Neural plasticity to stress and antidepressant treatment

Up-regulation of microtubule-associated protein 4 and drebrin A mRNA expression by antidepressants in rat hippocampus following chronic stress

We used the differential display-polymerase chain reaction (DD-PCR) protocol to identify genes related to antidepressant effects. Rats were subjected to different kinds of stress for 20 days, and then the antidepressants desipramine and fluoxetine were administered (10 mg/kg per day, i.p.) for 20 days. DD-PCR was performed and differentially expressed cDNAs were further confirmed by dot-blot hybridization. cDNA homology analysis revealed that desipramine up-regulated the expression of microtubule-associated protein 4 (MAP-4) mRNA and fluoxetine up-regulated the expression of drebrin A mRNA in the rat hippocampus compared with the chronically stressed group. This result suggests that MAP-4 and drebrin may be involved in the antidepressant like effects of desipramine and fluoxetine.

Prepartum, postpartum, and chronic depression effects on newborns

In order to assess the effects of the onset and chronicity of maternal depression on neonatal physiology, eighty pregnant women were assessed for depression during mid-pregnancy (M gestational age = 25.9 weeks) and shortly after delivery. The women were classified as reporting depressive symptoms 1) only during the prepartum assessment; 2) only during the postpartum assessment; 3) during both the prepartum and postpartum assessments; or 4) reporting no depressive symptoms at either the prepartum or the postpartum assessment. Maternal mood and biochemistry were assessed during pregnancy, and the EEG and biochemical characteristics of their 1-week-old infants were assessed shortly after birth. As predicted, the newborns of the mothers with prepartum and postpartum depressive symptoms had elevated cortisol and norepinephrine levels, lower dopamine levels, and greater relative right frontal EEG asymmetry. The infants in the prepartum group also showed greater relative right frontal EEG asymmetry and higher norepinephrine levels. These data suggest that effects on newborn physiology depend more on prepartum than postpartum maternal depression but may also depend on the duration of the depressive symptoms.

Characterization of fluoxetine plus olanzapine treatment in rats: a behavior, endocrine, and immediate-early gene expression analysis

A large number of individuals afflicted with psychiatric disorders, particularly depression with psychotic features, do not respond to conventional drug therapy. An option for this phenomenon is to augment a standard selective serotonin (5-HT) reuptake inhibitor with an atypical antipsychotic agent. In this regard, fluoxetine and olanzapine have been used concomitantly for treatment-resistant depression and bipolar depression. Although highly efficacious in terms of producing superior improvement of symptoms across a variety of psychological measures, the motor patterns, endocrine profiles, and intracellular signaling pathways affected by drug augmentation have not been determined. Here we show that fluoxetine (10 mg/kg) plus olanzapine (5 mg/kg) given to rats for 7 consecutive days (i.e., subchronic treatment) alters motor activity and diminishes spontaneous behaviors as measured by spatial position and angular path analyses. In addition, the same drug combination pattern sensitizes peak adrenal corticosterone secretion without altering serum glucose levels. We also show that subchronic fluoxetine and olanzapine exposure suppresses the induction of two immediate-early gene transcription factors (e.g., pCREB and FOS) that are associated with long-lasting changes in synaptic efficacy and structural modifications in the prefrontal cortex, piriform cortex, and hippocampus. These results suggest that fluoxetine plus olanzapine can interact in a fashion not predicted by the currently accepted model of fluoxetine monotherapy and provide insight into the synergistic actions of drug augmentation in patients with treatment-resistant depression.

Total sleep deprivation increases extracellular serotonin in the rat hippocampus

Sleep deprivation exerts antidepressant effects after only one night of deprivation, demonstrating that a rapid antidepressant response is possible. In this report we tested the hypothesis that total sleep deprivation induces an increase in extracellular serotonin (5-HT) levels in the hippocampus, a structure that has been proposed repeatedly to play a role in the pathophysiology of depression. Sleep deprivation was performed using the disk-over-water method. Extracellular levels of 5-HT were determined in 3 h periods with microdialysis and measured by high performance liquid chromatography coupled with electrochemical detection. Sleep deprivation induced an increase in 5-HT levels during the sleep deprivation day. During an additional sleep recovery day, 5-HT remained elevated even though rats displayed normal amounts of sleep. Stimulus control rats, which had been allowed to sleep, did not experience a significant increased in 5-HT levels, though they were exposed to a stressful situation similar to slee-deprived rats. These results are consistent with a role of 5-HT in the antidepressant effects of sleep deprivation.

Gene profile of electroconvulsive seizures: induction of neurotrophic and angiogenic factors

Electroconvulsive seizure therapy (ECS) is a clinically proven treatment for depression and is often effective even in patients resistant to chemical antidepressants. However, the molecular mechanisms underlying the therapeutic efficacy of ECS are not fully understood. One theory that has gained attention is that ECS and other antidepressants increase the expression of select neurotrophic factors that could reverse or block the atrophy and cell loss resulting from stress and depression. To further address this topic, we examined the expression of other neurotrophic-growth factors and related signaling pathways in the hippocampus in response to ECS using a custom growth factor microarray chip. We report the regulation of several genes that are involved in growth factor and angiogenic-endothelial signaling, including neuritin, stem cell factor, vascular endothelial growth factor (VEGF), VGF (nonacronymic), cyclooxygenase-2, and tissue inhibitor of matrix metalloproteinase-1. Some of these, as well as other growth factors identified, including VEGF, basic fibroblast growth factor, and brain-derived neurotrophic factor, have roles in mediating neurogenesis and cell proliferation in the adult brain. We also examined gene expression in the choroid plexus and found several growth factors that are enriched in this vascular tissue as well as regulated by ECS. These data suggest that an amplification of growth factor signaling combined with angiogenic mechanisms could have an important role in the molecular action of ECS. This study demonstrates the applicability of custom-focused microarray technology in addressing hypothesis-driven questions regarding the action of antidepressants.

Brain-derived neurotrophic factor as a potential risk locus for bipolar disorder: evidence, limitations, and implications

Brain-derived neurotrophic factor (BDNF) plays an important role in promoting and modifying growth, development, and survival of neuronal populations, and, in the mature nervous system, is involved in activity-dependent neuronal plasticity. Based on several lines of evidence, BDNF has been hypothesized to play an important role in the pathogenesis of mood disorder and the therapeutic action of at least some effective treatments. The gene encoding BDNF lies on the short arm of chromosome 11 in a region where some linkage studies of bipolar disorder have reported evidence for a susceptibility gene. BDNF can, thus, be considered as an attractive candidate gene for involvement in the pathogenesis of bipolar disorder, and two recent family-based association studies have provided evidence that one or more sequence variants within or near the BDNF gene show an association with disease susceptibility. These findings are of great interest and may open up a new chapter in the understanding of the causation and treatment of bipolar disorder. However, it is still early in the genetic investigation of BDNF in bipolar disorder, and it is important that these findings are replicated in large independent samples and that functional studies can confirm and characterize the pathogenic relevance of this genetic variation.

Reduced cell proliferation in the dentate gyrus is not correlated with the development of learned helplessness

BACKGROUND

A plethora of indirect findings suggests that mood disorders may be caused by or result in structural changes in the brain, namely decreased hippocampal cell proliferation.

METHODS

To test for these hypotheses, we used a rat model of depression, learned helplessness. Moderate unpredictable and inescapable foot shocks induced learned helplessness only in a portion of the rats. Rats that showed helpless behavior were compared to those behaving normally after inescapable shock. Proliferating cells in the dentate gyrus were labeled with BrdU (bromodeoxyuridine).

RESULTS

Helpless behavior appeared before the decrease of dentate gyrus cell proliferation was maximal. Cell proliferation was decreased to the same extent in animals that developed helplessness as those that were not helpless. Furthermore, immobilization stress, which reduced the rate of cell proliferation, did not induce learned helplessness.

CONCLUSION

These results are in line with reports that the rate of dentate gyrus cell proliferation is acutely down-regulated by stress, but the development of helpless behavior does not correlate with this process. Further studies will have to clarify if during learned helpless behavior neurogenesis is impaired by altered differentiation or survival of cells.

Positron emission tomography imaging in depression: a neural systems perspective

PET measures of regional glucose metabolism, although chemically nonspecific, are sensitive indices of brain function in the untreated state and following disparate treatments. The continued development of imaging and multivariate statistical strategies is expected to provide an important perspective toward the full characterization of the depression phenotype at the neural systems level. An additional goal is the development of routine, brain-based clinical algorithms that optimize diagnosis and treatment of individual depressed patients.

Prenatal stress in rats predicts immobility behavior in the forced swim test

Prenatally-stressed (PS) rats are characterized by a general impairment of the hypothalamo-pituitary-adrenal (HPA) axis and sleep disturbances indicating that this model has face validity with some clinical features observed in a subpopulation of depressed patients. The prolonged corticosterone secretion shown by PS rats in response to stress was positively correlated with an increased immobility behavior in the forced swim test. To investigate the predictive validity of this model, a separate group of animals was chronically treated with the antidepressant tianeptine (10 mg/kg i.p. for 21 days). Such chronic treatment reduced in PS rats immobility time in the forced swim test. These findings suggest that the PS rat is an interesting animal model for the evaluation of antidepressant treatment.

VEGF is necessary for exercise-induced adult hippocampal neurogenesis

Declining learning and memory function is associated with the attenuation of adult hippocampal neurogenesis. As in humans, chronic stress or depression in animals is accompanied by hippocampal dysfunction, and neurogenesis is correspondingly down regulated, in part, by the activity of the hypothalamic-pituitary-adrenal axis as well as glutamatergic and serotonergic networks. Antidepressants can reverse this effect over time but one of the most clinically effective moderators of stress or depression and robust stimulators of neurogenesis is simple voluntary physical exercise such as running. Curiously, running also elevates circulating stress hormone levels yet neurogenesis is doubled in running animals. In evaluating the signalling that running provides to the central nervous system in mice, we have found that peripheral vascular endothelial growth factor (VEGF) is necessary for the effects of running on adult hippocampal neurogenesis. Peripheral blockade of VEGF abolished running-induced neurogenesis but had no detectable effect on baseline neurogenesis in non-running animals. These data suggest that VEGF is an important element of a 'somatic regulator' of adult neurogenesis and that these somatic signalling networks can function independently of the central regulatory networks that are typically considered in the context of hippocampal neurogenesis.

Psychiatric drug discovery and development

This new conference on Psychiatric Drug Research was organised by the Strategic Research Institute and was chaired by P McGonigle (Wyeth Research, USA) and D Schoepp (Eli Lilly, USA). The 2-day meeting featured presentations from an international assembly of industrial and academic experts who have significantly contributed to the current body of knowledge in the field of psychotherapeutics. D Weinberger (NIMH, USA) gave an elegant keynote lecture on the application of genomics in psychopharmacology. Other presentations covered the latest technological advances, animal models and mechanistic approaches utilised in drug discovery for neuropsychiatric disorders and reviewed the current status of numerous novel targets resulting from these strategies.

Depressed new neurons--adult hippocampal neurogenesis and a cellular plasticity hypothesis of major depression

In a novel theory, a failure of adult hippocampal neurogenesis has been proposed to provide the biological and cellular basis of major depression. The as yet unresolved function of the new hippocampal neurons will have to be in the center of any attempt to prove this hypothesis. Only knowledge of normal functional relevance of new neurons will allow an assessment of their potential role in disturbed hippocampal function in depression; however, major depression is not primarily a hippocampal disorder. We therefore propose that consideration of the neurogenesis hypothesis of depression be the most prominent aspect of a more general cellular plasticity hypothesis.

Affective disorders, antidepressant drugs and brain metabolism

There is increasing evidence that affective disorders are associated with dysfunction of neurotransmitter postsynaptic transduction pathways and that chronic treatment with clinically active drugs results in adaptive modification of these pathways. Despite the close dependence of signal transduction on adenosine triphosphate (ATP) availability, the changes in energy metabolism in affective disorders are largely unknown. This question has been indirectly dealt with through functional imaging studies (PET, SPECT, MRS). Despite some inconsistencies, PET and SPECT studies suggest low activity in cortical (especially frontal) regions in depressed patients, both unipolar and bipolar, and normal or increased activity in the manic pole. Preliminary MRS studies indicate some alterations in brain metabolism, with reduced creatine phosphate and ATP levels in the brain of patients with affective disorders. However, the involvement of the energy metabolism in affective disorders is still debated. We propose direct neurochemical investigations on mitochondrial functional parameters of energy transduction, such as the activities of (a) the enzymatic systems of oxidative metabolic cycle (Kreb's cycle); (b) the electron transfer chain; (c) oxidative phosphorylation, and (d) the enzyme activities of ATP-requiring ATPases. These processes should be studied in affective disorders and in animals treated with antidepressant drugs or lithium.

Phenelzine treatment increases transcription factor AP-2 levels in rat brain

BACKGROUND

The elevations of noradrenaline (NA) and serotonin (5-HT) levels in response to acute serotonin reuptake inhibitor (SSRI) or tricyclic antidepressant (TCA) exposure are not consistent with the time course for the therapeutic action of these antidepressants. Thus, neuronal adaptations are needed for the therapeutic effect to arise. Transcription factor Activating Protein -2 (AP-2) is critical for mammalian neural gene expression. Several genes involved in brainstem CNS transmitter systems, especially the monoamines, have AP-2 binding sites in their regulatory regions. We have previously shown that treatment with citalopram and imipramin resulted in a decrease in AP-2alpha and AP-2beta levels in rat brain. We have also reported an association between a specific genotype of AP-2beta to personality traits, binge-eating disorder and platelet monoamine oxidase (MAO) activity.

RESULTS

Subchronic administration (10 days) of phenelzine (PLZ) increased the levels of AP-2alpha, AP-2beta and the DNA binding activity of AP-2 in nuclear extracts prepared from rat whole brain when compared with sham treated animals.

CONCLUSION

These data suggest that AP-2 is not involved in the therapeutic effect of antidepressants. Rather, the effects of antidepressants seen on the levels of AP-2 might be involved in the expression of side-effects during the lag-period.

Antagonism of the stress-induced increase in cortical norepinephrine output by the selective norepinephrine reuptake inhibitor reboxetine

We have previously shown that long-term treatment of rats with antidepressant drugs that affect the activity of noradrenergic and serotonergic neurons by different mechanisms, inhibits the increase in cortical norepinephrine output induced by stress. With the use of microdialysis, we have now evaluated the effects of reboxetine, an antidepressant drug that selectively inhibits norepinephrine reuptake, on the increase in cortical norepinephrine output elicited in rats by exposure to foot-shock stress or by the acute administration of N-methyl-beta-carboline-3-carboxamide (FG 7142) (20 mg/kg, i.p.). Foot-shock stress and FG 7142 each induced a marked increase in the cortical extracellular concentration of norepinephrine (+200 and +90%, respectively) in control rats. Long-term treatment with reboxetine (10 mg/kg, i.p., once a day for 21 days) reduced the effect of foot-shock stress and completely antagonized the effect of FG 7142 on cortical norepinephrine output. Our results suggest that changes in the activity of noradrenergic neurons in the cortex might be relevant to the anxiolytic and antidepressant effects of reboxetine.

Emerging evidence for a central epinephrine-innervated alpha 1-adrenergic system that regulates behavioral activation and is impaired in depression

Currently, most basic and clinical research on depression is focused on either central serotonergic, noradrenergic, or dopaminergic neurotransmission as affected by various etiological and predisposing factors. Recent evidence suggests that there is another system that consists of a subset of brain alpha(1B)-adrenoceptors innervated primarily by brain epinephrine (EPI) that potentially modulates the above three monoamine systems in parallel and plays a critical role in depression. The present review covers the evidence for this system and includes findings that brain alpha(1)-adrenoceptors are instrumental in behavioral activation, are located near the major monoamine cell groups or target areas, receive EPI as their neurotransmitter, are impaired or inhibited in depressed patients or after stress in animal models, and are restored by a number of antidepressants. This "EPI-alpha(1) system" may therefore represent a new target system for this disorder.

Increased expression of c-Jun transcription factor in cerebellar vermis of patients with schizophrenia

In the cerebellar vermis of schizophrenic patients, our previous studies have revealed alterations in the mitogen-activated protein (MAP) kinase signaling cascade and downstream transcription factors within the c-fos promoter. Since the proteins of the Fos and Jun families of immediate-early genes dimerize to form activating protein (AP)-1, the present study was conducted to examine the expression of Jun transcription factors in schizophrenic and control subjects. Using Western blot analysis, we determined the protein levels of c-Jun, Jun B, and Jun D as well as the levels of c-jun mRNA by relative RT-PCR in post-mortem samples from cerebellar vermis. The expression of c-Jun protein and c-jun mRNA was significantly increased in the cerebellar vermis of patients with schizophrenia, whereas no significant differences were found in the expression of Jun B or Jun D proteins. Studies in rats indicated that the abnormal expression of c-Jun transcription factor observed in schizophrenic patients was not related to post-mortem intervals or chronic treatment with antipsychotic medications. This study provides new insights into cerebellar abnormalities of schizophrenia at the level of expression of c-Jun that target key genes associated with the MAP kinase cascade.

Effects of chronic antidepressants and electroconvulsive shock on serotonergic neurotransmission in the rat hippocampus

The hippocampus may play a critical role in the pathophysiology and treatment of depression. There are two main lines of evidence for this: firstly, many of its functions correspond to those altered in depression, and secondly, many hippocampal functions are regulated by the serotonergic (5-HT) system, which is a common target of antidepressant treatments. Chronic effects of antidepressants and electroconvulsive shock (ECS) have been studied by various methods using electrophysiology, in vivo microdialysis or ex vivo neurochemical measurements. The aim of the current review is to point out possible correlations between these studies based on different methods and to suggest neurochemical mechanisms that result in the observed changes in hippocampal physiology and neurogenesis. These changes in hippocampal neurochemistry are reviewed and compared with the abnormalities associated with stress, corticosterone or depression.

The postnatal environment can counteract prenatal effects on cognitive ability, cell proliferation, and synaptic protein expression

Many environmental factors during the pre- or postnatal period can affect an individual's cognitive function and neural development throughout life. Little is known, however, about the combined effects of the pre- and postnatal environments on cognitive function of adult offspring and structural alterations in the adult brain. In this study, we confirmed that pre- or postnatal stress impaired learning and memory performance of rats. Conversely, pre- or postnatal enriched housing improved behavioral performance. These experience-dependent behavioral alterations were consistent with changes in 5-bromo-2'-deoxyuridine-labeled cell number in the granule cell layer of the hippocampus and in the expression level of synaptic markers such as neuronal cell adhesion molecule and synaptophysin, and expression of a neurotrophic factor, brain-derived neurotrophic factor. Postnatal stress appeared to have no influence on cell proliferation, however. We did find that postnatal environment could attenuate prenatal effects partly via a longitudinal cross-housing study, in which pups born to mothers housed under enriched conditions were reared under stressful conditions and vice versa. These results suggest that postnatal environmental manipulations can counteract the cognitive alterations in early adulthood and the structural changes in the young adult brain induced by prenatal experience.

S100B and response to treatment in major depression: a pilot study

S100B is a protein which exerts both detrimental and neurotrophic effects, depending on its concentration in brain tissue. An increase of S100B in micromolar concentrations is observed in traumatic brain conditions and is associated with poor outcome. Micromolar levels of extracellular S100B in vitro may have deleterious effects. However, in nanomolar concentrations S100B has multiple neurotrophic effects in vitro may in vivo be regarded as a hallmark of neuroprotective efforts. This pilot study addresses the hypothesis that S100B serum concentrations may be of predictive validity for the response to antidepressant treatment in patients with major depression. S100B plasma levels were determined in 25 patients with major depression and 25 matched healthy controls using an immunofluorimetric sandwich assay. S100B plasma levels were significantly higher in major depressive patients than in healthy controls and positively correlated with treatment response after 4 weeks of treatment. In a linear regression model, a significant predictive effect was found only for S100B and severity of depressive symptoms upon admission. These results suggest that neuroprotective functions of S100B counterbalance neurodegenerative mechanisms that are involved in the pathophysiology of major depression and in the response to antidepressant treatment.

New developments in electroconvulsive therapy and magnetic seizure therapy

New findings regarding the mechanisms of action of electro-convulsive therapy (ECT) have led to novel developments in treatment technique to further improve this highly effective treatment for major depression. These new approaches include novel placements, optimization of electrical stimulus parameters, and new methods for inducing more targeted seizures(eg, magnetic seizure therapy [MST]). MST is the use of transcranial magnetic stimulation to induce a seizure. Magnetic fields pass through tissue unimpeded, providing more control over the site and extent of stimulation than can be achieved with ECT. This enhanced control represents a means of focusing the treatment on target cortical structures thought to be essential to antidepressant response and reducing spread to medial temporal regions implicated in the cognitive side effects of ECT. MST is at an early stage of development. Preliminary results suggest that MST may have some advantages over ECT in terms of subjective side effects and acute cognitive functioning. Studies designed to address the antidepressant efficacy of MST are underway. As with all attempts to improve convulsive therapy technique, the clinical value of MST will need to be established through controlled clinical trials. This article reviews the experience to date with MST, and places this work in the broader context of other means of optimizing convulsive therapy in the treatment of depression.

Sleep deprivation reduces proliferation of cells in the dentate gyrus of the hippocampus in rats

The dentate gyrus (DG) of the adult hippocampus gives rise to progenitor cells, which have the potential to differentiate into neurons. To date it is not known whether sleep or sleep loss has any effect on proliferation of cells in the DG. Male rats were implanted for polysomnographic recording, and divided into treadmill sleep-deprived (SD), treadmill control (TC) and cage control (CC) groups. SD and TC rats were kept for 96 h on a treadmill that moved either for 3 s on/12 s off (SD group) or for 15 min on/60 min off (TC group) to equate total movement but permit sustained rest periods in TC animals. To label proliferating cells the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU) was injected after the first 48 h of the experimental procedure in all groups (50 mg kg-1, I.P.). The percentage of time awake per day was 93.2 % in the SD group vs. 59.6 % in the TC group and 49.9 % in the CC group (P < 0.001). Stereological analysis showed that the number of BrdU-positive cells in the DG of the dorsal hippocampus was reduced by 54 % in the SD group in comparison with the TC and by 68 % in comparison with the CC group. These results suggest that sleep deprivation reduces proliferation of cells in the DG of the dorsal hippocampus.

Molecular correlates of impaired prefrontal plasticity in response to chronic stress

Disturbed adaptations at the molecular and cellular levels following stress could represent compromised neural plasticity that contributes to the pathophysiology of stress-induced disorders. Evidence illustrates atrophy and cell death of stress-vulnerable neurones in the prefrontal cortex. Reduced plasticity may be realized through the destabilized function of selective proteins involved in organizing the neuronal skeleton and translating neurotrophic signals. To elucidate the mechanisms underlying these effects, rats were exposed to chronic footshock stress. Patterns of c-fos, phospho-extracellular-regulated protein kinases 1/2 (ERK1/2), calcineurin and phospho-cyclic-AMP response-element binding protein (CREB) expression were subsequently investigated. The results indicate chronic stress-induced impairments in prefrontal and cingulate signal transduction cascades underlying neuronal plasticity. The medial prefrontal cortex, demonstrated functional hyperactivity and dendritic phospho-ERK1/2 hyperphosphorylation, while reduced c-fos and calcineurin immunoreactivity occurred in the cingulate cortex. Significantly reduced phospho-CREB expression in both cortical regions, considering its implication in brain-derived neurotrophic factor (BDNF) transcription, suggests reduced synaptic plasticity. This data confirms the damaging effect of stress on cortical activity, on a molecular level. Due to the association of these markers in the regulation of BDNF signalling, these findings suggest a central role for intracellular neurotrophin transduction members in the pathways underlying cellular actions of stress in the brain.

The neurobiology and control of anxious states

Fear is an adaptive component of the acute "stress" response to potentially-dangerous (external and internal) stimuli which threaten to perturb homeostasis. However, when disproportional in intensity, chronic and/or irreversible, or not associated with any genuine risk, it may be symptomatic of a debilitating anxious state: for example, social phobia, panic attacks or generalized anxiety disorder. In view of the importance of guaranteeing an appropriate emotional response to aversive events, it is not surprising that a diversity of mechanisms are involved in the induction and inhibition of anxious states. Apart from conventional neurotransmitters, such as monoamines, gamma-amino-butyric acid (GABA) and glutamate, many other modulators have been implicated, including: adenosine, cannabinoids, numerous neuropeptides, hormones, neurotrophins, cytokines and several cellular mediators. Accordingly, though benzodiazepines (which reinforce transmission at GABA(A) receptors), serotonin (5-HT)(1A) receptor agonists and 5-HT reuptake inhibitors are currently the principle drugs employed in the management of anxiety disorders, there is considerable scope for the development of alternative therapies. In addition to cellular, anatomical and neurochemical strategies, behavioral models are indispensable for the characterization of anxious states and their modulation. Amongst diverse paradigms, conflict procedures--in which subjects experience opposing impulses of desire and fear--are of especial conceptual and therapeutic pertinence. For example, in the Vogel Conflict Test (VCT), the ability of drugs to release punishment-suppressed drinking behavior is evaluated. In reviewing the neurobiology of anxious states, the present article focuses in particular upon: the multifarious and complex roles of individual modulators, often as a function of the specific receptor type and neuronal substrate involved in their actions; novel targets for the management of anxiety disorders; the influence of neurotransmitters and other agents upon performance in the VCT; data acquired from complementary pharmacological and genetic strategies and, finally, several open questions likely to orientate future experimental- and clinical-research. In view of the recent proliferation of mechanisms implicated in the pathogenesis, modulation and, potentially, treatment of anxiety disorders, this is an opportune moment to survey their functional and pathophysiological significance, and to assess their influence upon performance in the VCT and other models of potential anxiolytic properties.

Chronic AMPA receptor potentiator (LY451646) treatment increases cell proliferation in adult rat hippocampus

Stress-induced neuronal atrophy and death in the hippocampus may play an important role in the etiology of clinical depression. Conventional antidepressants can stimulate hippocampal neurogenesis after chronic administration. AMPA receptor potentiators (ARPs) such as LY392098 and LY451616 are active in both the forced swim test and the tail suspension test, two behavioral despair procedures widely used to predict antidepressant efficacy. Unlike traditional antidepressants, this group of compounds does not affect extracellular concentrations of biogenic amines. In this study, we investigated the effect of LY451646 on progenitor cell proliferation in adult rat hippocampus. Male Sprague-Dawley rats (n = 4-5 per group) received either single or chronic (21 days) doses of LY451646 (0.025-0.5 mg/kg). Bromodeoxyuridine (BrdU) injections and immunohistochemistry were performed 30 min and 24 h after the last drug injection, respectively. Results show that chronic LY451646 treatment increased progenitor cell proliferation (approximately 45%) in the dentate gyrus in a dose-dependent manner. This upregulation of BrdU labeling appeared as an increase in the number of cells arranged in clusters. Similarly, a significant increase in the number of cells in clusters was observed after a single injection of LY451646 (0.05 mg/kg), although the increase in total number of BrdU-positive cells (approximately 30%) did not reach statistical significance. This is the first in vivo study showing the modulation of progenitor cell proliferation by an ARP. These findings suggest that the antidepressant-like activity of ARPs in animals may be attributed, at least in part, to the regulation of progenitor cell proliferation in the hippocampus.

Changes in synaptic properties in cortical-limbic communications induced by repeated treatments with fluvoxamine in rats

There is evidence indicating that dysregulation of coordinated interactions of the cortical-limbic circuitry is associated with anxiety and mood disorders. Our previous study has reported that an enhancement of long-term plasticity in the "limbic-cortical" pathway produced by repeated treatments with fluvoxamine may be involved in the clinical effects of a selective serotonin (5-HT) reuptake inhibitor (SSRI). Here we assessed the effects of single and repeated treatments with fluvoxamine on the synaptic transmission and plasticity in the "cortical-limbic" pathway in vivo. The evoked potentials in the basolateral amygdaloid complex (BLA) by stimulation of the medial prefrontal cortex (mPFC) in halothane-anesthetized rats were recorded. Single administration of fluvoxamine (10 and 30 mg/kg, i.p.) enhanced the efficacy of synaptic transmission at the mPFC-BLA synapses dose-dependently. The enhanced synaptic efficacy induced by 30 mg/kg fluvoxamine was suppressed after long-term administration of fluvoxamine (30 mg/kg per day x 21 days, orally). Repeated treatments with fluvoxamine affected short-term, but not long-term, synaptic plasticity in the mPFC-BLA pathway. These findings indicate that the 5-HTergic system contributes to modulation of synaptic changes in this pathway. Our results also suggest that different changes in synaptic properties in cortical-limbic communications induced by repeated treatments with fluvoxamine may be associated with therapeutic effects of SSRI.

Substance P receptor antagonist and clomipramine prevent stress-induced alterations in cerebral metabolites, cytogenesis in the dentate gyrus and hippocampal volume

The neuropeptide substance P and its receptor, the neurokinin 1 receptor (NK(1)R) have been proposed as possible targets for new antidepressant therapies. The present study investigated the effect of the NK(1)R antagonist L-760,735 and the tricyclic antidepressant clomipramine in the chronic psychosocial stress paradigm of adult male tree shrews. Animals were subjected to a 7-day period of psychosocial stress before the onset of daily oral administration of L-760,735 (10 mg kg(-1) day(-1)) or clomipramine (50 mg kg(-1) day(-1)). The psychosocial stress continued throughout the treatment period of 28 days. Brain metabolite concentrations were determined in vivo by proton magnetic resonance spectroscopy. Cell proliferation in the dentate gyrus and hippocampal volume were measured post mortem. Stress significantly decreased in vivo concentrations of N-acetyl-aspartate (-14%), creatine and phosphocreatine (-15%) and choline-containing compounds (-15%). The proliferation rate of the granule precursor cells in the dentate gyrus was reduced (-45%), and hippocampal volume was decreased (-14%). The stress-induced changes of brain metabolites, hippocampal volume and dentate cytogenesis rate were prevented by concomitant drug administration. Elevated myo-inositol concentrations after both treatments hint to an astrocytic enhancement. These results suggest that-despite a different pharmacological profile-the NK(1)R antagonist L-760,735, a member of a novel class of antidepressant drugs, has comparable neurobiological efficacy to tricyclic antidepressants such as clomipramine.

Tender points as predictors of distress and the pharmacologic management of fibromyalgia syndrome

The object of this study was to determine the association between tender point pain ratings, tender point counts and distress in people with fibromyalgia and to review the pharmacotherapy of fibromyalgia. Demographic, psychosocial, and health status information was collected from 316 health maintenance organization members with fibromyalgia. A manual tender point exam was conducted. Tender point counts predicted 3.0%, and tender point severity ratings predicted 8.3%, of the variance in distress. Little difference was found between the variance predicted for physical versus psychologic distress. A principal components analysis of all measures produced four distinct factors: global-physical functioning, tender points, psychologic, and physical. Tender point pain ratings and counts predicted a small but significant amount of variance in distress. In addition, FMS involves at least four rather distinct factors, one of which is related to tender points. Pharmacotherapeutic management is provided on a patient-specific basis including pharmacokinetics, pharmacodynamic, pathophysiologic, and psychosocial needs designed and modulated for each individual patient.

Enhancing neuronal plasticity and cellular resilience to develop novel, improved therapeutics for difficult-to-treat depression

There is growing evidence from neuroimaging and ostmortem studies that severe mood disorders, which have traditionally been conceptualized as neurochemical disorders, are associated with impairments of structural plasticity and cellular resilience. It is thus noteworthy that recent preclinical studies have shown that critical molecules in neurotrophic signaling cascades (most notably cyclic adenosine monophosphate [cAMP] response element binding protein, brain-derived neurotrophic factor, bcl-2, and mitogen activated protein [MAP] kinases) are long-term targets for antidepressant agents and antidepressant potentiating modalities. This suggests that effective treatments provide both trophic and neurochemical support, which serves to enhance and maintainnormal synaptic connectivity, thereby allowing the chemical signal to reinstate the optimal functioning of critical circuits necessary for normal affective functioning. For many refractory patients, drugs mimicking "traditional" strategies, which directly or indirectly alter monoaminergic levels, may be of limited benefit. Newer "plasticity enhancing" strategies that may have utility in the treatment of refractory depression include N-methyl-D-aspartate antagonists, alpha-amino-3-hydroxy-5-methylisoxazole propionate (AMPA) potentiators, cAMP phosphodiesterase inhibitors, and glucocorticoid receptor antagonists. Small-molecule agents that regulate the activity f growth factors, MAP kinases cascades, and the bcl-2 family of proteins are also promising future avenues. The development of novel, nonaminergic-based therapeutics holds much promise for improved treatment of severe, refractory mood disorders.

Cognitive impairment in patients with chronic pain: the significance of stress

This review article examines the role of emotional distress and other aspects of suffering in the cognitive impairment that often is apparent in patients with chronic pain. Research suggests that pain-related negative emotions and stress potentially impact cognitive functioning independent of the effects of pain intensity. The anterior cingulate cortex is likely an integral component of the neural system that mediates the impact of pain-related distress on cognitive functions, such as the allocation of attentional resources. A maladaptive physiologic stress response is another plausible cause of cognitive impairment in patients with chronic pain, but a direct role for dysregulation of the hypothalamic-pituitary-adrenocortical axis has not been systematically investigated.

Neurotrophic effects of electroconvulsive therapy: a proton magnetic resonance study of the left amygdalar region in patients with treatment-resistant depression

Negatively balanced neurotrophic factors may be important in precipitating clinical depression. Recently, it has been reported that antidepressant therapy may exert positive neurotrophic effects. The aim of this study was to detect probable neurotrophic changes during electroconvulsive therapy (ECT). For this purpose, N-acetylaspartate (NAA), an amino acid exclusively located in neurons, and other brain metabolites such as glutamine/glutamate (Glx), choline (Cho), and creatine (Cr) were measured in patients by localized proton magnetic resonance spectroscopy. A total of 28 severely depressed patients (DSM-IV) were enrolled, and the left amygdalar region was investigated by proton STEAM spectroscopy before and after unilateral ECT. The results were compared with 28 age- and gender-matched controls using nonparametric paired and unpaired tests. A significant increase in NAA was observed only in ECT responders (n=14; p=0.019). Five out of 14 nonresponders to ECT monotherapy were remeasured following a clinical improvement after continued ECT combined with antidepressants and were then found also to present a significant increase in NAA. In all successfully treated patients, parallel observations, that is, increased levels, were made for Glx, whereas Cho and Cr were unchanged. In conclusion, our preliminary finding of increased NAA concentrations after successful ECT may indicate a probable neurotrophic effect of ECT.

Choline rise in the rat hippocampus induced by electroconvulsive shock treatment

BACKGROUND

Human hippocampal choline decreases in major depression episodes. This decrease was recently measured by 1H magnetic resonance spectroscopy (MRS), and it has been found that its level normalizes during antidepressive electroconvulsive therapy. We hypothesized a hippocampal choline increase in the rat brain under electroconvulsive shock (ECS) treatment.

METHODS

Rat hippocampi (n = 28) were investigated via magnetic resonance spectroscopy and signal intensities of choline (Cho), total creatine (tCr), and N-acetyl aspartate (NAA) were measured and expressed as ratios before and after six ECS treatments.

RESULTS

After ECS treatment, hippocampal choline increases significantly: Cho/tCr ratio: +13% and Cho/NAA ratio: +19% increase.

CONCLUSIONS

We found a rise of relative choline concentration induced by ECS treatment in rat hippocampus measured in vivo with magnetic resonance spectroscopy. This increase corresponds to the increase of choline in human hippocampus after electroconvulsive shock treatment. Because choline measured via 1H-spectroscopy is believed to represent primarily phosphocholine and glycerophosphocholine, and therefore phospholipase A2 activity and membrane turnover, our results are in good agreement with reported ECS-induced hippocampal mossy fiber sprouting, increased synaptic plasticity, and neurogenesis.

Information for assistants of repeated transcranial magnetic stimulation

Repeated transcranial magnetic stimulation (rTMS) is an exciting new technology being used in psychiatric and neurological research in many centres around the world. rTMS has been accepted as a routine treatment of depression in Canada and Israel. To this point, it has been exclusively conducted by medical officers. As knowledge and experience grows, it is probable that professionals with other backgrounds will have the opportunity to play a role. The aim of this paper is to provide information that will be valuable to assistants. Electromagnetic principles are harnessed to deliver electric currents to localized regions of the cortex. rTMS does not involve anaesthesia or seizure. Side-effects appear to be few. Much remains uncertain, however, even including the most appropriate treatment parameters.

High-throughput confirmation of differential display PCR results using reverse Northern blotting

Nylon filter arrays spotted with differential display PCR (DD-PCR) clones and hybridized with radiolabeled cRNA generated from the source RNA pool (reverse Northern blot) provide a high-throughput means to screen clones for artifacts. Reverse Northern blots also confirm differential gene expression in parallel and require modest quantities of the source RNA pool. We describe a strategy to screen multiple candidates from DD-PCR by high-throughput ligation and transformation, followed by reverse Northern blotting. Purification of re-amplified DD-PCR clones and fabrication of nylon arrays was facilitated by a batch-processing protocol using the widely available Biomek laboratory robot and Bioworks scripts (available from the authors). A strategy to screen out DD-PCR product artifacts of an inappropriate size was also employed. Using these approaches, we identified several mRNAs that are differentially expressed in response to venlafaxine, fluoxetine or desipramine antidepressant treatment in rat C6 glioma cell lines and are candidates for full length clone isolation using 5'-RACE. Such an approach provides a rapid means to eliminate the high percentage of false positive clones from DD-PCR and enables independent confirmation of differential gene expression patterns generated by various experimental conditions.

Subchronic treatment with lithium increases nerve growth factor content in distinct brain regions of adult rats

There is compelling evidence that withdrawal of neurotrophins can lead to impaired neuronal function and even apoptotic death of neurons. Recent experimental evidence suggests that antidepressant drugs and electroconvulsive treatment might work by enhancing CNS levels of neurotrophins. In addition, Lithium (LI) has been shown to exert robust neuroprotective effects apart from its well known mood-stabilizing effects in humans. In this study we investigated the effects of subchronic (14 days) treatment with various doses of LI on the NGF content of several regions of the adult rat brain. LI treatment, which resulted in prophylactic LI serum concentrations (0.72 +/- 0.08 mMol l(-1)), induced a significant (P < 0.05) increase in NGF concentrations in the frontal cortex (+23.2%), hippocampus (+72%), amygdala (+74%) and limbic forebrain (+46.7%) compared to untreated controls, whereas no effects on NGF concentrations were observed in the striatum, the hypothalamus or the midbrain, even using various LI doses. Moreover, no significant change in NGF concentrations in the frontal cortex was observed after acute (1 day) treatment with LI. Our findings lend support to the notion that an enhancement of NGF production may be specifically involved in the mechanisms of action of antibipolar treatments.

Electroconvulsive stimuli alter nerve growth factor but not brain-derived neurotrophic factor concentrations in brains of a rat model of depression

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are proteins involved in neuronal survival and plasticity of dopaminergic, cholinergic and serotonergic neurons in the central nervous system (CNS). Moreover, it has been hypothesized that these molecules play a role in the pathophysiology as well as treatment of depression. Using an animal model of depression, the Flinders Sensitive Line (FSL) rats and their controls, the Flinders Resistant Line (FRL), we investigated the effects of electroconvulsive stimuli (ECS) on brain NGF and BDNF. ECS or SHAM ECS were administered eight times, with a 48-h interval between each treatment. NGF and BDNF were measured with enzyme-linked immunosorbent assay (ELISA). In the hippocampus ECS increased NGF concentration in FSL but not FRL rats. ECS decreased NGF concentration in the frontal cortex of FSL rats. In both FSL and FRL rats ECS increased NGF levels in the striatum. In contrast, ECS did not change BDNF concentration in hippocampus, frontal cortex and striatum of FSL and FRL rats. Our data support the notion that neurotrophin concentrations may be altered by ECS.

Interaction of "readthrough" acetylcholinesterase with RACK1 and PKCbeta II correlates with intensified fear-induced conflict behavior

Behavioral reactions to stress are altered in numerous psychiatric and neurodegenerative syndromes, but the corresponding molecular processes and signal transduction pathways are yet unknown. Here, we report that, in mice, the stress-induced splice variant of acetylcholinesterase, AChE-R, interacts intraneuronally with the scaffold protein RACK1 and through it, with its target, protein kinase CbetaII (PKCbetaII), which is known to be involved in fear conditioning. In stress-responsive brain regions of normal FVBN mice, the mild stress of i.p. injection increased AChE and PKCbetaII levels in a manner suppressible by antisense prevention of AChE-R accumulation. Injection stress also prolonged conflict between escape and hiding in the emergence into an open field test. Moreover, transgenic FVBN mice overexpressing AChE-R displayed prolonged delay to emerge into another field (fear-induced behavioral inhibition), associated with chronically intensified neuronal colabeling of RACK1 and PKCbetaII in stress-responsive brain regions. These findings are consistent with the hypothesis that stress-associated changes in cholinergic gene expression regulate neuronal PKCbetaII functioning, promoting fear-induced conflict behavior after stress.

Dose-related effects of chronic antidepressants on neuroprotective proteins BDNF, Bcl-2 and Cu/Zn-SOD in rat hippocampus

It has been proposed that antidepressants have neuroprotective effects on hippocampal neurons. To further test this hypothesis, brain-derived neurotrophic factor (BDNF), B cell lymphoma protein-2 (Bcl-2), and copper-zinc superoxide dismutase (Cu/Zn-SOD) were examined immunohistochemically in hippocampal neurons of Sprague-Dawley rats following daily treatment with 5 or 10 mg/kg of amitriptyline or venlafaxine for 21 days. At 5 mg/kg, both amitriptyline and venlafaxine increased the intensity of BDNF immunostaining in hippocampal pyramidal neurons, and the intensity of Bcl-2 immunostaining in hippocampal mossy fibers, but did not alter the Cu/Zn-SOD immunoreactivity. The high dose of venlafaxine, however, decreased the intensity of BDNF immunostaining in all subareas of the hippocampus and increased the intensity of Cu/Zn-SOD immunostaining in the dentate granular cell layer. The high dose of amitriptyline increased the intensity of Cu/Zn-SOD immunostaining, but did not affect the immunoreactivity of Bcl-2 or BDNF. These findings suggest that the chronic administration of amitriptyline or venlafaxine at 5 mg/kg, but not 10 mg/kg, may be neuroprotective to hippocampal neurons. These dose-related effects of antidepressant drugs on hippocampal neurons may have relevance to disparate findings in the field.

Differential effects of fluoxetine and imipramine on the phosphorylation of the transcription factor CREB and cell-viability

It has been shown that antidepressants increase the expression of CREB (cAMP-response-element-binding-protein) and BDNF (brain derived neurotrophic factor) in vivo. Apparently inconsistent to these survival-promoting properties for many years antidepressants are known to induce apoptosis in various cell types in vitro. In the present study we evaluated if the antidepressants imipramine and fluoxetine are capable to influence the translational expression and phosphorylation of CREB (pCREB) in cells known to be apoptosis-inducible by antidepressants. We therefore used jurkat cells and quantified apoptosis via propidiumiodid-staining and FACS-analysis. CREB-expression and -phosphorylation was quantified via western blot. Both antidepressants induced apoptosis within 24 h. Fluoxetin starts to induce significant apoptosis at a concentration of 20 microM, whereas imipramine at 100 microM. At these concentrations both antidepressants also increased the phosphorylation of CREB within 6 h. But even in concentrations to low to induce apoptosis both antidepressants still increased CREB-phosphorylation. Treating cells with lowest concentrations only imipramine revealed an increase of CREB-phosphorylation after long-time treatment over 3 weeks. In all experiments overall CREB-expression remained unchanged. In conclusion our experiments indicate that antidepressants are capable to increase CREB-phosphorylation without induction of apoptosis depending on concentration and duration of treatment. We further assume that antidepressants induce CREB-phosphorylation via signal transduction pathways that are different from those inducing apoptosis.

A common role for psychotropic medications: memory impairment

The psychopathologic profile of mental disorders is very diverse and psychotropic medications used to treat them differ in their chemical structure. Nevertheless, these drugs share these four characteristics: delayed onset of clinical response, not one of them can be said to cure, there is a high number of non-responders, and the mechanism responsible for their therapeutic action is not known. It is hypothesized that the action of psychotropic medications is memory impairment, understanding memory as the trace left in the nervous system not only by individual experiences but also by genetic and epigenetic phenomena. It is suggested that it would be beneficial to translate some research strategies from the neurobiology of learning and memory to the study of the effects of psychotropic medications. The hypothesis is briefly assessed according to the following three criteria: (a). the comparison between the molecular effects of psychotropic medications and the so-called molecular biology of learning and memory, (b). the effects of these drugs, preferentially after chronic use, on memory tests, and (c). the effects of drugs that impair memory on tests used for screening psychotropic medications. Finally, some general suggestions for future research are pointed out.

Mss4 gene is up-regulated in rat brain after chronic treatment with antidepressant and down-regulated when rats are anhedonic

Differential display reverse transcription-polymerase chain reaction was used to identify mRNAs that are differentially expressed in the brain of rats treated chronically with the reference tricyclic antidepressant, imipramine, in comparison with control rats. The gene encoding for a mutation suppressor for Sec4-8 yeast (Mss4) transcript is overexpressed in the amygdala of treated rats after 3 weeks of daily administration. This overexpression is also found in the hippocampus of rats treated chronically with either tianeptine or fluoxetine. Mss4 protein has the properties of a guanine nucleotide exchange factor, interacting with several members of the Rab family implicated in Ca(2+)-dependent exocytosis of neurotransmitters. Mss4 was also overexpressed in other brain structures as judged by in situ hybridization. The kinetics of the up-regulation of Mss4 gene expression measured by Northern blot during the imipramine, tianeptine, or fluoxetine treatments are consistent with an antidepressant effect that occurs after 3 weeks. In rats in which anhedonia was induced by chronic mild stress during 3 weeks, Mss4 transcripts were specifically down-regulated in hippocampus and amygdala compared with control rats. It is proposed that Mss4 protein, which stimulates exocytosis in vivo, participates in the potentiation of the activity of neurotransmitter pathways implicated in the action of several antidepressants and constitutes one of the common functional molecules induced after chronic antidepressant treatment.

Lithium induces brain-derived neurotrophic factor and activates TrkB in rodent cortical neurons: an essential step for neuroprotection against glutamate excitotoxicity

Mechanisms underlying the therapeutic effects of lithium for bipolar mood disorder remain poorly understood. Recent studies demonstrate that lithium has neuroprotective actions against a variety of insults in vitro and in vivo. This study was undertaken to investigate the role of the brain-derived neurotrophic factor (BDNF)/TrkB signaling pathway in mediating neuroprotection of lithium against glutamate excitotoxicity in cortical neurons. Pretreatment with either lithium or BDNF protected rat cerebral cortical neurons from glutamate excitotoxicity. The duration of treatment required to elicit maximal neuroprotection by BDNF (1 day) was much shorter than that by lithium (6 days). K252a, an inhibitor of Trk tyrosine kinases, and a BDNF neutralizing antibody suppressed the neuroprotective effect of lithium. Treatment of cortical neurons with lithium increased the cellular BDNF content in 3 days and the phosphorylation of TrkB at Tyr490 in 5 days, suggesting that long-term lithium administration enhances BDNF expression/secretion, leading to the activation of TrkB receptor. Lithium failed to protect against glutamate excitotoxicity in cortical neurons derived from homozygous and heterozygous BDNF knockout mice, although lithium fully protected cortical neurons prepared from wild type mice littermates. Taken together, these data suggest that the BDNF/TrkB pathway plays an essential role in mediating the neuroprotective effect of lithium.

Expression profile and up-regulation of PRAX-1 mRNA by antidepressant treatment in the rat brain

A protein associated with the peripheral-type benzodiazepine receptor (PRAX-1) has recently been cloned, but its regional distribution in the central nervous system and its function remain to be clarified. In situ hybridization was carried out to localize PRAX-1 mRNA in the rat brain and revealed a high expression of the transcript in limbic structures such as the CA1 region of the hippocampus, as well as the dentate gyrus, septum, amygdala, and the islands of Calleja. A dense hybridization signal was also observed in the nucleus accumbens, caudate nucleus, olfactory tubercle, pineal gland, and cerebellar cortex. PRAX-1 mRNA expression was largely neuronal; it colocalized with neuron-specific enolase but not glial fibrillary acidic protein. Long-term treatments (21 days) with the neuroleptic haloperidol increased PRAX-1 mRNA expression only in the dentate gyrus, whereas anxiolytic/anticonvulsant diazepam had no effect in any of the hippocampal region studied. Repeated electroconvulsive shock administration significantly enhanced PRAX1 expression in the CA1 subfield and dentate gyrus. Several classes of antidepressant treatment, including serotonin selective reuptake inhibitor (fluoxetine), mixed serotonin- and norepinephrine-uptake inhibitor (imipramine), and monoamine oxidase inhibitors (iproniazid and tranylcypromine), shared this effect. Furthermore, the selective nonpeptide NK2 receptor antagonist (S)-N-methyl-N-[4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl)butyl]benzamide (SR48968), which shows an antidepressant profile in animal studies, also enhanced PRAX-1 mRNA expression. These results point to a potential role of PRAX-1 function in the central nervous system and suggest that the up-regulation of PRAX-1 mRNA represents a common action of chronic antidepressant treatment.

Chronic psychosocial stress and concomitant repetitive transcranial magnetic stimulation: effects on stress hormone levels and adult hippocampal neurogenesis

BACKGROUND

Repetitive transcranial magnetic stimulation is increasingly used as a therapeutic tool in psychiatry and has been demonstrated to attenuate the activity of the stress hormone system. Stress-induced structural remodeling in the adult hippocampus may provide a cellular basis for understanding the impairment of neural plasticity in depressive illness. Accordingly, reversal of structural remodeling might be a desirable goal for antidepressant therapy. The present study investigated the effect of chronic psychosocial stress and concomitant repetitive transcranial magnetic stimulation treatment on stress hormone regulation and hippocampal neurogenesis.

METHODS

Adult male rats were submitted to daily psychosocial stress and repetitive transcranial magnetic stimulation (20 Hz) for 18 days. Cell proliferation in the dentate gyrus was quantified by using BrdU immunohistochemistry, and both the proliferation rate of progenitors and the survival rate of BrdU-labeled cells were evaluated. To characterize the activity of the hypothalamic-pituitary-adrenocortical system, plasma corticotropin and corticosterone concentrations were measured.

RESULTS

Chronic psychosocial stress resulted in a significant increase of stress hormone levels and potently suppressed the proliferation rate and survival of the newly generated hippocampal granule cells. Concomitant repetitive transcranial magnetic stimulation treatment normalized the stress-induced elevation of stress hormones; however, despite the normalized activity of the hypothalamic-pituitary-adrenocortical system, the decrement of hippocampal cell proliferation was only mildly attenuated by repetitive transcranial magnetic stimulation, while the survival rate of BrdU-labeled cells was further suppressed by the treatment.

CONCLUSIONS

These results support the notion that attenuation of the hypothalamic-pituitary-adrenocortical system is an important mechanism underlying the clinically observed antidepressant effect of repetitive transcranial magnetic stimulation, whereas this experimental design did not reveal beneficial effects of repetitive transcranial magnetic stimulation on adult hippocampal neurogenesis.

Neonatal viral infection decreases neuronal progenitors and impairs adult neurogenesis in the hippocampus

While adult neurogenesis has been demonstrated in the hippocampal dentate gyrus of several mammalian species, including humans, the impact of viral infections has not been well studied. To examine this question we used a model in which neonatal rats are infected with lymphocytic choriomeningitis virus (LCMV) leading to a gradual loss of dentate granule cells (DGCs), which becomes fully evident in adulthood. Stereological cell counts performed 8 months after infection revealed that the loss of mature DGCs was accompanied by an 84.2% reduction in proliferation of DGCs as measured by BrdU uptake. Moreover, there was a severe loss of Mash1-labeled neuronal progenitor cells (87 and 83% decrease in the granule cell layer and hilus, respectively). Thus, neurogenesis is impaired in this model of chronic DGC loss, perhaps due to a virus-induced impoverishment of DGC neuronal progenitors. The LCMV model could be exploited to examine pathophysiological mechanisms of neurodegeneration and to test pharmacological strategies aimed at increasing neurogenesis or rescuing multipotent progenitors.

Antidepressant drugs and cytokines in mood disorders

This article reviews recent developments in cytokine research that pertain to pharmacological treatment of mood disorders such as antidepressants and lithium. We review the possible involvement of cytokines in mood disorders and their role in the therapeutic effects of antidepressant drugs. Growing evidence suggests that specific cytokines signal the brain to generate neurochemical, neuroimmune, neuroendocrine and behavior changes. An imbalance of cytokines within the central nervous system (CNS), or even systemically, may play a role in the pathophysiology of mood disorders. Modulation of these cytokines by chronic antidepressant treatment may result in restored balance. However, the effect of antidepressants on cytokines is still unclear both in clinical and preclinical research due to limited data. Further research is needed to clarify the involvement of cytokines in mood disorders. Understanding this relationship may lead to rational, therapeutic improvements in antidepressant and mood stabilizing drugs.

Stimulatory effects of prostaglandin E2 on neurogenesis in the dentate gyrus of the adult rat

Neurogenesis in the dentate gyrus of adult rodents is elicited by transient global ischemia. Cyclooxygenase (COX) -2, a rate-limiting enzyme for prostanoid synthesis, is also induced by ischemia. We recently found that the administration of a non-selective COX inhibitor to ischemic animals suppressed cell proliferation in the subgranular zone (SGZ) at the dentate gyrus of the hippocampus. To clarify whether prostaglandin E2 (PGE2) synthesis by COX's is involved in neurogenesis, sulprostone, an analogue of PGE2, was injected into the rat hippocampus. Sulprostone injection increased the number of 5-bromo-2'-deoxyuridine (BrdU)-positive cells in the SGZ. BrdU-positive cells also expressed polysialylated isoforms of neural cell adhesion molecule and neuronal nuclear antigen. These results suggest that PGE2 plays an important role in the proliferation of cells in the SGZ.

Changes in CREB-phosphorylation during recovery from major depression

For decades psychiatrists have been looking for biological state markers measurable by easy blood test in order to follow up and predict early on treatment response in patients with major depression. In the present study we investigated whether or not measuring CREB (cAMP-response-element-binding-protein) phosphorylation in peripheral blood T lymphocytes is a state marker of treatment response. CREB is an ubiquitous key-element of intracellular signal transduction cascades and its transcriptional activity depends on phosphorylation at Ser-133. Several studies in animals demonstrated that the transcriptional activity of CREB is up-regulated by antidepressant treatment. Therefore, it has been hypothesized that antidepressant treatment exerts its therapeutic effect by this mechanism. In the present study, we investigated CREB-phosphorylation in T-lymphocytes of 20 patients before and in the end of week one and two of either psychopharmacological or psychotherapeutic treatment. After two weeks, 15 patients fulfilled the criteria of treatment response (i.e. 30% reduction in HAMD score compared to baseline), whereas five patients did not. In the end of week two, the responders showed a significant increase in CREB-phosphorylation (P = 0.018) compared to the non-responders. This was true for all patients with either treatment regimen. In conclusion, these results indicate for the first time that the increase in CREB-phosphorylation might be a molecular state marker for the response to antidepressant treatment.