Hippocampal mossy fiber sprouting induced by chronic electroconvulsive seizures

Brain-derived neurotrophic factor and its receptor tropomyosin-related kinase B in the mechanism of action of antidepressant therapies

The focus of this review is to critically examine and review the literature on the role of brain-derived neurotrophic factor (BDNF) and its primary receptor, tropomyosin-related kinase B (TrkB), in the actions of pharmacologically diverse antidepressant treatments for depression. This will include a review of the studies on the regulation of BDNF and TrkB by different types of antidepressant drug treatments and animal in models of depression, as well as altered levels of BDNF and TrkB in the blood and postmortem brain of patients with depression. Results from clinical and basic studies have demonstrated that stress and depression decrease BDNF expression and neurogenesis and antidepressant treatment reverses or blocks these effects, leading to the neurotrophic hypothesis of depression. Clinical studies demonstrate an association between BDNF levels and several disorders, including depression, epilepsy, bipolar disorder, Parkinson's and Alzheimer's diseases. Physical activity and diet exert neurotrophic effects and positively modulate BDNF levels. A common single nucleotide polymorphism (SNP) in the BDNF gene, a methionine substitution for valine, is associated with alterations in brain anatomy and memory, but what role it has in clinical disorders is unclear. Findings suggest that early childhood events and adult stress produce neurodegenerative alterations in the brain that can eventually cause breakdown of information processing in the neuronal networks regulating mood. Antidepressant treatments elevate activity-dependent neuronal plasticity by activating BDNF, thereby gradually restoring network function and ultimately mood.

Effects of paroxetine or milnacipran on serum brain-derived neurotrophic factor in depressed patients

Brain-derived neurotrophic factor (BDNF) is an important member of the neurotrophin family of growth factors, abundant in the brain and periphery. Researchers have reported that serum BDNF levels in drug-free depressed patients are lower than those of healthy controls, and have proposed that these low levels might reflect a failure of neuronal plasticity in depression. In the present study, we investigated the effects of paroxetine, an SSRI, and milnacipran, an SNRI, on serum BDNF levels in depressed patients. Serum levels of BDNF were measured by ELISA before, 4 weeks, and 8 weeks after the start of treatment with antidepressants. Forty-two patients were randomly administered paroxetine (21 cases) or milnacipran (21 cases). A negative correlation was found between serum BDNF levels and baseline Ham-D scores. The response and remission rates for each drug were not significantly different. Serum BDNF levels in responders were significantly increased 2.6- and 1.8-fold 8 weeks after treatment with paroxetine or milnacipran, respectively. These results suggest that both drugs improve the depressive state by increasing BDNF levels.

Repeated electroconvulsive stimuli have long-lasting effects on hippocampal BDNF and decrease immobility time in the rat forced swim test

Electroconvulsive therapy is considered an effective treatment for severe depression. However, the mechanisms for its long-lasting antidepressant efficacy are poorly understood. In the present study, we investigated changes of the immobility time in the forced swim test and brain-derived neurotrophic factor (BDNF) protein after withdrawal from 14-day repeated electroconvulsive stimuli (ECS, 50 mA, 0.2 s) in rats. Immobility time in the forced swim test was markedly decreased 6 h after withdrawal following 14-day ECS treatment. Thereafter, prolongation of the withdrawal period gradually diminished the decreasing effect of immobility time, but significant effects persisted for up to 3 days after the withdrawal. Locomotor activity in the open-field test increased 6 h after withdrawal from the ECS treatment, and the enhanced effect persisted for at least 7 days. The BDNF protein level in the hippocampus was markedly increased 6 h after the withdrawal, and remained high for at least 7 days. These findings provide further evidence that repeated ECS has long-lasting effect on increase in BDNF and locomotor activity and decrease in immobility time in the forced swim test.

Brain-derived neurotrophic factor (BDNF) polymorphisms G196A and C270T are not associated with response to electroconvulsive therapy in major depressive disorder

The aim of the present study was to examine an association of brain-derived neurotrophic factor (BDNF) polymorphisms G196A and C270T and the response to electroconvulsive therapy (ECT) in major depressive disorder (MDD). The study group consisted of 119 patients consecutively admitted for ECT in the Department of Psychiatry, Tampere University Hospital. All patients fulfilled the diagnostic criteria of DSM-IV for MDD. ECT was administered three times a week with a brief pulse constant current device. The Montgomery and Asberg Depression Rating Scale (MADRS) was used as an outcome measure of depression. Genotyping was performed using fluorescent allele-specific TaqMan probes. No association between either G196A or C270T and the response to ECT was found in the whole population. There were no significant differences in responses between men and women or between psychotic and non-psychotic patients. However, within subgroups such as in psychotic and in late-onset depression CC genotype of C270T may predict good response. BDNF may not be associated with response to ECT in general, but some association in subgroups may exist.

Inflammation and depression: is there a causal connection with dementia?

Epidemiological studies show that there is a correlation between chronic depression and the likelihood of dementia in later life. There is evidence that inflammatory changes in the brain are pathological features of both depression and dementia. This suggests that an increase in inflammation-induced apoptosis, together with a reduction in the synthesis of neurotrophic factors caused by a rise in brain glucocorticoids, may play a role in the pathology of these disorders. A reduction in the neuroprotective components of the kynurenine pathway, such as kynurenic acid, and an increase in the neurodegenerative components, 3- hydroxykynurenine and quinolinic acid, contribute to the pathological changes. Such changes are postulated to cause neuronal damage and thereby predispose chronically depressed patients to dementia.

Unmasking recurrent excitation generated by mossy fiber sprouting in the epileptic dentate gyrus: an emergent property of a complex system

Seizure-induced sprouting of the mossy fiber pathway in the dentate gyrus has been observed nearly universally in experimental models of limbic epilepsy and in the epileptic human hippocampus. The observation of progressive mossy fiber sprouting induced by kindling demonstrated that even a few repeated seizures are sufficient to alter synaptic connectivity and circuit organization. As it is now recognized that seizures induce synaptic reorganization in hippocampal and cortical pathways, the implications of seizure-induced synaptic reorganization for circuit properties and function have been subjects of intense interest. Detailed anatomical characterization of the sprouted mossy fiber pathway has revealed that the overwhelming majority of sprouted synapses in the inner molecular layer of the dentate gyrus form recurrent excitatory connections, and are thus likely to contribute to recurrent excitation and potentially to enhanced susceptibility to seizures. Nevertheless, difficulties in detecting functional abnormalities in circuits reorganized by mossy fiber sprouting and the fact that some sprouted axons appear to form synapses with inhibitory interneurons have been cited as evidence that sprouting may not contribute to seizure susceptibility, but could form recurrent inhibitory circuits and be a compensatory response to prevent seizures. Quantitative analysis of the synaptic connections of the sprouted mossy fiber pathway, assessment of the functional features of sprouted circuitry using reliable physiological measures, and the perspective of complex systems analysis of neural circuits strongly support the view that the functional effects of the recurrent excitatory circuits formed by mossy fiber sprouting after seizures or injury emerge only conditionally and intermittently, as observed with spontaneous seizures in human epilepsy. The recognition that mossy fiber sprouting is induced after hippocampal injury and seizures and contributes conditionally to emergence of recurrent excitation has provided a conceptual framework for understanding how injury and seizure-induced circuit reorganization may contribute to paroxysmal network synchronization, epileptogenesis, and the consequences of repeated seizures, and thus has had a major influence on understanding of fundamental aspects of the epilepsies.

Loss of synapses in the entorhinal-dentate gyrus pathway following repeated induction of electroshock seizures in the rat

The goal of this study was to answer the question of whether repeated administration of electroconvulsive shock (ECS) seizures causes structural changes in the entorhinal-dentate projection system, whose neurons are known to be particularly vulnerable to seizure activity. Adult rats were administered six ECS seizures, the first five of which were spaced by 24-hr intervals, whereas the last two were only 2 hr apart. Stereological approaches were employed to compare the total neuronal and synaptic numbers in sham- and ECS-treated rats. Golgi-stained material was used to analyze dendritic arborizations of the dentate gyrus granule cells. Treatment with ECS produced loss of neurons in the entorhinal layer III and in the hilus of the dentate gyrus. The number of neurons in the entorhinal layer II, which provides the major source of dentate afferents, and in the granular layer of the dentate gyrus, known to receive entorhinal projections, remained unchanged. Despite this, the number of synapses established between the entorhinal layer II neurons and their targets, dentate granule cells, was reduced in ECS-treated rats. In addition, administration of ECS seizures produced atrophic changes in the dendritic arbors of dentate granule cells. The total volumes of entorhinal layers II, III, and V-VI were also found to be reduced in ECS-treated rats. By showing that treatment with ECS leads to partial disconnection of the entorhinal cortex and dentate gyrus, these findings shed new light on cellular processes that may underlie structural and functional brain changes induced by brief, generalized seizures.

Cyclic AMP response element binding protein and brain-derived neurotrophic factor: molecules that modulate our mood?

Depression is the major psychiatric ailment of our times, afflicting approximately 20% of the population. Despite its prevalence, the pathophysiology of this complex disorder is not well understood. In addition, although antidepressants have been in existence for the past several decades, the mechanisms that underlie their therapeutic effects remain elusive. Building evidence implicates a role for the plasticity of specific neuro-circuitry in both the pathophysiology and treatment of depression. Damage to limbic regions is thought to contribute to the etiology of depression and antidepressants have been reported to reverse such damage and promote adaptive plasticity. The molecular pathways that contribute to the damage associated with depression and antidepressant-mediated plasticity are a major focus of scientific enquiry. The transcription factor cyclic AMP response element binding protein (CREB) and the neurotrophin brain-derived neurotrophic factor (BDNF) are targets of diverse classes of antidepressants and are known to be regulated in animal models and in patients suffering from depression. Given their role in neuronal plasticity, CREB and BDNF have emerged as molecules that may play an important role in modulating mood. The purpose of this review is to discuss the role of CREB and BDNF in depression and as targets/mediators of antidepressant action.

Nonpharmacological, somatic treatments of depression: electroconvulsive therapy and novel brain stimulation modalities

Until recently, a review of nonpharmacological, somatic treatments of psychiatric disorders would have included only electroconvulsive therapy (ECT). This situation is now changing very substantially. Although ECT remains the only modality in widespread clinical use, several new techniques are under investigation. Their principal indication in the psychiatric context is the treatment of major depression, but other applications are also being studied. All the novel treatments involve brain stimulation, which is achieved by different technological methods. The treatment closest to the threshold of clinical acceptability is transcranial magnetic stimulation (TMS). Although TMS is safe and relatively easy to administer, its efficacy has still to be definitively established. Other modalities, at various stages of research development, include magnetic seizure therapy (MST), deep brain stimulation (DBS), and vagus nerve stimulation (VNS). We briefly review the development and technical aspects of these treatments, their potential role in the treatment of major depression, adverse effects, and putative mechanism of action. As the only one of these treatment modalities that is in widespread clinical use, more extended consideration is given to ECT Although more than half a century has elapsed since ECT was first introduced, it remains the most effective treatment for major depression, with efficacy in patients refractory to antidepressant drugs and an acceptable safety profile. Although they hold considerable promise, the novel brain stimulation techniques reviewed here will be need to be further developed before they achieve clinical acceptability.

Abnormalities of neurogenesis in the R6/2 mouse model of Huntington's disease are attributable to the in vivo microenvironment

Huntington's disease (HD) is an autosomal dominant neurodegenerative condition characterized by movement disorders, psychiatric disturbance, and cognitive decline. There are no treatments to halt or reverse the disease. Mammalian neurogenesis persists into adulthood in the subventricular zone (SVZ) and dentate gyrus (DG) of the hippocampus. In 2001, our laboratory published the hypothesis that neurogenesis is impaired in neurodegenerative diseases and that this may contribute to disease progression. Since then, it has been shown that neurogenesis is reduced in the DG of transgenic HD mice but increased in the SVZ of HD patients. We sought to characterize neurogenesis further. We found that, in the DG of the transgenic R6/2 mouse model of HD, newborn cell proliferation and morphology, but not differentiation or survival, was compromised. In R6/2 mice, neurogenesis failed to upregulate in the DG in response to seizures. Basal SVZ neurogenesis was similar between R6/2 mice and their wild-type littermates. There was no difference in the in vitro growth of adult neural precursor cells (NPCs) between genotypes. These results suggest that abnormal neurogenesis in the R6/2 mouse is not attributable to an intrinsic impairment of the NPC itself but is attributable to the environment in which the cell is located.

Diacylglycerol kinase epsilon modulates rapid kindling epileptogenesis

PURPOSE

Diacylglycerol kinase epsilon (DGKepsilon) regulates seizure susceptibility and long-term potentiation through arachidonoyl-inositol lipid signaling. We studied the significance of arachidonoyl-diacylglycerol (20:4 DAG) in epileptogenesis in DGKepsilon-deficient mice undergoing rapid kindling epileptogenesis.

METHODS

Tripolar electrode units were implanted in right dorsal hippocampi of male DGKepsilon(+/+) and DGKepsilon(-/-) mice. Ten days after surgery, kindling was achieved by stimulating 6 times daily for 4 days with a subconvulsive electrical stimulation (10-s train of 50-Hz biphasic pulses, 75-200 muA amplitude) at 30-min intervals. After 1 week, mice were rekindled. EEGs were recorded and analyzed to characterize epileptogenic events as spikes, sharp waves, or abnormal amplitudes and rhythms. Right hippocampi were analyzed by histology [Timm's staining, neuropeptide Y (NPY) and glial fibrillary acidic protein immunoreactivity], and for DNA fragmentation (TUNEL).

RESULTS

DGKepsilon(-/-) mice had significantly fewer motor seizure and epileptic events compared with DGKepsilon(+/+) mice from the second day of stimulation. These differences were maintained during rekindling. DGKepsilon(-/-) mice also exhibited low-amplitude spike-wave complexes, short spreading depression, and predominant lower-frequency (1-4 Hz) bands throughout stimulation, whereas DGKepsilon(+/+) mice exhibited increased high-frequency bands (4-8 Hz; 8-15 Hz) from the second day of stimulation, as determined by power spectral analysis. DGKepsilon(-/-) mice displayed no sprouting in the supragranular area or NPY inmunoreactivity in the hilus and had weak astrocyte reactivation in all hippocampal areas. No TUNEL-positive cells were detected in any group of mice.

CONCLUSIONS

DGKepsilon modulates kindling epileptogenesis through inositol lipid signaling. Because arachidonate-containing diacylglycerol phosphorylation to phosphatidic acid is selectively blocked in DGKepsilon(-/-) mice, we postulate that the shortage of arachidonoyl-moiety inositol lipids and/or the messengers derived thereof is a key signaling event in epileptogenesis.

Increase in synaptic hippocampal zinc concentration following chronic but not acute zinc treatment in rats

Electroconvulsive seizures (ECS), one of the most effective treatments of depression, induce mossy fiber sprouting (when assayed by means of synaptic zinc method), and this indicates an increase in the synaptic zinc level in the hippocampus following such therapy. The aim of the present study was to investigate the influence of acute and chronic zinc hydroaspartate administration on the synaptic and total zinc level in the rat hippocampus. We used two methods of zinc determination: (1) zinc-selenium method, which images the pool of synaptic zinc, and (2) flame atomic absorption spectrometry, which assays the total concentration of zinc. Our results indicate that chronic (14 x 65 mg/kg), but not acute, zinc hydroaspartate administration intraperitoneally (i.p.) increases the pool of synaptic zinc in the majority of rat hippocampal layers (by 72-190%), except for the stratum moleculare and stratum radiatum CA, and perforant path DG. On the other hand, no changes were found in total hippocampal zinc level, measured by flame atomic absorption spectrometry. These data suggest that chronic zinc treatment increases the pool of synaptic zinc in the hippocampus, and this effect is similar to that observed following chronic ECS treatment. The measurement of zinc concentration in the whole hippocampus by the flame atomic absorption spectrometry method is not sensitive enough to detect such subtle alteration.

Recruitment of the Sonic hedgehog signalling cascade in electroconvulsive seizure-mediated regulation of adult rat hippocampal neurogenesis

Electroconvulsive seizure (ECS) induces structural remodelling in the adult mammalian brain, including an increase in adult hippocampal neurogenesis. The molecular mechanisms that underlie this increase in the proliferation of adult hippocampal progenitors are at present not well understood. We hypothesized that ECS may recruit the Sonic hedgehog (Shh) pathway to mediate its effects on adult hippocampal neurogenesis, as Shh is known to enhance the proliferation of neuronal progenitors and is expressed in the adult basal forebrain, a region that sends robust projections to the hippocampus. Here we demonstrate that the ECS-induced increase in proliferation of adult hippocampal progenitors was completely blocked in animals treated with cyclopamine, a pharmacological inhibitor of Shh signalling. Our results suggest that both acute and chronic ECS enhance Shh signalling in the adult hippocampus, as we observed a robust upregulation of Patched (Ptc) mRNA, a component of the Shh receptor complex and a downstream transcriptional target of Shh signalling. This increase was rapid and restricted to the dentate gyrus, where the adult hippocampal progenitors reside. In addition, both acute and chronic ECS decreased Smoothened (Smo) mRNA, the other component of the Shh receptor complex, selectively within the dentate gyrus. However, ECS did not appear to influence Shh expression within the basal forebrain, the site from which it has been suggested to be anterogradely transported to the hippocampus. Together, our findings demonstrate that ECS regulates the Shh signalling cascade and indicate that the Shh pathway may be an important mechanism through which ECS enhances adult hippocampal neurogenesis.

Kappa opioid control of seizures produced by a virus in an animal model

Epilepsy remains a major medical problem of unknown aetiology. Potentially, viruses can be environmental triggers for development of seizures in genetically vulnerable individuals. An estimated half of encephalitis patients experience seizures and approximately 4% develop status epilepticus. Epilepsy vulnerability has been associated with a dynorphin promoter region polymorphism or low dynorphin expression genotype, in man. In animals, the dynorphin system in the hippocampus is known to regulate excitability. The present study was designed to test the hypothesis that reduced dynorphin expression in the dentate gyrus of hippocampus due to periadolescent virus exposure leads to epileptic responses. Encephalitis produced by the neurotropic Borna disease virus in the rat caused epileptic responses and dynorphin to disappear via dentate granule cell loss, failed neurogenesis and poor survival of new neurons. Kappa opioid (dynorphin) agonists prevented the behavioural and electroencephalographic seizures produced by convulsant compounds, and these effects were associated with an absence of dynorphin from the dentate gyrus granule cell layer and upregulation of enkephalin in CA1 interneurons, thus reproducing a neurochemical marker of epilepsy, namely low dynorphin tone. A key role for kappa opioids in anticonvulsant protection provides a framework for exploration of viral and other insults that increase seizure vulnerability and may provide insights into potential interventions for treatment of epilepsy.

The effect of antidepressant treatment on N-acetyl aspartate levels of medial frontal cortex in drug-free depressed patients

The medial frontal cortex has been shown to modulate emotional behavior and stress responses, suggesting that the dysfunction of this region may be involved in the pathogenesis of depressive symptoms. The present study was performed to determine whether there was any effect of antidepressant treatment on the metabolite levels in the left medial frontal cortex as measured by proton magnetic resonance spectroscopy in depressed patients. Twenty patients diagnosed as having major depressive disorder according to DSM-IV and 18 healthy volunteer subjects were included in the study. Twelve of patients had their first episode and were drug-naïve. Other depressed patients were drug-free for at least 4 weeks. The severity of depression was assessed by HAM-D and Clinical Global Impression Scale-Severity (CGI-S). Single voxel, 8 cm(3), 1H MR spectra of left medial frontal cortex was acquired both before and following antidepressant treatment. The concentrations and ratios of N-acetyl aspartate (NAA), Creatine+Phosphocreatine (Cr+PCr) and Choline (Cho) were measured. Pretreatment NAA/Cr values of patients were lower than those of healthy controls, but this difference did not reach to statistically significant levels (t=1.83, df=36, p=0.07). However, antidepressant treatment had significant effect on NAA/Cr ratios (groupxtreatment interaction: F=9.93 df=1,36, p=0.03). After the treatment, NAA/Cr values of patients increased significantly compared to pretreatment values (t=3.32, df=19, p=0.004). No significant difference was observed between the post-treatment NAA/Cr values of patients and those of controls (t=1.64, df=36, p=0.19). Correlation analysis detected negative correlation between pretreatment CGI-S scores and NAA/Cr ratios (r=-0.51, p=0.02). This preliminary result suggests that there might be a possible defect in the neuronal integrity in the left medial frontal cortex (mainly left anterior cingulate cortex) of depressed patients. Antidepressant treatment with its neurotrophic effects might play a positive role in restoring the neuronal integrity. Further studies are needed to support these initial findings.

Repeated electroconvulsive stimuli increase brain-derived neurotrophic factor in ACTH-treated rats

Electroconvulsive therapy is considered to be an effective treatment for severe depression. We have already shown that the antidepressant-like effects of tricyclic antidepressants in the rat forced swim test are blocked by repeated treatment with adrenocorticotropic hormone (ACTH). In the present study, we investigated the effect of repeated electroconvulsive stimuli on the forced swim test and on brain-derived neurotrophic factor (BDNF) protein levels in ACTH-treated rats. Electroconvulsive stimuli (50 mA, 0.2 s) was administered 30 min after ACTH treatment (100 microg/rat, s.c.) once daily for 14 days. In both saline and ACTH-treated rats, repeated electroconvulsive stimuli for 6 or 14 days decreased the immobility time in the forced swim test and increased the BDNF protein levels in the hippocampus. However, repeated imipramine administration (10 mg/kg, i.p. for 14 days) had no effect on the hippocampus BDNF protein levels in ACTH-treated rats. These results suggest that electroconvulsive stimuli has decreasing effects of immobility time in the forced swim test in the tricyclic antidepressant-resistant depressive model of rats induced by repeated ACTH treatment, and that increased BDNF may be involved in this phenomenon.

Antidepressants and prolonged stress in rats modulate CAM-L1, laminin, and pCREB, implicated in neuronal plasticity

Previously, we reported an ability of NE to promote processes of plasticity in neuroblastoma cells, as observed by morphological changes such as an elongated granule-rich cell body and neuritegenesis, in addition to a progressive decrease in the pluripotent marker Oct4 and an increase in the growth cone marker GAP-43. This was accompanied by the induction of three plasticity genes forming a functional cluster, the cell adhesion molecule L1 (CAM-L1), laminin, and CREB, all involved in neuronal plasticity and neurite outgrowth. In the present study, we hypothesized that the regulation of CAM-L1, laminin, and CREB/pCREB by NE could mediate processes of plasticity in the mode of action of antidepressants, as well as in the long-term effects of stress, in rats, given the association of both with NE alterations and neuronal plasticity. In the first experiment, rats were chronically administered with antidepressants (21 days). In the second experiment, rats were exposed to chronic stress and examined 4 months later, a model shown to exhibit behavioral indices of stress. We found brain region-specific alterations in mRNA and protein levels of CAM-L1, laminin, and pCREB in rats chronically treated with the noradrenergic antidepressant desipramine and, to a lesser extent, in those treated with fluoxetine. Stressed rats presented a decrease in CAM-L1, laminin, and pCREB, specifically in brain areas implicated in stress. Our findings suggest that noradrenergic-regulated plasticity genes such as CAM-L1, laminin, and CREB play an important role both in stress and in the treatment of depression.

Ketamine pre-treatment dissociates the effects of electroconvulsive stimulation on mossy fibre sprouting and cellular proliferation in the dentate gyrus

Electroconvulsive stimulation (ECS), the experimental analogue of electroconvulsive therapy (ECT), has been shown to produce both functional and structural effects in the hippocampal formation in infrahuman species. These changes may relate to the antidepressant and cognitive effects of ECT observed in patients treated for severe depressive disorders. Recent studies have described both enhanced neurogenesis in the dentate gyrus of the hippocampus and sprouting of mossy fibre projections from granule cells. The behavioural significance of these effects remains uncertain. In this study, we examined whether ketamine, a clinically available non-competitive NMDA receptor channel blocker, could block both of these "trophic" effects. Rats were given a course of eight spaced ECS or sham treatments under either halothane or ketamine anaesthesia. The thymidine analogue bromodeoxyuridine was administered to assess the degree of hippocampal cell proliferation and mossy fibre sprouting was quantified using the Timm staining method. Pre-treatment with ketamine dissociated these effects such that mossy fibre sprouting was attenuated significantly, while cell proliferation was unaffected. This dissociation may prove useful in determining the behavioural significance of these hippocampal changes, if any, for either the antidepressant or cognitive consequences of ECT.

Microtubule affinity-regulating kinase 1 (MARK1) is activated by electroconvulsive shock in the rat hippocampus

Electroconvulsive shock (ECS) induces phosphorylation and dephosphorylation of many signaling molecules in the rat brain. While studying phosphorylated proteins in the rat brain after ECS, we observed a 100-kDa protein that cross-reacted with anti-phospho-p70 S6 kinase antibody, which was subsequently purified and identified as microtubule affinity-regulating kinase 1 (MARK1). Purified MARK1 was phosphorylated at the Ser and Thr residues. MARK1 activation and subsequent Tau phosphorylation in the hippocampus after ECS was confirmed by an in-gel kinase assay using tau protein as a substrate. MARK1 was maximally activated between 2 and 5 min after ECS, and Tau phosphorylation at Ser262 was also increased at 2 min and lasted to 1 h after ECS. Taken together, we concluded that ECS activated MARK1 and subsequently phosphorylated Tau at Ser262. Both MARK1 activity and Tau phosphorylation were increased in the rat hippocampus after chronic ECS where axonal remodeling was apparent. In order to investigate the physiologic stimuli which are involved in the activation of MARK1, SH-SY 5Y cells were treated with brain-derived neurotrophic factor or 60 mm KCl. Both stimuli were capable of inducing MARK activation.

Electroconvulsive Shock Induces Neuron Death in the Mouse Hippocampus: Correlation of Neurodegeneration with Convulsive Activity

The relationship between convulsive activity evoked by repeated electric shocks and structural changes in the hippocampus of Balb/C mice was studied. Brains were fixed two and seven days after the completion of electric shocks, and sections were stained by the Nissl method and immunohistochemically for apoptotic nuclei (the TUNEL method). In addition, the activity of caspase-3, the key enzyme of apoptosis, was measured in brain areas immediately after completion of electric shocks. The number of neurons decreased significantly in field CA1 and the dentate fascia, but not in hippocampal field CA3. The numbers of cells in CA1 and CA3 were inversely correlated with the intensity of convulsions. Signs of apoptotic neuron death were not seen, while caspase-3 activity was significantly decreased in the hippocampus after electric shocks. These data support the notion that functional changes affect neurons after electric shock and deepen our understanding of this view, providing direct evidence that there are moderate (up to 10%) but significant levels of neuron death in defined areas of the hippocampus. Inverse correlations of the numbers of cells with the extent of convulsive activity suggest that the main cause of neuron death is convulsions evoked by electric shocks.

Antidepressant-elicited changes in gene expression: remodeling of neuronal circuits as a new hypothesis for drug efficacy

Although antidepressants have been used clinically for more than 50 years, no consensus has been reached concerning their precise molecular mechanism of action. Pharmacogenomics is a powerful tool that can be used to identify genes affected by antidepressants or by other effective therapeutic manipulations. Using this tool, others and we have identified as candidate molecular targets several genes or expressed sequence tags (ESTs) that are induced by chronic antidepressant treatment. In this article, we review antidepressant-elicited changes in gene expression, focusing especially on the remodeling of neuronal circuits that results. This refocusing motivates our hypothesis that this plasticity represents the mechanism for drug efficacy, and thus a causal event for clinical improvement. Defining the roles of these molecules in drug-induced neural plasticity is likely to transform the course of research on the biological basis of antidepressants. Such detailed knowledge will have profound effects on the diagnosis, prevention, and treatment of depression. Consideration of novel biological approaches beyond the "monoamine hypothesis" of depression is expected to evoke paradigm shifts in the future of antidepressant research.

Electroconvulsive shock decreases binding to 5-HT2 receptors in nonhuman primates: an in vivo positron emission tomography study with [18F]setoperone

BACKGROUND

Dysfunction within the serotonin (5-HT) system plays a major role in the etiology of human depression, and treatment with antidepressant drugs downregulates 5-HT(2) receptors in rodents and humans. The consequences of another effective antidepressant treatment, electroconvulsive therapy (ECT), on 5-HT(2) receptors are less established.

METHODS

We studied the effects of a course of electroconvulsive shock (ECS) on 5-HT(2) receptor binding in nonhuman primates in vivo using positron emission tomography (PET) and the radiotracer [(18)F]setoperone. Seven adult male rhesus monkeys received two bilateral ECS treatments per week for 3 weeks; PET scans were performed before treatment, and 24 hours, 1 week, and 4-6 weeks after completion of the course of ECS. Regions of interest were placed throughout the cortex, and the data analyzed as the ratio of specific:nonspecific radioactivity accumulation, with the cerebellum used as a measure of nonspecific binding.

RESULTS

Serotonin 5-HT(2) binding was significantly decreased at 24 hours and 1 week post-ECS, but returned to baseline 4-6 weeks posttreatment.

CONCLUSIONS

These results show for the first time in a primate species that chronic ECS decreases binding to 5-HT(2) receptors and indicate that 5-HT(2) receptor downregulation may be a common effect of both pharmacologic and nonpharmacologic antidepressant treatments.

Adult neurogenesis: from precursors to network and physiology

The discovery that the adult mammalian brain creates new neurons from pools of stemlike cells was a breakthrough in neuroscience. Interestingly, this particular new form of structural brain plasticity seems specific to discrete brain regions, and most investigations concern the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampal formation (HF). Overall, two main lines of research have emerged over the last two decades: the first aims to understand the fundamental biological properties of neural stemlike cells (and their progeny) and the integration of the newly born neurons into preexisting networks, while the second focuses on understanding its relevance in brain functioning, which has been more extensively approached in the DG. Here, we propose an overview of the current knowledge on adult neurogenesis and its functional relevance for the adult brain. We first present an analysis of the methodological issues that have hampered progress in this field and describe the main neurogenic sites with their specificities. We will see that despite considerable progress, the levels of anatomic and functional integration of the newly born neurons within the host circuitry have yet to be elucidated. Then the intracellular mechanisms controlling neuronal fate are presented briefly, along with the extrinsic factors that regulate adult neurogenesis. We will see that a growing list of epigenetic factors that display a specificity of action depending on the neurogenic site under consideration has been identified. Finally, we review the progress accomplished in implicating neurogenesis in hippocampal functioning under physiological conditions and in the development of hippocampal-related pathologies such as epilepsy, mood disorders, and addiction. This constitutes a necessary step in promoting the development of therapeutic strategies.

Influence of low dietary histamine on seizure development of chemical kindling induced by pentylenetetrazol in rats

AIM

To determine the role of dietary low histamine on the seizure development of pentylenetetrazol (PTZ)-induced kindling in rats.

METHODS

After 14 d of feeding on a low histamine diet (LH, containing 0.145 mumol/g of histamine), the rats were chemically kindled by repeated intraperitoneal injection of a subconvulsant dose of PTZ (35 mg/kg) once every 48 h, and seizure activity of kindling was recorded for 30 min. Histamine in brain samples was analyzed using a high performance liquid chromatography system with a fluorescence spectrofluorometer.

RESULTS

The LH diet induced an increase in seizure response (seizure susceptibility) to the first trial of PTZ, and resulted in facilitation of subsequent PTZ kindling process (seizure development). The histamine levels in the cortex, hippocampus, and hypothalamus of LH-treated rats decreased significantly and these changes correlated well with seizure behavior (r = 0.875, 0.651, and 0.796, respectively). In addition, chronic kindled seizures resulted in a significant increase of the histamine content in the cortex and hypothalamus in the LH-fed groups.

CONCLUSION

These findings indicate that the histamine in daily food could influence the brain histaminergic function, and play an important role in regulating seizure susceptibility.

Alterations in cell adhesion molecule L1 and functionally related genes in major depression: a postmortem study

BACKGROUND

Current research in depression aims to delineate genes involved in neuronal plasticity that are altered in the disease or its treatment. We have shown antidepressant induced increases in three interrelated genes, cell adhesion molecule L1 (CAM-L1), laminin, and cAMP response element binding protein (CREB), and a reciprocal decrease in these genes consequent to stress. Presently we hypothesized that CAM-L1, CREB, and laminin may be altered in post mortem brains of depressed subjects.

METHODS

Studies were performed in the prefrontal and in the ventral parieto-occipital cortices, of 59 brains from depressed, bipolar, and schizophrenic subjects, and normal controls, obtained from the Stanley Foundation Brain Collection. mRNA and protein levels were determined by RT-PCR and Western blot analysis, respectively.

RESULTS

Levels of CAM-L1 and of phosphorylated CREB (pCREB) were increased in the prefrontal cortex of the depressed group, while CAM-L1, laminin and pCREB were decreased in the parieto-occipital cortex. Depressed subjects receiving antidepressants differed from subjects not receiving antidepressants in the expression of CAM-L1 and laminin in the parieto-occipital cortex, and in the expression of pCREB in the prefrontal cortex.

CONCLUSIONS

The present findings of specific alterations in depression and antidepressant treatment particularly in CAM-L1 suggest that this gene may play an important role in the pathophysiology and treatment of depression.

Mood stabilizer valproate promotes ERK pathway-dependent cortical neuronal growth and neurogenesis

Manic-depressive illness has been conceptualized as a neurochemical illness. However, brain imaging and postmortem studies reveal gray-matter reductions, as well as neuronal and glial atrophy and loss in discrete brain regions of manic-depressive patients. The roles of such cerebral morphological deficits in the neuropathophysiology and therapeutic mechanisms of manic-depressive illness are unknown. Valproate (2-propylpentanoate) is a commonly used mood stabilizer. The ERK (extracellular signal-regulated kinase) pathway is used by neurotrophic factors to regulate neurogenesis, neurite outgrowth, and neuronal survival. We found that chronic treatment of rats with valproate increased levels of activated phospho-ERK44/42 in neurons of the anterior cingulate, a region in which we found valproate-induced increases in expression of an ERK pathway-regulated gene, bcl-2. Valproate time and concentration dependently increased activated phospho-ERK44/42 and phospho-RSK1 (ribosomal S6 kinase 1) levels in cultured cortical cells. These increases were attenuated by Raf and MEK (mitogen-activated protein kinase/ERK kinase) inhibitors. Although valproate affects the functions of GSK-3 (glycogen synthase kinase-3) and histone deacetylase (HDAC), its effects on the ERK pathway were not fully mimicked by selective inhibitors of GSK-3 or HDAC. Similar to neurotrophic factors, valproate enhanced ERK pathway-dependent cortical neuronal growth. Valproate also promoted neural stem cell proliferation-maturation (neurogenesis), demonstrated by bromodeoxyuridine (BrdU) incorporation and double staining of BrdU with nestin, Tuj1, or the neuronal nuclei marker NeuN (neuronal-specific nuclear protein). Chronic treatment with valproate enhanced neurogenesis in the dentate gyrus of the hippocampus. Together, these data demonstrate that valproate activates the ERK pathway and induces ERK pathway-mediated neurotrophic actions. This cascade of events provides a potential mechanism whereby mood stabilizers alleviate cerebral morphometric deficits associated with manic-depressive illness.

Is mood chemistry?

The chemical hypothesis of depression suggests that mood disorders are caused by a chemical imbalance in the brain, which can be corrected by antidepressant drugs. However, recent evidence indicates that problems in information processing within neural networks, rather than changes in chemical balance, might underlie depression, and that antidepressant drugs induce plastic changes in neuronal connectivity, which gradually lead to improvements in neuronal information processing and recovery of mood.

Proposed multigenic Composite Inheritance in major depression

Various rationale have been considered in the familial inheritance pattern of major depression ranging from simple one-gene Mendelian inheritance to pseudo-additive gene action. We instead predict broad genetic expressivity patterns in the progeny of parents where at least one parent has recurrent major depression. In keeping with this idea, we feel that recurrent major depression could involve an expression imbalance of "normal" genes either exclusively or along with allelic variation(s). The patterns of pathology are theoretically conceptualized as qualitative and quantitative, meaning that expressivity of the genetic pattern in these children may range from minimal to complete even among siblings. Thus, prediction of the particular genetic pattern expressed by a particular child might prove difficult. The complex inheritance pattern that we propose is referred to as Composite Inheritance. Composite Inheritance considers that both the up- and down-regulation of luxury genes and housekeeping genes are involved in this dichotomous qualitative inheritance pattern and also the wide quantitative expressivity. The luxury genes include such genes as those coding for the neurotransmitter transporters and receptors. The housekeeping genes found to date include those that code for proteins involved in gene transcription, secondary signaling systems, fatty acid metabolism and transport, and intracellular calcium homeostasis. Other luxury and housekeeping genes no doubt remain to be discovered. Our current research utilizes an empirical approach involving advanced genomics and specialized pattern recognition mathematics in families having at least one parent with recurrent major depression. The goal of our research is to develop a pattern recognition system of genetic expressivity in major depression to which prevention and early intervention may be tailored.

Electroconvulsive seizure treatment increases cell proliferation in rat frontal cortex

Recent studies have demonstrated increased neurogenesis in adult hippocampus in response to electroconvulsive seizure (ECS) or antidepressant drug treatment. Adult neurogenesis in the subgranular zone of the hippocampus and the subventricular zone is well established, whereas neuronal proliferation outside of these areas under unstimulated conditions is not observed. Since mood disorders are likely to involve brain regions in addition to hippocampus, particularly the frontal cortex, it is likely that antidepressant treatments produce cellular changes in these brain regions as well. In this study, we have investigated the effect of repeated ECS administration on the proliferation of cells in the frontal cortex, and we have examined the phenotype of these cells 4 weeks after labeling with a cell division marker. We found that ECS treatment increases the number of newly divided cells in the frontal cortex and that these new cells express markers of either endothelial cells or oligodendrocytes, but not neurons. It is possible that increased proliferation of these cell types in the frontal cortex could reverse the loss of glial cell number and the reduced volume that has been reported in the frontal cortex of depressed patients.

Does electrode placement predict time to rehospitalization?

We sought to determine whether electrode placement influenced time to rehospitalization. A retrospective review of an elderly, depressed population that had received bitemporal, bifrontal or 6 x RUL ECT was examined to determine time to rehospitalization. Bitemporal ECT was associated with a statistically significant reduction in the number of (P = 0.026) and time to (P = 0.025), rehospitalization. Bitemporal ECT may be a preferred electrode placement, not only because of its demonstrated effectiveness across a range of diagnoses, but for its previously undocumented capacity to delay rehospitalization.

Brain-derived neurotrophic factor induces hyperexcitable reentrant circuits in the dentate gyrus

Aberrant sprouting and synaptic reorganization of the mossy fiber (MF) axons are commonly found in the hippocampus of temporal lobe epilepsy patients and result in the formation of excitatory feedback loops in the dentate gyrus, a putative cellular basis for recurrent epileptic seizures. Using ex vivo hippocampal cultures, we show that prolonged hyperactivity induces MF sprouting and the resultant network reorganizations and that brain-derived neurotrophic factor (BDNF) is necessary and sufficient to evoke these pathogenic plasticities. Hyperexcitation induced an upregulation of BDNF protein expression in the MF pathway, an effect mediated by L-type Ca2+ channels. The neurotrophin receptor tyrosine kinase (Trk)B inhibitor K252a or function-blocking anti-BDNF antibody prevented hyperactivity-induced MF sprouting. Even under blockade of neural activity, local application of BDNF to the hilus, but not other subregions, was capable of initiating MF axonal remodeling, eventually leading to dentate hyperexcitability. Transfecting granule cells with dominant-negative TrkB prevented axonal branching. Thus, excessive activation of L-type Ca2+ channels causes granule cells to express BDNF, and extracellularly released BDNF stimulates TrkB receptors present on the hilar segment of the MFs to induce axonal branching, which may establish hyperexcitable dentate circuits.

A role for glia in the action of electroconvulsive therapy

In this article, we consider possible mechanisms of action for electroconvulsive therapy (ECT) based on evidence regarding cellular changes in affective and psychotic illnesses. Postmortem investigations of major depression and schizophrenia have revealed abnormalities in the number of neuronal and glial cells. Such cellular changes could indicate a perturbed balance between neurogenesis and neuronal death in the adult brain. Psychotropic drugs and ECT have been shown to stimulate neurogenesis, giving rise to the hypothesis that this generation of new cells mediates some of their therapeutic effect. A possible trophic effect on glial cells has not been examined. Since glial cells are essential for proper neuronal function, treatments that alter glial function would have significant effects on brain function. We suggest that the effectiveness of ECT is, in part, related to its effect on glial cells. This testable hypothesis may advance our understanding and treatment of psychiatric disorders.

Critical role of brain-derived neurotrophic factor in mood disorders

The purpose of this review is to integrate what is currently known about the role of brain-derived neurotrophic factor (BDNF) in the pathophysiology of mood disorders including major depressive disorder (MDD) and bipolar disorder (BD). We reviewed the pre-clinical and clinical papers demonstrating that BDNF plays a role in the pathophysiology of mood disorders and in the mechanism of action of therapeutic agents. Pre-clinical studies suggest that the expression of BDNF might be a downstream target of antidepressant treatments and mood stabilizers such as lithium and valproate, and that BDNF exerts antidepressant activity in animal models of depression. Furthermore, BDNF protects against stress-induced neuronal damage, and it might affect neurogenesis in the hippocampus, which is thought to be involved in the pathogenesis of mood disorders. Clinical studies have demonstrated that serum levels of BDNF in drug-naive patients with MDD are significantly decreased as compared with normal controls, and that BDNF might be an important agent for therapeutic recovery from MDD. Moreover, recent findings from family-based association studies have suggested that the BDNF gene is a potential risk locus for the development of BD. These findings suggest that BDNF plays a critical role in the pathophysiology of mood disorders and in the activity of therapeutic agents in patients with mood disorders. New agents capable of enhancing BDNF levels may lead aid the development of novel therapeutic drugs for patients with mood disorders.

Reciprocal changes of CD44 and GAP-43 expression in the dentate gyrus inner molecular layer after status epilepticus in mice

Mossy fiber sprouting (MFS), a common feature of human temporal lobe epilepsy and many epilepsy animal models, contributes to hippocampal hyperexcitability. The molecular events responsible for MFS are not well understood, although the growth-associated protein GAP-43 has been implicated in rats. Here, we focus on the hyaluronan receptor CD44, which is involved in routing of retinal axons during development and is upregulated after injury in many tissues including brain. After pilocarpine-induced status epilepticus (SE) in mice most hilar neurons died and neuropeptide Y (NPY) immunoreactivity appeared in the dentate inner molecular layer (IML) after 10-31 days indicative of MFS. Strong CD44 immunoreactivity appeared in the IML 3 days after pilocarpine, then declined over the next 4 weeks. Conversely, GAP-43 immunoreactivity was decreased in the IML at 3-10 days after pilocarpine-induced SE. After SE induced by repeated kainate injections, mice did not show any hilar cell loss or changes in CD44 or GAP-43 expression in the IML, and MFS was absent at 20-35 days. Thus, after SE in mice, early loss of GAP-43 and strong CD44 induction in the IML correlated with hilar cell loss and subsequent MFS. CD44 is one of the earliest proteins upregulated in the IML and coincides with early sprouting of mossy fibers, although its function is still unknown. We hypothesize that CD44 is involved in the response to axon terminal degeneration and/or neuronal reorganization preceding MFS.

New aspects of neurotransmitter release and exocytosis: dynamic and differential regulation of synapsin I phosphorylation by acute neuronal excitation in vivo

Synapsin I is a synaptic vesicle-associated protein that is phosphorylated at multiple sites by various protein kinases. It has been proposed to play an important role in the regulation of neurotransmitter release and the organization of cytoskeletal architecture in the presynaptic terminal. In the present minireview, I describe the dynamic changes in synapsin I phosphorylation induced by acute neuronal excitation in vivo, and discuss its regulation by protein kinases and phosphatases and its functional significance in vivo. When acute neuronal excitation was induced by electroconvulsive treatment (ECT) in rats, phosphorylation of synapsin I at multiple sites was decreased during brief seizure activity in hippocampal and parieto-cortical homogenates. After termination of the seizure activity, phosphorylation at mitogen-activated protein kinase-dependent sites was increased dramatically. Phosphorylation at a Ca(2+)/calmodulin-dependent protein kinase II-dependent site was also increased moderately afterwards. The dynamic and differential changes in synapsin I phosphorylation induced by acute neuronal excitation may be involved in plastic changes induced by ECT and may have some role in its effectiveness for the treatment of psychiatric diseases in humans.

Differential regulation of FAK and PYK2 tyrosine phosphorylation after electroconvulsive shock in the rat brain

It has been suggested that FAK and PYK2 have differential regulatory pathways and differential functions in the central nervous system. The authors have previously reported that electroconvulsive shock (ECS) activates PYK2 mediated signaling in the rat hippocampus. In the present article, the authors examined the effect of ECS on PYK2 and FAK mediated signaling in the rat cerebral cortex and hippocampus. Our results showed that ECS activated PYK2 more preferentially than FAK in both the cortex and the hippocampus. The association of Src-family kinases with FAK and PYK2 was also distinctively affected by ECS; Src was mainly associated with PYK2 while Yes was associated with FAK. The phosphorylation of FAK and PYK2 at the key tyrosine residue was not well correlated with the association with Src-family kinases.

New insights into the mechanisms of antidepressant therapy

Depressive disorders are among the most frequent psychiatric diseases in the Western world with prevalence numbers between 9% and 18%. They are characterized by depressed mood, a diminished interest in pleasurable activities, feelings of worthlessness or inappropriate guilt, decrease in appetite and libido, insomnia, and recurrent thoughts of death or suicide. Among other findings, reduced activity of monoaminergic neurotransmission has been postulated to play a role in the pathogenesis of depression. Consistent with this hypothesis, most antidepressive drugs exert their action by elevating the concentration of monoamines in the synaptic cleft. However, it is not the enhancement of monoaminergic signaling per se, but rather long-term, adaptive changes that may underlie the therapeutic effect. These include functional and structural changes that are discussed later. In addition, in the last years, evidence has emerged that remissions induced in patients using lithium or electroconvulsive therapy are accompanied by structural changes in neuronal networks thereby affecting synaptic plasticity in various regions of the brain.

Electrophysiological evidence of monosynaptic excitatory transmission between granule cells after seizure-induced mossy fiber sprouting

Mossy fiber sprouting is a form of synaptic reorganization in the dentate gyrus that occurs in human temporal lobe epilepsy and animal models of epilepsy. The axons of dentate gyrus granule cells, called mossy fibers, develop collaterals that grow into an abnormal location, the inner third of the dentate gyrus molecular layer. Electron microscopy has shown that sprouted fibers from synapses on both spines and dendritic shafts in the inner molecular layer, which are likely to represent the dendrites of granule cells and inhibitory neurons. One of the controversies about this phenomenon is whether mossy fiber sprouting contributes to seizures by forming novel recurrent excitatory circuits among granule cells. To date, there is a great deal of indirect evidence that suggests this is the case, but there are also counterarguments. The purpose of this study was to determine whether functional monosynaptic connections exist between granule cells after mossy fiber sprouting. Using simultaneous recordings from granule cells, we obtained direct evidence that granule cells in epileptic rats have monosynaptic excitatory connections with other granule cells. Such connections were not obtained when age-matched, saline control rats were examined. The results suggest that indeed mossy fiber sprouting provides a substrate for monosynaptic recurrent excitation among granule cells in the dentate gyrus. Interestingly, the characteristics of the excitatory connections that were found indicate that the pathway is only weakly excitatory. These characteristics may contribute to the empirical observation that the sprouted dentate gyrus does not normally generate epileptiform discharges.

Activation of protein kinase B (Akt) signaling after electroconvulsive shock in the rat hippocampus

Akt (protein kinase B, PKB) is one of the major downstream pathways of neurotrophin signaling and plays important roles in the cell survival and synaptic plasticity of the central nervous system. Electroconvulsive shock (ECS) has neurotrophic effect and it affects the synaptic plasticity. It can activate another major pathway of neurotrophin signaling, i.e., Ras-Raf-MEK-Erk cascade. In this paper, the authors investigated whether ECS can activate Akt signaling in the rat hippocampus. After a single ECS, the phosphorylation of Akt was increased, as were the signals detected by phospho-PDK1 substrate antibody, which suggests the activation of PDK1, an upstream molecule of Akt. The phosphorylation of downstream molecules of Akt, forkhead transcription factors (FKHR), endothelial nitric oxide synthase (eNOS), and glycogen synthase kinase-3beta (GSK-3beta) was also increased. The increased phosphorylation of Akt appeared within 5 min of ECS and its time frame paralleled that of the phosphorylation of Erks. Taken together, these results suggest that ECS activates Akt signaling over a similar time scale to that of Erks in the rat hippocampus.

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.

Specific creatine rise in learned helplessness induced by electroconvulsive shock treatment

Metabolic changes in the hippocampus formation can be investigated with in vivo magnetic resonance spectroscopy (MRS). Learned helplessness (LH) is a well validated animal model of depression which we established in Sprague-Dawley rats defining some as "learned helpless" (LH) or not "learned helpless" (NLH). Helpless and non-helpless rats received a course of daily administered electroconvulsive shocks (ECS) for 6 days. MRS measurements were performed on a 4.7 T animal scanner with an average voxel size within the rat hippocampus of 10 microl. In LH rats hippocampal creatine/NAA rose significantly (14%) whereas creatine/NAA of NLH rats showed no increase at all. A possible connection between hippocampal creatine levels and major depressive disorders as a reflection of changes in energy metabolism is discussed.

A ligand of the p65/p95 receptor suppresses perforant path kindling, kindling-induced mossy fiber sprouting, and hilar area changes in adult rats

Kindling, an animal model of epilepsy, results in an increased volume of the hilus of the dentate gyrus and sprouting of the mossy fiber pathway in the hippocampus. Our previous studies have revealed that chronic infusion of neurotrophins can regulate not only seizure development, but also these kindling-induced structural changes. Kindling, in turn, can alter the expression of neurotrophins and their receptors. We previously showed that intraventricular administration of a synthetic peptide that interferes with nerve growth factor stability and thus its binding to TrkA and p75(NTR) receptors suppressed kindling and sprouting. However, the precise involvement of TrkA, p75(NTR), and downstream signaling effectors of neurotrophins on kindling, sprouting and hilar changes are unknown. One of these downstream effectors is Ras. In the present study, we find that intraventricular infusion of the synthetic peptide Reo3Y, which binds to p65/p95 receptors and causes a rapid inactivation of Ras protein, impairs development of perforant path kindling, reduces the growth in afterdischarge duration, blocks kindling-induced mossy fiber sprouting in area CA3 of hippocampus and in inner molecular layer of the dentate gyrus, and prevents kindling-induced increases in hilar area. These results are consistent with a mediation of neurotrophin effects on kindling, hilar area, and axonal sprouting via Trk receptors, and suggest important roles for Ras in kindling and in kindling-induced structural changes.

Selective serotonin reuptake inhibitor discontinuation syndrome is associated with a rostral anterior cingulate choline metabolite decrease: a proton magnetic resonance spectroscopic imaging study

The selective serotonin reuptake inhibitor (SSRI) discontinuation syndrome (DS) is an important potential complication of treatment for major depression. We hypothesized that SSRI treatment discontinuation, resulting in change in clinical state, would be associated with reduced rostral anterior cingulate choline (Cho) metabolite ratios. Individuals with a DSM-III-R diagnosis of unipolar major depression who had been stabilized on paroxetine (n = 13) or fluoxetine (n = 13) were study subjects. They were monitored for change in clinical state (mood ratings, discontinuation symptoms) and underwent proton magnetic resonance spectroscopic imaging of the rostral anterior cingulate 3 days after medication substitution with active SSRI and placebo.Placebo-day Cho/Cre (choline/total creatine) metabolite ratios were decreased in four paroxetine and two fluoxetine subjects meeting DS criteria, as compared with asymptomatic subjects (Mann-Whitney z = -2.31, p =.021). Discontinuation syndrome is associated with a rostral anterior cingulate Cho/Cre metabolite ratio decrease that may reflect dynamics of rostral anterior cingulate function.

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.

Antidepressant-like effects of acute and chronic treatment with zinc in forced swim test and olfactory bulbectomy model in rats

The activity of zinc administered intraperitoneally, acutely (in single dose), sub-chronically (in triple doses) or chronically (once daily for 14 days) were assessed in the forced swim test (FST) and olfactory bulbectomy (OB) model of depression in rats. Previously, we have demonstrated that acute administration of zinc sulfate is active in FST in rats and mice. In the present study, zinc hydroaspartate in a dose of 65 mg/kg (11.5 mgZn/kg), all: acute, sub-chronic and chronic administration, reduced the immobility time in the FST in rats. Removal of olfactory bulbs (OB surgery) in rats is associated with variety of behavioral abnormalities such as deficit in a step-down passive avoidance or hyperactivity in the "open field" test. Both acute and chronic administration of zinc hydroaspartate reduced the number of trials needed to the learning passive avoidance and reduced the OB-induced hyperactivity in rats. At the time schedule following zinc hydroaspartate administration, when behavioral experiments were performed, the serum zinc concentrations were significantly higher than control-physiological values. These results confirm activity of zinc in the FST, show its antidepressant-like activity in the OB rat model of depression, demonstrate the lack of tolerance to these effects and suggest relationship of these antidepressant-like effects with the rise in serum zinc. These animal data further suggest antidepressant activity of zinc in human depression.

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.

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.