Repeated electroconvulsive stimulation, but not antidepressant drugs, induces mossy fibre sprouting in the rat hippocampus

Shape and volume changes of the superior lateral ventricle after electroconvulsive therapy measured with ultra-high field MRI

The subventricular zone (SVZ) of the lateral ventricles harbors neuronal stem cells in adult mammals. Rodent studies report neurogenic effects in the SVZ of electroconvulsive stimulation. We hypothesize that if this finding translates to depressed patients undergoing electroconvulsive therapy (ECT), this would be reflected in shape changes at the SVZ. Using T1-weighted MR images acquired at ultra-high field strength (7T), the shape and volume of the ventricles were compared from pre to post ECT after 10 ECT sessions (in patients twice weekly) or 5 weeks apart (controls) using linear mixed models with age and gender as covariates. Ventricle shape significantly changed and volume significantly decreased over time in patients for the left ventricle, but not in controls. The decrease in volume of the ventricles was associated to a decrease in depression scores, and an increase in the left dentate gyrus, However, the shape changes of the ventricles were not restricted to the neurogenic niche in the lateral walls of the ventricles, providing no clear evidence for neurogenesis as sole explanation of volume changes in the ventricles after ECT.

Volume increase in the dentate gyrus after electroconvulsive therapy in depressed patients as measured with 7T

Electroconvulsive therapy (ECT) is the most effective treatment for depression, yet its working mechanism remains unclear. In the animal analog of ECT, neurogenesis in the dentate gyrus (DG) of the hippocampus is observed. In humans, volume increase of the hippocampus has been reported, but accurately measuring the volume of subfields is limited with common MRI protocols. If the volume increase of the hippocampus in humans is attributable to neurogenesis, it is expected to be exclusively present in the DG, whereas other processes (angiogenesis, synaptogenesis) also affect other subfields. Therefore, we acquired an optimized MRI scan at 7-tesla field strength allowing sensitive investigation of hippocampal subfields. A further increase in sensitivity of the within-subjects measurements is gained by automatic placement of the field of view. Patients receive two MRI scans: at baseline and after ten bilateral ECT sessions (corresponding to a 5-week interval). Matched controls are also scanned twice, with a similar 5-week interval. A total of 31 participants (23 patients, 8 controls) completed the study. A large and significant increase in DG volume was observed after ECT (M = 75.44 mm³, std error = 9.65, p < 0.001), while other hippocampal subfields were unaffected. We note that possible type II errors may be present due to the small sample size. In controls no changes in volume were found. Furthermore, an increase in DG volume was related to a decrease in depression scores, and baseline DG volume predicted clinical response. These findings suggest that the volume change of the DG is related to the antidepressant properties of ECT, and may reflect neurogenesis.

Improvement in verbal memory performance in depressed in-patients after treatment with electroconvulsive therapy

OBJECTIVE

Electroconvulsive therapy (ECT) is a highly effective and well-tolerated therapy for severe and treatment-resistant depression. Cognitive side-effects are still feared by some patients and clinicians. Importantly, cognitive impairments are among the most disabling symptoms of depression itself.

METHODS

Patients suffering from a severe episode of depression were treated with either ECT or treatment as usual (TAU) in an in-patient setting. Matched healthy participants served as controls (HC). Verbal memory was tested with the California Verbal Learning Test (CVLT) before the specific treatment started (ECT = 15, TAU = 16, HC = 31) and 2 months after the last ECT session or 2 months after discharge respectively.

RESULTS

Before the specific treatment started, depressed patients performed substantially worse compared with HC in total, short- and long-delay recall in the CVLT, while the ECT group showed the worst performance. More severely depressed patients showed worse performances in these measures. Intriguingly, verbal memory showed a significant improvement in ECT-treated patients, but not in the other groups. No differences between the groups were found at follow-up.

CONCLUSION

Contrary to the widely feared assumption that ECT has long-term impact on memory functions, we found evidence that ECT is superior to TAU in improving verbal memory in depressed patients.

Rapid and lasting enhancement of dopaminergic modulation at the hippocampal mossy fiber synapse by electroconvulsive treatment

Electroconvulsive therapy (ECT) is an established effective treatment for medication-resistant depression with the rapid onset of action. However, its cellular mechanism of action has not been revealed. We have previously shown that chronic antidepressant drug treatments enhance dopamine D₁-like receptor-dependent synaptic potentiation at the hippocampal mossy fiber (MF)-CA3 excitatory synapse. In this study we show that ECT-like treatments in mice also have marked effects on the dopaminergic synaptic modulation. Repeated electroconvulsive stimulation (ECS), an animal model of ECT, strongly enhanced the dopamine-induced synaptic potentiation at the MF synapse in hippocampal slices. Significant enhancement was detectable after the second ECS, and further repetition of ECS up to 11 times monotonously increased the magnitude of enhancement. After repeated ECS, the dopamine-induced synaptic potentiation remained enhanced for more than 4 wk. These synaptic effects of ECS were accompanied by increased expression of the dopamine D₁ receptor gene. Our results demonstrate that robust neuronal activation by ECS induces rapid and long-lasting enhancement of dopamine-induced synaptic potentiation at the MF synapse, likely via increased expression of the D₁ receptor, at least in part. This rapid enhancement of dopamine-induced potentiation at the excitatory synapse may be relevant to the fast-acting antidepressant effect of ECT.

NEW & NOTEWORTHY

We show that electroconvulsive therapy (ECT)-like stimulation greatly enhances synaptic potentiation induced by dopamine at the excitatory synapse formed by the hippocampal mossy fiber in mice. The effect of ECT-like stimulation on the dopaminergic modulation was rapidly induced, maintained for more than 4 wk after repeated treatments, and most likely mediated by increased expression of the dopamine D1 receptor. These effects may be relevant to fast-acting strong antidepressant action of ECT.

Electroconvulsive shock attenuated microgliosis and astrogliosis in the hippocampus and ameliorated schizophrenia-like behavior of Gunn rat

Background

Although electroconvulsive therapy (ECT) is regarded as one of the efficient treatments for intractable psychiatric disorders, the mechanism of therapeutic action remains unclear. Recently, many studies indicate that ECT affects the immune-related cells, such as microglia, astrocytes, and lymphocytes. Moreover, microglial activation and astrocytic activation have been implicated in the postmortem brains of schizophrenia patients. We previously demonstrated that Gunn rats showed schizophrenia-like behavior and microglial activation in their brains. The present study examined the effects of electroconvulsive shock (ECS), an animal counterpart of ECT, on schizophrenia-like behavior, microgliosis, and astrogliosis in the brain of Gunn rats.

Methods

The rats were divided into four groups, i.e., Wistar sham, Wistar ECS, Gunn sham, and Gunn ECS. ECS groups received ECS once daily for six consecutive days. Subsequently, prepulse inhibition (PPI) test was performed, and immunohistochemistry analysis was carried out to determine the activation degree of microglia and astrocytes in the hippocampus by using anti-CD11b and anti-glial fibrillary acidic protein (GFAP) antibody, respectively.

Results

We found PPI deficit in Gunn rats compared to Wistar rats, and it was significantly improved by ECS. Immunohistochemistry analysis revealed that immunoreactivity of CD11b and GFAP was significantly increased in Gunn rats compared to Wistar rats. ECS significantly attenuated the immunoreactivity of both CD11b and GFAP in Gunn rats.

Conclusions

ECS ameliorated schizophrenia-like behavior of Gunn rats and attenuated microgliosis and astrogliosis in the hippocampus of Gunn rats. Accordingly, therapeutic effects of ECT may be exerted, at least in part, by inhibition of glial activation. These results may provide crucial information to elucidate the role of activated glia in the pathogenesis of schizophrenia and to determine whether future therapeutic interventions should attempt to up-regulate or down-regulate glial functions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0688-2) contains supplementary material, which is available to authorized users.

Zinc and imipramine reverse the depression-like behavior in mice induced by chronic restraint stress

Depression is a common psychopathological disorders. Studies of depression have indicated that zinc play a role in the depression pathophysiology and treatment. In present study, we examined the effects of zinc and imipramine supplement alone or combination of zinc and imipramine in mice induced by chronic restraint stress (CRS). Moreover, the possible roles of zinc receptor (G protein-coupled receptor 39, GPR39)-related pathway was investigated. Decreased weight and increased corticosterone (CORT) were observed after 3 weeks CRS exposure. It was shown that CRS induced lower serum zinc, higher hippocampal zinc, increased immobility time in tail suspension test and decreased movement distance in spontaneous activity test, which could be normalized by zinc (30 mg/kg) and imipramine (20 mg/kg) supplement alone and combination of zinc (15 mg/kg) and imipramine (5 mg/kg) for 3 weeks after CRS exposure. Moreover, the changes in mRNA expressions of GPR39, cAMP-response element binding protein (CREB), brain-derived neurotropic factor (BDNF) and n-methytl-d-aspartate receptors (NMDAR) could be reversed by the same treatment mentioned above. These results suggested that zinc dyshomeostasis in serum and hippocampus and depression-like behavior in CRS exposure animals observed in present study could be normalized by zinc and imipramine. The combination of zinc and imipramine in low dose has synergetic effects. The possible mechanism might be correlated to GPR39 receptor-related pathway.

Effect of Liraglutide on Corneal Kindling Epilepsy Induced Depression and Cognitive Impairment in Mice

GLP-1 play important role in neuroprotection and GLP-1 receptor deficit mice showed decreased seizure threshold and increased cognitive impairment. Therefore, study was premeditated to investigate the effect of liraglutide (GLP-1 analogue) on cornel kindling epilepsy induced co-morbidities in mice. Corneal kindling was induced by electrical stimulation (6 mA, 50 Hz, 3 s); twice daily for 13 days. Liraglutide (75 and 150 µg/kg) and phenytoin (20 mg/kg) were administered in corneal kindled groups. On day 14, elevated plus maze, passive shock avoidance paradigms were performed, and on day 15, retention was taken. On day 16 tail suspension test were performed. On 20th day challenge test was performed with same electrical stimulation and retention was observed on elevated plus maze and passive avoidance paradigm. Animal were sacrificed on 21st day for biochemical (LPO, GSH, and nitrite) and neurochemical (GABA, glutamate, DA, NE, 5-HT and their metabolites) estimation. Electrical stimulation by corneal electrode for 13 days developed generalized clonic seizures, increased cognitive impairment, oxidative stress and neurochemical alteration in mice brain. Co-treatment with liraglutide (75 and 150 μg/kg) significantly prevented the seizure severity, restored behavioural activity, oxidative stress and restored the altered level of neurotransmitters observed in corneal kindled mouse.

Effect of electroconvulsive therapy on gray matter volume in major depressive disorder

BACKGROUND

Although the clinical efficacy of electroconvulsive therapy (ECT) is well established, the underlying mechanisms of action remain elusive. The aim of this study was to elucidate structural changes of the brain following ECT in patients with major depressive disorder (MDD).

METHOD

Fifteen patients with MDD underwent magnetic resonance imaging scanning before and after ECT. Their gray matter volumes were compared between pre- and post-ECT.

RESULTS

There were significant volume increases after ECT in the bilateral medial temporal cortices, inferior temporal cortices, and right anterior cingulate. Further, the increase ratio was correlated with the clinical improvement measured by the Hamilton Depression Rating scale.

LIMITATION

All subjects were treated with antidepressants that could have a neurotoxic or neuroprotective effect on the brain.

CONCLUSIONS

We found that there were significant increases of gray matter volume in medial temporal lobes following ECT, suggesting that a neurotrophic effect of ECT could play a role in its therapeutic effect.

Effects of brief pulse and ultrabrief pulse electroconvulsive stimulation on rodent brain and behaviour in the corticosterone model of depression

Brief pulse electroconvulsive therapy (BP ECT; pulse width 0.5-1.5 ms) is the most effective treatment available for severe depression. However, its use is associated with side-effects. The stimulus in ultrabrief pulse ECT (UBP ECT; pulse width 0.25-0.3 ms) is more physiological and has been reported to be associated with less cognitive side-effects, but its antidepressant effectiveness is not yet well established. Using electroconvulsive stimulation (ECS), the animal model of ECT, we previously reported UBP ECS to be significantly less effective than well-established BP ECS in eliciting behavioural, molecular and cellular antidepressant-related effects in naïve rats. We have now compared the effects of BP and UBP ECS in an animal model of depression related to exogenous supplementation with the stress-induced glucocorticoid hormone, corticosterone. Corticosterone administration resulted in an increase in immobility time in the forced swim test (FST) (p < 0.01) and decreases in the expression of brain-derived neurotrophic factor (BDNF) (p < 0.05) and glial fibrillary acidic protein (GFAP) (p < 0.001) in the hippocampus and frontal cortex. There was no significant difference in the duration or type of seizure induced by BP (0.5 ms) or UBP (0.3 ms) ECS. UBP ECS proved to be as effective as BP ECS at inducing a behavioural antidepressant response in the FST with a significant decrease (p < 0.001) in immobility seen following administration of ECS. Both forms of ECS also induced significant increases in BDNF protein (p < 0.01) expression in the hippocampus. BP ECS (p < 0.05) but not UBP ECS induced a significant increase in GFAP levels in the hippocampus and frontal cortex. Overall, UBP ECS effectively induced antidepressant-related behavioural and molecular responses in the corticosterone supplementation model, providing the first preclinical data on the potential role of this form of ECS to treat a depression phenotype related to elevated corticosterone.

Hippocampal neurogenesis and antidepressive therapy: shocking relations

Speculations on the involvement of hippocampal neurogenesis, a form of neuronal plasticity, in the aetiology of depression and the mode of action of antidepressive therapies, started to arise more than a decade ago. But still, conclusive evidence that adult neurogenesis contributes to antidepressive effects of pharmacological and physical therapies has not been generated yet. This review revisits recent findings on the close relation between the mode(s) of action of electroconvulsive therapy (ECT), a powerful intervention used as second-line treatment of major depression disorders, and the neurogenic response to ECT. Following application of electroconvulsive shocks, intricate interactions between neurogenesis, angiogenesis, and microglia activation, the hypothalamic-pituitary-adrenal axis and the secretion of neurotrophic factors have been documented. Furthermore, considering the fact that neurogenesis strongly diminishes along aging, we investigated the response to electroconvulsive shocks in young as well as in aged cohorts of mice.

Electroconvulsive therapy increases hippocampal and amygdala volume in therapy refractory depression: a longitudinal pilot study

Electroconvulsive therapy (ECT) is the most potent biological therapy in depression. Animal studies suggest that ECT acts via neuroplasticity effects on limbic structures involved in the pathophysiology of depression but in vivo evidence at the human system level is scarce. Therefore, the aim of the present study was to investigate the effect of ECT on hippocampus and amygdala volume in 15 antidepressant-free patients with treatment refractory depression (seven males, range 42-63 years). ECT treatment was successful as indexed by a significant decrease in depressive symptoms (t14=13.6; p<0.001). Analysis of normalized volumetric data before and after ECT treatment revealed a significant volume increase of both hippocampus and amygdala (minimum p<0.005) with no evidence for a change in global brain volume. Though this change in volume cannot be clearly related to treatment effects, ECT is associated with broader neurotrophic effects other than mere adult neurogenesis in the hippocampus, which has been previously suggested as a core mechanism on the basis of animal data.

Orchestrated regulation of Nogo receptors, LOTUS, AMPA receptors and BDNF in an ECT model suggests opening and closure of a window of synaptic plasticity

Electroconvulsive therapy (ECT) is an efficient and relatively fast acting treatment for depression. However, one severe side effect of the treatment is retrograde amnesia, which in certain cases can be long-term. The mechanisms behind the antidepressant effect and the amnesia are not well understood. We hypothesized that ECT causes transient downregulation of key molecules needed to stabilize synaptic structure and to prevent Ca2+ influx, and a simultaneous increase in neurotrophic factors, thus providing a short time window of increased structural synaptic plasticity. Here we followed regulation of NgR1, NgR3, LOTUS, BDNF, and AMPA subunits GluR1 and GluR2 flip and flop mRNA levels in hippocampus at 2, 4, 12, 24, and 72 hours after a single episode of induced electroconvulsive seizures (ECS) in rats. NgR1 and LOTUS mRNA levels were transiently downregulated in the dentate gyrus 2, 4, 12 and 4, 12, 24 h after ECS treatment, respectively. GluR2 flip, flop and GluR1 flop were downregulated at 4 h. GluR2 flip remained downregulated at 12 h. In contrast, BDNF, NgR3 and GluR1 flip mRNA levels were upregulated. Thus, ECS treatment induces a transient regulation of factors important for neuronal plasticity. Our data provide correlations between ECS treatment and molecular events compatible with the hypothesis that both effects and side effects of ECT may be caused by structural synaptic rearrangements.

Potential roles of zinc in the pathophysiology and treatment of major depressive disorder

Incomplete response to monoaminergic antidepressants in major depressive disorder (MDD), and the phenomenon of neuroprogression, suggests a need for additional pathophysiological markers and pharmacological targets. Neuronal zinc is concentrated exclusively within glutamatergic neurons, acting as an allosteric modulator of the N-methyl D-aspartate and other receptors that regulate excitatory neurotransmission and neuroplasticity. Zinc-containing neurons form extensive associational circuitry throughout the cortex, amygdala and hippocampus, which subserve mood regulation and cognitive functions. In animal models of depression, zinc is reduced in these circuits, zinc treatment has antidepressant-like effects and dietary zinc insufficiency induces depressive behaviors. Clinically, serum zinc is lower in MDD, which may constitute a state-marker of illness and a risk factor for treatment-resistance. Marginal zinc deficiency in MDD may relate to multiple putative mechanisms underlying core symptomatology and neuroprogression (e.g. immune dysfunction, monoamine metabolism, stress response dysregulation, oxidative/nitrosative stress, neurotrophic deficits, transcriptional/epigenetic regulation of neural networks). Initial randomized trials suggest a benefit of zinc supplementation. In summary, molecular and animal behavioral data support the clinical significance of zinc in the setting of MDD.

The Role of Neurotrophins in Major Depressive Disorder

Neurotrophins and other growth factors have been advanced as critical modulators of depressive behavior. Support for this model is based on analyses of knockout and transgenic mouse models, human genetic studies, and screens for gene products that are regulated by depressive behavior and/or antidepressants. Even subtle alteration in the regulated secretion of brain-derived neurotrophic factor (BDNF), for example, due to a single nucleotide polymorphism (SNP)-encoded Val-Met substitution in proBDNF that affects processing and sorting, impacts behavior and cognition. Alterations in growth factor expression result in changes in neurogenesis as well as structural changes in neuronal cytoarchitecture, including effects on dendritic length and spine density, in the hippocampus, nucleus accumbens, and prefrontal cortex. These changes have the potential to impact the plasticity and stability of synapses in the CNS, and the complex brain circuitry that regulates behavior. Here we review the role that neurotrophins play in the modulation of depressive behavior, and the downstream signaling targets they regulate that potentially mediate these behavioral pro-depressant and antidepressant effects.

Differential aberrant sprouting in temporal lobe epilepsy with psychiatric co-morbidities

Psychiatric co-morbidities in epilepsy are common in patients with temporal lobe epilepsy (TLE). Pathological alterations in TLE are well characterised; however, neuropathologic data are relatively scale regarding the association between psychiatric diseases and epilepsy. Our objective was to evaluate the clinical data of 46 adult TLE patients with and without psychiatric co-morbidities and to correlate the data with hippocampal neuronal density and mossy fiber sprouting. Accordingly, patients were grouped as follows: TLE patients without history of psychiatric disorder (TLE, n=16), TLE patients with interictal psychosis (TLE+P, n=14), and TLE patients with major depression (TLE+D, n=16). Hippocampi from autopsies served as non-epileptic controls (n=10). TLE+P exhibited significantly diminished mossy fiber sprouting and decreased neuronal density in the entorhinal cortex when compared with TLE. TLE+P showed significantly poorer results in verbal memory tasks. TLE+D exhibited significantly increased mossy fiber sprouting length when compared with TLE and TLE+P. Further, a higher proportion of TLE+D and TLE+P presented secondarily generalised seizures than did TLE. Our results indicate that TLE patients with psychiatric disorders have distinct features when compared with TLE patients without psychiatric co-morbidities and that these changes may be involved in either the manifestation or the maintenance of psychiatric co-morbidities in epilepsy.

Exploration of new molecular mechanisms for antidepressant actions of electroconvulsive seizure

Electroconvulsive seizure (ECS) therapy 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. Here, I review studies that show molecular, cellular, and behavioral changes by ECS treatment, and discuss the functions of ECS to underlie the action of antidepressant effects. In hippocampus, these changes cover gene induction, increased adult neurogenesis, and electrophysiological reactivity. Especially, the role of vascular endothelial growth factor (VEGF) in neurogenesis is discussed. Among other gene expression changes in hippocampus, a role of cyclooxygenase (COX)-2, an inducible type of the rate-limiting enzyme of prostanoid synthesis, is focused. ECS-induced changes in other brain regions such as prefrontal cortex and hypothalamus, and ECS-induced behavioral changes are also reviewed. Understanding the molecular, cellular, and behavioral changes by ECS will provide a new view to find potential targets for novel antidepressant design that are highlighted by these findings.

Abnormal cingulate and prefrontal cortical neurochemistry in major depression after electroconvulsive therapy

BACKGROUND

Metabolic changes after electroconvulsive therapy (ECT) have been described in depressed patients, but results are heterogeneous. To determine the concentrations of N-acetyl-aspartate (NAA), choline-containing compounds, creatine + phosphocreatine (tCr), and glutamate in the left dorsolateral prefrontal cortex (DLPFC) and left anterior cingulum of depressed patients before and after ECT, we used proton magnetic resonance spectroscopy.

METHODS

Metabolite concentrations in the DLPFC and anterior cingulum were determined in 25 patients with major depressive disorder (MDD) and 27 healthy control subjects using the point resolved spectroscopy sequence. Neuropsychological and clinical parameters were determined before and after nine sessions of right unilateral ultrabrief pulse ECT.

RESULTS

In the cingulum, baseline glutamate and NAA levels were decreased in depressed patients. High glutamate at baseline predicted a greater treatment response. After ECT, increased NAA levels were observed in responders to treatment and tCr levels were significantly decreased across all depressive patients. In the left DLPFC, NAA levels were significantly decreased in responders to ECT compared with nonresponders. Autobiographic memory was deteriorated in all patients after ECT.

CONCLUSIONS

Low glutamatergic state in depressive patients emphasizes the role of dysfunctional glutamatergic neurotransmission in the pathophysiology of MDD. The low NAA level at baseline in the patients supports neurodegenerative changes in MDD. N-acetyl-aspartate levels might serve as early surrogate marker for dynamic metabolic changes due to ECT, reflecting both neuroprotection and lowered neuronal viability. The tCr decrease in the cingulum suggests altered mitochondrial energy metabolism.

Effects of repeated electroconvulsive seizure on cell proliferation in the rat hippocampus

Electroconvulsive therapy (ECT) is known as a successful treatment for severe depression. Despite great efforts, the biological mechanisms underlying the beneficial effects of ECT remain largely unclear. In this study, animals received a single, 10, or 20 applications of electroconvulsive seizure (ECS), and then cell proliferation and apoptosis were investigated in the subgranular zone (SGZ) of the dentate gyrus. We analyzed whether a series of ECSs could induce changes in the dentate gyrus in a dose-response fashion. A single-ECS seizure significantly increased cell proliferation in the SGZ by ∼2.3-fold compared to sham treatment. After 10 ECSs, a significant increase in cell proliferation was observed in the SGZ by ∼2.4-fold compared to sham treatment. Moreover, 10 ECSs induced a significant increase in cell proliferation by 1.3-fold compared to a single-ECS group. However, cell proliferation did not differ between the group with 20 ECSs and sham group. In addition, a significant increase in the number of apoptotic cells was found in the group with 10 ECSs, whereas no significant change in it was found in either a single ECS or 20 ECSs group compared to sham treatment. These findings indicate that the optimal number of treatments and duration of stimulation requires investigation. Further studies are needed to elucidate the intracellular mechanisms underlying both effective and excessive ECT.

Chronic treatment with zinc and antidepressants induces enhancement of presynaptic/extracellular zinc concentration in the rat prefrontal cortex

Zinc exhibits antidepressant-like activity in preclinical tests/models. Moreover, zinc homeostasis is implicated in the pathophysiology of affective disorders. The aim of the present study was to examine the effect of chronic zinc, citalopram and imipramine intraperitoneal administration on the presynaptic and extracellular zinc concentration in the rat prefrontal cortex and hippocampus. We used two methods: zinc-selenium histochemistry (which images the pool of presynaptic-vesicle zinc) and anodic stripping voltammetry (ASV) for zinc determination in microdialysate (which assays the extracellular zinc concentration). We report that chronic (14 ×) zinc (hydroaspartate, 10 and 65 mg/kg) and citalopram (20 mg/kg) administration increased the pool of presynaptic zinc (by 34, 50 and 37%, respectively) in the rat prefrontal cortex. The 21% increase induced by imipramine (20 mg/kg) was marginally significant. Likewise, zinc (hydroaspartate, 65 mg/kg), citalopram and imipramine increased the extracellular zinc (although with a different pattern: time point, area under the curve and/or basal level) in this brain region. Furthermore, zinc induced an increase in presynaptic (by 65%) and extracellular zinc (by 90%) in the hippocampus, while both citalopram and imipramine did not. These results indicate that all of the treatments increase presynaptic/extracellular zinc concentrations in the rat prefrontal cortex, which may then contribute to their antidepressant mechanisms. Alterations induced by zinc (but not antidepressants) administration in the hippocampus may be related to specific zinc mechanisms. All the data (previous and present) on the effect of antidepressant treatments on the presynaptic/extracellular zinc concentrations suggest the involvement of this biometal presynaptic/synaptic homeostasis in the antidepressant mechanism(s).

The expression of non-clustered protocadherins in adult rat hippocampal formation and the connecting brain regions

Non-clustered protocadherins (PCDHs) are calcium-dependent adhesion molecules which have attracted attention for their possible roles in the neuronal circuit formation during development and their implications in the neurological disorders such as autism and mental retardation. Previously, we found that a subset of the non-clustered PCDHs exhibited circuit-dependent expression patterns in thalamo-cortical connections in early postnatal rat brain, but such patterns disappeared in adulthood. In this study, we identified that the non-clustered PCDHs showed differential expression patterns along the septotemporal axis in the subregions of adult hippocampus and dentate gyrus with topographical preferences. The expressions of PCDH1, PCDH9, PCDH10 and PCDH20 showed septal preferences, whereas the expressions of PCDH8, PCDH11, PCDH17 and PCDH19 showed temporal preferences, suggesting that they play roles in the formation/maintenance of intrahippocampal circuits. PCDHs also exhibited the region-specific expression patterns in the areas connected to hippocampal formation such as entorhinal cortex, lateral septum, and basolateral amygdaloid complex. Furthermore, the expression levels of three PCDHs (PCDH8, PCDH19 and PCDH20) were regulated by the electroconvulsive shock stimulation of the brain in the adult hippocampus and dentate gyrus. These results suggest that non-clustered PCDHs are involved in the maintenance and plasticity of adult hippocampal circuitry.

Phenylbutyric acid prevents rats from electroconvulsion-induced memory deficit with alterations of memory-related proteins and tau hyperphosphorylation

Electroconvulsive therapy has been commonly applied in the treatment of refractory depression, but its cognitive side effects are noticed and restrict its application. The molecular mechanisms underlying the side effects remain elusive, and there is no efficient prevention. By employing a recognized electroconvulsive shock (ECS) rat model, we found in the present study that ECS induced spatial memory deficits with simultaneous decreases in synaptic proteins of N-methyl-D-aspartate receptor 2A/B (NR2A/B) and postsynaptic density 95 (PSD95), the immediate early gene c-Fos and cAMP response element binding (CREB) proteins, all of which are memory-related proteins. ECS also caused tau hyperphosphorylation at multiple Alzheimer-related phosphorylation sites with activation of glycogen synthase kinase-3beta (GSK-3beta), Akt and phospho-PKR-like endoreticulum (PERK), and inhibition of protein phosphatase-2A (PP)-2A. Intraperitoneal injection of phenylbutyric acid (PBA), an aromatic short chain fatty acid with the functions of molecule chaperon, prevented rats from the ECS-induced memory deficits, alterations of the memory-associated proteins, and tau hyperphosphorylation. Our data suggest that PBA may be potentially used for attenuating the side effects caused by electroconvulsive therapy.

Zinc: the brain's dark horse

Zinc is a life-sustaining trace element, serving structural, catalytic, and regulatory roles in cellular biology. It is required for normal mammalian brain development and physiology, such that deficiency or excess of zinc has been shown to contribute to alterations in behavior, abnormal central nervous system development, and neurological disease. In this light, it is not surprising that zinc ions have now been shown to play a role in the neuromodulation of synaptic transmission as well as in cortical plasticity. Zinc is stored in specific synaptic vesicles by a class of glutamatergic or "gluzinergic" neurons and is released in an activity-dependent manner. Because gluzinergic neurons are found almost exclusively in the cerebral cortex and limbic structures, zinc may be critical for normal cognitive and emotional functioning. Conversely, direct evidence shows that zinc might be a relatively potent neurotoxin. Neuronal injury secondary to in vivo zinc mobilization and release occurs in several neurological disorders such as Alzheimer's disease and amyotrophic lateral sclerosis, in addition to epilepsy and ischemia. Thus, zinc homeostasis is integral to normal central nervous system functioning, and in fact its role may be underappreciated. This article provides an overview of zinc neurobiology and reviews the experimental evidence that implicates zinc signals in the pathophysiology of neuropsychiatric diseases. A greater understanding of zinc's role in the central nervous system may therefore allow for the development of therapeutic approaches where aberrant metal homeostasis is implicated in disease pathogenesis.

Zinc supplementation augments efficacy of imipramine in treatment resistant patients: a double blind, placebo-controlled study

BACKGROUND

One of the main problems in the therapy of depression is the limited efficacy of antidepressants and the limited utility of augmentation strategies. Zinc, a non competitive NMDA receptor antagonist exhibits preclinical antidepressant efficacy. Moreover, a preliminary clinical report suggests augmentation of antidepressant therapy by zinc in depression.

METHODS

A placebo-controlled, double blind study of zinc supplementation in imipramine therapy was conducted in sixty, 18-55-year old, unipolar depressed patients fulfilling the DSM-IV criteria for major depression without psychotic symptoms. After a one week washout period, patients were randomized into two groups treated with imipramine (approximately 140 mg/day) and receiving once daily either placebo (n=30) or zinc supplementation (n=30, 25 mgZn/day) for 12 weeks.

RESULTS

No significant differences in CGI, BDI, HADRS and MADRS scores were demonstrated between zinc-supplemented and placebo-supplemented antidepressant treatment non-resistant patients. However, zinc supplementation significantly reduced depression scores and facilitated the treatment outcome in antidepressant treatment resistant patients.

CONCLUSION

Zinc supplementation augments the efficacy and speed of onset of therapeutic response to imipramine treatment, particularly in patients previously nonresponsive to antidepressant pharmacotherapies. These data suggest the participation of disturbed zinc/glutamatergic transmission in the pathophysiology of drug resistance.

Targeting the hippocampal mossy fiber synapse for the treatment of psychiatric disorders

It is widely known that new neurons are continuously generated in the dentate gyrus of the hippocampus in the adult mammalian brain. This neurogenesis has been implicated in depression and antidepressant treatments. Recent evidence also suggests that the dentate gyrus is involved in the neuropathology and pathophysiology of schizophrenia and other related psychiatric disorders. Especially, abnormal neuronal development in the dentate gyrus may be a plausible risk factor for the diseases. The synapse made by the mossy fiber, the output fiber of the dentate gyrus, plays a critical role in regulating neuronal activity in its target CA3 area. The mossy fiber synapse is characterized by remarkable activity-dependent short-term synaptic plasticity that is established during the postnatal development and is supposed to be central to the functional role of the mossy fiber. Any defects, including developmental abnormalities, in the dentate gyrus and drugs acting on the dentate gyrus can modulate the mossy fiber-CA3 synaptic transmission, which may eventually affect hippocampal functions. In this paper, I review recent evidence for involvement of the dentate gyrus and mossy fiber synapse in psychiatric disorders and discuss potential importance of drugs targeting the mossy fiber synapse either directly or indirectly in the therapeutic treatments of psychiatric disorders.

Neuropeptides in depression: role of VGF

The monoamine hypothesis of depression is increasingly called into question by newer theories that revolve around changes in neuronal plasticity, primarily in the hippocampus, at both the structural and the functional levels. Chronic stress negatively regulates hippocampal function while antidepressants ameliorate the effects of stress on neuronal morphology and activity. Both stress and antidepressants have been shown to affect levels of brain-derived neurotrophic factor (BDNF) whose transcription is dependent on cAMP response element binding protein (CREB). BDNF itself has antidepressant-like actions and can induce transcription of a number of molecules. One class of genes regulated by both BDNF and serotonin (5-HT) are neuropeptides including VGF (non-acryonimic) which has a novel role in depression. Neuropeptides are important modulators of neuronal function but their role in affective disorders is just emerging. Recent studies demonstrate that VGF, which is also a CREB-dependent gene, is upregulated by antidepressant drugs and voluntary exercise and is reduced in animal models of depression. VGF enhances hippocampal synaptic plasticity as well as neurogenesis in the dentate gyrus but the mechanisms of antidepressant-like actions of VGF in behavioral paradigms are not known. We summarize experimental data describing the roles of BDNF, VGF and other neuropeptides in depression and how they may be acting through the generation of new neurons and altered synaptic activity. Understanding the molecular and cellular changes that underlie the actions of neuropeptides and how these adaptations result in antidepressant-like effects will aid in developing drugs that target novel pathways for major depressive disorders.

Effects of repeated citalopram treatments on chronic mild stress-induced growth associated protein-43 mRNA expression in rat hippocampus

Although growth associated protein-43 (GAP-43) is known to play a significant role in the regulation of axonal growth and the formation of new neuronal connections in the hippocampus, there is only a few studies on the effects of acute stress on GAP-43 mRNA expression in the hippocampus. Moreover, the effects of repeated citalopram treatment on chronic mild stress (CMS)-induced changes in GAP-43 mRNA expression in the hippocampus have not been explored before. To explore this question, male rats were exposed to acute immobilization stress or CMS. Also, citalopram was given prior to stress everyday during CMS procedures. Acute immobilization stress significantly increased GAP-43 mRNA expression in all subfields of the hippocampus, while CMS significantly decreased GAP-43 mRNA expression in the dentate granule cell layer (GCL). Repeated citalopram treatment decreased GAP-43 mRNA expression in the GCL compared with unstressed controls, but this decrease was not further potentiated by CMS exposure. Similar decreases in GAP-43 mRNA expression were observed in CA1, CA3 and CA4 areas of the hippocampus only after repeated citalopram treatment in CMS-exposed rats. This result indicates that GAP-43 mRNA expression in the hippocampus may differently respond to acute and chronic stress, and that repeated citalopram treatment does not change CMS-induced decreases in GAP-43 mRNA expression in the GCL.

Region specific hypothalamic neuronal activation and endothelial cell proliferation in response to electroconvulsive seizures

BACKGROUND

Major depression is often associated with disturbances in basal biological functions regulated by the hypothalamus. Electroconvulsive therapy (ECT), an efficient anti-depressant treatment, alters the activity of hypothalamic neurons. We have previously shown an increased proliferation of endothelial cells in specific areas of the rat hippocampus in response to electroconvulsive seizure (ECS) treatment, an animal model for ECT. Here we examine the effect of ECS treatment on neuronal activation and endothelial cell proliferation in mid-hypothalamus.

METHODS

Rats received one daily ECS treatment for 5 days and cell proliferation was detected by bromodeoxyuridine (BrdU). The number of cells double-labeled for BrdU and the endothelial cell marker rat endothelial cell antigen-1 was determined. Neuronal activation in response to acute ECS treatment was detected as c-Fos immunoreactivity in an additional experiment.

RESULTS

We demonstrate a correlating pattern of increases in neuronal activation and increased endothelial cell proliferation in the paraventricular nucleus, the supraoptic nucleus, and the ventromedial nucleus of the hypothalamus after ECS treatment.

CONCLUSIONS

Hypothalamic areas with the largest increase in neuronal activation after ECS treatment exhibit increased endothelial cell proliferation. We suggest that similar angiogenic responses to ECT might counteract hypothalamic dysfunction in depressive disorder.

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.

Memory performance in severely depressed patients treated by electroconvulsive therapy

OBJECTIVES

Depression is accompanied by disturbed implicit (unconscious) and explicit (conscious) memory functions. The aim was the assessment of immediate and delayed verbal and visual memory functions, concentration/attention during the course of electroconvulsive therapy (ECT) treatment.

METHODS

Twenty severely depressed, drug-treatment resistant, elderly patients were assessed with the Wechsler Memory Scale-Revised (WMS-R) before and at the end of the ECT series.

RESULTS

Patients revealed deficits in acquisition (immediate verbal and visual memory), attention/concentration, and retrieval of information (delayed memory) before ECT. After ECT, significant improvements were observed in immediate memory but not in delayed memory. Although higher total stimulation levels (millicoulombs) (P = 0.015) were associated with improvements in immediate visual memory, we found that longer duration of convulsions (P = 0.016) as well as lower levels of stimulation at last ECT (P = 0.036) were associated with improvements in immediate verbal memory. Moreover, we found that stimulation energy (millicoulombs) in total and at last ECT was the best predictor among several clinical and ECT parameters of improved visual memory and concentration and decreased verbal and general memory.

CONCLUSIONS

Prefrontal cortex-related memory processes, especially immediate memory encoding, improved after ECT, whereas long-term memory remained impaired, indicating that severely depressed patients remain cognitively inferior to normal subjects despite clinically successful treatment. This study may yield a better understanding of the time course of memory alterations in severely depressed patients receiving ECT. Improvement of immediate memory may be essential for establishing normal daily activities of life in the recovery phase of depression.

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.

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

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

The role of the phosphatidylinositide 3-kinase–protein kinase B pathway in schizophrenia

Neuroanatomical studies of brains from schizophrenic patients report evidence for neuronal dystrophy, while in genetic studies in schizophrenia there is evidence for mutations in growth factors and the downstream enzymes phosphatidylinositide 3-kinase (PI3K) and protein kinase B (PKB). Since the PI3K-PKB pathway is involved in cellular growth and proliferation, reduced activity of this cascade in schizophrenia could at least partly explain the neuronal dystrophy. Risk factors for schizophrenia, such as corticosteroids and cannabis, suppress the activity of the PI3K-PKB pathway. Conversely, estrogen and vitamin D, 2 factors with a moderate protective activity in schizophrenia, electroconvulsive shock therapy, and chronic treatment with antipsychotic compounds stimulate the pathway. Reduced activity of the PI3K-PKB pathway makes the brain more susceptible to virus infections, anoxia, and obstetric complications (recognized risk factors for schizophrenia), whereas a diminution of growth factor levels towards the end of puberty could contribute to an increase in schizophrenia symptoms observed around that time. On the other hand, constitutive (over)activation of the PI3K-PKB pathway increases cancer risk. Consequently, the presumed hypoactivity of the PI3K-PKB cascade might provide a partial explanation for the remarkable epidemiological finding of a reduced cancer rate in schizophrenic patients. Recognition of the role of a dysfunctional PI3K-PKB pathway in schizophrenia might help in the discovery of hitherto undetected causative gene mutations and could also lead to novel therapeutic approaches. However, a major challenge that remains to be solved is how the PI3K-PKB pathway can be activated without increasing the risk of cancer.

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.

Evidence for increased expression of the vesicular glutamate transporter, VGLUT1, by a course of antidepressant treatment

The therapeutic effect of a course of antidepressant treatment is believed to involve a cascade of neuroadaptive changes in gene expression leading to increased neural plasticity. Because glutamate is linked to mechanisms of neural plasticity, this transmitter may play a role in these changes. This study investigated the effect of antidepressant treatment on expression of the vesicular glutamate transporters, VGLUT1-3 in brain regions of the rat. Repeated treatment with fluoxetine, paroxetine or desipramine increased VGLUT1 mRNA abundance in frontal, orbital, cingulate and parietal cortices, and regions of the hippocampus. Immunoautoradiography analysis showed that repeated antidepressant drug treatment increased VGLUT1 protein expression. Repeated electroconvulsive shock (ECS) also increased VGLUT1 mRNA abundance in regions of the cortex and hippocampus compared to sham controls. The antidepressant drugs and ECS did not alter VGLUT1 mRNA abundance after acute administration, and no change was detected after repeated treatment with the antipsychotic agents, haloperidol and chlorpromazine. In contrast to VGLUT1, the different antidepressant treatments did not commonly increase the expression of VGLUT2 or VGLUT3 mRNA. These data suggest that a course of antidepressant drug or ECS treatment increases expression of VGLUT1, a key gene involved in the regulation of glutamate secretion.

Vagal nerve stimulation: a review of its applications and potential mechanisms that mediate its clinical effects

Vagal nerve stimulation (VNS) is an approved treatment for epilepsy and is currently under investigation as a therapy for other disorders, including depression, anxiety and Alzheimer's disease. This review examines the pre-clinical and clinical literature relating to VNS. A brief historical perspective is given, followed by consideration of the efficacy of the various clinical applications of VNS. Finally, what is known about the mechanism by which VNS exerts clinical benefit is considered. It is concluded that although the precise mechanism of action of VNS is still unknown, the search for the mechanism has the potential to lend new insight into the neuropathology of depression. It is important that prior assumptions about the influence of VNS on particular aspects of brain function do not constrain the investigations.

Identification of novel electroconvulsive shock-induced and activity-dependent genes in the rat brain

Electroconvulsive shock (ECS) has been used as an effective treatment for patients suffering from major depression disorders and schizophrenia. However, the exact mechanisms underlying the action of ECS are poorly understood. Using high-density oligonucleotide microarrays, we identified 60 ECS-induced genes whose gene products are involved in the neuronal signaling, neuritogenesis and tissue remodeling. In situ hybridization and depolarization-dependent expression assay were performed to characterize 4 genes (lysyl oxidase, Ab1-046, SOX11, and T-type calcium channel 1G subunit) which have not yet been reported to be induced by ECS. Interestingly, the induction of these genes was observed mainly in the dentate gyrus of hippocampal formation and piriform cortex, where ECS-induced neural activation is highlighted, and depolarization of cultured cortical neurons also induced the expression of these genes. Taken together, our results suggest that therapeutic actions of ECS may be manifested by the activity-dependent induction of genes related to the plastic changes of the brain such as neuronal signaling neuritogenesis, and tissue remodeling.

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.

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.

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.

Regulation of GAP-43 expression by chronic desipramine treatment in rat cultured hippocampal cells

BACKGROUND

The importance of molecular and cellular changes in hippocampus in major depression and in the mechanism of action of antidepressants has become increasingly clear. Identification of novel targets for antidepressants in hippocampus is important to understanding their therapeutic effects.

METHODS

We used cDNA microarray to measure the expression patterns of multiple genes in primary cultured rat hippocampal cells. In situ hybridization and Northern and immunoblotting analysis were used to determine brain regional distribution and mRNA and protein levels of target genes.

RESULTS

After comparing hybridized signals between control and desipramine treated groups, we found that chronic treatment with desipramine increased the expression of six genes and decreased the expression of two genes. One of the upregulated genes is growth associated protein GAP-43. In situ hybridization revealed that desipramine increased GAP-43 gene expression in dentate gyrus but not other brain regions. Northern and immunoblotting analysis revealed that desipramine increased GAP-43 mRNA and protein levels. GAP-43 expression is also increased by another antidepressant, tranylcypromine, but not by lithium or haloperidol.

CONCLUSIONS

Because GAP-43 regulates growth of axons and modulates the formation of new connections, our findings suggest that desipramine may have an effect on neuronal plasticity in the central nervous system.

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.

Antidepressants and neuroplasticity

OBJECTIVE

We review the literature on the cellular changes that underlie the structural impairments observed in brains of animals exposed to stress and in subjects with depressive disorders. We discuss the molecular, cellular and structural adaptations that underlie the therapeutic responses of different classes of antidepressants and contribute to the adaptive plasticity induced in the brain by these drugs.

METHODS

We review results from various clinical and basic research studies.

RESULTS

Studies demonstrate that chronic antidepressant treatment increases the rate of neurogenesis in the adult hippocampus. Studies also show that antidepressants up-regulate the cyclic adenosine monophosphate (cAMP) and the neurotrophin signaling pathways involved in plasticity and survival. In vitro and in vivo data provide direct evidence that the transcription factor, cAMP response element-binding protein (CREB) and the neurotrophin, brain derived-neurotrophic factor (BDNF) are key mediators of the therapeutic response to antidepressants.

CONCLUSIONS

These results suggest that depression maybe associated with a disruption of mechanisms that govern cell survival and neural plasticity in the brain. Antidepressants could mediate their effects by increasing neurogenesis and modulating the signaling pathways involved in plasticity and survival.