Cortical grey matter reductions associated with treatment-resistant chronic unipolar depression. Controlled magnetic resonance imaging study

Bipolar and major depressive disorder: neuroimaging the developmental-degenerative divide

Both major depressive disorder and bipolar disorder are the subject of a voluminous imaging and genetics literature. Here, we attempt a comprehensive review of MRI and metabolic PET studies conducted to date on these two disorders, and interpret our findings from the perspective of developmental and degenerative models of illness. Elevated activity and volume loss of the hippocampus, orbital and ventral prefrontal cortex are recurrent themes in the literature. In contrast, dorsal aspects of the PFC tend to display hypometabolism. Ventriculomegaly and white matter hyperintensities are intimately associated with depression in elderly populations and likely have a vascular origin. Important confounding influences are medication, phenotypic and genetic heterogeneity, and technological limitations. We suggest that environmental stress and genetic risk variants interact with each other in a complex manner to alter neural circuitry and precipitate illness. Imaging genetic approaches hold out promise for advancing our understanding of affective illness.

Chronic 13-cis-retinoic acid administration disrupts network interactions between the raphe nuclei and the hippocampal system in young adult mice

Previously, we showed that chronic administration of 13-cis-retinoic acid (13-cis-RA) induces depression-related behaviors in mice and that 13-cis-RA alters components of the serotonergic system in vitro. Work by others has shown that 13-cis-RA reduces hippocampal neurogenesis in mice and orbitofrontal cortex metabolism in humans. In the current study, we measured cytochrome oxidase activity, a metabolic marker that reflects steady state neuronal energy demand, in various regions of the brain to determine the effects of 13-cis-RA on neuronal metabolic activity and network interactions between the raphe nuclei and the hippocampal system. Brain cytochrome oxidase activity in young adult male mice was analyzed following 6 weeks of daily 13-cis-RA (1 mg/kg) or vehicle injection and behavioral testing. Chronic 13-cis-RA administration significantly decreased cytochrome oxidase activity only in the inferior rostral linear nucleus of the raphe. However, covariance analysis of interregional correlations in cytochrome oxidase activity revealed that 13-cis-RA treatment caused a functional uncoupling between the dorsal raphe nuclei and the hippocampus. Furthermore, a path analysis indicated that a network comprising lateral habenula to dorsal raphe to hippocampus was effectively uncoupled in 13-cis-RA treated animals. Finally, cytochrome oxidase activity in the dentate gyrus of 13-cis-RA treated mice was inversely correlated with depression-related behavior. Taken together, these data show that 13-cis-RA alters raphe metabolism and disrupts functional connectivity between the raphe nuclei and the hippocampal formation, which may contribute to the observed increase in depression-related behaviors.

Improving the prediction of treatment response in depression: integration of clinical, cognitive, psychophysiological, neuroimaging, and genetic measures

Antidepressants are important in the treatment of depression, and selective serotonin reuptake inhibitors are first-line pharmacologic options. However, only 50% to 70% of patients respond to first treatment and <40% remit. Since depression is associated with substantial morbidity, mortality, and family burden, it is unfortunate and demanding on health resources that patients must remain on their prescribed medications for at least 4 weeks without knowing whether the particular antidepressant will be effective. Studies have suggested a number of predictors of treatment response, including clinical, psychophysiological, neuroimaging, and genetics, each with varying degrees of success and nearly all with poor prognostic sensitivity and specificity. Studies are yet to be conducted that use multiple measures from these different domains to determine whether sensitivity and specificity can be improved to predict individual treatment response. It is proposed that a focus on standardized testing methodologies across multiple testing modalities and their integration will be crucial for translation of research findings into clinical practice.

Reduced caudate gray matter volume in women with major depressive disorder

Previous brain-imaging studies have reported that major depressive disorder (MDD) is characterized by decreased volumes of several cortical and subcortical structures, including the hippocampus, amygdala, anterior cingulate cortex, and caudate nucleus. The purpose of the present study was to identify structural volumetric differences between MDD and healthy participants using a method that allows a comparison of gray and white matter volume across the whole brain. In addition, we explored the relation between symptom severity and brain regions with decreased volumes in MDD participants. The study group comprised 22 women diagnosed with MDD and 25 healthy women with no history of major psychiatric disorders. Magnetic resonance brain images were analyzed using optimized voxel-based morphometry to examine group differences in regional gray and white matter volume. Compared with healthy controls, MDD participants were found to have decreased gray matter volume in the bilateral caudate nucleus and the thalamus. No group differences were found for white matter volume, nor were there significant correlations between gray matter volumes and symptom severity within the MDD group. The present results suggest that smaller volume of the caudate nucleus may be related to the pathophysiology of MDD and may account for abnormalities of the cortico-striatal-pallido-thalamic loop in MDD.

Effects of vagus nerve stimulation on rat hippocampal progenitor proliferation

Vagus nerve stimulation (VNS), used in the treatment of epilepsy, was approved recently for treatment-resistant depression. The mechanisms of action of the VNS anti-depressive effects are not yet fully elucidated. Modulation of hippocampal neurogenesis has been proposed as an important factor in depression pathogenesis. We evaluated the effects of VNS on hippocampal progenitor turnover in the adult rat brain. Rats receiving VNS at the output current of 0.75 mA VNS for 2 days showed a significant 50% increase in dentate gyrus BrdU-incorporation consistent with an increase in progenitor proliferation. Output currents of 0.5 or 1.5 mA yielded non-significant trends for increased BrdU-labeling indicating an inverted U-shaped proliferative dose response to VNS as previously reported for other VNS-induced effects. Specific analysis for progenitor survival revealed no effects by VNS on dentate gyrus BrdU-labeling. These results suggest that VNS induced an increase in the number of available progenitor cells in the adult rat dentate gyrus by a mechanism presumably involving increased progenitor proliferation.

Salivary cortisol and suicidal behavior--a follow-up study

INTRODUCTION

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA)-axis is a common finding in major depressive disorder. Similar studies on suicide attempters are less abundant, and the results are divergent. The main aim of the present study was to investigate HPA-axis parameters by the time of a suicide attempt and at follow-up in search for associations between HPA-axis function and suicidal behavior.

METHODS

Thirty-five suicide attempters and 16 non-suicidal controls were admitted to a psychiatric ward between the years of 1986 and 1992. Corticotrophin-releasing hormone (CRH) in cerebrospinal fluid and urinary cortisol were obtained for the suicide attempters. The patients were followed up approximately 12 years after the index admission. Cortisol was measured in saliva, and additional suicide attempts and current psychiatric symptoms were registered.

RESULTS

At follow-up, evening salivary cortisol was lower in suicide attempters compared to controls. Low cortisol levels at follow-up were associated with severe psychiatric symptoms. Among women, repeated suicide attempts were associated with low morning and lunch salivary cortisol, and in this subgroup we also found significant correlations between salivary cortisol at follow-up, and CRH as well as urinary cortisol at index.

CONCLUSION

We found evidence for an association between low HPA-axis activity and suicidal behavior. This could be due to long-lasting and severe psychiatric morbidity, which in turn has exhausted the HPA-axis of these patients. The potential role of hypocortisolism should be given more attention in studies on suicidal patients.

The subgenual anterior cingulate cortex in mood disorders

The anterior cingulate cortex (ACC) ventral to the genu of the corpus callosum has been implicated in the modulation of emotional behavior on the basis of neuroimaging studies in humans and lesion analyses in experimental animals. In a combined positron emission tomography/magnetic resonance imaging study of mood disorders, we demonstrated that the mean gray matter volume of this "subgenual" ACC (sgACC) cortex is abnormally reduced in subjects with major depressive disorder (MDD) and bipolar disorder, irrespective of mood state. Neuropathological assessments of sgACC tissue acquired postmortem from subjects with MDD or bipolar disorder confirmed the decrement in gray matter volume, and revealed that this abnormality was associated with a reduction in glia, with no equivalent loss of neurons. In positron emission tomography studies, the metabolic activity was elevated in this region in the depressed relative to the remitted phases of the same MDD subjects, and effective antidepressant treatment was associated with a reduction in sgACC activity. Other laboratories replicated and extended these findings, and the clinical importance of this treatment effect was underscored by a study showing that deep brain stimulation of the sgACC ameliorates depressive symptoms in treatment-resistant MDD. This article discusses the functional significance of these findings within the context of the preclinical literature that implicates the putative homologue of this region in the regulation of emotional behavior and stress response. In experimental animals, this region participates in an extended "visceromotor network" of structures that modulates autonomic/neuroendocrine responses and neurotransmitter transmission during the neural processing of reward, fear, and stress. These data thus hold important implications for the development of neural models of depression that can account for the abnormal motivational, neuroendocrine, autonomic, and emotional manifestations evident in human mood disorders.

Mourning and melancholia revisited: correspondences between principles of Freudian metapsychology and empirical findings in neuropsychiatry

Freud began his career as a neurologist studying the anatomy and physiology of the nervous system, but it was his later work in psychology that would secure his place in history. This paper draws attention to consistencies between physiological processes identified by modern clinical research and psychological processes described by Freud, with a special emphasis on his famous paper on depression entitled 'Mourning and melancholia'. Inspired by neuroimaging findings in depression and deep brain stimulation for treatment resistant depression, some preliminary physiological correlates are proposed for a number of key psychoanalytic processes. Specifically, activation of the subgenual cingulate is discussed in relation to repression and the default mode network is discussed in relation to the ego. If these correlates are found to be reliable, this may have implications for the manner in which psychoanalysis is viewed by the wider psychological and psychiatric communities.

A magnetic resonance imaging study of the entorhinal cortex in treatment-resistant depression

Despite a growing interest in this area, we continue to lack an understanding of the pathophysiology of depression and of treatment-resistant depression (TRD) in particular. The role of the medial temporal lobe, particularly the hippocampus, has been widely implicated in the aetiology of depression. However, related structures such as the entorhinal cortex have not been systematically examined. This research study aimed to examine possible abnormalities in the volume of the entorhinal cortex (ERC) in TRD patients. A group of 45 TRD patients and 30 healthy age- and sex-matched controls underwent magnetic resonance imaging (MRI). ERC volumes were manually traced from MRI data using ANALYZE software. An analysis of variance was conducted between subject groups and in the sexes separately while controlling for the effects of brain size via intracranial volume (ICV). Results revealed significant reductions in the volume of the left ERC of female patients. Although preliminary, our findings suggest that anatomical abnormalities in the ERC may confer vulnerability to treatment resistance. Confirmatory longitudinal studies are required to determine whether these abnormalities predate the onset of depression or are the result of a more chronic, treatment-resistant course of illness.

Gray matter reduction associated with psychopathology and cognitive dysfunction in unipolar depression: a voxel-based morphometry study

BACKGROUND

Functional neuroimaging studies on both cognitive processing and psychopathology in patients with major depression have reported several functionally aberrant brain areas within limbic-cortical circuits. However, less is known about the relationship between psychopathology, cognitive deficits and regional volume alterations in this patient population.

METHODS

By means of voxel-based morphometry (VBM) and a standardized neuropsychological test battery, we examined 15 patients meeting DSM-IV criteria for major depression disorder and 14 healthy controls in order to investigate the relationship between affective symptoms, cognitive deficits and structural abnormalities.

RESULTS

Patients with depression showed reduced gray matter concentration (GMC) in the left inferior temporal cortex (BA 20), the right orbitofrontal (BA 11) and the dorsolateral prefrontal cortex (BA 46). Reduced gray matter volume (GMV) was found in the left hippocampal gyrus, the cingulate gyrus (BA 24/32) and the thalamus. Structure-cognition correlation analyses revealed that decreased GMC of the right medial and inferior frontal gyrus was associated with both depressive psychopathology and worse executive performance as measured by the Wisconsin Card Sorting Test (WCST). Furthermore, depressive psychopathology and worse performance during the WCST were associated with decreased GMV of the hippocampus. Decreased GMV of the cingulate cortex was associated with worse executive performance.

LIMITATIONS

Moderate illness severity, medication effects, and the relatively small patient sample size should be taken into consideration when reviewing the implications of these results.

CONCLUSIONS

The volumetric results indicate that regional abnormalities in gray matter volume and concentration may be associated with both psychopathological changes and cognitive deficits in depression.

Anterior cingulate cortex does not differ between patients with major depression and healthy controls, but relatively large anterior cingulate cortex predicts a good clinical course

The anterior cingulate cortex (ACC) is involved in the regulation of emotion processing, and its volume has been found to be reduced in patients with major depression. Furthermore, larger ACC volumes have been associated with faster symptom improvement under therapy. The aims of the study were to examine whether volumes of the anterior cingulate cortex are altered and are related to the clinical course of major depression. Subjects comprised 78 inpatients with major depression and 78 age-, gender- and handedness- matched healthy volunteers, who were investigated with structural magnetic resonance imaging (MRI). The ACC was subdivided into the subgenual, pre-callosal, rostral-anterior and caudal-anterior ACC. No significant differences were observed for ACC volumes between patients and healthy controls. Left ACC volumes showed a significant negative correlation with the number of hospitalizations. These findings suggest that ACC volumes are not altered in patients with major depression, but that patients with larger ACC have a better clinical outcome than patients with smaller ACC.

Hippocampus shape analysis and late-life depression

Major depression in the elderly is associated with brain structural changes and vascular lesions. Changes in the subcortical regions of the limbic system have also been noted. Studies examining hippocampus volumetric differences in depression have shown variable results, possibly due to any volume differences being secondary to local shape changes rather than differences in the overall volume. Shape analysis offers the potential to detect such changes. The present study applied spherical harmonic (SPHARM) shape analysis to the left and right hippocampi of 61 elderly subjects with major depression and 43 non-depressed elderly subjects. Statistical models controlling for age, sex, and total cerebral volume showed a significant reduction in depressed compared with control subjects in the left hippocampus (F_1,103 = 5.26; p = 0.0240) but not right hippocampus volume (F_1,103 = 0.41; p = 0.5213). Shape analysis showed significant differences in the mid-body of the left (but not the right) hippocampus between depressed and controls. When the depressed group was dichotomized into those whose depression was remitted at time of imaging and those who were unremitted, the shape comparison showed remitted subjects to be indistinguishable from controls (both sides) while the unremitted subjects differed in the midbody and the lateral side near the head. Hippocampal volume showed no difference between controls and remitted subjects but nonremitted subjects had significantly smaller left hippocampal volumes with no significant group differences in the right hippocampus. These findings may provide support to other reports of neurogenic effects of antidepressants and their relation to successful treatment for depressive symptoms.

Making sense of neuroimaging in psychiatry

OBJECTIVE

Neuroimaging of psychiatric disorders has increased exponentially in the last decade; however, much of the uptake thus far has been in the realm of research. We anticipate that clinical use of neuroimaging modalities in psychiatry will increase dramatically in the near future and suggest that clinicians need to be aware of the potential applications.

METHOD

The authors conducted an extensive MEDLINE, EMBASE, PubMED and PsychInfo search of the published literature (1965-2007) using a variety of search terms to find relevant articles. Bibliographies of retrieved papers were further scrutinised for publications of interest, as were indices of books. Articles that reported clinically significant findings and research reports conducted using pertinent neuroimaging modalities were reviewed in detail.

RESULTS

The review suggests that exciting neuroimaging advances are being made that have relevance to psychiatry. Novel neuroimaging applications with potential clinical utility are rapidly emerging and the accessibility and use of these technologies will increase in coming years. Clinically meaningful findings have begun to emerge in mood disorders, post-traumatic stress disorder, schizophrenia and dementia. Coupling multimodal imaging with genetics and pharmacotherapeutic studies will further assist in understanding the pathophysiology of neuropsychiatric disorders.

CONCLUSION

It is important that clinicians understand the benefits and limitations of modern neuroimaging techniques and are also suitably equipped to appraise future developments. The use of neuroimaging in evaluating psychopathology is likely to impact upon the future nosology of psychiatric disorders, and assist in diagnosis and clinical management. The integrated use of neuroimaging in conjunction with clinical assessments promises to improve clinical care and markedly alter psychiatric practice.

Volumetric neuroimaging investigations in mood disorders: bipolar disorder versus major depressive disorder

BACKGROUND

As patients with mood disorders manifest heterogeneity in phenomenology, pathophysiology, etiology, and treatment response, a biological classification of mental disease is urgently needed to advance research. Patient and methodological variability complicates the comparison of neuroimaging study results and limits heuristic model development and a biologically-based diagnostic schema.

OBJECTIVE

We have critically reviewed and compared the magnetic resonance neuroimaging literature to determine the degree and directionality of volumetric changes in brain regions putatively implicated in the pathophysiology of major depressive disorder (MDD) versus bipolar disorder (BD).

METHODS

A total of 140 published magnetic resonance imaging investigations evaluating subjects with BD or MDD were selected to provide a summary and interpretation of volumetric neuroimaging results in MDD and BD. Further commentary on the pathophysiological implications, and putative cellular and pharmacological mechanisms, is also provided.

RESULTS

While whole brain volumes of patients with mood disorders do not differ from those of healthy controls, regional deficits in the frontal lobe, particularly in the anterior cingulate and the orbitofrontal cortex, appear to consistently differentiate subjects with mood disorders from the general population. Preliminary findings also suggest that subcortical structures, particularly the striatum, amygdala, and hippocampus, may be differentially affected in MDD and BD.

CONCLUSIONS

Structural neuroimaging studies have consistently identified regional abnormalities in subjects with mood disorders. Future studies should strive to definitively establish the influence of age and medication.

Geriatric depression and cognitive impairment

Cognitive impairment is common in geriatric depression, and depressed individuals with co-morbid cognitive impairment are at increased risk for a number of adverse medical, psychiatric and cognitive outcomes. This review focuses on clinical issues surrounding the co-occurrence of these two conditions within the context of current research. We (1) review the clinical criteria and prevalence of depression, as well as co-morbid cognitive impairment, (2) discuss factors associated with persistent cognitive impairment in depression, including dementia, and (3) review research relevant to the assessment and treatment of cognitive impairment and dementia in the context of depression. We conclude that current research on depression and cognition can inform clinical decisions that reduce the occurrence of adverse outcomes. Clinicians are encouraged to develop proactive approaches for treatment, which may include combinations of pharmacological and psychotherapeutic interventions.

Restoring melancholia in the classification of mood disorders

The present DSM criteria for major depression poorly identify samples for treatment selection, prognosis, and assessments of pathophysiology. Melancholia, in contrast, is a disorder with definable clinical signs that can be verified by laboratory tests and treatment response. It identifies more specific populations than the present system and deserves individual identification in psychiatric classification. Its re-introduction will refine diagnosis, prognosis, treatment selection, and studies of pathophysiology of a large segment of the psychiatrically ill.

Stress, depression, and neuroplasticity: a convergence of mechanisms

Increasing evidence demonstrates that neuroplasticity, a fundamental mechanism of neuronal adaptation, is disrupted in mood disorders and in animal models of stress. Here we provide an overview of the evidence that chronic stress, which can precipitate or exacerbate depression, disrupts neuroplasticity, while antidepressant treatment produces opposing effects and can enhance neuroplasticity. We discuss neuroplasticity at different levels: structural plasticity (such as plastic changes in spine and dendrite morphology as well as adult neurogenesis), functional synaptic plasticity, and the molecular and cellular mechanisms accompanying such changes. Together, these studies elucidate mechanisms that may contribute to the pathophysiology of depression. Greater appreciation of the convergence of mechanisms between stress, depression, and neuroplasticity is likely to lead to the identification of novel targets for more efficacious treatments.

The role of neurotrophic factors in adult hippocampal neurogenesis, antidepressant treatments and animal models of depressive-like behavior

Major depressive disorder (MDD) is characterized by structural and neurochemical changes in limbic structures, including the hippocampus, that regulate mood and cognitive functions. Hippocampal atrophy is observed in patients with depression and this effect is blocked or reversed by antidepressant treatments. Brain-derived neurotrophic factor and other neurotrophic/growth factors are decreased in postmortem hippocampal tissue from suicide victims, which suggests that altered trophic support could contribute to the pathophysiology of MDD. Preclinical studies demonstrate that exposure to stress leads to atrophy and cell loss in the hippocampus as well as decreased expression of neurotrophic/growth factors, and that antidepressant administration reverses or blocks the effects of stress. Accumulating evidence suggests that altered neurogenesis in the adult hippocampus mediates the action of antidepressants. Chronic antidepressant administration upregulates neurogenesis in the adult hippocampus and this cellular response is required for the effects of antidepressants in certain animal models of depression. Here, we review cellular (e.g. adult neurogenesis) and behavioral studies that support the neurotrophic/neurogenic hypothesis of depression and antidepressant action. Aberrant regulation of neuronal plasticity, including neurogenesis, in the hippocampus and other limbic nuclei may result in maladaptive changes in neural networks that underlie the pathophysiology of MDD.

Early preweaning methamphetamine and postweaning rearing conditions interfere with the development of peripheral stress parameters and neural growth factors in gerbils

Adrenal steroid hormones and neuronal growth factors are two interacting systemic factors that mediate the environment's influence on the brain's structure and function. In order to further elucidate their role and relationship in the effects of early stressful experience and isolated rearing (IR), this study measured blood corticosterone titres and relative adrenal weights and assessed nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) concentrations in brain regions of both hemispheres of young adult Mongolian gerbils injected on postnatal day 14 with a single high dose of methamphetamine (MA) or saline and raised after weaning either in an enriched or an impoverished environment. Irrespective of MA challenge, IR decreased corticosterone titres to about half, but increased relative adrenal weights. BDNF concentrations were decreased by IR in saline-injected animals in the left prefrontal and parietal cortices and right entorhinal and hippocampal cortices, and in the subcortical regions of both hemispheres. NGF concentrations were unaltered by IR in saline-injected animals, but increased in MA challenged animals in the entorhinal/hippocampal cortices and subcortical areas of both hemispheres. MA application induced shifts of the lateral asymmetry in NGF contents in prefrontal and entorhinal cortices. The results suggest that an early pharmacological traumatization can set a switch for further brain development, and that growth factor concentrations might possibly be influenced by peripheral stress hormones.

Hippocampal volume reduction and HPA-system activity in major depression

Structural imaging studies investigating hippocampal volumes in patients suffering from major depression have yielded mixed results. Here, 24 unipolar depressed in-patients and 14 healthy controls carefully matched for age, gender, and years of education underwent quantitative magnetic resonance imaging (MRI). Saliva cortisol was measured at 0800 and 1600 h in patients during a one-week wash-out and the following 4 weeks. Hippocampal volumes were significantly reduced in the patient group even after adjusting for intracranial brain volume (ICV) and age. Across groups, age was significantly negatively correlated with uncorrected hippocampal volumes. In patients, severity of disease (baseline HAMD scores) and baseline cortisol levels were not related to hippocampal volumes. However, there was a negative association between duration of the index episode before hospitalization and hippocampal volumes. Additionally, hippocampal volumes were significantly negatively correlated with duration of illness. Finally, we observed a trend for higher hippocampal volumes in those patients who showed a subsequent decrease in cortisol levels under pharmacotherapy.

Hippocampal neurogenesis, depressive disorders, and antidepressant therapy

There is a growing body of evidence that neural stem cells reside in the adult central nervous system where neurogenesis occurs throughout lifespan. Neurogenesis concerns mainly two areas in the brain: the subgranular zone of the dentate gyrus in the hippocampus and the subventricular zone, where it is controlled by several trophic factors and neuroactive molecules. Neurogenesis is involved in processes such as learning and memory and accumulating evidence implicates hippocampal neurogenesis in the physiopathology of depression. We herein review experimental and clinical data demonstrating that stress and antidepressant treatments affect neurogenesis in opposite direction in rodents. In particular, the stimulation of hippocampal neurogenesis by all types of antidepressant drugs supports the view that neuroplastic phenomena are involved in the physiopathology of depression and underlie—at least partly—antidepressant therapy.

Cerebral volume measurements and subcortical white matter lesions and short-term treatment response in late life depression

BACKGROUND

Late life depression is associated with volumetric reductions of gray matter and increased prevalence of subcortical white matter lesions. Previous studies have shown a poorer treatment outcome in those with more severe structural brain abnormalities. In this study, quantitative and semi-quantitative magnetic resonance imaging (MRI) measures were studied in relation to response to a 12-week controlled antidepressant monotherapy trial.

METHODS

MRI (1.5 T) brain scans of 42 elderly inpatients with major depression, of which 23 were non-responder to a controlled 12-week antidepressant monotherapy trial, were acquired. In addition, clinical outcome was assessed after a one year period. Measures were volumes of global cerebral and subcortical structures.

RESULTS

After controlling for confounding, no differences were found between non-responders and responders after 12 weeks and after one year in volumes of cerebral gray and white matter, orbitofrontal cortex, hippocampus and white matter lesions.

CONCLUSIONS

Structural brain measures associated with late life depression may not be related to short-term treatment response.

Life-Long Hippocampal Neurogenesis: Environmental, Pharmacological and Neurochemical Modulations

It is now well documented that active neurogenesis does exist throughout the life span in the brain of various species including human. Two discrete brain regions contain progenitor cells that are capable of differentiating into neurons or glia, the subventricular zone and the dentate gyrus of the hippocampal formation. Recent studies have shown that neurogenesis can be modulated by a variety of factors, including stress and neurohormones, growth factors, neurotransmitters, drugs of abuse, and also strokes and traumatic brain injuries. In particular, the hippocampal neurogenesis may play a role in neuroadaptation associated with pathologies, such as cognitive disorders and depression. The increased neurogenesis at sites of injury may represent an attempt by the central nervous system to regenerate after damage. We herein review the most significant data on hippocampal neurogenesis in brain under various pathological conditions, with a special attention to mood disorders including depression and addiction.

Comorbidity implications in brain disease: Neuronal substrates of symptom profiles

The neuronal substrates underlying aspects of comorbidity in brain disease states may be described over psychiatric and neurologic conditions that include affective disorders, cognitive disorders, schizophrenia, obsessive-compulsive disorder, substance abuse disorders as well as the neurodegenerative disorders. Regional and circuitry analyses of biogenic amine systems that are implicated in neural and behavioural pathologies are elucidated using neuroimaging, electrophysiological, neurochemical, neuropharmacological and neurobehavioural methods that present demonstrations of the neuropathological phenomena, such as behavioural sensitisation, cognitive impairments, maladaptive reactions to environmental stress and serious motor deficits. Considerations of neuronal alterations that may or may not be associated with behavioural abnormalities examine differentially the implications of discrete areas within brains that have been assigned functional significance; in the case of the frontal lobes, differential deficits of ventromedial and dorsolateral prefrontal cortex may be associated with different aspects of cognition, affect, remission or response to medication thereby imparting a varying aspect to any investigation of comorbidity.

A longitudinal analysis of neurocognitive function in unipolar depression

Neurocognitive function is reduced in major depression, but uncertainties remain about if and to what extent improvement in neurocognitive function follows remission of depressive symptoms. A total of 30 patients with Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) diagnosis of unipolar major depressive disorder (MDD) at baseline were tested neuropsychologically again, after a mean test-retest interval of 2 years. At retest, patients were partly or completely recovered from depression. Remission of depression was followed by improvement in verbal memory function up to the level of healthy controls, but no associations between improvement in depression and improvement in other dimensions of neurocognitive function were found. Neurocognitive function at baseline was not predictive of improvement in depressive symptoms over time. The present study provided some support for the state hypothesis as to the association between neurocognitive impairment and depression.

Cognitive impairment and fMRI in major depression

Cognitive impairment in depression may be one of the more practically important aspects of the illness, responsible for much of its morbidity. It also is at the heart of its psychopathology, may contribute to strategies of treatment, and may give us a more easily quantifiable measure of impaired function to correlate with brain activity. Functional magnetic resonance imaging (fMRI) is ideally suited to examine brain function in depression. It has the correct time window to repeatedly sample cognitive task performance; it does not require exposure to radioactive tracers and can therefore be repeated many times; it also can be linked with high resolution structural images acquired in the same imaging session that help identify the regions of activation and support the spatial transformation necessary to compare the scans of different subjects. fMRI has already produced a series of consistent results in depression, identifying increased activity of rostral anterior cingulate and other medial prefrontal structures during effortful tasks and on occasion also increased dorsolateral prefrontal activity, suggesting increased possibly compensatory activity to maintain task performance. Investigating the interplay between limbic (orbitomedial) and 'cognitive' dorsolateral structures clearly has the potential to clarify important illness mechanisms of depressive illness.

Use of magnetic resonance imaging in tracking the course and treatment of schizophrenia

Confirming the early conceptualization of Bleuler (1911) and Kraepelin (1919), magnetic resonance imaging (MRI) studies have demonstrated structural and functional brain abnormalities, predominantly involving the frontal and temporal lobes, in schizophrenia. Most of the abnormalities are already present at illness onset. However, there is, growing evidence for treatment-related neural changes in schizophrenia, such as enlargement of the caudate nucleus (neurotoxic effect) with the use of typical antipsychotics and increases in cortical volumes and improved functional responses (neurotrophic effect) with the use of atypical antipsychotics. More recently, brain changes during the prodrome and transition-to-illness stages of schizophrenia have begun to be characterized. Another area of importance is the use of MRI, as a biological marker, to monitor and define partial or full resistance to medication. Understanding the trait- and state-related influences of brain abnormalities during the course of the illness is critical for developing effective treatment and possibly prevention strategies in schizophrenia.

Morphometric and psychometric comparisons between non-substance-abusing patients with posttraumatic stress disorder and normal controls

BACKGROUND

Hippocampal decrease in size in response to posttraumatic stress disorder (PTSD) is still a subject of controversy. The aims of this study were to: (1) confirm previous hippocampus findings in PTSD patients compared to controls, using ethnically similar study groups where alcohol and drug abuse were non-existent; (2) test influence of disease duration as well as depression scores on possible morphological changes; (3) test whether the voxel-based morphometry (VBM) data confirm the group differences seen in the region of interest (ROI) analysis, and (4) test the associations between the cognitive test scores and the morphological changes.

METHODS

VBM and ROI-based analysis were applied in 23 patients and 17 healthy controls. Culture-neutral cognitive tests were used.

RESULTS

The ROI-based method showed significantly decreased gray matter volumes for global hippocampal volume, as in a separate analysis of left and right sides in the PTSD group. Total volume of the hippocampus was significantly decreased on the left side, as in the global assessment. A multiple regression VBM model showed significant voxel clusters for group affiliation in the right hippocampus, modelling lowering of gray matter associated with the PTSD group. Disease duration was shown to be negatively correlated to bilateral hippocampal volume and high depression score to bilateral gray matter parahippocampal volume. No significant correlations were found between hippocampal or parahippocampal volumes and cognitive functions.

CONCLUSION

The present and previous studies showed that morphologic differences do not appear to be due to drug or alcohol abuse. The VBM data partially confirm the group differences seen in the ROI-based method in the medial temporal lobe. The fact that the significantly lower score on the short-term memory test in the PTSD group is not correlated to hippocampal volume may suggest a more general basis for such memory impairment.

Repeated brief social defeat episodes in mice: effects on cell proliferation in the dentate gyrus

Stressful experiences can affect hippocampal structure and function and can suppress new cell birth in the adult hippocampus in several species. Here we examine how repeated intermittent social defeat affects cell proliferation in the dentate gyrus (DG) in mice. Adult male CFW mice were subjected to 10 daily social defeat episodes, 3 defeat episodes within one day or a single defeat episode. Intruder mice were injected with 5-bromo-2'-deoxyuridine (BrdU, 200mg/kg, i.p.) 1h after the last fight, and incorporation of BrdU into proliferating cells in the DG was quantified. In a third experiment, aggressive resident mice were allowed to fight with an intruder mouse every day for 10 days, and these residents were injected with BrdU 1h after the last aggressive encounter. There was a significant decrease in cell proliferation in mice that received 10 social defeats, confirming and extending earlier results. This decrease is correlated with the intensity of the defeat experiences, as quantified by frequency of attack bites. Cell proliferation was slightly inhibited after a single defeat, although this effect was not significant. Three defeats within a 5-h period had no effect on levels of proliferation. Offensive aggressive stress in the residents did not result in any changes in hippocampal cell proliferation. These data indicate that repeated intermittent social defeat experienced over multiple days suppresses proliferation in the DG, and this may have important implications for our understanding of hippocampal changes related to stress psychopathologies.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Persistence of neuropsychologic deficits in the remitted state of late-life depression

OBJECTIVE

Cognitive impairment in late-life depression (LLD) is prevalent, disabling, and persists despite the remission of depressive symptoms. This article characterizes neuropsychologic functioning during remission in LLD.

METHODS

The authors examined longitudinal performance on a comprehensive neuropsychologic battery in 56 nondemented subjects age 60 or older who initially presented with an episode of nonpsychotic unipolar major depression and 40 nondemented, age- and education-equated comparison subjects with no history of depression. Subjects were assessed at baseline (in a depressed state) and one year later (when remitted).

RESULTS

After one year, 45% of the LLD subjects were cognitively impaired despite remission of depression. Visuospatial ability, information-processing speed, and delayed memory were most frequently impaired; 94% of the patients who were impaired at baseline remained impaired one year later. Twenty-three percent of the patients who were cognitively normal while depressed developed impairment one year later.

CONCLUSIONS

Most older individuals who are cognitively impaired during a depressive episode remain impaired when their depression remits. In addition, a substantial proportion of older depressed individuals who are cognitively intact when depressed are likely to be impaired one year later, although their depression has remitted.

Chronic stress induces upregulation of brain-derived neurotrophic factor (BDNF) mRNA and integrin alpha5 expression in the rat pineal gland

Chronic stress affects brain areas involved in learning and emotional responses. These alterations have been related with the development of cognitive deficits in major depression. Moreover, stress induces deleterious actions on the epithalamic pineal organ, a gland involved in a wide range of physiological functions. The aim of this study was to investigate whether the stress effects on the pineal gland are related with changes in the expression of neurotrophic factors and cell adhesion molecules. Using reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, we analyzed the effect of chronic immobilization stress on the BDNF mRNA and integrin alpha5 expression in the rat pineal gland. We found that BDNF is produced in situ in the pineal gland. Chronic immobilization stress induced upregulation of BDNF mRNA and integrin alpha5 expression in the rat pineal gland but did not produce changes in beta-actin mRNA or in GAPDH expression. Stressed animals also evidenced an increase in anxiety-like behavior and acute gastric lesions. These results suggest that BDNF and integrin alpha5 may have a counteracting effect to the deleterious actions of immobilization stress on functionally stimulated pinealocytes. Furthermore, this study proposes that the pineal gland may be a target of glucocorticoid damage during stress.

Hippocampal volume and cognitive function in anorexia nervosa

We hypothesised that hippocampal volume would be reduced in underweight anorexia nervosa (AN) and associated with impaired hippocampus-dependent cognitive function. Hippocampal and whole brain volumes were measured in 16 women with AN and 16 matched healthy women using magnetic resonance imaging (MRI) and a manual tracing method. Participants also completed the Doors and People Test of hippocampus-dependent memory and an IQ test. After adjustment for total cerebral volume, there was significant bilateral reduction in hippocampal volume in the AN group (8.2% right; 7.5% left). There was no evidence of impaired hippocampus-dependent cognitive function and no evidence of a relationship between hippocampal volume and clinical features of AN. The reduced hippocampal volume in anorexia nervosa is not associated with changes in cognitive function. To understand the cause and consequence of hippocampal size and function, it will be important to integrate endocrine, neuropsychological and neuroimaging studies.

Recent developments and current controversies in depression

In this review of the last 5 years' developments in research into depression we focus on recent advances and current controversies. We cover epidemiology and basic science as well as the treatment of depression in adults in all its forms. Depression in , as well as in has been covered in recent Seminars in The Lancet. Depression in adulthood remains a very common and under-treated condition, resulting in a high degree of disability. Increasingly detailed knowledge about impairment of information processing in depression is being supplemented by quantitative studies of the brain processes underlying these impairments. Most patients improve with present treatments. The mechanisms of action of antidepressants are not fully understood; the hypothesis that reversing hippocampal cell loss in depression may be their active principle is a fascinating new development. Moral panic about the claim that antidepressant serotonin reuptake inhibitors cause patients to commit suicide and become addicted to their medication may have disconcerted the public and members of the medical profession. We will try to describe the considerable effort that has gone into collecting evidence to enlighten this debate.

Hippocampal neurogenesis: Opposing effects of stress and antidepressant treatment

The hippocampus is one of several limbic brain structures implicated in the pathophysiology and treatment of mood disorders. Preclinical and clinical studies demonstrate that stress and depression lead to reductions of the total volume of this structure and atrophy and loss of neurons in the adult hippocampus. One of the cellular mechanisms that could account for alterations of hippocampal structure as well as function is the regulation of adult neurogenesis. Stress exerts a profound effect on neurogenesis, leading to a rapid and prolonged decrease in the rate of cell proliferation in the adult hippocampus. In contrast, chronic antidepressant treatment up-regulates hippocampal neurogenesis, and could thereby block or reverse the atrophy and damage caused by stress. Recent studies also demonstrate that neurogenesis is required for the actions of antidepressants in behavioral models of depression. This review discusses the literature that has lead to a neurogenic hypothesis of depression and antidepressant action, as well as the molecular and cellular mechanisms that underlie the regulation of adult neurogenesis by stress and antidepressant treatment.

Possible structural abnormality of the brainstem in unipolar depressive illness: a transcranial ultrasound and diffusion tensor magnetic resonance imaging study

BACKGROUND

Most empirically derived antidepressants increase monoamine levels. The nuclei of cells synthesising these monoamines are located in the brainstem, and projection tracts such as the medial forebrain bundle reach virtually all other brain areas. Two studies of unipolar depressive illness using transcranial ultrasound have reported reduced echogenicity of the brainstem midline in unipolar depressed patients. This may be consistent with disruption of white matter tracts, including the medial forebrain bundle, and it has been suggested that the effect of such disruption could be reversed by antidepressants.

OBJECTIVE

To replicate these findings in a group of unipolar depressed patients and controls.

METHODS

Fifteen unipolar depressed patients and 15 controls were studied using transcranial ultrasound imaging and diffusion tensor magnetic resonance imaging (DT-MRI).

RESULTS

No difference in echogenicity of the brainstem midline of unipolar depressed patients was found. A possible trend (Cohen's d = 0.39) in the direction of previous studies was found. Although the echogenicity of the brainstem midline of the control group was found to be similar to previous reports, there was no reduction in the patient group. Additionally, no structural abnormality of the brainstem was identified using DT-MRI.

CONCLUSIONS

While these data do not replicate the findings of previous studies reporting a significant reduction in the echogenicity of the brainstem midline in unipolar depressed patients, the ultrasound investigation indicated that there may be a trend in this direction. Given the importance of identifying the causes of depressive illness, it is important that other groups attempt similar studies.

Face emotion perception and executive functioning deficits in depression

Frontal, limbic and temporal regions of the brain important in emotion perception and executive functioning also have been implicated in the etiology and maintenance of depression; yet, the relationships among these topics remain poorly understood. The present study evaluated emotion perception and executive functioning among 21 depressed women and 20 nondepressed women controls. Depressed women performed significantly worse than controls in emotion perception accuracy and in inhibitory control, an aspect of executive functioning, whereas the groups did not differ in other cognitive tests assessing memory, visual-spatial, motor, and attention skills. The findings suggest that emotion perception and executive functioning are disproportionately negatively affected relative to other cognitive functions, even in a high-functioning group of mildly depressed women. Measures of emotion perception and executive functioning may be of assistance in objectively measuring functional capability of the ventral and dorsal neural systems, respectively, as well as in the diagnosis of depression.

IDO and interferon-alpha-induced depressive symptoms: a shift in hypothesis from tryptophan depletion to neurotoxicity

Studies show that administration of interferon (IFN)-alpha causes a significant increase in depressive symptoms. The enzyme indoleamine 2,3-dioxygenase (IDO), which converts tryptophan (TRP) into kynurenine (KYN) and which is stimulated by proinflammatory cytokines, may be implicated in the development of IFN-alpha-induced depressive symptoms, first by decreasing the TRP availability to the brain and second by the induction of the KYN pathway resulting in the production of neurotoxic metabolites. Sixteen patients with chronic hepatitis C, free of psychiatric disorders and eligible for IFN-alpha treatment, were recruited. Depressive symptoms were measured using the Montgomery Asberg Depression Rating Scale (MADRS). Measurements of TRP, amino acids competing with TRP for entrance through the blood-brain barrier, KYN and kynurenic acid (KA), a neuroprotective metabolite, were performed using high-performance liquid chromatography. All assessments were carried out at baseline and 1, 2, 4, 8, 12 and 24 weeks after treatment was initiated. The MADRS score significantly increased during IFN-alpha treatment as did the KYN/TRP ratio, reflecting IDO activity, and the KYN/KA ratio, reflecting the neurotoxic challenge. The TRP/CAA (competing amino acids) ratio, reflecting TRP availability to the brain, did not significantly change during treatment. Total MADRS score was significantly associated over time with the KYN/KA ratio, but not with the TRP/CAA ratio. Although no support was found that IDO decreases TRP availability to the brain, this study does support a role for IDO activity in the pathophysiology of IFN-alpha-induced depressive symptoms, through its induction of neurotoxic KYN metabolites.

Life stress, the "kindling" hypothesis, and the recurrence of depression: considerations from a life stress perspective

Major depression is frequently characterized by recurrent episodes over the life course. First lifetime episodes of depression, however, are typically more strongly associated with major life stress than are successive recurrences. A key theoretical issue involves how the role of major life stress changes from an initial episode over subsequent recurrences. The primary conceptual framework for research on life stress and recurrence of depression is the "kindling" hypothesis (R. M. Post, 1992). Despite the strengths of the kindling hypothesis, a review of the research literature reveals inconsistencies and confusion about life stress and its implications for the recurrence of depression. Adopting a life stress perspective, the authors introduce 3 major themes that resolve the inconsistencies in the current literature. They integrate these themes and extrapolate the ideas with available data to develop a preliminary framework for evaluating competing explanatory models and to guide research on life stress and the recurrence of depression.

Reduced hippocampal volumes and memory loss in patients with early- and late-onset depression

BACKGROUND

Hippocampal volume reduction has been reported inconsistently in people with major depression.

AIMS

To evaluate the interrelationships between hippocampal volumes, memory and key clinical, vascular and genetic risk factors.

METHOD

Totals of 66 people with depression and 20 control participants underwent magnetic resonance imaging and clinical assessment. Measures of depression severity, psychomotor retardation, verbal and visual memory and vascular and specific genetic risk factors were collected.

RESULTS

Reduced hippocampal volumes occurred in older people with depression, those with both early-onset and late-onset disorders and those with the melancholic subtype. Reduced hippocampal volumes were associated with deficits in visual and verbal memory performance.

CONCLUSIONS

Although reduced hippocampal volumes are most pronounced in late-onset depression, older people with early-onset disorders also display volume changes and memory loss. No clear vascular or genetic risk factors explain these findings. Hippocampal volume changes may explain how depression emerges as a risk factor to dementia.

Recovery of hippocampal cell proliferation and BDNF levels, both of which are reduced by repeated restraint stress, is accelerated by chronic venlafaxine

The present study investigated the poststress (PS) cellular and molecular changes in the hippocampus of rats subjected to repeated restraint stress (RS) and the effects of chronic administration of an antidepressant drug, venlafaxine, on these changes. It was found that RS suppressed hippocampal cell proliferation, decreased brain-derived neurotrophic factor (BDNF) levels, and increased both the levels of copper/zinc superoxide dismutase (Cu/Zn-SOD) and the number of Cu/Zn-SOD immunostained hippocampal interneurons. In venlafaxine-treated rats, the changes in cell proliferation, BDNF levels, and the number of Cu/Zn-SOD interneurons returned to control levels on PS Days 21, 14, 7, respectively. In vehicle-injected rats, BDNF and the number of Cu/Zn-SOD interneurons returned to control levels on PS Days 21 and 14, respectively, but cell proliferation was still suppressed on PS Day 21. The stress-induced elevation of Cu/Zn-SOD protein remained during the 3-week PS period, and it was further increased by about 20% after 3 weeks of venlafaxine administration.

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

The advance of neuroimaging techniques has resulted in a burgeoning of studies reporting abnormalities in brain structure and function in a number of neuropsychiatric disorders. Measurement of hippocampal volume has developed as a useful tool in the study of neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. From this database, the methodology of all original manual tracing protocols were studied. These protocols differed in a number of important factors for accurate hippocampal volume determination including magnetic field strength, the number of slices assessed and the thickness of slices, hippocampal orientation correction, volumetric correction, software used, inter-rater reliability, and anatomical boundaries of the hippocampus. The findings are discussed in relation to optimizing determination of hippocampal volume.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

Magnetic resonance imaging (MRI) has opened a new window to the brain. Measuring hippocampal volume with MRI has provided important information about several neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. Smaller hippocampal volumes have been reported in epilepsy, Alzheimer's disease, dementia, mild cognitive impairment, the aged, traumatic brain injury, cardiac arrest, Parkinson's disease, Huntington's disease, Cushing's disease, herpes simplex encephalitis, Turner's syndrome, Down's syndrome, survivors of low birth weight, schizophrenia, major depression, posttraumatic stress disorder, chronic alcoholism, borderline personality disorder, obsessive-compulsive disorder, and antisocial personality disorder. Significantly larger hippocampal volumes have been correlated with autism and children with fragile X syndrome. Preservation of hippocampal volume has been reported in congenital hyperplasia, children with fetal alcohol syndrome, anorexia nervosa, attention-deficit and hyperactivity disorder, bipolar disorder, and panic disorder. Possible mechanisms of hippocampal volume loss in neuropsychiatric disorders are discussed.

Anatomical MRI study of hippocampus and amygdala in patients with current and remitted major depression

Morphometric MRI studies suggest decreased hippocampal volumes in currently depressed patients, with conflicting findings for the amygdala. We studied these temporal lobe structures and superior temporal gyrus (STG) in patients with current and remitted major depression. We scanned 31 unmedicated depressed patients (21 currently depressed, 10 remitted) and 31 matched healthy controls with a 3D SPGR sequence in a 1.5 Tesla GE Signa Imaging System. There was a trend towards smaller left amygdala volumes in all depressed patients compared with healthy controls. We found significantly smaller hippocampal volumes bilaterally in currently depressed patients than in remitted patients. Furthermore, we found a statistically significant inverse correlation between length of illness and left hippocampus volumes and right superior temporal gyrus volumes. Our finding of smaller hippocampi in currently depressed patients is consistent with the hypothesis that hypercortisolism could result in hippocampal neurotoxicity in major depression. A smaller hippocampal size may be more characteristic of the depressive state and not be present in remitted patients.

Cellular changes in the postmortem hippocampus in major depression

BACKGROUND

Imaging studies report that hippocampal volume is decreased in major depressive disorder (MDD). A cellular basis for reduced hippocampal volume in MDD has not been identified.

METHODS

Sections of right hippocampus were collected in 19 subjects with MDD and 21 normal control subjects. The density of pyramidal neurons, dentate granule cell neurons, glia, and the size of the neuronal somal area were measured in systematic, randomly placed three-dimensional optical disector counting boxes.

RESULTS

In MDD, cryostat-cut hippocampal sections shrink in depth a significant 18% greater amount than in control subjects. The density of granule cells and glia in the dentate gyrus and pyramidal neurons and glia in all cornv ammonis (CA)/hippocampal subfields is significantly increased by 30%-35% in MDD. The average soma size of pyramidal neurons is significantly decreased in MDD.

CONCLUSION

In MDD, the packing density of glia, pyramidal neurons, and granule cell neurons is significantly increased in all hippocampal subfields and the dentate gyrus, and pyramidal neuron soma size is significantly decreased as well. It is suggested that a significant reduction in neuropil in MDD may account for decreased hippocampal volume detected by neuroimaging. In addition, differential shrinkage of frozen sections of the hippocampus suggests differential water content in hippocampus in MDD.

Chronic olanzapine or fluoxetine administration increases cell proliferation in hippocampus and prefrontal cortex of adult rat

BACKGROUND

There has been increasing evidence that atypical antipsychotics are effective in the treatment of mood disorders or for augmenting 5-hydroxytryptamine selective reuptake inhibitors for treatment-resistant depression.

METHODS

Upregulation of neurogenesis in the adult hippocampus is a marker of antidepressant activity, and the present study investigated the influence of the atypical antipsychotic drug olanzapine on cell proliferation in the hippocampus of adult rat. The regulation of cell proliferation in the prelimbic cortex of adult rat was also examined.

RESULTS

Chronic (21 days) olanzapine administration increased the number of newborn cells in the dentate gyrus of the hippocampus to the same extent as fluoxetine. Olanzapine or fluoxetine treatment also increased the number of proliferating cells in the prelimbic cortex. In contrast, there was no effect of either drug in the subventricular zone or primary motor cortex, and there was a trend for an increase in the striatum. Subchronic (7 days) administration of olanzapine had no effect on cell proliferation in hippocampus or prelimbic cortex, consistent with the time course for the effect of fluoxetine and the therapeutic actions of antidepressant treatment. The combination of olanzapine plus fluoxetine did not result in a greater induction of cell proliferation in either brain region. Analysis of the cell phenotype demonstrated that approximately 20% of the newborn cells in the prelimbic cortex differentiated into endothelial cells but not neurons, in contrast to the dentate gyrus, where most newborn cells differentiated into neurons.

CONCLUSIONS

The results demonstrate that antidepressant or atypical antipsychotic medications can increase the proliferation of glia in limbic brain structures, an effect that could reverse the loss of glia that has been observed in depressed patients.