The neuropathology of aminergic nuclei in Alzheimer's disease

Ectopic cell cycle events link human Alzheimer's disease and amyloid precursor protein transgenic mouse models

Nerve cells that re-enter a cell cycle will die rather than divide, a fact that likely underlies the neurodegeneration in Alzheimer's disease (AD). Several mouse models of familial AD have been created, and although many display amyloid plaques in their brains, none captures the extensive pattern of nerve cell death found in the human disease. Using both immunocytochemistry and fluorescent in situ hybridization, we show that neurons in three different mouse models reproduce the ectopic cell cycling found in human AD. The temporal and spatial appearance of the cell cycle events in the mouse closely mimics the human disease progression. The cell-cycle events are evident 6 months before the first amyloid deposits and significantly precede the appearance of the first CD45+ microglia. These data suggest that the ectopic initiation of cell-cycle processes in neurons is an early sign of neuronal distress in both human and mouse AD. The close phenotypic correspondence indicates a previously unsuspected level of fidelity of the mouse model to the human disease. Finally, the relative timing suggests that neither the activated microglia nor the amyloid plaques themselves are necessary to initiate the pathogenic events in AD.

The management of inappropriate vocalisation in dementia: a hierarchical approach

BACKGROUND

Patients with dementia can demonstrate noisy behaviours such as screaming, repetitive speech, moaning and singing. Such behaviours can be grouped under the title of "Inappropriate Vocalisation" which is used in this article to describe any noise making which impacts detrimentally upon patients, families or those in a caring role. Inappropriate vocalisation is notoriously difficult to treat and clinicians may have to rely on a "trial and error" approach when attempting to limit the distress it causes.

OBJECTIVES

This paper applies a hierarchical approach to Behavioural and Psychological Symptoms of Dementia (BPSD) in attempting to tackle inappropriate vocalisation systematically. Nine steps are ranked within three stages, with evidence for each intervention being considered sequentially in terms of the likelihood for success as the authors attempt to review the relevant literature.

METHODS

The authors performed a search of the medline database using the key words "screaming," "shouting," "persistent vocalisation" and "inappropriate vocalisation" combined with the key word "dementia". Further searches of the references of medline generated articles revealed a second group of articles of use in this review.

RESULTS

The search generated 53 reviews, research papers, case studies or letters, 36 of which are referenced in this article and the remaining references drawn from reading by the authors around the subject and related problems.

CONCLUSION

Interventions for inappropriate vocalisation in dementia are not limited to medication. Environmental factors and behavioural approaches are considered ahead of pharmacotherapy as the concepts of Underlying Illness, Hidden Meaning and Empirical Treatments are used to structure consideration of important, and sometimes overlooked, issues including pain, depression and overall level of stimulation.

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.

Depression in the elderly: pathological study of raphe and locus ceruleus

Depressive symptoms in the elderly are common and disabling and constitute a risk factor for the development of Alzheimer's disease (AD). One hypothesis worth exploring is that depression in the elderly is related to development of AD pathology at subcortical sites before such pathology develops in the hippocampus and neocortex. We describe here an autopsy study of the locus ceruleus (LC) and raphe nuclei (RN) in nine subjects with depression and 18 age and sex matched controls that were included in a community-based study of cognitive function and ageing (MRC-CFAS). We found no relationship between depression and (1) mean counts of serotonergic or total RN neuronal profiles (2) noradrenergic or total LC neuronal profiles (3) counts of neurofibrillary tangles in these nuclei, or (4) size of neurones in the RN. Nor were these parameters related to age or sex of the subjects. We conclude that depression in the elderly is unlikely to be related to RN or LC neurone counts or RN cell size or to AD-type pathology in these nuclei. However, because of the small numbers of cases studied and our inability to carry out a full stereological study because of tissue limitations the findings are preliminary.

Depressive symptoms, sex, and risk for Alzheimer's disease

Depression associates with increased risk for dementia and Alzheimer's disease (AD), although it is unclear whether it represents an actual risk factor or a prodrome. To determine the relative hazard of premorbid depressive symptomatology for development of dementia and AD, we studied risk for incident dementia and AD over a 14-year period in 1,357 community-dwelling men and women participating in the 40-year prospective Baltimore Longitudinal Study of Aging. Screening for depressive symptoms, comprehensive medical and neuropsychological evaluations were prospectively collected every 2 years. Time-dependent proportional hazards of development of AD or dementia were calculated separately for men and women, with symptoms of depression detected at 2-, 4-, and 6-year intervals before onset of dementia symptoms. Vascular risk factors were analyzed as covariates. Premorbid depressive symptoms significantly increased risk for dementia, particularly AD in men but not in women. Hazard ratios were approximately two times greater than for individuals without history of depressive symptoms, an effect independent of vascular disease. We conclude that the impact of depressive symptoms on risk for dementia and AD may vary with sex. Further studies assessing separately the role of depression as a risk factor in men and women are necessary.

The effect of citalopram on gene expression profile of Alzheimer lymphocytes

Antidepressants are widely used in the treatment of mood disorders associated with dementia, however little information is available on their effect at the molecular level. In certain neurodegenerative disorders, such as in Alzheimer's disease, lymphocytes have been used to assess mirror changes that thought to occur in the brain. Gene expression profiles of lymphocytes from Alzheimer patients have been shown to differ from that seen with controls. To address this issue in light of antidepressant treatment, we used lymphocytes derived from Alzheimer's disease patients and control individuals to assess the impact of the selective serotonine reuptake inhibitor citalopram on gene expression using a cDNA microarray representing 3200 distinct human genes. Sequences that are differentially regulated after treatment with citalopram were identified and categorized based on similarities in biological functions. This analysis revealed that the overexpression of genes in control and Alzheimer white blood cells by citalopram are implicated in cell survival. Apart from this, citalopram did not markedly alter genes involved in other molecular functions in control cells. In contrast, alteration of genes implicated in ionic currents, cell-adhesion, immune mechanism, and adrenergic functions, were also observed in Alzheimer lymphocytes. The expression of genes of Alzheimer lymphocytes by citalopram is modulated differently which may correlate with the pathology.

Noradrenergic mechanisms in neurodegenerative diseases: a theory

A deficiency in the noradrenergic system of the brain, originating largely from cells in the locus coeruleus (LC), is theorized to play a critical role in the progression of a family of neurodegenerative disorders that includes Parkinson's disease (PD) and Alzheimer's disease (AD). Consideration is given here to evidence that several neurodegenerative diseases and syndromes share common elements, including profound LC cell loss, and may in fact be different manifestations of a common pathophysiological process. Findings in animal models of PD indicate that the modification of LC-noradrenergic activity alters electrophysiological, neurochemical and behavioral indices of neurotransmission in the nigrostriatal dopaminergic system, and influences the response of this system to experimental lesions. In models related to AD, noradrenergic mechanisms appear to play important roles in modulating the activity of the basalocortical cholinergic system and its response to injury, and to modify cognitive functions including memory and attention. Mechanisms by which noradrenaline may protect or promote recovery from neural damage are reviewed, including effects on neuroplasticity, neurotrophic factors, neurogenesis, inflammation, cellular energy metabolism and excitotoxicity, and oxidative stress. Based on evidence for facilitatory effects on transmitter release, motor function, memory, neuroprotection and recovery of function after brain injury, a rationale for the potential of noradrenergic-based approaches, specifically alpha2-adrenoceptor antagonists, in the treatment of central neurodegenerative diseases is presented.

Depression in the elderly: new concepts and therapeutic approaches

Depression is one of the leading causes of suffering in the elderly, but it is often under-diagnosed and under-treated, partly due to the false belief that depression is a common aspect of aging. Depression in the elderly is frequently comorbid with medical illnesses, may often be expressed by somatic complaints, and may be a risk factor for other diseases such as dementia and coronary artery disease. Depression decreases the quality of life and increases disability and the risk of mortality, also due to suicide. Although several effective antidepressant drugs are available, with a favorable therapeutic index, non-pharmacological treatments, such as psychotherapy and exercise, should receive greater attention, since combination therapy is probably more effective.

Effects of beta-amyloid protein on serotoninergic, noradrenergic, and cholinergic markers in neurons of the pontomesencephalic tegmentum in the rat

The effects on serotoninergic, noradrenergic and cholinergic markers on neurons of the pontomesencephalic tegmentum nuclei were studied in rats following local administration of fibrillar beta-amyloid peptide (Abeta1-40) into the left retrosplenial cortex. Focal deposition of Abeta in the retrosplenial cortex resulted in a loss of serotoninergic neurons in the dorsal and median raphe nuclei. The dorsal raphe nucleus showed a statistically significant reduction of 31.7% in the number of serotoninergic neurons and a decrease (up to 17.38%) in neuronal density in comparison with the same parameters in uninjected controls. A statistically significant reduction of 50.3%, together with a significant decrease of 53.94% in the density of serotoninergic neurons, was also observed in the median raphe nucleus as compared with control animals. Furthermore, a significant reduction of 35.07% in the number of noradrenergic neurons as well as a statistically significant decrease of 56.55% in the density of dopamine-beta-hydroxylase-immunoreactive neurons were also found in the locus coeruleus as compared with the corresponding hemisphere in uninjected controls. By contrast, a reduction of 24.37% in the number of choline acetyltransferase-positive neurons and a slight decrease (up to 22.28%) in the density of cholinergic neurons, which were not statistically significant, was observed in the laterodorsal tegmental nucleus in comparison with the same parameters in control animals. These results show that three different neurochemically defined populations of neurons in the pontomesencephalic tegmentum are affected by the neurotoxicity of Abeta in vivo and that Abeta might indirectly affect serotoninergic, noradrenergic and cholinergic innervation in the retrosplenial cortex.

Interactions Between Phasic Alerting and Spatial Orienting: Effects of Normal Aging and Alzheimer's Disease

The effects of aging and Alzheimer's disease (AD) on phasic alerting and exogenous spatial orienting were examined within a single precuing task. Phasic alerting decreased with normal aging and was completely eliminated with AD. AD patients also demonstrated an increased spatial orienting effect, attributable to an increased benefit from spatial orienting that was associated with a decreased benefit from nonselective alerting. These results suggest that performance within the precuing paradigm reflects the product of an interaction between nonselective alerting processes and spatially selective orienting processes. The results also highlight the importance of simultaneously assessing alerting and orienting within the same task, because changes attributable to alerting may otherwise be attributed incorrectly to changes in 1 or more processes associated with spatial orienting.

Behavioral and psychologic symptoms of dementia

Although tremendous strides with regard to identification and treatment of BPSD have been made over the last several decades, much work remains. Presently, BPSD research opportunities are at their greatest. The increasing worldwide social and economic impact of BPSD, however, requires that researchers, clinicians, and scientists develop a global network focused on collaboration and innovation. In particular, research must address cross-culturally applicable methods for assessment, exploration of the environmental relationships of BPSD and the underlying biologic and psychologic substrates, longitudinal evaluation, determination of the frequency and underlying pathogenic mechanisms, and development of a clearly defined treatment method profile with specific reference to different types of BPSD [134].

Crucial role of TrkB ligands in the survival and phenotypic differentiation of developing locus coeruleus noradrenergic neurons

The role of glial cell-line derived neurotrophic factor (GDNF) and neurotrophins in the development of locus coeruleus noradrenergic neurons was evaluated. We found that two neurotrophic factors previously reported to prevent the degeneration of lesioned adult central noradrenergic neurons, GDNF and neurotrophin 3 (NT3), do not play significant roles in the prenatal development of locus coeruleus noradrenergic neurons, as demonstrated by: (1) the lack of alterations in double Gdnf/Nt3 null mutant mice; and (2) the lack of survival-promoting effects of GDNF and/or NT3 in rat E13.5 primary cultures. In contrast, null mutant mice for TrkB, the tyrosine kinase receptor for brain-derived neurotrophic factor and neurotrophin 4, displayed a clear loss of locus coeruleus noradrenergic neurons. In accordance with this, treatment of rat E13.5 primary cultures with TrkB ligands prevented the early loss of noradrenergic neurons and maintained their survival for up to 6 days in vitro. Moreover, an additional 5-10-fold increase in the number of tyrosine hydroxylase positive noradrenergic neurons was detected after 12 hours in culture. This second effect of TrkB ligands involved neither proliferation nor survival, because the number of BrdU- or TUNEL-positive noradrenergic neurons did not change and the effect was elicited by delayed administration of either factor. Because TrkB ligands increased the number of tyrosine hydroxylase-positive cells expressing Phox2a, a paired homeodomain protein required for the development of locus coeruleus noradrenergic neurons, but did not affect the number of Phox2a-positive tyrosine hydroxylase-negative cells, our results suggest that the second effect of TrkB ligands may involve promoting or inducing a noradrenergic phenotype. In summary, our findings suggest that, unlike NT3 and GDNF, TrkB ligands are required and sufficient to promote the development of central noradrenergic neurons.

Depression in Alzheimer's disease: heterogeneity and related issues

Several studies have demonstrated that the great majority of Alzheimer's disease (AD) patients suffer "noncognitive" neuropsychiatric symptoms. Depression is one of the most frequent neuropsychiatric comorbidities of AD. Affecting up to 50% of AD patients, depression in AD is associated with serious negative consequences for patients and their caregivers. Yet available studies on the natural course, etiology, and treatment of depression in AD have been few and equivocal. Heterogeneity in research methodology and etiology of depression in AD might have contributed to inconsistent findings across studies. Recently, the National Institute of Mental Health (NIMH) convened the Depression of Alzheimer's Disease Workgroup, which proposed provisional diagnostic criteria for depression of Alzheimer's Disease (NIMH-dAD). These criteria may provide a framework for future studies to clarify the unresolved issues in nosology, etiology, and treatment of depression in AD. A longitudinal cohort study of depression in incident AD cases may provide further syndrome refinement that would facilitate investigation of the etiology and treatment of depression in AD.

Neuronal cell death is preceded by cell cycle events at all stages of Alzheimer's disease

Cell cycle events play a major role in the loss of neurons in advanced Alzheimer's disease (AD). It is currently unknown, however, whether the same is true for the neuronal losses in early disease stages. To explore this issue we analyzed brain autopsy material from individuals clinically categorized with mild cognitive impairment (MCI), many if not most of whom will progress to AD. Immunocytochemistry for three cell cycle-related proteins, proliferating cell nuclear antigen, cyclin D, and cyclin B, was performed on sections from hippocampus, basal nucleus of Meynert, and entorhinal cortex. The results obtained from MCI cases were compared with material from individuals diagnosed with AD and those without cognitive impairment. In both hippocampus and basal nucleus, there was a significant percentage of cell cycle immunopositive neurons in the MCI cases. These percentages were similar to those found in the AD cases but significantly higher than non-cognitively impaired controls. In entorhinal cortex, the density of cell cycle-positive neurons was greater in MCI than in AD. However, we observed large variations in the percentages of immunopositive neurons from individual to individual. These findings lend support to the hypothesis that both the mechanism of cell loss (a cell cycle-induced death) and the rate of cell loss (a slow atrophy over several months) are identical at all stages of the AD disease process. The implication of the findings for human clinical trials is discussed.

Depression and Alzheimer's disease: symptom or comorbidity?

Alzheimer's disease is the most frequent form of dementia, where behavioral and cognitive disruption symptoms coexist. Depression, apathy, anxiety, and other conduct disorders are the complaints most often reported by caregivers. Fifty subjects were referred to our Institute with a diagnosis of probable Alzheimer's disease. Cognitive impairment was equally distributed among the subjects. Patients, aged 68 to 76 years old, were randomized to receive inhibitors of cholinesterase (Donepezil, 5 mg/day) alone, or inhibitors of cholinesterase plus selective serotonin reuptake inhibitors (SSRIs) (citalopram HBr, 20 mg/day). We followed up all the patients for one year, with particular concern for neuropsychological aspects associated with eventual behavioral changes. Results indicate that SSRI intake seems to be effective for depression, decreasing it and improving quality of life for both patients and caregivers. Side effects in both groups were few, and there were no study withdrawals. This paper discusses the relationship between dementia and depression, and presents our finding that depressive symptoms, if specifically treated, tend to reduce caregiver stress and improve well-being in patients with Alzheimer's disease.

Comorbidity of depression with other medical diseases in the elderly

A major factor in the context of evaluating depression in the elderly is the role of medical problems. With aging there is a rapid increase in the prevalence of a number of medical disorders, including cancer, heart disease, Parkinson's disease, Alzheimer's disease, stroke, and arthritis. In this article, we hope to bring clarity to the definition of comorbidity and then discuss a number of medical disorders as they relate to depression. We evaluate medical comorbidity as a risk factor for depression as well as the converse, that is, depression as a risk factor for medical illness. Most of the disorders that we focus on occur in the elderly, with the exception of HIV infection. This review focuses exclusively on unipolar disorder. The review summarizes the current state of the art and also makes recommendations for future directions.

Depression in Alzheimer's disease: is there a temporal relationship between the onset of depression and the onset of dementia?

Alzheimer's disease (AD) patients often present with concurrent major depression (MD). To investigate the reasons for this comorbidity, e.g. MD being a risk factor for AD, or both diagnoses having a common neurobiology, the temporal relationship between the first onset of AD and of MD during lifetime was investigated-57 out of 146 AD patients had a lifetime diagnosis of MD. The correlation between the ages at onset of MD and dementia was calculated. The incidence of MD in AD patients in several 5-year-intervals before and after the onset of AD was compared with the average incidence of MD in the present AD sample and with the expected incidence of MD in the general population. No significant correlation between the onset of AD and of MD could be found after controlling for age, gender and the Mini-Mental-State. However, the incidence of MD 5 years before and after the onset of AD significantly exceeded the expected incidences-MD is only partially related to AD. However, the increased incidence of MD within 5 years before and after the onset of dementia may indicate that a common neurobiological process causes cognitive decline and depression in a subsample of AD patients.

Depression in Alzheimer's disease: overview and treatment

Psychiatric disturbances affect as many as 90% of patients with Alzheimer's disease (AD) and are a major focus of treatment. Depression is one of the most frequent psychiatric complications of AD, affecting as many as 50% of patients. In this context, depression is a significant public health problem that has a series of serious adverse consequences for patients and their caregivers. There has been little research into the course or treatment of depression associated with AD. This is in part due to the absence of validated operational criteria for defining depression in AD. Recently, the National Institute of Mental Health (NIMH) convened an expert consensus panel to develop draft criteria for depression of Alzheimer's disease (NIMH-dAD) and to establish research priorities in this area. This article provides an overview of recent knowledge with regard to depression in AD with a special emphasis on its treatment. We conclude with recommendations for further research in this area.

The relationship between delusions and depression in Alzheimer's disease

OBJECTIVES

The aim of this investigation was to study the relationship between delusions and depression in Alzheimer's disease (AD).

DESIGN

This was a cross-sectional, case control study.

SETTING

Neuropsychiatry Service, the Johns Hopkins School of Medicine, USA.

PARTICIPANTS

303 community-residing patients with probable AD according to NINCDS/ADRDA criteria were included in the study. Seventy-five patients with delusions only were compared to a control group of 228 patients who had neither delusions nor hallucinations. Patients with only hallucinations or both delusions and hallucinations were excluded.

MEASURES

Patients were assessed clinically for the presence of delusions using the DSM-IV glossary definitions. They were also rated on standardized measures of depression, cognitive impairment, staging of dementia, general medical health, and functional impairment.

RESULTS

There was an association between delusions and depression among patients with AD. Before adjustment for other variables, the presence of depression conferred a 1.8-fold (95% confidence intervals (CI) = 1.0-3.1; p = 0.04) higher risk of delusions. After adjustment for multiple other variables, this risk increased further to 6.8-fold (95% CI = 2.1-21.6; p = 0.001). CONCLUSIONS; Delusions in AD are strongly associated with depression after statistical adjustment for all confounding variables, which might distort this association. This finding has implications for our understanding of the etio-pathogenesis and management of delusions and depression in AD.

Neurturin is a neuritogenic but not a survival factor for developing and adult central noradrenergic neurons

Noradrenergic neurons of the locus coeruleus (LC) express the receptor tyrosine kinase c-ret, which binds ligands of the glial cell line-derived neurotrophic factor (GDNF) family. In the present study, we evaluated the function of neurturin (NTN), a GDNF family ligand whose function on LC neurons is unknown. Interestingly, we found that tyrosine hydroxylase (TH)-positive neurons in the LC express both GFRalpha1 and 2 receptors in a developmentally regulated fashion, suggesting a function for their preferred ligands: GDNF and NTN, respectively. Moreover, our results show that NTN mRNA expression is developmentally down-regulated in the LC and peaks in the postnatal hippocampus and cerebral cortex, during the target innervation period. In order to examine the function of NTN, we next performed LC primary cultures, and found that neither GDNF nor NTN promoted the survival of TH-positive neurons. However, both factors efficiently induced neurite outgrowth in noradrenergic neurons (147% and 149% over controls, respectively). Similarly, grafting of fibroblast cell lines engineered to express high levels of NTN did not prevent the loss of LC noradrenergic neurons in a 6-hydroxydopamine (6-OHDA) lesion model, but induced the sprouting of TH-positive cells. Thus our findings show that NTN does not promote the survival of LC noradrenergic neurons, but induces neurite outgrowth in developing noradrenergic neurons in vitro and in a model of neurodegeneration in vivo. These data, combined with data in the literature, suggest that GDNF family ligands are able to independently regulate neuronal survival and/or neuritogenesis.

The prevalence, diagnosis and treatment of depression in dementia patients in chronic care facilities in the last six months of life

OBJECTIVE

To assess the prevalence, diagnosis and treatment of depression among dementia patients and normal controls in chronic care facilities in the last six months of life.

METHOD

We reviewed perimortal data concerning dementia severity, depressive symptoms and diagnoses, and medication use for 279 dementia patients and 24 normal controls brought to autopsy through an Alzheimer's Disease Resource Center.

RESULTS

Major depression was highly prevalent among both dementia patients and normal controls in chronic care facilities in the last six months of life. This depression was under-diagnosed by physicians. Documentation of depressive symptoms by medical support staff has improved over time. However, physician diagnosis of depression has not improved. Recognition of depression was significantly lower for patients with severe dementia. Depression was under-treated in both dementia patients and normal controls, although treatment rates may be increasing. Anxiolytics and hypnotics were often used in lieu of, or in addition to, antidepressant therapy.

CONCLUSIONS

Major depression was highly prevalent in both dementia patients and normal controls, indicating that depression is an important issue for the elderly in the last six months of life irrespective of cognitive status. Under-diagnosis of depression may be an important clinical issue. As physician diagnosis of depression has not improved with time, further physician training and/or awareness initiatives may be warranted. Depression, a treatable cause of excess morbidity and mortality, was undertreated in all groups studied. However, treatment rates may be improving. The prevalent use of anxiolytics and hypnotics for depressed patients is problematic.

A positive association between 5HT re-uptake binding sites and depression in dementia with Lewy bodies

BACKGROUND

Depression is a common and distressing problem in the context of dementia, and is significantly more common in Dementia with Lewy bodies (DLB) than in Alzheimer's disease. The neurochemical basis for depression in DLB has not been investigated.

AIM

To investigate the association between depression and 5HT transporter re-uptake binding in DLB patients.

METHOD

A representative cohort of dementia patients received annual assessments, which included a standardised evaluation of depression until death. At post-mortem, (3H) cyanoimipramine autoradiography was used to quantify 5HT transporter re-uptake sites in the hippocampus and adjacent temporal cortex (Brodmann Area-BA 36, and 20); and parietal neocortex (BA 7a).

RESULTS

Twenty-one cases were evaluated neurochemically, of whom seven had experienced a major depressive disorder. Major depression was associated with a significant preservation of 5HT transporter re-uptake sites in the parietal neocortex compared with non-affected cases (BA 7a area 1 t = 3.3, P = 0.004; BA 7a area 3 t = 3.8, P = 0.001).

CONCLUSION

This preliminary report is important in challenging some of the assumptions about cortical monoamine functioning in depressed dementia.

Noradrenergic changes, aggressive behavior, and cognition in patients with dementia

BACKGROUND

We wished to examine the integrity of the noradrenergic system in patients with Alzheimer's disease, mixed/other dementias and controls, and possible relationships between changes in the noradrenergic system and the presence of behavioral and psychiatric signs and symptoms in dementia.

METHODS

Alpha(2) adrenoceptor sites were measured by radioligand binding in three cortical regions of 46 individuals with dementia and 33 elderly normal controls together with cortical noradrenaline concentration and locus coeruleus cell and neurofibrillary tangle counts.

RESULTS

The alpha(2) adrenergic receptor density was unaltered in patients with Alzheimer's disease, mixed/other dementias compared with controls; however, there was a loss of locus coeruleus cells in subjects with dementia, reaching 50% within the rostral nucleus. In addition, a significant reduction was seen in the midtemporal cortical noradrenaline concentration (31% decrease) in patients with Alzheimer's disease. In subjects with dementia, there was a positive correlation between aggressive behavior and magnitude of rostral locus coeruleus cell loss, while the reduction in noradrenaline concentration correlated with cognitive impairment.

CONCLUSIONS

Subgroups of patients with Alzheimer's disease may have different neurochemical changes from patients lacking these changes. Therefore, this study may have implications for the treatment of behavioral and psychiatric signs and symptoms in dementia, particularly aggressive behavior in patients with dementia.

Neuropsychiatric disturbance in Alzheimer's disease clusters into three groups: the Cache County study

OBJECTIVE

We investigated the frequency and inter-relationship of neuropsychiatric disturbances in a population sample of persons suffering from Alzheimer's disease (AD).

METHOD

Screening 5,092 elderly residents (90% of the population aged 65 and older) of Cache County, Utah, for dementia, we identified 198 persons with AD using a comprehensive neuropsychiatric examination protocol. This examination included the Neuropsychiatric Inventory (NPI), a widely used measure of dementia-associated neuropsychiatric disturbances.

RESULTS

Overall, 60% of individuals with AD reported one or more neuropsychiatric symptoms. A latent class analysis revealed that these participants could be classified into three groups (classes) based on their neuropsychiatric symptom profile. The largest class included cases with no neuropsychiatric symptoms (40%) or with a mono-symptomatic disturbance (19%). A second class (28%) exhibited a predominantly affective syndrome, while a third class (13%) had a psychotic syndrome.

CONCLUSION

Data from this first US population-based study of AD-associated neuropsychiatric disturbances suggest that a significant majority of persons with AD suffer from one or more neuropsychiatric disturbance. Based on phenomenological study, the spectrum of neuropsychiatric symptoms in AD can be empirically classified into three groups: an affective syndrome, a psychotic syndrome and other neuropsychiatric disturbance. The biologic and predictive validity of this classification merits further investigation.

Alzheimer's disease: a review for the ophthalmologist

Alzheimer's disease is the most prevalent dementia. Definitive diagnosis is made only at autopsy, although "probable" diagnoses are made using clinical criteria. Patients with Alzheimer's disease demonstrate severe deficits in memory with cortical features of language difficulty and visuomotor spatial deficits. They also may present with psychotic symptoms of delusions and hallucinations, and personality and behavioral changes. Advancing age, genetics, and environmental risk factors are important in the development of Alzheimer's disease. Visual abnormalities have been described in Alzheimer's disease and may be related to the development of visual hallucinations. Although palliative treatments exist for the cognitive loss and behavioral symptoms, future treatments will focus on both delay of onset and slowing of progression of the disease. Continued research is needed to further understand this devastating disorder, which may in turn lead to more successful treatments.

Depressive syndromes in dementia

BACKGROUND

Depressive syndromes in dementia are common, treatment is challenging and controlled intervention studies are small in number. The goal of this paper is to review known information about the etiology, epidemiology and treatment of these syndromes, as summarized at the recent Canadian Consensus Conference on Dementia.

METHODS

A number of Medline searches were performed (most recently updated in October 2000) using the subject categories dementia and depression, or apathy or emotional lability and other relevant articles were also reviewed. The background article was edited and amended at the Consensus Conference on Dementia. Final recommendations appearing in the summary article by Patterson et al were accepted by the group consensus process. Clinical discussion and informational updates were added for the current text by the authors.

RESULTS

Depressive syndromes, ranging in severity from isolated symptoms to full depressive disorders, increase in dementia. While clear-cut depressive disorder is increased in this population, sub-syndromal disorders are even more common and cause considerable distress. Antidepressant treatment may improve the quality of life in depressed, demented people, although it is less successful than in those without cognitive impairment and carries more risk of iatrogenic effects.

CONCLUSIONS

Physicians should be alert to the presence of depressive syndromes in dementia. Depressive illness should be treated and, when necessary, referral should be made to an appropriate specialist. Treatment must minimize iatrogenic effects. Although there is some support for treatment of syndromes that do not meet criteria for depressive disorder or dysthymia, the first line of intervention in these situations should involve nonpharmacological approaches.

Suicide and Alzheimer's pathology in the elderly: a case-control study

BACKGROUND

The single most important risk factor for Alzheimer's pathology is age. Elderly individuals are also at increased risk for suicide, but comprehensive studies of the association between Alzheimer's pathology and suicide are lacking. We designed the current study to determine if Alzheimer's disease changes are overrepresented in elderly people committing suicide.

METHODS

The design is a case-control study. Cases (n = 28) were subjects older than 60 years of age who completed suicide. For each case, two age- and gender-matched individuals who died naturally were selected as control subjects (n = 56). Neuropathologic examination of hippocampal sections was performed blindly and included a modified Braak scoring system and semiquantitative assessment of neurofibrillary tangles, amyloid deposition, Lewy bodies, and Lewy-associated neurites. Data were analyzed by conditional logistic regression.

RESULTS

The brains of individuals who committed suicide had higher modified Braak scores than those of matching control subjects (p =.0028). The number of neurofibrillary tangles in CA1 was not an independent predictor of suicide status in the statistical analysis (p =.16), although the distribution was more highly skewed among the cases (75th percentile of 10.5 for cases, vs. 2 for control subjects).

CONCLUSIONS

Severe Alzheimer's disease pathology is overrepresented in elderly patients who complete suicide.

The selective vulnerability of brainstem nuclei to Alzheimer's disease

In a study of thioflavin S-stained serial sections from the entire brainstem, we found that the inferior and superior colliculi and the autonomic, monoaminergic, cholinergic, and classical reticular nuclei were affected with varying degrees of severity and frequencies in 32 patients with Alzheimer's disease, whereas no changes were seen in the brainstems of 26 control subjects. The majority of the affected nuclei in patients with Alzheimer's disease exhibit either neurofibrillary tangles or senile plaques, and only a few display both. However, when sections were immunostained with the antibodies 10D5 and AT8 or ALZ50, both beta-amyloid and hyperphosphorylated epitopes of tau protein were found to be present in various concentrations in all the affected nuclei. Our findings suggest that each brainstem nucleus has a distinct vulnerability to Alzheimer's disease-related pathological changes. Given that each nucleus has idiosyncratic neuroanatomical connections and prevailing neurochemical characteristics, the heterogeneous collection of brainstem nuclei can be considered a suitable anatomical ground for further investigation of selective vulnerability in Alzheimer's disease. The finding of severe pathological changes in some brainstem nuclei also raises the possibility that the dysfunction of these nuclei may contribute to the cognitive defects and increased rates of morbidity and mortality in patients with Alzheimer's disease.

Pharmacotherapy of behavioral and psychological symptoms of dementia: time for a different paradigm?

Behavioral and psychological symptoms of dementia can occur in 60-80% of patients with Alzheimer's disease or other dementing illnesses, and are important in that they are a source of significant caregiver stress and often precipitate nursing home placement. These symptoms, namely, aggression, delusions, hallucinations, apathy, anxiety, and depression, are clinically managed with a variety of psychotropic drugs such as antipsychotics, antidepressants, antiepileptic drugs, and benzodiazepines. Various advances in the neuropathophysiology and pharmacotherapy must be considered in the optimal design of regimens for patients with these symptoms.

The evolution of Alzheimer's disease-related cytoskeletal pathology in the human raphe nuclei

The cross-sectional analyses currently available show that the Alzheimer's disease (AD)-related cytoskeletal alterations within the human brain affect variously susceptible areas of the cerebral cortex in a uniform sequence with very little interpatient variability. This sequence has been divided for research and comparative purposes into six stages (cortical NFT/NT-stages I-VI). Among the subcortical nuclei affected in AD are those belonging to the raphe system. Efforts were focused on the lesions present in these nuclei to see in which of the six stages the AD-related cytoskeletal anomalies begin and whether a correlation exists between the AD-related pathology developing within the cerebral cortex and the cytoskeletal damage that occurs in the nuclei of the raphe system. To this end, serial sections from the brainstems of 27 post-mortem cases with stages I-VI of cortical cytoskeletal lesions were examined. The cytoskeletal pathology was visualized using the modified silver iodide-Gallyas staining technique and the antibody AT8. The latter is directed specifically against the abnormally phosphorylated cytoskeletal protein tau. The dorsal raphe nucleus manifests the cytoskeletal lesions early on (stages I-II). The central and linear raphe nuclei, by contrast, do so initially in stages III-IV, and the caudal raphe nuclei register the first changes in stages V-VI. In stages V and VI, the dorsal raphe nucleus displays the most severe cytoskeletal pathology within the raphe system, followed by the central and linear raphe nuclei, whereas the cytoskeletal anomalies in the caudal raphe nuclei are slight. The developing damage within the nuclei of the raphe system correlates with the stages I-VI and, furthermore, progresses in the oral raphe nuclei in close connection with the evolution of the pathological process in cortical projection destinations of these nuclei. As the source of the ascending serotonergic system, the involvement of the oral raphe nuclei may be partially responsible for the early manifestation of the non-cognitive and emotional deficiencies possibly traceable to dysfunctions within the ascending serotonergic system.

Neurobehavioral and neuropsychiatric symptoms in Alzheimer's disease: characteristics and treatment

Neuropsychiatric symptoms are common in Alzheimer's disease. Personality changes, mood disturbance, and psychosis are frequently seen and may coexist in the same patient. Neuropsychiatric symptoms may signal the onset of disease and often fluctuate and recur. These symptoms are associated with a more rapid cognitive and functional decline that can lead to institutionalization. Cholinergic therapy, disease-modifying therapy, and psychotropic medications can improve these symptoms.

Immunocytochemical study of the dorsal and median raphe nuclei in patients with Alzheimer's disease prospectively assessed for behavioural changes

The dorsal and median raphe nuclei were examined with immunocytochemistry to display the 5-HT neurones in 16 cases of post-mortem-proven Alzheimer's disease (AD) and 12 age and sex-matched controls. The AD cases had been prospectively assessed during life for expression of behavioural changes as well as for cognitive decline. A significant (P < 0.001) 41% reduction in density of dorsal raphe neurones was found along with a significant (P < 0.02) 29% reduction in density of median raphe neurones in AD. There were significantly more neurofibrillary tangles in both dorsal and median raphe nuclei in AD than in controls (P < 0.001). There was no correlation between reduction in neurone density in these nuclei and behavioural change, cognitive decline, neurofibrillary tangle counts in these nuclei or plaque and tangle pathology in frontal and temporal cortex. It was concluded from these findings that the raphe nuclei are significantly affected by the pathology of AD and that plasticity in the 5-HT system is the probable reason for the lack of correlation of reduced 5-HT neurone density and clinical disease parameters.

Depression and risk of cognitive decline and Alzheimer's disease. Results of two prospective community-based studies in The Netherlands

BACKGROUND

Depression may be associated with cognitive decline in elderly people with impaired cognition.

AIMS

To investigate whether depressed elderly people with normal cognition are at increased risk of cognitive decline and Alzheimer's disease.

METHODS

Two independent samples of older people with normal cognition were selected from the community-based Amsterdam Study of the Elderly (AMSTEL) and the Longitudinal Aging Study Amsterdam (LASA). In AMSTEL, depression was assessed by means of the Geriatric Mental State Schedule. Clinical diagnoses of incident Alzheimer's disease were made using a two-step procedure. In LASA, depression was assessed with the Center for Epidemiologic Studies Depression Scale. Cognitive decline was defined as a drop of > or = 3 on the Mini-Mental State Examination at follow-up.

RESULTS

Both in the AMSTEL and the LASA sample, depression was associated with an increased risk of Alzheimer's disease and cognitive decline, respectively, but only in subjects with higher levels of education.

CONCLUSIONS

In a subgroup of more highly educated elderly people, depression may be an early manifestation of Alzheimer's disease before cognitive symptoms become apparent.

Brain alterations in depression

This article describes a number of studies by our research group to find brain structures that may be involved in the symptoms of idiopathic depression, depression in Alzheimer's disease and depression in Parkinson's disease. Until recently, idiopathic depression has generally been related to deficiencies of aminergic systems. In Alzheimer patients we found a strong decrease in the number of neurons in the locus coeruleus and brain noradrenaline concentrations, but in depressed Alzheimer patients we did not find an extra de crease. This is in agreement with the finding that there is no cell loss in the locus coeruleus in idiopathic depression. We did find, however, that the number of corticotropin-releasing hormone-, vasopressin- and oxytocin expressing neurons, the number of corticotropin-releasing hormone neurons co-expressing vasopressin and the amount of corticotropin-releasing hormone -mRNA in idiopathic depression were strongly increased in the paraventricular nucleus of the hypothalamus. This result supports the hypothesis on the pathogenetic involvement of the hypothalamo-pituitary-adrenal axis in depression and is of clinical relevance, since it may provide a theoretical rationale for antidepressive therapy with CRH antagonists.

Relationship of behavioral and psychological symptoms to cognitive impairment and functional status in Alzheimer's disease

OBJECTIVE

This cross-sectional study examined the relationship of behavioral and psychological symptoms to cognitive and functional impairment in Alzheimer's disease (AD).

DESIGN

One hundred and fourteen patients were evaluated consecutively at a university-affiliated outpatient memory disorders clinic and diagnosed with possible or probable Alzheimer's disease (AD) according to NINCDS-ADRDA criteria. Subjects were assessed with the Behavioral Pathology in Alzheimer's Disease Scale (BEHAVE-AD), Revised Memory and Behavior Problem Checklist (RMBPC), Blessed Dementia Scale (BDS), and Mini-Mental State Examination (MMSE).

RESULTS

Several symptoms of behavioral pathology showed associations with MMSE scores, including activity disturbances, delusions, and hallucinations. After controlling for the variance associated with the MMSE, activity disturbances, diurnal disturbances, delusions, and hallucinations were linked with BDS scores.

CONCLUSIONS

The results suggest that some non-cognitive symptoms may be related to the neurobiologic mechanisms underlying the increased cognitive dysfunction in AD. Specific symptoms of behavioral pathology may also impact a patient's ability to perform important self-maintenance behaviors.

Cortical cholinergic denervation elicits vascular A beta deposition

Selective destruction of the cholinergic nucleus basalis magnocellularis (nbm) in the rabbit by the p75 neurotrophin receptor (NTR) immunoglobulin G (IgG) complexed to the toxin saporin leads to the deposition of amyloid-beta (A beta) in and around cerebral blood vessels. In some instances, the perivascular A beta resemble the diffuse deposits observed in Alzheimer's disease (AD). We propose that cortical cholinergic deprivation results, among other perturbations, in the loss of vasodilation mediated by acetylcholine. In addition to a dysfunctional cerebral blood flow, alterations in vascular chemistry affecting endothelial and smooth muscle cells may result in cerebral hypoperfusion and a breached blood-brain barrier (BBB). The selective removal of the rabbit nbm and A beta accumulation may serve as an important nontransgenic, and more physiological, model for the testing of pharmacological and immunological agents designed to control the deposition and the deleterious effects of A beta in AD.

[Expressions of depression in Alzheimer's disease. The current scientific debate]

This overview analyses findings coming from researches that considered the interaction between depression and Alzheimer's disease (AD).

METHOD

Information was collected from the Medline database and from a reasoned manual analysis of the published studies.

RESULTS

The prevalence of depressive symptoms in patients with AD is elevated (40-50%). The role of depression in the pathogenesis of AD (independent, prodromal symptom, factor of risk) still must be defined. Data on family history of depression suggest that AD could act as stimulus triggering depression from a basis of a genetic vulnerability. From a biological point of view the onset of depression could derive from an unbalance between cholinergic and noradrenergic systems. Psychological understanding sees depression as a reaction of mourning for the cognitive deficit. Current diagnostic instruments validated on patients with AD constitute a good aid for the clinician and the researcher. The identification of depression coexisting with AD is difficult, in absence of clear affective symptoms, since the cognitive, psychomotor and vegetative symptoms belong both to depression and to AD. The affective disorders most frequently reported are major depression and dysthymia. The use of antidepressant drugs with the lowest anticholinergic profile is strongly recommended. Good results have been obtained also using various psychotherapeutic interventions adapted for dementia sufferers.

CONCLUSIONS

The current scientific debate is based on information still limited and sparse. Future analyses should consider a better definition of the hypotheses related to psychopathology in AD, a standardised definition of cases and selection procedures and a prospective longitudinal design.

Neuropsychiatric aspects of Alzheimer's disease

The increase in research studies focusing on neuropsychiatric symptoms over the last decade has greatly increased our knowledge base, particularly with regard to the frequency of these symptoms and their impact on both patients and carers. We still have a poor understanding of the natural course of these symptoms and their biologic correlates, however, and more specific treatment studies are needed to inform clinical management.

Clinical and neurobiological correlates of D10S1423 genotype in Alzheimer's disease

BACKGROUND

In a previous genome survey, we detected associations of alleles at six microsatellite loci with typical-onset AD, including the 234bp allele of the D10S1423 locus. The goal of the current study was to explore the clinical, neuropathological, and neurochemical correlates of the D10S1423 234bp allele in a group of 50 autopsy-confirmed cases of Alzheimer's disease (AD) who lacked other brain diseases.

METHODS

Clinical assessments were performed as part of a longitudinal study of AD and related disorders. Autopsies were performed using standardized methods and diagnoses were made according to established criteria. Genotyping, morphometry, and neurochemical analyses were performed using postmortem brain tissue.

RESULTS

Patients with AD who carried the D10S1423 234bp allele manifested substantial reductions in dopamine levels in all six cortical regions examined. In contrast, carriers tended to have higher concentrations of cortical norepinephrine and revealed a dosage effect of the D10S1423 234bp allele.

CONCLUSIONS

These findings support the results of our genome survey and suggest that a novel susceptibility gene for AD resides near the D10S1423 locus. The characterization of biologically meaningful subtypes, including genotypic subtypes with particular neurobiological derangements, may be important for the advancement of experimental therapeutics in AD.

Clinical and neurobiological correlates of DXS1047 genotype in Alzheimer's disease

BACKGROUND

The goal of the current study was to explore the clinical, neuropathological, and neurochemical correlates of the DXS1047 202 bp allele in a group of 50 autopsy-confirmed cases of Alzheimer's disease (AD) who lacked other concomitant brain diseases. We previously published the results of a genome survey for novel risk loci for typical-onset (> or = 60 years) AD conducted at 10 cM resolution (Zubenko et al 1998a, b). This survey detected associations of alleles at six microsatellite loci with AD, including the 202 bp allele of the DXS1047 locus that resides within Xq25 on the human cytogenetic map.

METHODS

Clinical assessments were performed as part of a longitudinal study of AD and related disorders. Autopsies were performed using standardized methods and the resulting diagnoses were made according to established criteria. Genotyping, morphometry, and neurochemical analyses were performed using postmortem brain tissue.

RESULTS

Patients with AD who carried the DXS1047 202 bp allele manifested cortical norepinephrine levels that ranged from 2.1 to 3.6 times the corresponding values for noncarriers (p = .002), controlling for the potential effects of gender, age at symptomatic onset or death, and postmortem interval. In contrast, carriers tended to have lower cortical levels of dopamine (p = .10).

CONCLUSIONS

These findings support the results of our previous genome survey and suggest that the DXS1047 locus, or a locus in close proximity, modulates biological variables relevant to the pathophysiology of AD. In addition to providing insights into the clinical biology of AD, the characterization of biologically meaningful subtypes, including genotypic subtypes associated with particular neurobiological derangements, may be important to the advancement of experimental therapeutics in AD.

Distribution and retrograde transport of trophic factors in the central nervous system: functional implications for the treatment of neurodegenerative diseases

Neurotrophins play a crucial role in the maintenance, survival and selective vulnerability of various neuronal populations within the normal and diseased brain. Several families of growth promoting substances have been identified within the central nervous system (CNS) including the superfamily of nerve growth factor related neurotrophin factors, glial derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF). In addition, other non-neuronal growth factors such as fibroblast growth factor (FGF) have also been identified. This article reviews the trophic anatomy of these factors within the CNS. Intraventricular and intraparenchymal injections of exogenous nerve growth factor result in retrograde labeling mainly within the cholinergic basal forebrain. Distribution of brain derived neurotrophic factor (BDNF) following intraventricular injection is minimal due to the binding to the trkB receptor along the ventricular wall. In contrast, intraparenchymal injections of BDNF results in widespread retrograde transport throughout the CNS. BDNF has also been shown to be transported anterogradely within the CNS. Infusion of GDNF into the CNS results in retrograde transport limited to the nigrostriatal pathway. Hippocampal injections of NT-3 retrogradely label mainly basal forebrain neurons. Retrograde transport of radiolabeled CNTF has only been observed in sensory neurons of the sciatic nerve. Following intraventricular and intraparenchymal infusion of radiolabeled bFGF, retrograde neuronal labeling was found in the telecephalon, diencephalon, mesencephalon and pons. In contrast retrograde labeling for aFGF was found only in the hypothalamus and midbrain. Since select neurotrophins traffic anterogradely and retrogradely within the nervous system, these proteins could be used to treat neurological diseases such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.

Increased activity of surviving locus ceruleus neurons in Alzheimer's disease

In Alzheimer's disease (AD) there is neuronal loss in the locus ceruleus (LC), and the noradrenergic system may be even more affected in depressed AD patients. However, this neuronal loss may go together with an increase in activity of the remaining noradrenergic neurons. We prospectively evaluated 16 AD patients (6 depressed, 5 transiently depressed, and 5 nondepressed) and 10 controls. We determined norepinephrine and its metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) in various brain areas, and compared these data with previously established neuron numbers in the LC in the same patients. We could not confirm earlier studies reporting lower norepinephrine concentrations in depressed than in nondepressed dementia patients. The mean norepinephrine concentrations in AD patients were significantly lower than those in control patients, whereas the mean concentrations of MHPG were not different. Moreover, we found significant inverse relationships between the number of remaining pigmented LC neurons and the MHPG/norepinephrine ratio in the frontal cortex and LC. These data are the first to provide direct evidence for the hypothesis that remaining LC neurons are activated to compensate for decreased cerebral norepinephrine levels in AD, by demonstrating that the MHPG/norepinephrine ratio is significantly higher in AD, indicating increased metabolism.

Ectopic cell cycle proteins predict the sites of neuronal cell death in Alzheimer's disease brain

Alzheimer's disease (AD) is a major dementing illness characterized by regional concentrations of senile plaques, neurofibrillary tangles, and extensive neuronal cell death. Although cell and synaptic loss is most directly linked to the severity of symptoms, the mechanisms leading to the neuronal death remain unclear. Based on evidence linking neuronal death during development to unexpected reappearance of cell cycle events, we investigated the brains of 12 neuropathologically verified cases of Alzheimer's disease and eight age-matched, disease-free controls for the presence of cell cycle proteins. Aberrant expression of cyclin D, cdk4, proliferating cell nuclear antigen, and cyclin B1 were identified in the hippocampus, subiculum, locus coeruleus, and dorsal raphe nuclei, but not inferotemporal cortex or cerebellum of AD cases. With only one exception, control subjects showed no significant expression of cell cycle markers in any of the six regions. We propose that disregulation of various components of the cell cycle is a significant contributor to regionally specific neuronal death in AD.

Pathophysiology of the locus coeruleus in suicide

Clinical and basic research findings implicate a role for brain norepinephrine in the pathophysiology of psychiatric disorders that can lead to suicide. However, the precise biological abnormality of neurons that produce norepinephrine in the brain in these disorders has not been elucidated. We have studied the biochemistry of the locus coeruleus (LC), the principal source of brain norepinephrine, from suicide victims and from age-matched, natural or accidental death control subjects. Levels of tyrosine hydroxylase (rate-limiting enzyme in norepinephrine biosynthesis) and amounts of binding to a2 adrenoceptors (norepinephrine receptors) are elevated in the LC of suicide victims as compared to control subjects. These biological abnormalities in the LC from suicide victims are very similar to biochemical changes observed in the rat LC following repeated exposure to environmental stimuli that activate the LC or to treatment with pharmacological agents that deplete brain norepinephrine. It is hypothesized that persons who commit suicide have experienced chronic activation of the LC, resulting in depletion of synaptic norepinephrine and compensatory changes in concentrations of noradrenergic proteins.