Increased Brain-derived Neurotrophic Factor Protein Levels Research Articles

TAK-653, an AMPA receptor potentiator with minimal agonistic activity, produces an antidepressant-like effect with a favorable safety profile in rats

The N-methyl-d-aspartate receptor antagonist, ketamine, exhibits rapid and sustained antidepressant activity in patients with treatment-resistant depression (TRD), but its use is associated with psychotomimetic side effects. Evidence has suggested that the activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors followed by activation of the mechanistic target of rapamycin (mTOR) signaling pathway and production of brain derived neurotrophic factor (BDNF) protein may underlie the antidepressant efficacy of ketamine. In this study, we characterized the antidepressant-like effects of TAK-653, a novel AMPA receptor potentiator with virtually no agonistic activity. In rat primary cortical neurons, TAK-653 significantly increased phosphorylated and activated forms of mTOR and p70S6 kinase and their upstream regulators Akt and extracellular signal-regulated kinase (ERK). TAK-653 also significantly increased BDNF protein levels in rat primary cortical neurons. Ketamine at 30 mg/kg, i.p. produced antidepressant-like effects in the reduction of submissive behavior model (RSBM) in rats. Ketamine's antidepressant-like effect was blocked by pretreatment with the AMPA receptor antagonist NBQX at 10 mg/kg, i.p., indicating the essential role of AMPA receptor activation in the antidepressant-like effect of ketamine. Consistent with this finding, a sub-chronic administration of TAK-653 for 6 days produced significant antidepressant-like effect in the rat RSBM. Unlike ketamine, however, TAK-653 did not induce a hyperlocomotor response in rats, which is a behavioral index associated with psychotomimetic side effects in humans. TAK-653 may be a promising drug for the treatment of major depressive disorders including TRD with the potential for an improved safety profile compared with ketamine.

Alterations in BDNF Protein Concentrations in the Hippocampus do not Explain the Pro-Neurogenic Effect of Citalopram on Adult Neurogenesis.

Brain-derived neurotrophic factor (BDNF) has been implicated in the pro-neurogenic effect of selective serotonin reuptake inhibitors. In this study, we used Tph2 -/- mice lacking brain serotonin to dissect the interplay between BDNF and the serotonin system in mediating the effects of antidepressant pharmacotherapy on adult neurogenesis in the hippocampus. Besides citalopram (CIT), we tested tianeptine (TIA), an antidepressant whose mechanism of action is not well understood. Specifically, we examined cell survival and endogenous concentrations of BDNF following daily injection of the drugs. Twenty-one days of CIT, but not of TIA, led to a significant increase in the survival of newly generated cells in the dentate gyrus of wild-type mice, without a significant effect on BDNF protein levels by either treatment. In Tph2 -/- mice, adult neurogenesis was consistently increased. Furthermore, Tph2 -/- mice showed increased BDNF protein levels, which were not affected by TIA but were significantly reduced by CIT. We conclude that the effects of CIT on adult neurogenesis are not explained by changes in BDNF protein concentrations in the hippocampus.

Activation of brain-derived neurotrophic factor signaling in the basal forebrain reverses acute sleep deprivation-induced fear memory impairments.

IntroductionThe mechanisms underlying sleep deprivation‐induced memory impairments and relevant compensatory signaling pathways remain elusive. We tested the hypothesis that increased brain‐derived neurotrophic factor (BDNF) expression in the basal forebrain following acute sleep deprivation was a compensatory mechanism to maintain fear memory performance.MethodsAdult male Wistar rats were deprived of 6‐hr total sleep from the beginning of the light cycle. The effects of sleep deprivation on BDNF protein expression and activation of downstream tropomyosin receptor kinase B (TrkB)/phospholipase C‐γ1 (PLCγ1) signaling in the basal forebrain and fear memory consolidation were examined. BDNF or selective downstream TrkB receptor antagonist ANA‐12 was further injected into the basal forebrain bilaterally to observe the changes in fear memory consolidation in response to modulation of the BDNF/TrkB signaling.ResultsSix hours of sleep deprivation‐induced both short‐ and long‐term fear memory impairments. Increased BDNF protein expression and TrkB and PLCγ1 phosphorylation in the basal forebrain were observed after sleep deprivation. Microinjection of BDNF into the basal forebrain partly reversed fear memory deficits caused by sleep deprivation, which were accompanied by increased BDNF protein levels and TrkB/PLCγ1 activation. After ANA‐12 microinjection, sleep deprivation‐induced activation of the BDNF/TrkB pathway was inhibited and impairments of fear memory consolidation were further aggravated.ConclusionsAcute sleep deprivation induces compensatory increase of BDNF expression in the basal forebrain. Microinjection of BDNF into the basal forebrain mitigates the fear memory impairments caused by sleep deprivation by activating TrkB/PLCγ1 signaling.

Repeated treatment with nitric oxide synthase inhibitor attenuates learned helplessness development in rats and increases hippocampal BDNF expression.

Nitric oxide synthase (NOS) inhibitors induce antidepressant-like effects in animal models sensitive to acute drug treatment such as the forced swimming test. However, it is not yet clear if repeated treatment with these drugs is required to induce antidepressant-like effects in preclinical models. The aim of this study was to test the effect induced by acute or repeated (7 days) treatment with 7-nitroindazole (7-NI), a preferential inhibitor of neuronal NOS, in rats submitted to the learned helplessness (LH) model. In addition, we aimed at investigating if 7-NI treatment would increase brain-derived neurotrophic factor (BDNF) protein levels in the hippocampus, similarly to the effect of prototype antidepressants. Animals were submitted to a pre-test (PT) session with inescapable footshocks or habituation (no shocks) to the experimental shuttle box. Six days later they were exposed to a test with escapable footshocks. Independent groups received acute (a single injection after PT or before test) or repeated (once a day for 7 days) treatment with vehicle or 7-NI (30 mg/kg). Repeated, but not acute, treatment with 7-NI attenuated LH development. The effect was similar to repeated imipramine treatment. Moreover, in an independent experimental group, only repeated treatment with 7-NI and imipramine increased BDNF protein levels in the hippocampus. The results suggest the nitrergic system could be a target for the treatment of depressive-like conditions. They also indicate that, similar to the positive control imipramine, the antidepressant-like effects of NOS inhibition could involve an increase in hippocampal BDNF levels.

Rotigotine, a dopamine receptor agonist, increased BDNF protein levels in the rat cortex and hippocampus.

Brain-derived neurotrophic factor (BDNF) critically controls the fate and function of the neuronal network and has received much attention as a target of many brain diseases. Dopaminergic system dysfunction has also been implicated in a variety of neuropsychiatric diseases. Rotigotine, a non-ergot dopamine receptor agonist, is used in the treatment of Parkinson's disease and restless legs syndrome. To investigate the effects of rotigotine on neuronal functions both in vivo and in vitro, rats and primary cortical neurons were administered rotigotine, and the mRNA and protein expression levels of BDNF, its receptor TrkB and downstream signaling molecules, and synaptic proteins were determined. We found that BDNF protein was increased in the cortex and hippocampus of rats after 7days of rotigotine treatment. In contrast, BDNF mRNAs were reduced 6h after rotigotine treatment in cultured neurons presumably through the transient suppression of neuronal activity. We identified differential expression of D1, D2, and D3 receptors in the rat brain and cultured neurons. The observed increase in the expression of BDNF protein in the cortex and hippocampus after subchronic administration of rotigotine suggests that it may exert its medical effect in part through improving BDNF function in the brain. In addition, our results highlight the complex relationships between rotigotine and BDNF expression, which depend on the brain region, time course, and dose of the drug.

Transcranial ultrasound stimulation promotes brain-derived neurotrophic factor and reduces apoptosis in a mouse model of traumatic brain injury

BackgroundThe protein expressions of brain-derived neurotrophic factor (BDNF) can be elevated by transcranial ultrasound stimulation in the rat brain. ObjectiveThe purpose of this study was to investigate the effects and underlying mechanisms of BDNF enhancement by low-intensity pulsed ultrasound (LIPUS) on traumatic brain injury (TBI). MethodsMice subjected to controlled cortical impact injury were treated with LIPUS in the injured region daily for a period of 4 days. Western blot analysis and immunohistochemistry were performed to assess the effects of LIPUS. ResultsThe results showed that the LIPUS treatment significantly promoted the neurotrophic factors BDNF and vascular endothelial growth factor (VEGF) at day 4 after TBI. Meanwhile, LIPUS also enhanced the phosphorylation of Tropomyosin-related kinase B (TrkB), Akt, and cAMP-response element binding protein (CREB). Furthermore, treatment with LIPUS significantly decreased the level of cleaved caspase-3. The reduction of apoptotic process was inhibited by the anti-BDNF antibody. ConclusionsIn short, post-injury LIPUS treatment increased BDNF protein levels and inhibited the progression of apoptosis following TBI. The neuroprotective effects of LIPUS may be associated with enhancements of the protein levels of neurotrophic factors, at least partially via the TrkB/Akt-CREB signaling pathway.

The Impact of Chronic Early Administration of Psychostimulants on Brain Expression of BDNF and Other Neuroplasticity-Relevant Proteins.

Frequently, healthy individuals, children, and students are using stimulants to treat attention deficit hyperactivity disorder (ADHD)-like symptoms or to enhance cognitive capacity, attention and concentration. Methylphenidate, the most common treatment for ADHD, similarly to cocaine, blocks the dopamine reuptake, leading to increase in dopamine level in the synaptic cleft. Brain-derived neurotrophic factor (BDNF) and other neuroplasticity-relevant proteins have a major role in cellular plasticity during development and maturation of the brain. Young Sprague Dawley rats (postnatal days (PND) 14) were treated chronically with either cocaine or methylphenidate. The rats were examined behaviorally and biochemically at several time points (PND 35, 56, 70, and 90). We found age-dependent, but stimulant-independent, alterations in the mRNA expression levels of microtubule-associated protein tau, doublecortin, and synaptophysin. The PND 90 rats, treated with methylphenidate at an early age, exhibited increased BDNF protein levels in the prefrontal cortex compared to the saline-treated group. Despite the treatment effects at the biochemical level, cocaine and methylphenidate treatments at an early age had only minor effects on the behavioral parameters measured at older ages. The biochemical alterations may reflect neuroprotective or neuroplastic effects of chronic methylphenidate treatment at an early age.

Adaptations in brain reward circuitry underlie palatable food cravings and anxiety induced by high-fat diet withdrawal

To identify the emotional and motivational processes that reinstate palatable food intake following removal of high-fat diet (HFD) and associated neuroadaptations tied to neurochemical and behavioural changes underlying dopaminergic function. Adult male C57Bl6 mice were placed on a HFD (58% kcal fat) or ingredient-matched, low-fat diet (LFD; 11% kcal fat) for 6 weeks. At the end of diet-regimen mice were either maintained on their respective diets, or HFD and LFD were replaced with normal chow (withdrawal). Effort-based operant responding for sucrose and high-fat food rewards was measured along with basal and stress-induced corticosterone levels and anxiety (elevated-plus maze). Protein levels for tyrosine hydroxylase (TH), corticosterone releasing factor type 1 receptor (CRF-R1), brain-derived neurotrophic factor (BDNF), phospho-CREB (pCREB) and ΔFosB (truncated splice variant of FosB) were assessed in the amygdala, nucleus accumbens (NAc) and ventral tegmental area (VTA) via western immunoblotting. Six weeks of HFD resulting in significant weight gain elicited sucrose anhedonia, anxiety-like behaviour and hypothalamic-pituitary-adrenocortical axis (HPA) hypersensitivity to stress. Withdrawal from HFD but not LFD-potentiated anxiety and basal corticosterone levels and enhanced motivation for sucrose and high-fat food rewards. Chronic high-fat feeding reduced CRF-R1 and increased BDNF and pCREB protein levels in the amygdala and reduced TH and increased ΔFosB protein in NAc and VTA. Heightened palatable food reward in mice withdrawn from HFD coincided with increased BDNF protein levels in NAc and decreased TH and pCREB expression in the amygdala. Anhedonia, anxiety and sensitivity to stressors develops during the course of HFD and may have a key role in a vicious cycle that perpetuates high-fat feeding and the development of obesity. Removal of HFD enhances stress responses and heightens vulnerability for palatable foods by increasing food-motivated behaviour. Lasting changes in dopamine and plasticity-related signals in reward circuitry may promote negative emotional states, overeating and palatable food relapse.

Curcumin produces antidepressant effects via activating MAPK/ERK-dependent brain-derived neurotrophic factor expression in the amygdala of mice

The potential antidepressant effects of curcumin have been demonstrated in various animal models of depression, however, there is little information regarding the site and mechanisms of curcumin in promoting antidepressant effects. The present study attempts to explore the mechanisms underlying the antidepressant-like action of curcumin by measuring the contents of brain derived neurotrophic factor (BDNF) in the amygdala of animal model of depression. The results showed that treatment with curcumin (40mg/kg, i.p.) significantly reduced depressive-like behaviors of mice in the forced swim test. Chronic administration of curcumin (40mg/kg, i.p., 21 days) increased BDNF protein levels in the amygdala and this enhancement was suppressed by pretreatment with the extracellular signal-regulated kinase (ERK) inhibitor SL327. Additionally, the increased levels of ERK phosphoryation in the amygdala by curcumin were blocked by the ERK inhibitor, and inhibition of this kinase prevented the antidepressant effects of curcumin. All of these effects of curcumin, were essentially identical to that observed with the clinical antidepressant, fluoxetine. These results suggest that the antidepressant-like effects of curcumin in the forced swim test are mediated, at least in part, by an ERK-regulated increase of BDNF expression in the amygdala of mice.

Memantine treatment reverses anhedonia, normalizes corticosterone levels and increases BDNF levels in the prefrontal cortex induced by chronic mild stress in rats

Memantine is a N-methyl-D-aspartate (NMDA) receptor antagonist and several studies have pointed to the NMDA receptor antagonists as a potential therapeutic target for the treatment of depression. The present study was aimed to evaluate the behavioral and physiological effects of administration of memantine in rats exposed to the chronic mild stress (CMS) model. To this aim, after 40 days of exposure to CMS procedure, rats were treated with memantine (20 mg/kg) for 7 days. In this study, sweet food consumption, adrenal gland weight, corticosterone levels, and brain-derived-neurotrophic factor (BDNF) protein levels in the prefrontal cortex, hippocampus and amygdala were assessed. Our results demonstrated that chronic stressful situations induced anhedonia, hypertrophy of adrenal gland weight, and an increase of corticosterone levels in rats, but did not alter BDNF protein levels in the rat brain. Memantine treatment reversed anhedonia and the increase of adrenal gland weight, normalized corticosterone levels and increased BDNF protein levels in the prefrontal cortex in stressed rats. Finally, these findings further support the hypothesis that NMDA receptor antagonists such as memantine could be helpful in the pharmacological treatment of depression.

Natural Antisense Makes Sense for Gene-specific Activation in Brain

The upregulation of specific genes in vivo has been an elusive goal for gene therapy when compared with the wide repertoire of methods available to silence genes or modify mRNA splicing patterns. In the latest issue of Nature Biotechnology, Modarresi and colleagues1 accomplished in vivo upregulation of brain-derived neurotrophic factor (BDNF), a relevant therapeutic target for a number of neurodegenerative diseases. Rather than using small molecules or microRNA inhibitors, which could lead to activation of off-target genes, Modarresi et al.1 upregulated BDNF by inhibiting a natural antisense transcript (NAT) in response to the local delivery of oligonucleotides to the central nervous systems of mice.

Chronic antidepressant administration alleviates frontal and hippocampal BDNF deficits in CUMS rat

Stress activates the hypothalamo–pituitary–adrenal (HPA) axis, regulates the expression of brain-derived neurotrophic factor (BDNF) in the brain, and mediates mood. Antidepressants alleviate stress and up-regulate BDNF gene expression. In this study, we investigated the effect of chronic unpredictable mild stress (CUMS) and the different kinds of antidepressant treatments on the HPA axis and the BDNF expression in the rat brain. Adult Wistar male rats were exposed to a six-week CUMS procedure and received different antidepressant treatments including venlafaxine, mirtazapine, and fluoxetine. Immunohistochemistry and real-time PCR were used to measure BDNF expression levels in the rat brain, and ELISAs were used to investigate the plasma corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels. CUMS significantly decreased the BDNF protein level in the DG, CA1, and CA3 of the hippocampus and increased plasma CORT level. Chronic antidepressant treatments all significantly increased BDNF protein levels in the hippocampus and the pre-frontal cortex. In addition, venlafaxine and mirtazapine inhibited the increase of plasma CORT level. These results suggested that an increase in the BDNF level in the brain could be a pivotal mechanism of various antidepressants to exert their therapeutic effects.

Chronic administration of harmine elicits antidepressant-like effects and increases BDNF levels in rat hippocampus

A growing body of evidence has pointed to the β-carboline harmine as a potential therapeutic target for the treatment of major depression. The present study was aimed to evaluate behavioural and molecular effects of the chronic treatment with harmine and imipramine in rats. To this aim, rats were treated for 14 days once a day with harmine (5, 10 and 15 mg/kg) and imipramine (10, 20 and 30 mg/kg) and then subjected to the forced swimming and open-field tests. Harmine and imipramine, at all doses tested, reduced immobility time of rats compared with the saline group. Imipramine increased the swimming time at 20 and 30 mg/kg and harmine increased swimming time at all doses. The climbing time increased in rats treated with imipramine (10 and 30 mg/kg) and harmine (5 and 10 mg/kg), without affecting spontaneous locomotor activity. Brain-derived neurotrophic factor (BDNF) hippocampal levels were assessed in imipramine and harmine-treated rats by ELISA sandwich assay. Interestingly, chronic administration of harmine at the higher doses (10 and 15 mg/kg), but not imipramine, increased BDNF protein levels in rat hippocampus. Finally, these findings further support the hypothesis that harmine could bring about behavior and molecular effects, similar to antidepressants drugs.

Angiotensin II-Induced Expression of Brain-Derived Neurotrophic Factor in Human and Rat Adrenocortical Cells

Angiotensin II (Ang II) is a major regulator of steroidogenesis in adrenocortical cells, and is also an effective inducer of cytokine and growth factor synthesis in several cell types. In microarray analysis of H295R human adrenocortical cells, the mRNA of brain-derived neurotrophic factor (BDNF), a neurotrophin widely expressed in the nervous system, was one of the most up-regulated genes by Ang II. The aim of the present study was the analysis of the Ang II-induced BDNF expression and BDNF-induced effects in adrenocortical cells. Real-time PCR studies have shown that BDNF is expressed in H295R and rat adrenal glomerulosa cells. In H295R cells, the kinetics of Ang II-induced BDNF expression was faster than that of aldosterone synthase (CYP11B2). Inhibition of calmodulin kinase by KN93 did not significantly affect the Ang II-induced stimulation of BDNF expression, suggesting that it occurs by a different mechanism from the CYP11B2-response. Ang II also caused candesartan-sensitive, type-1 Ang II receptor-mediated stimulation of BDNF gene expression in primary rat glomerulosa cells. In rat adrenal cortex, BDNF protein was localized to the subcapsular region. Ang II increased BDNF protein levels both in human and rat cells, and BDNF secretion of H295R cells. Ang II also increased type-1 Ang II receptor-mediated BDNF expression in vivo in furosemide-treated rats. In rat glomerulosa cells, BDNF induced tropomyosin-related kinase B receptor-mediated stimulation of EGR1 and TrkB expression. These data demonstrate that Ang II stimulates BDNF expression in human and rat adrenocortical cells, and BDNF may have a local regulatory function in adrenal glomerulosa cells.

Neurochemical and behavioural effects of acute and chronic memantine administration in rats: Further support for NMDA as a new pharmacological target for the treatment of depression?

A growing body of evidence has pointed to the NMDA receptor antagonists as a potential therapeutic target for the treatment of major depression. The present study was aimed to evaluate behavioural and molecular effects of the acute and chronic treatment with memantine and imipramine in rats. To this aim, rats were acutely or chronically for 14 days once a day treated with memantine (5, 10 and 20 mg/kg) and imipramine (10, 20 and 30 mg/kg) and then subjected to the forced swimming and open-field tests. The acute treatment with memantine at all doses and imipramine at doses (20 and 30 mg/kg) reduced immobility time of rats compared to the saline group ( p < 0.05), without affecting spontaneous locomotor activity and chronic treatment with memantine and imipramine, at all doses tested, reduced immobility time of rats compared to the saline group ( p < 0.05), without affecting spontaneous locomotor activity. Brain-derived neurotrophic factor (BDNF) hippocampal levels were assessed in imipramine- and memantine-treated rats by ELISA sandwich assay. Interesting enough, acute administration, but not chronic administration of memantine at higher dose (20 mg/kg) increased BDNF protein levels in the rat hippocampus ( p < 0.05). Finally, these findings further support the hypothesis that NMDA receptor could be a new pharmacological target for the treatment of depression.

Modulation of brain-derived neurotrophic factor as a potential neuroprotective mechanism of action of omega-3 fatty acids in a parkinsonian animal model

While we recently reported the beneficial effects of omega-3 polyunsaturated fatty acids (n−3 PUFAs) in a mouse model of Parkinson's disease (PD), the mechanisms of action remain largely unknown. Here, we specifically investigated the contribution of the brain-derived neurotrophic factor (BDNF) to the neuroprotective effect of n−3 PUFA observed in a mouse model of PD generated by a subacute exposure to MPTP using a total of 7 doses of 20 mg/kg over 5 days. The ten-month high n−3 PUFA treatment which preceded the MPTP exposure induced an increase of BDNF mRNA expression in the striatum, but not in the motor cortex of animals fed the high n−3 PUFA diet. In contrast, n−3 PUFA treatment increased BDNF protein levels in the motor cortex of MPTP-treated mice, an effect not observed in vehicle-treated mice. The mRNA expression of the high-affinity BDNF receptor tropomyosin-related kinase B (TrkB) was increased in the striatum of MPTP-treated mice fed the high n−3 PUFA diet compared to vehicle and MPTP-treated mice on the control diet and to vehicle mice on the high n−3 PUFA diet. These data suggest that the modulation of BDNF expression contributes, in part, to n−3 PUFA-induced neuroprotection in an animal model of PD.

Changes in spatial memory and BDNF expression to concurrent dietary restriction and voluntary exercise

Substantial data suggest that cognitive function can be influenced by many lifestyle activities associated with changes in energy metabolism such as exercise and diet. In the current study, we investigated the combined effects of voluntary exercise (access to running wheels) and dietary restriction (every other day fasting, EODF) on spatial memory formation and on the levels of brain-derived neurotrophic factor (BDNF) in the hippocampus of Wistar male rats. Spatial learning and memory formation was assessed using the radial arm water maze (RAWM) paradigm, while BDNF protein was measured using ELISA test. Voluntary exercise and/or EODF were instituted for 6 weeks. Voluntary exercise alone significantly enhanced short-term, intermediate-term, and long-term memory formation, and increased BDNF protein levels in the hippocampus. EODF enhanced mean running wheel activity by approximately twofold. However, EODF did not modulate the effects of exercise on memory formation and expression of BDNF. In addition, EODF alone had no effect on memory and BDNF protein in the hippocampus. In conclusion, results of this study indicate that exercise enhanced while EODF had neutral effect on both spatial memory formation and hippocampus BDNF levels.

Cystamine prevents haloperidol‐induced decrease of BDNF/TrkB signaling in mouse frontal cortex

The role of brain-derived neurotrophic factor (BDNF) has been implicated in the pathophysiology as well as treatment outcome of schizophrenia. Rodent studies indicate that several antipsychotic drugs have time-dependent (and differential) effects on BDNF levels in the brain. Earlier studies from our laboratory have indicated that long-term treatment with haloperidol (HAL) decreases BDNF, reduced GSH and anti-apoptotic marker, Bcl-xl protein levels and increases the expression of pro-apoptotic proteins in rat frontal cortex. Furthermore, findings from human as well as rodent studies suggest that treatment of schizophrenia must involve the neuroprotective strategies to improve the neuropathology and thereby clinical outcome. In the present study, we investigated the potential of cystamine (CYS), an anti-oxidant and anti-apoptotic compound, to prevent HAL-induced reduction in BDNF, GSH, and Bcl-xl protein levels in mice and the signaling mechanism(s) involved in the beneficial effects of CYS. The results indicated that CYS as well as cysteamine (the FDA-approved precursor of CYS) increased BDNF protein levels in mouse frontal cortex 7 days after treatment. CYS co-treatment prevented chronic HAL treatment-induced reduction in BDNF, GSH, and Bcl-xl protein levels. CYS treatment enhanced TrkB-tyrosine phosphorylation and activated Akt and extracellular signal-regulated kinase (ERK)1/2, downstream molecules of TrkB signaling. In addition, in vitro experiments with mouse cortical neurons showed that CYS prevented the HAL-induced reduction in neuronal cell viability and BDNF protein levels, and increase in apoptosis. BDNF-neutralizing antibody as well as K252a, a selective inhibitor of neurotrophin signaling blocked the CYS-mediated neuroprotection. Moreover, CYS-mediated neuroprotection is also blocked by LY294002, a phosphatidylinositol 3-kinase inhibitor or PD98059, a mitogen-activated protein kinase kinase (MEK) inhibitor. Thus, CYS protects cortical neurons through a mechanism involving TrkB receptor activation, and a signaling pathway involving phosphatidylinositol 3-kinase and MAPK. The findings from the present study may be helpful for the development of novel neuroprotective strategies to improve the treatment outcome of schizophrenia.

Locomotor exercise alters expression of pro‐brain‐derived neurotrophic factor, brain‐derived neurotrophic factor and its receptor TrkB in the spinal cord of adult rats

Previous evidence indicates that locomotor exercise is a powerful means of increasing brain-derived neurotrophic factor (BDNF) and its signal transduction receptor TrkB mRNA levels, immunolabeling intensity and number of BDNF- and TrkB-immunopositive cells in the spinal cord of adult rats but the contribution of specific cell types to changes resulting from long-term activity is unknown. As changes in BDNF protein distribution due to systemic stimuli may reflect either its in-situ synthesis or its translocation from other sources, we investigated where BDNF and TrkB mRNA are expressed in the spinal lumbar segments. We report on the cell types defined by size, BDNF mRNA levels and number of cells with TrkB transcripts in sedentary and exercised animals following 28 days of treadmill walking. In the majority of cells, exercise increased perikaryonal levels of BDNF mRNA but did not affect TrkB transcript levels. Bidirectional changes in a number of TrkB mRNA-expressing cells occurred in small groups of ventral horn neurons. An increase in BDNF transcripts was translated into changes in pro-BDNF and BDNF levels. A 7-day walking regimen increased BDNF protein levels similarly to 28-day treadmill walking. Our observations indicate that long- and short-term locomotor activity of moderate intensity produce stimuli sufficient to recruit a majority of spinal cells to increased BDNF synthesis, suggesting that continuous tuning of pro-BDNF and BDNF levels permits spinal networks to undergo trophic modulation not requiring changes in TrkB mRNA supply.

Olfactory bulbectomy in mice leads to increased BDNF levels and decreased serotonin turnover in depression-related brain areas

The olfactory bulbectomy in rodents has been proposed as an animal model for depression. According to the neurotrophin and monoamine hypotheses of depression, the present study examined neurotrophin and monoamine (serotonin, norepinephrine, dopamine) levels in several depression-related brain regions of mice subjected to olfactory bulbectomy. As expected, bulbectomized animals revealed behavioral alterations such as locomotor hyperactivity and reduced gain of bodyweight, regarded as correlates of a depressive-like state. Compared to sham-operated animals, bulbectomized mice demonstrated significantly increased brain-derived neurotrophic factor (BDNF), but regular nerve growth factor (NGF), protein levels in hippocampus (+108%) and frontal cortex (+48%) 16 days after olfactory bulbectomy. In these brain regions as well as in the hypothalamus, bulbectomy also caused a reduction of the molar ratio of 5-hydroxyindoleacetic acid to serotonin (5-HT) indicating a decrease in 5-HT turnover. Similarly, a hypofunction of the dopamine (DA) turnover was evident only in the hypothalamus in response to olfactory bulbectomy, presenting a decrease in the ratio 3,4 dihydroxyphenylacetic acid/DA with increased levels of DA. In all other brain areas investigated the levels of DA, its metabolite DOPAC and norepinephrine remained unaltered. Thus, olfactory bulbectomy seems to be a valid animal model also in mice related to serotonergic dysfunctions resembling bulbectomized rats that are a well-known model of hyposerotoninergic agitated depression. With respect to the common BDNF hypothesis of depression--predicting decreased BDNF expression in depression-related brain areas--the novel and challenging conclusions concern the increased BDNF protein levels in target regions of the cholinergic basal forebrain system in bulbectomized mice.