperlocomotion in these Tg mice may be indicative of the therapeutic effect of brexpiprazole on AAD, as demonstrated in the clinical trials.

Cognitive Effects of Three β-Adrenoceptor Acting Drugs in Healthy Volunteers and Patients with Parkinson's Disease

Background

Noradrenergic signaling declines in Parkinson's disease (PD) following locus coeruleus neurodegeneration. Epidemiologic studies demonstrate that β-acting drugs slow PD progression.

Objective

The primary objective was to compare the safety and effects of 3 β-adrenoceptor (β-AR) acting drugs on central nervous system (CNS) function after a single dose in healthy volunteers (HVs) and evaluate the effects of multiple doses of β-AR acting drugs in HVs and PD-patients.

Methods

In Part A, HVs received single doses of 32 mg salbutamol, 160μg clenbuterol, 60 mg pindolol and placebo administered in a randomized, 4-way cross-over study. In Part B (randomized cross-over) and Part C (parallel, 2:1 randomized), placebo and/or clenbuterol (20μg on Day 1, 40μg on Day 2, 80μg on Days 3-7) were administered. CNS functions were assessed using the NeuroCart test battery, including pupillometry, adaptive tracking and recall tests.

Results

Twenty-seven HVs and 12 PD-patients completed the study. Clenbuterol improved and pindolol reduced the adaptive tracking and immediate verbal recall performance. Clenbuterol and salbutamol increased and pindolol decreased pupil-to-iris ratios. Clenbuterol was selected for Parts B and C. In Part B, clenbuterol significantly increased performance in adaptive tracking with a tendency toward improved performance in immediate and delayed verbal recall. In Part C trends toward improved performance in immediate and delayed verbal recall were observed in PD-patients. Typical cardiovascular peripheral β2-AR effects were observed with clenbuterol.

Conclusions

This study demonstrates the pro-cognitive effects of clenbuterol in HVs with similar trends in PD-patients. The mechanism of action is likely activation of β2-ARs in the CNS.

Locus Coeruleus and Noradrenergic Pharmacology in Neurodegenerative Disease

Adrenoceptors (ARs) throughout the brain are stimulated by noradrenaline originating mostly from neurons of the locus coeruleus, a brainstem nucleus that is ostensibly the earliest to show detectable pathology in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The α1-AR, α2-AR, and β-AR subtypes expressed in target brain regions and on a range of cell populations define the physiological responses to noradrenaline, which includes activation of cognitive function in addition to modulation of neurometabolism, cerebral blood flow, and neuroinflammation. As these heterocellular functions are critical for maintaining brain homeostasis and neuronal health, combating the loss of noradrenergic tone from locus coeruleus degeneration may therefore be an effective treatment for both cognitive symptoms and disease modification in neurodegenerative indications. Two pharmacologic approaches are receiving attention in recent clinical studies: preserving noradrenaline levels (e.g., via reuptake inhibition) and direct activation of target adrenoceptors. Here, we review the expression and role of adrenoceptors in the brain, the preclinical studies which demonstrate that adrenergic stimulation can support cognitive function and cerebral health by reversing the effects of noradrenaline depletion, and the human data provided by pharmacoepidemiologic analyses and clinical trials which together identify adrenoceptors as promising targets for the treatment of neurodegenerative disease.

Translation, reliability and validity of Persian version of Adolescent/Adult Sensory Profile in dementia

Our study aimed at the reliability and validity of the Persian version of the Adolescent/Adult Sensory Profile (AASP). This study was conducted on 130 people with dementia as well as 77 healthy elderlies. After translating the AASP into Persian, its content validity was determined based on 9 experts working in the same field. Cronbach's alpha and the Intraclass correlation coefficient (ICC) were calculated to assess the internal consistency and test-retest reliability of the Persian version of AASP. The two groups of people with dementia and healthy elderlies were compared in terms of scores in the four quadrants by performing an Independent t-test. All items in the Content Validity Ratio (CVR) and Content Validity Index (CVI) received an acceptable score. The Cronbach's alpha score for different parts of AASP was also calculated (α between 0.894 and 0.916; p < 0.001). The test-retest reliability of sub-tests of AASP was excellent (ICC between 0.885 and 0.948; p < 0.001). There was a statistically significant difference between the healthy Elderlies and dementia persons for low registration, sensory avoiding quadrants (p < 0.05). The Persian version of the AASP questionnaire is a reliable and valid questionnaire for people with dementia in Iran.

Mechanism of stress-induced attacks in an episodic neurologic disorder

Stress is the most common trigger among episodic neurologic disorders. In episodic ataxia type 2 (EA2), physical or emotional stress causes episodes of severe motor dysfunction that manifest as ataxia and dystonia. We used the tottering (tg/tg) mouse, a faithful animal model of EA2, to dissect the mechanisms underlying stress-induced motor attacks. We find that in response to acute stress, activation of α1-adrenergic receptors (α1-Rs) on Purkinje cells by norepinephrine leads to their erratic firing and consequently motor attacks. We show that norepinephrine induces erratic firing of Purkinje cells by disrupting their spontaneous intrinsic pacemaking via a casein kinase 2 (CK2)-dependent signaling pathway, which likely reduces the activity of calcium-dependent potassium channels. Moreover, we report that disruption of this signaling cascade at a number of nodes prevents stress-induced attacks in the tottering mouse. Together, our results suggest that norepinephrine and CK2 are required for the initiation of stress-induced attacks in EA2 and provide previously unidentified targets for therapeutic intervention.

Emotion Processing Dysfunction in Alzheimer's Disease: An Overview of Behavioral Findings, Systems Neural Correlates, and Underlying Neural Biology

We described behavioral studies to highlight emotional processing deficits in Alzheimer's disease (AD). The findings suggest prominent deficit in recognizing negative emotions, pronounced effect of positive emotion on enhancing memory, and a critical role of cognitive deficits in manifesting emotional processing dysfunction in AD. We reviewed imaging studies to highlight morphometric and functional markers of hippocampal circuit dysfunction in emotional processing deficits. Despite amygdala reactivity to emotional stimuli, hippocampal dysfunction conduces to deficits in emotional memory. Finally, the reviewed studies implicating major neurotransmitter systems in anxiety and depression in AD supported altered cholinergic and noradrenergic signaling in AD emotional disorders. Overall, the studies showed altered emotions early in the course of illness and suggest the need of multimodal imaging for further investigations. Particularly, longitudinal studies with multiple behavioral paradigms translatable between preclinical and clinical models would provide data to elucidate the time course and underlying neurobiology of emotion processing dysfunction in AD.

Brain Volume Predicts Behavioral and Psychological Symptoms in Alzheimer's Disease

BACKGROUND

Behavioral and psychological symptoms of dementia (BPSD) are frequent and troublesome for patients and caregivers. Considering possible preventive approaches, a better understanding of underlying neural correlates of BPSD is crucial.

OBJECTIVE

The aim is to assess whether brain regional volume predicts behavioral changes in mild AD.

METHODS

This work took part from the PACO study, a multicenter and prospective study that included 252 patients with mild AD from 2009 to 2014. Fifty-three patients were retained. Forty healthy matched control subjects from the ADNI cohort were included as controls. Voxel-based morphometry analysis was conducted to assess regional brain volume using baseline MRI scans as a predictor of future behavioral changes over a period of 18 months. Behavior was assessed at baseline and longitudinally at 6-month intervals using the shortened form of the Neuropsychiatric Inventory (NPI).

RESULTS

The volume of 23 brain structures in frontal, temporal, parietal, occipital, subcortical regions and cerebellum predicted the evolution of NPI scores. Frontal volume was the most powerful predictor with frontal gyri, anterior cingulate cortex, and orbital gyri being particularly involved.

CONCLUSION

To our knowledge, this is the first study assessing regional brain volumes as predictors of behavioral changes considered at earlier stages of AD. Up to 23 brain structures were associated with an increased risk of developing BPSD. Frontal lobe volume was the strongest predictor of future evolution of NPI. The involvement of multiple structures in the prediction of behavior suggests a role of the main large-scale networks involved in cognition.

Alzheimer's disease: An evolving understanding of noradrenergic involvement and the promising future of electroceutical therapies

Alzheimer's disease (AD) poses a significant global health concern over the next several decades. Multiple hypotheses have been put forth that attempt to explain the underlying pathophysiology of AD. Many of these are briefly reviewed here, but to-date no disease-altering therapy has been achieved. Despite this, recent work expanding on the role of noradrenergic system dysfunction in both the pathogenesis and symptomatic exacerbation of AD has shown promise. The role norepinephrine (NE) plays in AD remains complicated but pre-tangle tau has consistently been shown to arise in the locus coeruleus (LC) of patients with AD decades before symptom onset. The current research reviewed here indicates NE can facilitate neuroprotective and memory-enhancing effects through β adrenergic receptors, while α2A adrenergic receptors may exacerbate amyloid toxicity through a contribution to tau hyperphosphorylation. AD appears to involve a disruption in the balance between these two receptors and their various subtypes. There is also a poorly characterized interplay between the noradrenergic and cholinergic systems. LC deterioration leads to maladaptation in the remaining LC-NE system and subsequently inhibits cholinergic neuron function, eventually leading to the classic cholinergic disruption seen in AD. Understanding AD as a dysfunctional noradrenergic system, provides new avenues for the use of advanced neural stimulation techniques to both study and therapeutically target the earliest stages of neuropathology. Direct LC stimulation and non-invasive vagus nerve stimulation (VNS) have both demonstrated potential use as AD therapeutics. Significant work remains, though, to better understand the role of the noradrenergic system in AD and how electroceuticals can provide disease-altering treatments.

Purkinje Cell-Specific Knockout of Tyrosine Hydroxylase Impairs Cognitive Behaviors

Tyrosine hydroxylase (Th) expression has previously been reported in Purkinje cells (PCs) of rodents and humans, but its role in the regulation of behavior is not understood. Catecholamines are well known for facilitating cognitive behaviors and are expressed in many regions of the brain. Here, we investigated a possible role in cognitive behaviors of PC catecholamines, by mapping and testing functional roles of Th positive PCs in mice. Comprehensive mapping analyses revealed a distinct population of Th expressing PCs primarily in the posterior and lateral regions of the cerebellum (comprising about 18% of all PCs). To identify the role of PC catecholamines, we selectively knocked out Th in PCs using a conditional knockout approach, by crossing a Purkinje cell-selective Cre recombinase line, Pcp2-Cre, with a floxed tyrosine hydroxylase mouse line (Thlox/lox) to produce Pcp2-Cre;Thlox/lox mice. This manipulation resulted in approximately 50% reduction of Th protein expression in the cerebellar cortex and lateral cerebellar nucleus, but no reduction of Th in the locus coeruleus, which is known to innervate the cerebellum in mice. Pcp2-Cre;Thlox/lox mice showed impairments in behavioral flexibility, response inhibition, social recognition memory, and associative fear learning relative to littermate controls, but no deficits in gross motor, sensory, instrumental learning, or sensorimotor gating functions. Catecholamines derived from specific populations of PCs appear to support cognitive functions, and their spatial distribution in the cerebellum suggests that they may underlie patterns of activation seen in human studies on the cerebellar role in cognitive function.

Adrenergic β receptor activation reduces amyloid β1-42-mediated intracellular Zn2+ toxicity in dentate granule cells followed by rescuing impairment of dentate gyrus LTP

Adrenergic β receptor activation prevents human soluble amyloid β (Aβ)-induced impairment of long-term potentiation (LTP) in slices. On the basis of the evidence that human Aβ_1-42-induced impairment of LTP is due to Aβ_1-42-mediated Zn²⁺ toxicity, we postulated that adrenergic β receptor activation reduces Aβ_1-42-mediated intracellular Zn²⁺ toxicity followed by rescuing Aβ_1-42 toxicity. To test the effect of adrenergic β receptor activation, LTP was recorded at perforant pathway-dentate granule cell synapses of anesthetized rats 60 min after Aβ_1-42 injection into the dentate granule cell layer. Human Aβ_1-42-induced impairment of LTP was rescued by co-injection of isoproterenol, an adrenergic β receptor agonist, but not by co-injection of phenylephrine, an adrenergic α₁ receptor agonist. Isoproterenol did not reduce Aβ_1-42 uptake into dentate granule cells, but reduced increase in intracellular Zn²⁺ in dentate granule cells induced by Aβ_1-42. In contrast, phenylephrine did not reduce both Aβ_1-42 uptake and increase in intracellular Zn²⁺ by Aβ_1-42. In the case of human Aβ_1-40 and rat Aβ_1-42, which do not increase intracellular Zn²⁺, human Aβ_1-40- and rat Aβ_1-42-induced impairments of LTP were not rescued by co-injection of isoproterenol. The present study indicates that adrenergic β receptor activation reduces Aβ_1-42-mediated increase in intracellular Zn²⁺ in dentate granule cells, resulting in rescuing Aβ_1-42-induced impairment of LTP. It is likely that noradrenergic neuron activation by stimulating the locus coeruleus is effective for rescuing Aβ_1-42-induced cognitive decline that is caused by intracellular Zn²⁺ dysregulation in the hippocampus.

Resistance, vulnerability and resilience: A review of the cognitive cerebellum in aging and neurodegenerative diseases

In the context of neurodegeneration and aging, the cerebellum is an enigma. Genetic markers of cellular aging in cerebellum accumulate more slowly than in the rest of the brain, and it generates unknown factors that may slow or even reverse neurodegenerative pathology in animal models of Alzheimer's Disease (AD). Cerebellum shows increased activity in early AD and Parkinson's disease (PD), suggesting a compensatory function that may mitigate early symptoms of neurodegenerative pathophysiology. Perhaps most notably, different parts of the brain accumulate neuropathological markers of AD in a recognized progression and generally, cerebellum is the last brain region to do so. Taken together, these data suggest that cerebellum may be resistant to certain neurodegenerative mechanisms. On the other hand, in some contexts of accelerated neurodegeneration, such as that seen in chronic traumatic encephalopathy (CTE) following repeated traumatic brain injury (TBI), the cerebellum appears to be one of the most susceptible brain regions to injury and one of the first to exhibit signs of pathology. Cerebellar pathology in neurodegenerative disorders is strongly associated with cognitive dysfunction. In neurodegenerative or neurological disorders associated with cerebellar pathology, such as spinocerebellar ataxia, cerebellar cortical atrophy, and essential tremor, rates of cognitive dysfunction, dementia and neuropsychiatric symptoms increase. When the cerebellum shows AD pathology, such as in familial AD, it is associated with earlier onset and greater severity of disease. These data suggest that when neurodegenerative processes are active in the cerebellum, it may contribute to pathological behavioral outcomes. The cerebellum is well known for comparing internal representations of information with observed outcomes and providing real-time feedback to cortical regions, a critical function that is disturbed in neuropsychiatric disorders such as intellectual disability, schizophrenia, dementia, and autism, and required for cognitive domains such as working memory. While cerebellum has reciprocal connections with non-motor brain regions and likely plays a role in complex, goal-directed behaviors, it has proven difficult to establish what it does mechanistically to modulate these behaviors. Due to this lack of understanding, it's not surprising to see the cerebellum reflexively dismissed or even ignored in basic and translational neuropsychiatric literature. The overarching goals of this review are to answer the following questions from primary literature: When the cerebellum is affected by pathology, is it associated with decreased cognitive function? When it is intact, does it play a compensatory or protective role in maintaining cognitive function? Are there theoretical frameworks for understanding the role of cerebellum in cognition, and perhaps, illnesses characterized by cognitive dysfunction? Understanding the role of the cognitive cerebellum in neurodegenerative diseases has the potential to offer insight into origins of cognitive deficits in other neuropsychiatric disorders, which are often underappreciated, poorly understood, and not often treated.

Neuropharmacology of the Neuropsychiatric Symptoms of Dementia and Role of Pain: Essential Oil of Bergamot as a Novel Therapeutic Approach

Aging of the population makes of dementia a challenge for health systems worldwide. The cognitive disturbance is a serious but not the only issue in dementia; behavioral and psychological syndromes known as neuropsychiatric symptoms of dementia remarkably reduce the quality of life. The cluster of symptoms includes anxiety, depression, wandering, delusions, hallucinations, misidentifications, agitation and aggression. The pathophysiology of these symptoms implicates all the neurotransmitter systems, with a pivotal role for the glutamatergic neurotransmission. Imbalanced glutamatergic and GABAergic neurotransmissions, over-activation of the extrasynaptic N-methyl-D-aspartate (NMDA) receptors and alterations of the latter have been linked to the development of neuropsychiatric symptoms experienced by almost the entire demented population. Drugs with efficacy and safety for prevention or long term treatment of these disorders are not available yet. Aromatherapy provides the best evidence for positive outcomes in the control of agitation, the most resistant symptom. Demented patients often cannot verbalize pain, resulting in unrelieved symptoms and contributing to agitation. Bergamot essential oil provides extensive preclinical evidence of analgesic properties. Incidentally, the essential oil of bergamot induces anxyolitic-like effects devoid of sedation, typical of benzodiazepines, with a noteworthy advantage for demented patients. These data, together with the reported safety profile, form the rational basis for bergamot as a neurotherapeutic to be trialed for the control of behavioral and psychological symptoms of dementia.

The Emerging Role of Altered Cerebellar Synaptic Processing in Alzheimer's Disease

The role of the cerebellum in Alzheimer's disease (AD) has been neglected for a long time. Recent studies carried out using transgenic mouse models have demonstrated that amyloid-β (Aβ) is deposited in the cerebellum and affects synaptic transmission and plasticity, sometimes before plaque formation. A wide variability of motor phenotype has been observed in the different murine models of AD, without a consistent correlation with the extent of cerebellar histopathological changes or with cognitive deficits. The loss of noradrenergic drive may contribute to the impairment of cerebellar synaptic function and motor learning observed in these mice. Furthermore, cerebellar neurons, particularly granule cells, have been used as in vitro model of Aβ-induced neuronal damage. An unexpected conclusion is that the cerebellum, for a long time thought to be somehow protected from AD pathology, is actually considered as a region vulnerable to Aβ toxic damage, even at the early stage of the disease, with consequences on motor performance.

Importance of GPCR-Mediated Microglial Activation in Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with impairment of cognition, memory deficits and behavioral abnormalities. Accumulation of amyloid beta (Aβ) is a characteristic hallmark of AD. Microglia express several GPCRs, which, upon activation by modulators, mediate microglial activation and polarization phenotype. This GPCR-mediated microglial activation has both protective and detrimental effects. Microglial GPCRs are involved in amyloid precursor protein (APP) cleavage and Aβ generation. In addition, microglial GPCRs are featured in the regulation of Aβ degradation and clearance through microglial phagocytosis and chemotaxis. Moreover, in response to Aβ binding on microglial Aβ receptors, they can trigger multiple inflammatory pathways. However, there is still a lack of insight into the mechanistic link between GPCR-mediated microglial activation and its pathological consequences in AD. Currently, the available drugs for the treatment of AD are mostly symptomatic and dominated by acetylcholinesterase inhibitors (AchEI). The selection of a specific microglial GPCR that is highly expressed in the AD brain and capable of modulating AD progression through Aβ generation, degradation and clearance will be a potential source of therapeutic intervention. Here, we have highlighted the expression and distribution of various GPCRs connected to microglial activation in the AD brain and their potential to serve as therapeutic targets of AD.

Computational modeling and biomarker studies of pharmacological treatment of Alzheimer's disease (Review)

Alzheimer's disease (AD) is a complex and multifactorial disease. In order to understand the genetic influence in the progression of AD, and to identify novel pharmaceutical agents and their associated targets, the present study discusses computational modeling and biomarker evaluation approaches. Based on mechanistic signaling pathway approaches, various computational models, including biochemical and morphological models, are discussed to explore the strategies that may be used to target AD treatment. Different biomarkers are interpreted on the basis of morphological and functional features of amyloid β plaques and unstable microtubule‑associated tau protein, which is involved in neurodegeneration. Furthermore, imaging and cerebrospinal fluids are also considered to be key methods in the identification of novel markers for AD. In conclusion, the present study reviews various biochemical and morphological computational models and biomarkers to interpret novel targets and agonists for the treatment of AD. This review also highlights several therapeutic targets and their associated signaling pathways in AD, which may have potential to be used in the development of novel pharmacological agents for the treatment of patients with AD. Computational modeling approaches may aid the quest for the development of AD treatments with enhanced therapeutic efficacy and reduced toxicity.

The neurochemistry of agitation in Alzheimer's disease: a systematic review

OBJECTIVE

To provide an up-to-date systematic review of the characteristics, methodology and findings of studies that have investigated the neurochemistry of agitation in Alzheimer's disease (AD).

METHODS

Electronic databases were searched for published peer-reviewed articles which provided data on any neurotransmitter system in relation to agitation in AD. Screening of titles and abstracts and data extraction from full texts were conducted in duplicate.

RESULTS

Forty-five studies were included. Monoamines (serotonin, dopamine and noradrenaline) were most commonly investigated. A variety of methods were used to investigate the neurochemistry underlying agitation in AD and, although there were several conflicting findings, there was evidence of serotonergic deficit, relatively preserved dopaminergic function and compensatory overactivity of postsynaptic noradrenergic neurons in agitation in AD.

CONCLUSIONS

Disruption of the dynamic balance between multiple neurotransmitter systems could impair functional neural networks involved in affective regulation and executive function. Differences in study design and methodology may have contributed to conflicting findings. Future studies that overcome these limitations (e.g. using standardized criteria to define agitation) and employ neuroimaging methods such as MRI/PET to investigate specific neural networks are needed to clarify the role of neurotransmitter alterations in these patients.

Monoaminergic neuropathology in Alzheimer's disease

None of the proposed mechanisms of Alzheimer's disease (AD) fully explains the distribution patterns of the neuropathological changes at the cellular and regional levels, and their clinical correlates. One aspect of this problem lies in the complex genetic, epigenetic, and environmental landscape of AD: early-onset AD is often familial with autosomal dominant inheritance, while the vast majority of AD cases are late-onset, with the ε4 variant of the gene encoding apolipoprotein E (APOE) known to confer a 5-20 fold increased risk with partial penetrance. Mechanisms by which genetic variants and environmental factors influence the development of AD pathological changes, especially neurofibrillary degeneration, are not yet known. Here we review current knowledge of the involvement of the monoaminergic systems in AD. The changes in the serotonergic, noradrenergic, dopaminergic, histaminergic, and melatonergic systems in AD are briefly described. We also summarize the possibilities for monoamine-based treatment in AD. Besides neuropathologic AD criteria that include the noradrenergic locus coeruleus (LC), special emphasis is given to the serotonergic dorsal raphe nucleus (DRN). Both of these brainstem nuclei are among the first to be affected by tau protein abnormalities in the course of sporadic AD, causing behavioral and cognitive symptoms of variable severity. The possibility that most of the tangle-bearing neurons of the LC and DRN may release amyloid β as well as soluble monomeric or oligomeric tau protein trans-synaptically by their diffuse projections to the cerebral cortex emphasizes their selective vulnerability and warrants further investigations of the monoaminergic systems in AD.

G-protein coupled receptors as therapeutic targets for neurodegenerative and cerebrovascular diseases

Neurodegenerative and cerebrovascular diseases are frequent in elderly populations and comprise primarily of dementia (mainly Alzheimer's disease) Parkinson's disease and stroke. These neurological disorders (NDs) occur as a result of neurodegenerative processes and represent one of the most frequent causes of death and disability worldwide with a significant clinical and socio-economic impact. Although NDs have been characterized for many years, the exact molecular mechanisms that govern these pathologies or why they target specific individuals and specific neuronal populations remain unclear. As research progresses, many similarities appear which relate these diseases to one another on a subcellular level. Discovering these similarities offers hope for therapeutic advances that could ameliorate the conditions of many diseases simultaneously. G-protein coupled receptors (GPCRs) are the most abundant receptor type in the central nervous system and are linked to complex downstream pathways, manipulation of which may have therapeutic application in many NDs. This review will highlight the potential use of neurotransmitter GPCRs as emerging therapeutic targets for neurodegenerative and cerebrovascular diseases.

Beta 2-adrenergic receptor activation enhances neurogenesis in Alzheimer's disease mice

Impaired hippocampal neurogenesis is one of the early pathological features of Alzheimer's disease. Enhancing adult hippocampal neurogenesis has been pursued as a potential therapeutic strategy for Alzheimer's disease. Recent studies have demonstrated that environmental novelty activates β₂-adrenergic signaling and prevents the memory impairment induced by amyloid-β oligomers. Here, we hypothesized that β₂-adrenoceptor activation would enhance neurogenesis and ameliorate memory deficits in Alzheimer's disease. To test this hypothesis, we investigated the effects and mechanisms of action of β₂-adrenoceptor activation on neurogenesis and memory in amyloid precursor protein/presenilin 1 (APP/PS1) mice using the agonist clenbuterol (intraperitoneal injection, 2 mg/kg). We found that β₂-adrenoceptor activation enhanced hippocampal neurogenesis, ameliorated memory deficits, and increased dendritic branching and the density of dendritic spines. These effects were associated with the upregulation of postsynaptic density 95, synapsin 1 and synaptophysin in APP/PS1 mice. Furthermore, β₂-adrenoceptor activation decreased cerebral amyloid plaques by decreasing APP phosphorylation at Thr668. These findings suggest that β₂-adrenoceptor activation enhances neurogenesis and ameliorates memory deficits in APP/PS1 mice.

β2-Adrenoceptor agonists as novel, safe and potentially effective therapies for Amyotrophic lateral sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is a chronic and progressive neuromuscular disease for which no cure exists and better treatment options are desperately needed. We hypothesize that currently approved β2-adrenoceptor agonists may effectively treat the symptoms and possibly slow the progression of ALS. Although β2-agonists are primarily used to treat asthma, pharmacologic data from animal models of neuromuscular diseases suggest that these agents may have pharmacologic effects of benefit in treating ALS. These include inhibiting protein degradation, stimulating protein synthesis, inducing neurotrophic factor synthesis and release, positively modulating microglial and systemic immune function, maintaining the structural and functional integrity of motor endplates, and improving energy metabolism. Moreover, stimulation of β2-adrenoceptors can activate a range of downstream signaling events in many different cell types that could account for the diverse array of effects of these agents. The evidence supporting the possible therapeutic benefits of β2-agonists is briefly reviewed, followed by a more detailed review of clinical trials testing the efficacy of β-agonists in a variety of human neuromuscular maladies. The weight of evidence of the potential benefits from treating these diseases supports the hypothesis that β2-agonists may be efficacious in ALS. Finally, ways to monitor and manage the side effects that may arise with chronic administration of β2-agonists are evaluated. In sum, effective, safe and orally-active β2-agonists may provide a novel and convenient means to reduce the symptoms of ALS and possibly delay disease progression, affording a unique opportunity to repurpose these approved drugs for treating ALS, and rapidly transforming the management of this serious, unmet medical need.

Genetic suppression of β2-adrenergic receptors ameliorates tau pathology in a mouse model of tauopathies

Accumulation of the microtubule-binding protein tau is a key event in several neurodegenerative disorders referred to as tauopathies, which include Alzheimer's disease, frontotemporal lobar degeneration, Pick's disease, progressive supranuclear palsy and corticobasal degeneration. Thus, understanding the molecular pathways leading to tau accumulation will have a major impact across multiple neurodegenerative disorders. To elucidate the pathways involved in tau pathology, we removed the gene encoding the beta-2 adrenergic receptors (β2ARs) from a mouse model overexpressing mutant human tau. Notably, the number of β2ARs is increased in brains of AD patients and epidemiological studies show that the use of beta-blockers decreases the incidence of AD. The mechanisms underlying these observations, however, are not clear. We show that the tau transgenic mice lacking the β2AR gene had a reduced mortality rate compared with the parental tau transgenic mice. Removing the gene encoding the β2ARs from the tau transgenic mice also significantly improved motor deficits. Neuropathologically, the improvement in lifespan and motor function was associated with a reduction in brain tau immunoreactivity and phosphorylation. Mechanistically, we provide compelling evidence that the β2AR-mediated changes in tau were linked to a reduction in the activity of GSK3β and CDK5, two of the major tau kinases. These studies provide a mechanistic link between β2ARs and tau and suggest the molecular basis linking the use of beta-blockers to a reduced incidence of AD. Furthermore, these data suggest that a detailed pharmacological modulation of β2ARs could be exploited to develop better therapeutic strategies for AD and other tauopathies.

[(18)F]-(fluoromethoxy)ethoxy)methyl)-1H-1,2,3-triazol-1-yl)propan-2-ol ([(18)F FPTC) a novel PET-ligand for cerebral beta-adrenoceptors

Cerebral β-adrenergic receptors (β-ARs) play important roles in normal brain and changes of β-AR expression are associated with several neuropsychiatric illnesses. Given the high density of β-AR in several brain regions, quantification of β-AR levels using PET is feasible. However, there is a lack of radiotracers with suitable biological properties and meeting safety requirements for use in humans. We developed a PET tracer for β-AR by (18)F-fluorination of 1-((9H-carbazol-4-yl)oxy)-3-4(4-((2-(2-(fluoromethoxy)-ethoxy)methyl)-1H-1,2,3-triazol-1-yl)propan-2-ol ((18)F-FPTC).

METHODS

[(18)F] FPTC was synthesized by Cu(I)-catalyzed alkyne-azide cycloaddition. First, (18)F-PEGylated alkyne was prepared by (18)F-fluorination of the corresponding tosylate. Next (18)F-PEGylated alkyne was reacted with an azidoalcohol derivative of 4-hydroxycarbazol in the presence of the phosphoramidite Monophos as a ligand and Cu(I) as a catalyst. After purification with radio-HPLC, the binding properties of [(18)F FPTC were tested in β-AR-expressing C6-glioma cells in vitro and in Wistar rats in vivo using microPET.

RESULTS

The radiochemical yield of (18)F-PEGylated alkyne was 74%-89%. The click reaction to prepare [(18)F]FPTC proceeded in 10min with a conversion efficiency of 96%. The total synthesis time was 55min from the end of bombardment. Specific activities were >120GBq/μmol. Propranolol strongly and dose-dependently inhibited the binding of both [(125)I]-ICYP and [(18)F]FPTC to C6 glioma cells, with IC50 values in the 50-60 nM range. However, although both FPTC and propranolol inhibited cellular [(125)I]ICYP binding, FPTC decreased [(125)I]ICYP uptake by only 25%, whereas propranolol reduced it by 83%. [(18)F]FPTC has the appropriate lipophilicity to penetrate the blood brain barrier (logP +2.48). The brain uptake reached a maximum within 2min after injection of 20-25MBq [(18)F]FPTC. SUV values ranged from 0.4 to 0.6 and were not reduced by propranolol. Cerebral distribution volume of the tracer (calculated from a Logan plot) was increased rather than decreased after propranolol treatment.

CONCLUSION

'Click chemistry' was successfully applied to the synthesis of [(18)F]FPTC resulting in high radiochemical yields. [(18)F]FPTC showed specific binding in vitro, but not in vivo. Based on the logP value and its ability to block [(125)I]ICYP binding to C6 cells, FPTC may be a lead to suitable cerebral β-AR ligands.

The role of Beta-adrenergic receptor blockers in Alzheimer's disease: potential genetic and cellular signaling mechanisms

According to genetic studies, Alzheimer's disease (AD) is linked to beta-adrenergic receptor blockade through numerous factors, including human leukocyte antigen genes, the renin-angiotensin system, poly(adenosine diphosphate-ribose) polymerase 1, nerve growth factor, vascular endothelial growth factor, and the reduced form of nicotinamide adenine dinucleotide phosphate. Beta-adrenergic receptor blockade is also implicated in AD due to its effects on matrix metalloproteinases, mitogen-activated protein kinase pathways, prostaglandins, cyclooxygenase-2, and nitric oxide synthase. Beta-adrenergic receptor blockade may also have a significant role in AD, although the role is controversial. Behavioral symptoms, sex, or genetic factors, including Beta 2-adrenergic receptor variants, apolipoprotein E, and cytochrome P450 CYP2D6, may contribute to beta-adrenergic receptor blockade modulation in AD. Thus, the characterization of beta-adrenergic receptor blockade in patients with AD is needed.

Advances in the pharmacological treatment of Parkinson's disease: targeting neurotransmitter systems

For several decades, the dopamine precursor levodopa has been the primary therapy for Parkinson's disease (PD). However, not all of the motor and non-motor features of PD can be attributed solely to dopaminergic dysfunction. Recent clinical and preclinical advances provide a basis for the identification of additional innovative therapeutic options to improve the management of the disease. Novel pharmacological strategies must be optimized for PD by: (i) targeting disturbances of the serotonergic, noradrenergic, glutamatergic, GABAergic, and cholinergic systems in addition to the dopaminergic system, and (ii) characterizing alterations in the levels of neurotransmitter receptors and transporters that are associated with the various manifestations of the disease.

Pinpointing beta adrenergic receptor in ageing pathophysiology: victim or executioner? Evidence from crime scenes

G protein-coupled receptors (GPCRs) play a key role in cellular communication, allowing human cells to sense external cues or to talk each other through hormones or neurotransmitters. Research in this field has been recently awarded with the Nobel Prize in chemistry to Robert J. Lefkowitz and Brian K. Kobilka, for their pioneering work on beta adrenergic receptors (βARs), a prototype GPCR. Such receptors, and β2AR in particular, which is extensively distributed throughout the body, are involved in a number of pathophysiological processes. Moreover, a large amount of studies has demonstrated their participation in ageing process. Reciprocally, age-related changes in regulation of receptor responses have been observed in numerous tissues and include modifications of βAR responses. Impaired sympathetic nervous system function has been indeed evoked as at least a partial explanation for several modifications that occur with ageing. This article represents an updated presentation of the current knowledge in the field, summarizing in a systematic way the major findings of research on ageing in several organs and tissues (crime scenes) expressing βARs: heart, vessels, skeletal muscle, respiratory system, brain, immune system, pancreatic islets, liver, kidney and bone.

Aβ damages learning and memory in Alzheimer's disease rats with kidney-yang deficiency

Previous studies demonstrated that Alzheimer's disease was considered as the consequence produced by deficiency of Kidney essence. However, the mechanism underlying the symptoms also remains elusive. Here we report that spatial learning and memory, escape, and swimming capacities were damaged significantly in Kidney-yang deficiency rats. Indeed, both hippocampal Aβ(40) and 42 increases in Kidney-yang deficiency contribute to the learning and memory impairments. Specifically, damage of synaptic plasticity is involved in the learning and memory impairment of Kidney-yang deficiency rats. We determined that the learning and memory damage in Kidney-yang deficiency due to synaptic plasticity impairment and increases of Aβ(40) and 42 was not caused via NMDA receptor internalization induced by Aβ increase. β-Adrenergic receptor agonist can rescue the impaired long-term potential (LTP) in Kidney-yang rats. Taken together, our results suggest that spatial learning and memory inhibited in Kidney-yang deficiency might be induced by Aβ increase and the decrease of β(2) receptor function in glia.

β2-adrenergic receptor and astrocyte glucose metabolism

Astrocyte glucose metabolism functions to maintain brain activity in both normal and stress conditions. Dysregulation of astrocyte glucose metabolism relates to development of neuronal disease, such as multiple sclerosis and Alzheimer's disease. In response to acute stress, beta2-adrenergic receptor is activated and initiates multiple signaling events mediated by Gs, Gi, arrestin, or other effectors depending on specific cellular contexts. In astrocytes, beta2-adrenergic receptor promotes glucose uptake through GLUT1 and accelerates glycogen degradation via coupling to Gs and second messenger cAMP-dependent pathway. Beta2-adrenergic receptor may regulate other steps in astrocyte glucose metabolism, such as lactate production or transduction. Inappropriate regulation of beta2-adrenergic receptor activity can disrupt normal glucose metabolism, and leads to accelerate neuronal disease development. It was demonstrated that the absence of beta2-adrenergic receptor in astrocytes occurred in multiple sclerosis patients, and the increased beta2-adrenergic receptor activity relates to Alzheimer's disease. A clear view of beta2-adrenergic receptor-mediated signaling pathways in regulating astrocyte glucose metabolism could help us to develop neuronal diseases treatment by targeting to the beta2-adrenergic receptor.

Neurotransmitter receptors and cognitive dysfunction in Alzheimer's disease and Parkinson's disease

Cognitive dysfunction is one of the most typical characteristics in various neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease (advanced stage). Although several mechanisms like neuronal apoptosis and inflammatory responses have been recognized to be involved in the pathogenesis of cognitive dysfunction in these diseases, recent studies on neurodegeneration and cognitive dysfunction have demonstrated a significant impact of receptor modulation on cognitive changes. The pathological alterations in various receptors appear to contribute to cognitive impairment and/or deterioration with correlation to diversified mechanisms. This article recapitulates the present understandings and concepts underlying the modulation of different receptors in human beings and various experimental models of Alzheimer's disease and Parkinson's disease as well as a conceptual update on the underlying mechanisms. Specific roles of serotonin, adrenaline, acetylcholine, dopamine receptors, and N-methyl-D-aspartate receptors in Alzheimer's disease and Parkinson's disease will be interactively discussed. Complex mechanisms involved in their signaling pathways in the cognitive dysfunction associated with the neurodegenerative diseases will also be addressed. Substantial evidence has suggested that those receptors are crucial neuroregulators contributing to cognitive pathology and complicated correlations exist between those receptors and the expression of cognitive capacities. The pathological alterations in the receptors would, therefore, contribute to cognitive impairments and/or deterioration in Alzheimer's disease and Parkinson's disease. Future research may shed light on new clues for the treatment of cognitive dysfunction in neurodegenerative diseases by targeting specific alterations in these receptors and their signal transduction pathways in the frontal-striatal, fronto-striato-thalamic, and mesolimbic circuitries.

Distinct adrenergic system changes and neuroinflammation in response to induced locus ceruleus degeneration in APP/PS1 transgenic mice

Degeneration of locus ceruleus (LC) neurons and subsequent reduction of norepinephrine (NE) in LC projection areas represent an early pathological indicator of Alzheimer's disease (AD). In order to study the effects of NE depletion on cortical and hippocampal adrenergic system changes, LC degeneration was induced in 3-month-old APP/PS1 mice by the neurotoxin N-(2-chloroethyl)-N-ethyl-bromo-benzylamine (dsp4). Dsp4 induced a widespread loss of norepinephrine transporter binding in multiple brain structures already at 4.5 months. This was accompanied by changes of α-1-, α-2-, and β-1-adreneroceptor binding sites as well as altered adrenoceptor mRNA expression. In parallel, we observed increased micro- and astrogliosis in cortical and hippocampal structures in dsp4-treated groups. In addition, the expression of the pro-inflammatory cytokines CCL2 and IL-1β were induced in both, dsp4-treated and APP/PS1-transgenic mice, whereas IL-1α was only up-regulated in dsp4-treated APP/PS1 mice. Concerning amyloid β (Aβ) deposition, we observed an elevation of Aβ1-42 levels in aged dsp4-treated APP/PS1 mice. These data support the hypothesis that LC degeneration leads to dysregulation of adrenergic receptors and exacerbation of Aβ-induced neuroinflammation, both of which are exploitable for early disease marker development.

Binding of amyloid beta peptide to beta2 adrenergic receptor induces PKA-dependent AMPA receptor hyperactivity

Progressive decrease in neuronal function is an established feature of Alzheimer's disease (AD). Previous studies have shown that amyloid beta (Abeta) peptide induces acute increase in spontaneous synaptic activity accompanied by neurotoxicity, and Abeta induces excitotoxic neuronal death by increasing calcium influx mediated by hyperactive alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors. An in vivo study has revealed subpopulations of hyperactive neurons near Abeta plaques in mutant amyloid precursor protein (APP)-transgenic animal model of Alzheimer's disease (AD) that can be normalized by an AMPA receptor antagonist. In the present study, we aim to determine whether soluble Abeta acutely induces hyperactivity of AMPA receptors by a mechanism involving beta(2) adrenergic receptor (beta(2)AR). We found that the soluble Abeta binds to beta(2)AR, and the extracellular N terminus of beta(2)AR is critical for the binding. The binding is required to induce G-protein/cAMP/protein kinase A (PKA) signaling, which controls PKA-dependent phosphorylation of GluR1 and beta(2)AR, and AMPA receptor-mediated excitatory postsynaptic currents (EPSCs). beta(2)AR and GluR1 also form a complex comprising postsynaptic density protein 95 (PSD95), PKA and its anchor AKAP150, and protein phosphotase 2A (PP2A). Both the third intracellular (i3) loop and C terminus of beta(2)AR are required for the beta(2)AR/AMPA receptor complex. Abeta acutely induces PKA phosphorylation of GluR1 in the complex without affecting the association between two receptors. The present study reveals that non-neurotransmitter Abeta has a binding capacity to beta(2)AR and induces PKA-dependent hyperactivity in AMPA receptors.

Dietary and genetic compromise in folate availability reduces acetylcholine, cognitive performance and increases aggression: critical role of S-adenosyl methionine

Folate deficiency has been associated with age-related neurodegeneration. One direct consequence of folate deficiency is a decline in the major methyl donor, S-adenosyl methionine (SAM). We demonstrate herein that pro-oxidant stress and dietary folate deficiency decreased levels of acetylcholine and impaired cognitive performance to various degrees in normal adult mice (9-12 months of age, adult mice heterozygously lacking 5',10'-methylene tetrahydrofolate reductase, homozygously lacking apolipoprotein E, or expressing human ApoE2, E3 or E4, and aged (2-2.5 year old) normal mice. Dietary supplementation with SAM in the absence of folate restored acetylcholine levels and cognitive performance to respective levels observed in the presence of folate. Increased aggressive behavior was observed among some but not all genotypes when maintained on the deficient diet, and was eliminated in all cases supplementation with SAM. Folate deficiency decreased levels of choline and N-methyl nicotinamide, while dietary supplementation with SAM increased methylation of nicotinamide to generate N-methyl nicotinamide and restored choline levels within brain tissue. Since N-methyl nicotinamide inhibits choline transport out of the central nervous system, and choline is utilized as an alternative methyl donor, these latter findings suggest that SAM may maintain acetylcholine levels in part by maintaining availability of choline. These findings suggest that dietary supplementation with SAM represents a useful therapeutic approach for age-related neurodegeneration which may augment pharmacological approaches to maintain acetylcholine levels, in particular during dietary or genetic compromise in folate usage.

Effects of dietary supplementation with N-acetyl cysteine, acetyl-L-carnitine and S-adenosyl methionine on cognitive performance and aggression in normal mice and mice expressing human ApoE4

In addition to cognitive impairment, behavioral changes such as aggressive behavior, depression, and psychosis accompany Alzheimer's Disease. Such symptoms may arise due to imbalances in neurotransmitters rather than overt neurodegeneration. Herein, we demonstrate that combined administration of N-acetyl cysteine (an antioxidant and glutathione precursor that protects against A beta neurotoxicity), acetyl-L-carnitine (which raises ATP levels, protects mitochondria, and buffers A beta neurotoxicity), and S-adenosylmethionine (which facilitates glutathione usage and maintains acetylcholine levels) enhanced or maintain cognitive function, and attenuated or prevented aggression, in mouse models of aging and neurodegeneration. Enhancement of cognitive function was rapidly reversed upon withdrawal of the formulation and restored following additional rounds supplementation. Behavioral abnormalities correlated with a decline in acetylcholine, which was also prevented by this nutriceutical combination, suggesting that neurotransmitter imbalance may contribute to their manifestation. Treatment with this nutriceutical combination was able to compensate for lack of dietary folate and vitamin E, coupled with administration of dietary iron as a pro-oxidant (which collectively increase homocysteine and oxidative damage to brain tissue), indicating that it provided antioxidant neuroprotection. Maintenance of neurotransmitter levels and prevention of oxidative damage underscore the efficacy of a therapeutic approach that utilizes a combination of neuroprotective agents.

Activation of beta2-adrenergic receptor stimulates gamma-secretase activity and accelerates amyloid plaque formation

Amyloid plaque is the hallmark and primary cause of Alzheimer disease. Mutations of presenilin-1, the gamma-secretase catalytic subunit, can affect amyloid-beta (Abeta) production and Alzheimer disease pathogenesis. However, it is largely unknown whether and how gamma-secretase activity and amyloid plaque formation are regulated by environmental factors such as stress, which is mediated by receptors including beta(2)-adrenergic receptor (beta(2)-AR). Here we report that activation of beta(2)-AR enhanced gamma-secretase activity and thus Abeta production. This enhancement involved the association of beta(2)-AR with presenilin-1 and required agonist-induced endocytosis of beta(2)-AR and subsequent trafficking of gamma-secretase to late endosomes and lysosomes, where Abeta production was elevated. Similar effects were observed after activation of delta-opioid receptor. Furthermore, chronic treatment with beta(2)-AR agonists increased cerebral amyloid plaques in an Alzheimer disease mouse model. Thus, beta(2)-AR activation can stimulate gamma-secretase activity and amyloid plaque formation, which suggests that abnormal activation of beta(2)-AR might contribute to Abeta accumulation in Alzheimer disease pathogenesis.

Measuring sensory processing patterns of older Chinese people: psychometric validation of the adult sensory profile

The Adult Sensory Profile (ASP) evaluates the sensory experiences of adults in the categories of auditory, visual, taste/smell, touch, movement, and activity level. It generates four sensory processing patterns including low registration, sensation seeking, sensory sensitivity, and sensation avoiding. This study examined the psychometric properties of the Chinese version of ASP (ASP-CV) for older Hong Kong Chinese adults. Ninety-six participants with normal cognitive functioning and 33 participants with dementia were recruited. All participants were involved in the investigation of internal consistency and construct validity. One sub-sample from each group was selected for test-retest reliability and inter-rater reliability respectively. The ASP-CV demonstrated excellent inter-rater reliability and test-retest reliability (r = 0.91-0.99 and 0.76-0.88 respectively), and satisfactory internal consistency (alpha = 0.58-0.72). The construct validity of ASP-CV was supported by the known-groups method, in which participants with dementia differed significantly from their healthy counterparts in the patterns of 'low registration' (F(1, 127) = 9.69, p = 0.002), 'sensory sensitivity' (F(1, 127) = 4.63, p = 0.033), and 'sensation avoiding' (F(1, 127) = 15.87, p < 0.001). In conclusion, ASP-CV is reliable and valid to measure sensory processing functions of older Hong Kong Chinese people. Further studies are suggested to examine the factor structure of and the equivalence of self-report and proxy report of ASP-CV.

Neuron specific alpha-adrenergic receptor expression in human cerebellum: implications for emerging cerebellar roles in neurologic disease

Recent data suggest novel functional roles for cerebellar involvement in a number of neurologic diseases. Function of cerebellar neurons is known to be modulated by norepinephrine and adrenergic receptors. The distribution of adrenergic receptor subtypes has been described in experimental animals, but corroboration of such studies in the human cerebellum, necessary for drug treatment, is still lacking. In the present work we studied cell-specific localizations of alpha1 adrenergic receptor subtype mRNA (alpha 1a, alpha 1b, alpha 1d), and alpha2 adrenergic receptor subtype mRNA (alpha 2a, alpha 2b, alpha 2c) by in situ hybridization on cryostat sections of human cerebellum (cortical layers and dentate nucleus). We observed unique neuron-specific alpha1 adrenergic receptor and alpha2 adrenergic receptor subtype distribution in human cerebellum. The cerebellar cortex expresses mRNA encoding all six alpha adrenergic receptor subtypes, whereas dentate nucleus neurons express all subtype mRNAs, except alpha 2a adrenergic receptor mRNA. All Purkinje cells label strongly for alpha 2a and alpha 2b adrenergic receptor mRNA. Additionally, Purkinje cells of the anterior lobe vermis (lobules I to V) and uvula/tonsil (lobules IX/HIX) express alpha 1a and alpha 2c subtypes, and Purkinje cells in the ansiform lobule (lobule HVII) and uvula/tonsil express alpha 1b and alpha 2c adrenergic receptor subtypes. Basket cells show a strong signal for alpha 1a, moderate signal for alpha 2a and light label for alpha 2b adrenergic receptor mRNA. In stellate cells, besides a strong label of alpha 2a adrenergic receptor mRNA in all and moderate label of alpha 2b message in select stellate cells, the inner stellate cells are also moderately positive for alpha 1b adrenergic receptor mRNA. Granule and Golgi cells express high levels of alpha 2a and alpha 2b adrenergic receptor mRNAs. These data contribute new information regarding specific location of adrenergic receptor subtypes in human cerebellar neurons. We discuss our observations in terms of possible modulatory roles of adrenergic receptor subtypes in cerebellar neurons responding to sensory and autonomic input signals, and review species differences in cerebellar adrenergic receptor expression.

Neurotransmitter deficits in behavioural and psychological symptoms of Alzheimer's disease

Behavioural and psychological symptoms of dementia (BPSD) occur in 50-90% of Alzheimer's disease (AD) patients. Imbalance of different neurotransmitters (acetylcholine, dopamine, noradrenaline and serotonin), involvement of specific brain regions responsible for emotional activities (parahippocampal gyrus, dorsal raphe and locus coeruleus) and cortical hypometabolism have been proposed as neurobiological substrate of BPSD. Compared to with respect to the neurochemical component, the cholinergic dysfunction seems to play a major role in contributing to BPSD occurrence. This view is also supported by the findings of recent trials with cholinesterase inhibitors, showing that these drugs are effective in controlling and/or improving BPSD, independent on effects on cognitive dysfunction. On the site of psychotropic drugs, atypical or novel antipsychotics represent the reference drugs for treating BPSD, whereas classic antipsychotic drugs for their profile and the potential side effects should be avoided.

The Therapeutic Use of Music on Agitated Behavior in Those With Dementia

Clinically, nursing has long recognized dementia behaviors--agitation, aggression, wandering, and general confusion--to be a significant patient problem as well as a major stress to nursing staff and caregivers. Although there is no cure, much can be done to improve these patients' daily care and, ultimately, their quality of life.

Propranolol for disruptive behaviors in nursing home residents with probable or possible Alzheimer disease: a placebo-controlled study

OBJECTIVE

Enhanced behavioral responsiveness to central nervous system (CNS) norepinephrine (NE) in Alzheimer disease (AD) may contribute to the pathophysiology of disruptive behaviors such as aggression, uncooperativeness with necessary care, irritability, and pressured pacing. We evaluated the efficacy of the beta-adrenergic antagonist propranolol for treatment-resistant disruptive behaviors and overall behavioral status in nursing home residents with probable or possible AD.

METHODS

Thirty-one subjects (age 85 +/- 8 [SD]) with probable or possible AD and persistent disruptive behaviors that interfered with necessary care were randomized to propranolol (n = 17) or placebo (n = 14) in a double-blind study. Stable doses of previously prescribed psychotropics were maintained at pre-study dose during the study. Following a propranolol or placebo dose titration period of up to 9 days (per a dosing algorithm), subjects were maintained on maximum achieved dose for 6 weeks. Primary outcome measures were the Neuropsychiatric Inventory (NPI) and the Clinical Global Impression of Change (CGIC).

RESULTS

Propranolol augmentation (mean achieved dose 106 +/- 38 mg/d) was significantly more effective than placebo for improving overall behavioral status on the total NPI score and CGIC. Improvement in individual NPI items within propranolol subjects was significant only for "agitation/aggression" and "anxiety," and reached borderline statistical significance favoring propranolol over placebo only for "agitation/aggression." Pressured pacing and irritability did not appear responsive to propranolol. In propranolol subjects rated "moderately improved" or "markedly improved" on the CGIC at the end of the double-blind study phase, improvement of overall behavioral status had diminished substantially after 6 months of open-label propranolol treatment.

CONCLUSION

Short-term propranolol augmentation treatment appeared modestly effective and well tolerated for overall behavioral status in nursing home residents with probable or possible AD complicated by disruptive behaviors. Propranolol may be helpful specifically for aggression and uncooperativeness (the behaviors assessed by the NPI "agitation/aggressiveness" item). However, the usefulness of propranolol in this very old and frail population was limited by the high frequency of relative contraindications to beta-adrenergic antagonist treatment and diminution of initial behavioral improvements over time.

Vertigo and Motion Sickness. Part I: Vestibular Anatomy and Physiology

Control of the symptoms of vertigo and motion sickness requires consideration of the neurophysiology of areas both intrinsic and extrinsic to the vestibular system proper. We review the essential anatomy and physiology of the vestibular system and the associated vomiting reflex.

A Model of Consequences of Need-Driven, Dementia-Compromised Behavior

PURPOSE

To extend the original need-driven, dementia-compromised behavior (NDB) model by explaining the consequences of behavioral symptoms for the person with dementia.

ORGANIZING CONSTRUCT AND METHODS

Literature is reviewed and the consequences of expressing needs through need-driven, dementia-compromised behaviors are posited. The consequences of need-driven, dementia-compromised behavior (C-NDB) theory is proposed as a framework to improve understanding of the person with dementia and the consequences of behavioral symptoms and unmet needs.

FINDINGS

Instead of normative verbal communication, people with significant dementia commonly communicate need via non-normative behaviors, making it difficult for caregivers to know that the person has a need and the extent of such need. Not meeting needs of people with dementia affects the person with dementia, care factors, and contextual factors. Cascading effects occur in which not meeting the original need results in new needs and behavioral symptoms.

CONCLUSIONS

This framework indicates the consequences of expressing need behaviorally rather than verbally and shows that caregiver actions might moderate the events that lead to many needs being unresolved. Suggestions are made regarding future research questions deduced from the model.

Effect of the BACE intervention on agitation of people with dementia

PURPOSE

This study tests the effectiveness of the theoretically driven BACE (i.e., Balancing Arousal Controls Excesses) intervention in decreasing agitation in residents of long-term care with moderate or severe dementia.

DESIGN AND METHODS

A pretest-posttest double-blinded experimental design with random assignment was used with a sample of 78 participants. The BACE intervention controls the daily activity schedule so that there is a balance between a person's high-arousal and low-arousal states. The outcome measure was observed agitation.

RESULTS

When time spent in arousal imbalance at pretest was controlled for, a repeated measures analysis of covariance revealed a statistically significant Group x Time interaction, F(1, 69) = 4.26, p =.043, with a partial eta(2) =.06. The average change in agitation for the treatment group was a decrease of 8.43 points (SD = 12.01) from pretest to posttest, an effect size of.7.

IMPLICATIONS

The results of this study support the theory that balancing arousal states by using an individualized approach is effective in decreasing agitation levels of people with dementia.

Growth hormone response to clonidine predicts aggression in Alzheimer's disease

OBJECTIVE

The neurobiology of aggression in Alzheimer's Disease (AD) remains unknown. The objective of this study was to determine if altered central noradrenergic (NE) responsiveness is related to aggression in AD.

METHODS

Fifteen institutionalized, non-depressed elderly (11 males, four females, mean age 81.5 +/- 5.5) with probable AD, severe cognitive impairment (MMSE mean 3.3 +/- 4.6) and significant behavioral disturbances (Neuropsychiatric Inventory (NPI) score > or = 8) were studied. Growth Hormone (GH) response to clonidine challenge (5 microg/kg) was used as an index of central alpha(2)-adrenergic function.

RESULTS

When patients were divided into those with preserved GH response (GH maximum change from baseline > 0, n = 6) and those with blunted GH response (GH maximum change from baseline < or = 0, n = 9) there were significant differences in levels of aggression as measured by the Cohen-Mansfield Agitation Inventory (CAMI) physical aggression subscale (p = .026). Patients with blunted GH response also had significantly higher levels of aggression against others on the retrospective Overt Aggression Scale (p = 0.027).

CONCLUSIONS

Certain types of physically aggressive behaviors are associated with a blunted GH response to clonidine challenge. This finding is consistent with compensatory down-regulation of post-synaptic alpha(2)-adrenergic receptors in response to enhanced NE outflow in aggressive AD patients.