Bi-phasic change in BDNF gene expression following antidepressant drug treatment

Selective Noradrenergic Activation of BDNF Translation by Mirtazapine

Antidepressants are known for their neurotrophic effects, particularly through the regulation of brain-derived neurotrophic factor (BDNF) expression. Mirtazapine, a tetracyclic noradrenergic and specific serotonergic antidepressant (NaSSA) has been observed to upregulate BDNF, though its underlying mechanism remains unclear. In this study, we used the human neuroblastoma SH-SY5Y cell line to investigate whether mirtazapine could enhance BDNF translation by modulating serotonin and/or norepinephrine and their receptors. A 1-h stimulation with 1 or 10 µM mirtazapine led to downregulation of serotonergic receptors 5HT1A, while increasing ADRA2A and ADRB2 receptors. Mirtazapine at 10 µM upregulated endogenous BDNF after 3h, but not 1h stimulation. To investigate the translation of major BDNF transcripts, we used chimeric BDNF-luciferase constructs with the untranslated 5'UTR exons I, IIc, IV, or VI, and the long version of the 3'UTR. Luciferase assays and Western blotting revealed that mirtazapine selectively enhanced exon-IIc-BDNF-long3'UTR-Luciferase translation. This increase was associated with norepinephrine release and was inhibited by blocking ADRA2A or ADRB2 adrenoceptors for the exon-IIc-BDNF-long3'UTR-Luciferase, and ADR2B for endogenous BDNF. These findings provide a new perspective on the critical role of the noradrenergic system in mediating mirtazapine's effects on BDNF translation. We propose a novel mechanism of action in which mirtazapine promotes norepinephrine release and noradrenergic responses by upregulating ADRA2A and ADRB2 while downregulating serotonergic receptors.

Clinical application of transcutaneous auricular vagus nerve stimulation: a scoping review

PURPOSE

Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging non-invasive neuromodulation therapy. This study aimed to explore the therapeutic use of taVNS, optimal stimulation parameters, effective sham protocols, and safety.

METHODS

A scoping review was conducted. Five databases and grey literature were searched. The data extracted included stimulation parameters, adverse events (AEs), and therapeutic effects on clinical outcomes.

RESULTS

109 studies were included. taVNS was used across 21 different clinical populations, most commonly in psychiatric, cardiac, and neurological disorders. Overall, 2,214 adults received active taVNS and 1,017 received sham taVNS. Reporting of stimulation parameters was limited and inconsistent. taVNS appeared to have a favourable therapeutic effect across a wide range of clinical populations with varied parameters. Three sham protocols were reported but their effectiveness was documented in only two of the 54 sham-controlled studies. Most reported adverse events were localised to stimulation site.

CONCLUSION

There is growing evidence for taVNS therapeutic effect. taVNS appears safe and tolerable. Sham protocols need evaluation. Standardised and comprehensive reporting of both stimulation parameters and adverse events is required. Two different questionnaires have been proposed to evaluate adverse events and the effectiveness of sham methods in blinding participants.

Long-term administration of paroxetine increases cortical EEG beta and gamma band activities in healthy awake rats

Understanding the electrophysiological properties of antidepressant medications is important to resolve the response heterogeneity of these drugs in clinical practice. Administration of paroxetine, a selective serotonin reuptake inhibitor, has been shown to increase serotonin levels that affect cortical activities in healthy subjects. However, the extent to which cortical oscillations can be altered by ongoing administration of paroxetine is not known. Here, we develop EEG biomarkers showing long-term effects of paroxetine. EEG changes were analyzed using Neuroscan in healthy wakeful rats administered paroxetine (4 mg/kg/day) for six weeks. Subsequent EEG recordings taken at 3 and 6 weeks after treatment showed differences in cortical oscillations obtained from both hemispheres and frontal-central-parietal regions. Chronic paroxetine administration resulted in an increase in gamma band activity. Comparison of EEG frequency bands of paroxetine and saline groups showed an enhancement in higher frequency activities at third weeks after the treatment. Higher activity of alpha oscillations in the temporal cortex was persistent at sixth week of the administration. Overall, our results suggest that chronic paroxetine administration affects cortical oscillations across an expansive network.

MDMA-assisted psychotherapy for PTSD: Growing evidence for memory effects mediating treatment efficacy

The application of MDMA in conjunction with psychotherapy has in recent years seen a resurgence of clinical, scientific, and public interest in the treatment of posttraumatic stress disorder (PTSD). Clinical trials have shown promising safety and efficacy, but the mechanisms underlying this treatment form remain largely unestablished. This article explores recent preclinical and clinical evidence suggesting that the treatment's efficacy may be influenced by the mnemonic effects of MDMA. We review data on the effects of MDMA on fear extinction and fear reconsolidation and the utility of these processes for PTSD treatment. We corroborate our findings by incorporating research from cognitive psychology and psychopharmacology and offer recommendations for future research.

Exploring the Therapeutic Effect of Neurotrophins and Neuropeptides in Neurodegenerative Diseases: at a Glance

Neurotrophins and neuropeptides are the essential regulators of peripheral nociceptive nerves that help to induce, sensitize, and maintain pain. Neuropeptide has a neuroprotective impact as it increases trophic support, regulates calcium homeostasis, and reduces excitotoxicity and neuroinflammation. In contrast, neurotrophins target neurons afflicted by ischemia, epilepsy, depression, and eating disorders, among other neuropsychiatric conditions. Neurotrophins are reported to inhibit neuronal death. Strategies maintained for "brain-derived neurotrophic factor (BDNF) therapies" are to upregulate BDNF levels using the delivery of protein and genes or compounds that target BDNF production and boosting BDNF signals by expanding with BDNF mimetics. This review discusses the mechanisms of neurotrophins and neuropeptides against acute neural damage as well as highlighting neuropeptides as a potential therapeutic agent against Parkinson's disease (PD), Huntington's disease (HD), Alzheimer's disease (AD), and Machado-Joseph disease (MJD), the signaling pathways affected by neurotrophins and their receptors in both standard and diseased CNS systems, and future perspectives that can lead to the potent application of neurotrophins and neuropeptides in neurodegenerative diseases (NDs).

The Melanocortin System: A Promising Target for the Development of New Antidepressant Drugs

Major depression is one of the most prevalent mental disorders, causing significant human suffering and socioeconomic loss. Since conventional antidepressants are not sufficiently effective, there is an urgent need to develop new antidepressant medications. Despite marked advances in the neurobiology of depression, the etiology and pathophysiology of this disease remain poorly understood. Classical and newer hypotheses of depression suggest that an imbalance of brain monoamines, dysregulation of the hypothalamic-pituitary-adrenal axis (HPAA) and immune system, or impaired hippocampal neurogenesis and neurotrophic factors pathways are cause of depression. It is assumed that conventional antidepressants improve these closely related disturbances. The purpose of this review was to discuss the possibility of affecting these disturbances by targeting the melanocortin system, which includes adrenocorticotropic hormone-activated receptors and their peptide ligands (melanocortins). The melanocortin system is involved in the regulation of various processes in the brain and periphery. Melanocortins, including peripherally administered non-corticotropic agonists, regulate HPAA activity, exhibit anti-inflammatory effects, stimulate the levels of neurotrophic factors, and enhance hippocampal neurogenesis and neurotransmission. Therefore, endogenous melanocortins and their analogs are able to complexly affect the functioning of those body’s systems that are closely related to depression and the effects of antidepressants, thereby demonstrating a promising antidepressant potential.

Fast antidepressant action of ketamine in mouse models requires normal VGLUT1 levels from prefrontal cortex neurons

The NMDA antagonist ketamine demonstrated a fast antidepressant activity in treatment-resistant depression. Pre-clinical studies suggest that de novo synthesis of the brain-derived neurotrophic factor (BDNF) in the PFC might be involved in the rapid antidepressant action of ketamine. Applying a genetic model of impaired glutamate release, this study aims to further identify the molecular mechanisms that could modulate antidepressant action and resistance to treatment. To that end, mice knocked-down for the vesicular glutamate transporter 1 (VGLUT1+/-) were used. We analyzed anhedonia and helpless behavior as well as the expression of the proteins linked to glutamate transmission in the PFC of mice treated with ketamine or the reference antidepressant reboxetine. Moreover, we analyzed the acute effects of ketamine in VGLUT1+/- mice pretreated with chronic reboxetine or those that received a PFC rescue expression of VGLUT1. Chronic reboxetine rescued the depressive-like phenotype of the VGLUT1+/- mice. In addition, it enhanced the expression of the proteins linked to the AMPA signaling pathway as well as the immature form of BDNF (pro-BDNF). Unlike WT mice, ketamine had no effect on anhedonia or pro-BDNF expression in VGLUT1+/- mice; it also failed to decrease phosphorylated eukaryote elongation factor 2 (p-eEF2). Nevertheless, we found that reboxetine administered as pretreatment or PFC overexpression of VGLUT1 did rescue the antidepressant-like activity of acute ketamine in the mice. Our results strongly suggest that not only do PFC VGLUT1 levels modulate the rapid-antidepressant action of ketamine, but also highlight a possible mechanism for antidepressant resistance in some patients.

Gαs, adenylyl cyclase, and their relationship to the diagnosis and treatment of depression

The relationship between depression, its etiology and therapy, and the cAMP signaling system have been studies for decades. This review will focus on cAMP, G proteins and adenylyl cyclase and depression or antidepressant action. Both human and animal studies are compared and contrasted. It is concluded that there is some synteny in the findings that cAMP signaling is attenuated in depression and that this is reversed by successful antidepressant therapy. The G protein that activates adenylyl cyclase, Gα_s, appears to have diminished access to adenylyl cyclase in depression, and this is rectified by successful antidepressant treatment. Unfortunately, attempts to link specific isoforms of adenylyl cyclase to depression or antidepressant action suffer from discontinuity between human and animal studies.

BDNF receptor TrkB as the mediator of the antidepressant drug action

Brain-derived neurotrophic factor (BDNF) signaling through its receptor TrkB has for a long time been recognized as a critical mediator of the antidepressant drug action, but BDNF signaling has been considered to be activated indirectly through the action of typical and rapid-acting antidepressants through monoamine transporters and glutamate NMDA receptors, respectively. However, recent findings demonstrate that both typical and the fast-acting antidepressants directly bind to TrkB and thereby allosterically potentiate BDNF signaling, suggesting that TrkB is the direct target for antidepressant drugs. Increased TrkB signaling particularly in the parvalbumin-expressing interneurons orchestrates iPlasticity, a state of juvenile-like enhanced plasticity in the adult brain. iPlasticity sensitizes neuronal networks to environmental influences, enabling rewiring of networks miswired by adverse experiences. These findings have dramatically changed the position of TrkB in the antidepressant effects and they propose a new end-to-end model of the antidepressant drug action. This model emphasizes the enabling role of antidepressant treatment and the active participation of the patient in the process of recovery from mood disorders.

Single and Repeated Exposure to Cannabidiol Differently Modulate BDNF Expression and Signaling in the Cortico-Striatal Brain Network

Cannabidiol (CBD) is a phytocannabinoid contained in the Cannabis sativa plant, devoid of psychotomimetic effects but with a broad-spectrum pharmacological activity. Because of its pharmacological profile and its ability to counteract the psychoactive Δ9-tetrahydrocannabinol (Δ9THC), CBD may be a potential treatment for several psychiatric and neurodegenerative disorders. In this study, we performed a dose−response evaluation of CBD modulatory effects on BDNF, a neurotrophin subserving pleiotropic effects on the brain, focusing on the cortico-striatal pathway for its unique role in the brain trafficking of BDNF. Male adult rats were exposed to single and repeated CBD treatments at different dosing regimen (5, 15, and 30 mg/kg), to investigate the rapid modulation of the neurotrophin (1 h after the single treatment) as well as a potential drug-free time point (24 h after the repeated treatment). We show here, for the first time, that CBD can be found in the rat brain and, specifically, in the medial prefrontal cortex (mPFC) following single or repeated exposure. In fact, we found that CBD is present in the mPFC of rats treated either acutely or repeatedly with the phytocannabinoid, with a clear dose−response profile. From a molecular standpoint, we found that single, but not repeated, CBD exposure upregulates BDNF in the mPFC, while the repeated exposure increased BDNF only in the striatum, with a slight decrease in the mPFC. Together, these data reveal a CBD dose-dependent and anatomically specific modulation of BDNF, which may be functionally relevant and may represent an added value for CBD as a supplement.

Is there a relationship between morphological and functional platelet changes and depressive disorder?

BACKGROUND

Blood platelets, due to shared biochemical and functional properties with presynaptic serotonergic neurons, constituted, over the years, an attractive peripheral biomarker of neuronal activity. Therefore, the literature strongly focused on the investigation of eventual structural and functional platelet abnormalities in neuropsychiatric disorders, particularly in depressive disorder. Given their impact in biological psychiatry, the goal of the present paper was to review and critically analyze studies exploring platelet activity, functionality, and morpho-structure in subjects with depressive disorder.

METHODS

According to the PRISMA guidelines, we performed a systematic review through the PubMed database up to March 2020 with the search terms: (1) platelets in depression [Title/Abstract]"; (2) "(platelets[Title]) AND depressive disorder[Title/Abstract]"; (3) "(Platelet[Title]) AND major depressive disorder[Title]"; (4) (platelets[Title]) AND depressed[Title]"; (5) (platelets[Title]) AND depressive episode[Title]"; (6) (platelets[Title]) AND major depression[Title]"; (7) platelet activation in depression[All fields]"; and (8) platelet reactivity in depression[All fields]."

RESULTS

After a detailed screening analysis and the application of specific selection criteria, we included in our review a total of 106 for qualitative synthesis. The studies were classified into various subparagraphs according to platelet characteristics analyzed: serotonergic system (5-HT2A receptors, SERT activity, and 5-HT content), adrenergic system, MAO activity, biomarkers of activation, responsivity, morphological changes, and other molecular pathways.

CONCLUSIONS

Despite the large amount of the literature examined, nonunivocal and, occasionally, conflicting results emerged. However, the findings on structural and metabolic alterations, modifications in the expression of specific proteins, changes in the aggregability, or in the responsivity to different pro-activating stimuli, may be suggestive of potential platelet dysfunctions in depressed subjects, which would result in a kind of hyperreactive state. This condition could potentially lead to an increased cardiovascular risk. In line with this hypothesis, we speculated that antidepressant treatments would seem to reduce this hyperreactivity while representing a potential tool for reducing cardiovascular risk in depressed patients and, maybe, in other neuropsychiatric conditions. However, the problem of the specificity of platelet biomarkers is still at issue and would deserve to be deepened in future studies.

Electroconvulsive shock increases neurotrophy and neurogenesis: Time course and treatment session effects

Increasing evidence suggests that hippocampal neurotrophy may be related to the development of major depressive disorders. Neurogenesis, which can be regulated by neurotrophic factors, is also involved in antidepressant efficacy. This paper reviewed literature on neurotrophic signaling and cell proliferation after electroconvulsive shock (ECS) treatment. All articles were from PubMed, Web of Science, and Scopus databases between 2000 and 2020. The keywords used in the literature search are: "ECS," "ECT," "electroconvulsive seizure," "electroconvulsive shock," "electroconvulsive therapy," "neurotrophic factor," "nerve growth factor," "neurotrophins," "neurogenesis," and "cell proliferation." Eighty-two articles were included in the final analysis. It was shown that compared with acute ECS, repeated ECS increased neurotrophin expression in more brain regions at higher levels and was maintained for a longer time. Similarly, ECS increased cell proliferation in a dose- and time-dependent manner. The increase in cell proliferation was positively correlated with the amount of ECS administered and the newly born cells survived for a long time. The effects of ECS in inducing increases in neurotrophin levels and neurogenesis may contribute to brain function changes and antidepressant effects. Future research may focus on optimal sessions of ECT treatment to obtain the best therapeutic effect.

Brain-derived neurotrophic factor in Alzheimer's disease and its pharmaceutical potential

Synaptic abnormalities are a cardinal feature of Alzheimer's disease (AD) that are known to arise as the disease progresses. A growing body of evidence suggests that pathological alterations to neuronal circuits and synapses may provide a mechanistic link between amyloid β (Aβ) and tau pathology and thus may serve as an obligatory relay of the cognitive impairment in AD. Brain-derived neurotrophic factors (BDNFs) play an important role in maintaining synaptic plasticity in learning and memory. Considering AD as a synaptic disorder, BDNF has attracted increasing attention as a potential diagnostic biomarker and a therapeutical molecule for AD. Although depletion of BDNF has been linked with Aβ accumulation, tau phosphorylation, neuroinflammation and neuronal apoptosis, the exact mechanisms underlying the effect of impaired BDNF signaling on AD are still unknown. Here, we present an overview of how BDNF genomic structure is connected to factors that regulate BDNF signaling. We then discuss the role of BDNF in AD and the potential of BDNF-targeting therapeutics for AD.

Trace amine-associated receptor 1 (TAAR1): Potential application in mood disorders: A systematic review

There is a need for innovation with respect to therapeutics in psychiatry. Available evidence indicates that the trace amine-associated receptor 1 (TAAR1) agonist SEP-363856 is promising, as it improves measures of cognitive and reward function in schizophrenia. Hedonic and cognitive impairments are transdiagnostic and constitute major burdens in mood disorders. Herein, we systematically review the behavioural and genetic literature documenting the role of TAAR1 in reward and cognitive function, and propose a mechanistic model of TAAR1's functions in the brain. Notably, TAAR1 activity confers antidepressant-like effects, enhances attention and response inhibition, and reduces compulsive reward seeking without impairing normal function. Further characterization of the responsible mechanisms suggests ion-homeostatic, metabolic, neurotrophic, and anti-inflammatory enhancements in the limbic system. Multiple lines of evidence establish the viability of TAAR1 as a biological target for the treatment of mood disorders. Furthermore, the evidence suggests a role for TAAR1 in reward and cognitive function, which is attributed to a cascade of events that are relevant to the cellular integrity and function of the central nervous system.

A Review of the Potential Use of Pinene and Linalool as Terpene-Based Medicines for Brain Health: Discovering Novel Therapeutics in the Flavours and Fragrances of Cannabis

"Medicinal cannabis" is defined as the use of cannabis-based products for the treatment of an illness. Investigations of cannabis compounds in psychiatric and neurological illnesses primarily focus on the major cannabinoids, cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC), which are hypothesised to benefit multiple illnesses manifesting cognitive impairment, neurodegeneration and neuro-inflammation, as well as chronic pain, epilepsy and post-traumatic stress disorder, respectively. The cannabis plant contains >500 compounds, including terpenes responsible for the flavour and fragrance profiles of plants. Recently, research has begun providing evidence on the potential use of certain plant-derived terpenes in modern medicine, demonstrating anti-oxidant, anti-inflammatory, and neuroprotective effects of these compounds. This review examined the effects of two key terpenes, pinene and linalool, on parameters relevant to neurological and psychiatric disorders, highlighting gaps in the literature and recommendations for future research into terpene therapeutics. Overall, evidence is mostly limited to preclinical studies and well-designed clinical trials are lacking. Nevertheless, existing data suggests that pinene and linalool are relevant candidates for further investigation as novel medicines for illnesses, including stroke, ischemia, inflammatory and neuropathic pain (including migraine), cognitive impairment (relevant to Alzheimer's disease and ageing), insomnia, anxiety, and depression. Linalool and pinene influence multiple neurotransmitter, inflammatory and neurotrophic signals as well as behaviour, demonstrating psycho-activity (albeit non-intoxicating). Optimising the phytochemical profile of cannabis chemovars to yield therapeutic levels of beneficial terpenes and cannabinoids, such as linalool, pinene and CBD, could present a unique opportunity to discover novel medicines to treat psychiatric and neurological illnesses; however, further research is needed.

The Role of Annexin A1 and Formyl Peptide Receptor 2/3 Signaling in Chronic Corticosterone-Induced Depression-Like behaviors and Impairment in Hippocampal-Dependent Memory

BACKGROUND

The activity of the Hypothalamic-Pituitary-Adrenal (HPA) axis is commonly dysregulated in stress-related psychiatric disorders. Annexin A1 (ANXA1), an endogenous ligand of Formyl Peptide Receptor (FPR) 2/3, is a member of the family of phospholipid- and calcium-binding proteins with a well-defined role in the delayed early inhibitory feedback of Glucocorticoids (GC) in the pituitary gland and implicated in the occurrence of behavioural disorders such as anxiety.

OBJECTIVE

The present study aimed to evaluate the potential role of ANXA1 and its main receptor, as a cellular mediator of behavioural disorders, in a model of Corticosterone (CORT)-induced depression and subsequently, the possible correlation between the depressive state and impairment of hippocampal memory.

METHODS

To induce the depression model, Wild-Type (WT), ANXA1 Knockout (KO), and FPR2/3 KO mice were exposed to oral administration of CORT for 28 days dissolved in drinking water. Following this, histological, biochemical and behavioural analyses were performed.

RESULTS

FPR2/3 KO and ANXA1 KO mice showed improvement in anxiety and depression-like behaviour compared with WT mice after CORT administration. In addition, FPR2/3 KO and ANXA1 KO mice showed a reduction in histological alterations and neuronal death in hippocampal sections. Moreover, CORT+ FPR2/3 KO and ANXA1 KO, exhibited a higher expression of Brain-Derived Neurotrophic Factor (BDNF), phospho-ERK, cAMP response element-binding protein (pCREB) and a decrease in Serotonin Transporter Expression (SERT) compared to WT(CORT+) mice.

CONCLUSION

In conclusion, the absence of the ANXA1 protein, even more than the absence of its main receptor (FPR 2/3), was fundamental to the inhibitory action of GC on the HPA axis; it also maintained the hippocampal homeostasis by preventing neuronal damage associated with depression.

The Relationship between Overweight/Obesity and Executive Control in College Students: The Mediating Effect of BDNF and 5-HT

The main aim of this study was to explore the association between overweight/obesity and executive control (EC) in young adults, and to further analyze the mediating effect of brain-derived neurotrophic factor (BDNF) and serotonin (5-hydroxytryptamine (5-HT)) on the relationship between overweight/obesity and EC. A total of 449 college students aged between 18 and 20 years were recruited for the study between March and December 2019. Their height and weight were then measured professionally. Subsequently, body mass index (BMI) was calculated as weight (kg) divided by the square of height (m). The EC of the participants was then estimated using the Flanker task, while their serum BDNF levels and 5-HT levels were measured using an enzyme-linked immunosorbent assay (ELISA) kit. Finally, the multiple intermediary models in SPSS were used to analyze the mediating effect of 5-HT and BDNF between overweight/obesity and EC. The result show that the overweight/obesity of college students was positively correlated with the response of EC (p ≤ 0.005). However, it was negatively correlated with BDNF (p ≤ 0.05) and 5-HT (p ≤ 0.05). Moreover, BDNF (p ≤ 0.001) and 5-HT (p ≤ 0.001) were negatively correlated with the response of EC. The BDNF level played a partial mediating role between overweight/obesity and EC that accounted for 7.30% of the total effect value. Similarly, the 5-HT of college students played a partial mediating role between overweight/obesity and EC that accounted for 8.76% of the total effect value. Gender and age had no regulatory effect on the relationship between overweight/obesity, BDNF, 5-HT, and EC. This study provides the evidence that 5-HT and BDNF mediated the association between overweight/obesity and executive control. It is indicated that 5-HT and BDNF might be the biological pathways underpinning the link between overweight/obesity and executive control.

Neuronal activity regulated pentraxin (narp) and GluA4 subunit of AMPA receptor may be targets for fluoxetine modulation

Fluoxetine is the foremost prescribed antidepressant. Drugs acting on monoaminergic system may also regulate glutamatergic system. Indeed, the investigation of proteins associated with this system, such as Narp (neuronal activity-dependent pentraxin) and GluA4 subunit of AMPA receptor may reveal poorly explored modulations triggered by conventional antidepressants. This study aimed to uncover neurochemical mechanisms underlying the chronic fluoxetine treatment, mainly by evaluating these protein targets in the prefrontal cortex and in the hippocampus. Mice received a daily administration of fluoxetine (0.1, 1 or 10 mg/kg, p.o.) or potable water (vehicle group) for 21 days. These animals were submitted to the forced swim test (FST) to verify antidepressant-like responses and the open-field test (OFT) to assess locomotor activity. Modulation of signaling proteins was analyzed by western blot. Chronic treatment with fluoxetine (1 and 10 mg/kg) was effective, since it reduced the immobility time in the FST, without altering locomotor activity. Fluoxetine 10 mg/kg increased CREB phosphorylation and BDNF expression in the prefrontal cortex and hippocampus. Noteworthy, in the hippocampus fluoxetine also promoted Akt activation and augmented Narp expression. In the prefrontal cortex, a significant decrease in the expression of the GluA4 subunit and Narp were observed following fluoxetine administration (10 mg/kg). The results provide evidence of novel molecular targets potentially involved in the antidepressant effects of fluoxetine, since in mature rodents Narp and GluA4 are mainly expressed in the GABAergic parvalbumin-positive (PV+) interneurons. This may bring new insights into the molecular elements involved in the mechanisms underlying the antidepressant effects of fluoxetine.

Antidepressant Screening Demonstrated Non-Monotonic Responses to Amitriptyline, Amoxapine and Sertraline in Locomotor Activity Assay in Larval Zebrafish

Antidepressants are well-known drugs to treat depression and major depressive disorder for humans. However, the misuse and abuse of antidepressants keep increasing with several side effects reported. The aim of this study was to assess the potential adverse effects of 18 antidepressants by monitoring zebrafish larval locomotor activity performance based on the total distance traveled, burst movement count, and total rotation count at four dark-light intercalated phases. In general, zebrafish larvae displayed sedative effects after antidepressant exposure by showing a significant reduction in all of the locomotor activity-related endpoints. However, three antidepressants i.e., amitriptyline, amoxapine, and sertraline were able to trigger a significantly high locomotor activity in zebrafish larvae during the light cycle. These differences might be due to the pharmacologic differences among the antidepressants. In addition, since each antidepressant possesses a different dosage range from the other, overdoses of these antidepressants might also be the causes of these differences. Furthermore, based on these results, a further study was conducted to observe the effect of these three antidepressants in lower concentrations. From the results, biphasic effects in terms of zebrafish larval locomotor activity were demonstrated by these drugs. Even though further studies are still required to validate the mechanism, these findings indicate that these antidepressants might share a common mechanism responsible for their effects on zebrafish larval locomotor activity although there were some differences in potency of these effects.

Attenuating effect of paroxetine on memory impairment following cerebral ischemia-reperfusion injury in rat: The involvement of BDNF and antioxidant capacity

Memory impairments are frequently reported in patients suffering from brain ischemic diseases. Oxidative/nitrosative stress, synaptic plasticity, and brain-derived neurotrophic factor (BDNF) are involved in the physiopathology of brain ischemia-induced memory disorders. In the present study, the effect of paroxetine as an efficacious antidepressant medication with antioxidant properties was evaluated on passive avoidance memory deficit following cerebral ischemia in rats. Transient occlusion of common carotid arteries was applied to induce ischemia-reperfusion injury in male Wistar rats. Paroxetine (5, 10, 20 mg/kg) was administered intraperitoneally once daily before (for 3 days) or after (for 7 days) the induction of ischemia. A week after ischemia-reperfusion injury, passive avoidance memory, long-term potentiation (LTP), BDNF levels, total antioxidant capacity, the activity of antioxidant enzymes (including catalase, glutathione peroxidase, and superoxide dismutase), the concentration of malondialdehyde (MDA), and nitric oxide (NO) were investigated in the hippocampus. In the passive avoidance test, paroxetine significantly increased the step-through latency and decreased the time spent in the dark compartment. This affirmative function of paroxetine on the passive avoidance memory was accompanied by the improvement of hippocampal LTP and an obvious augmentation in the BDNF contents. Besides, paroxetine caused a significant rise in the total antioxidant capacity and antioxidant enzyme activity; while decreased the hippocampal levels of NO and MDA. It was ultimately attained that paroxetine attenuates cerebral ischemia-induced passive avoidance memory dysfunction in rats by the enhancement of hippocampal synaptic plasticity and BDNF content together with the suppression of oxidative/nitrosative stress.

Antidepressants Promote and Prevent Cancers

The review states that antidepressants (ADs) increase brain-derived neurotrophic factor (BDNF) transmission concomitantly in the brain and the blood: ADs increasing BDNF synthesis in specific areas of the central nervous system (CNS) could presumably affect megakaryocyte's production of platelets. ADs increase BDNF levels in the CNS and improve mood. In the blood, ADs increase BDNF release from platelets. The hypothesis presented here is that the release of BDNF from platelets contributes to the ADs effects on neurogenesis and on tumor growth in the cancer disease. Oncological studies indicate that chemicals ADs exert an aggravating effect on the cancer disease, possibly by promoting proplatelets formation and enhancing BDNF release from platelets in the tumor.

Chronic harmine treatment has a delayed effect on mobility in control and socially defeated rats

INTRODUCTION

Depression is characterized by behavioral, cognitive and physiological changes, imposing a major burden on the overall wellbeing of the patient. Some evidence indicates that social stress, changes in growth factors (e.g., brain-derived neurotrophic factor (BDNF)), and neuroinflammation are involved in the development and progression of the disease. The monoamine oxidase A inhibitor drug harmine was suggested to have both antidepressant and anti-inflammatory properties and may, therefore, be a potential candidate for treatment of depression.

AIM

The goal of this study was to assess the effects of harmine on behavior, brain BDNF levels, and microglia activation in control rats and a rat model of social stress.

MATERIAL AND METHODS

Rats were submitted to 5 consecutive days of repeated social defeat (RSD) or control conditions. Animals were treated daily with harmine (15 mg/kg) or vehicle from day 3 until the end of the experiment. To assess the effects of harmine treatment on behavior, the sucrose preference test (SPT) was performed on days 1, 6, and 15, the open field test (OFT) on days 6 and 14, and the novel object recognition test (NOR) on day 16. Brain microgliosis was assessed using [11C]PBR-28 PET on day 17. Animals were terminated on day 17, and BDNF protein concentrations in the hippocampus and frontal cortex were analyzed using ELISA.

RESULTS

RSD significantly decreased bodyweight and increased anxiety and anhedonia-related parameters in the OFT and SPT on day 6, but these behavioral effects were not observed anymore on day 14/15. Harmine treatment caused a significant reduction in bodyweight gain in both groups, induced anhedonia in the SPT on day 6, and significantly reduced the mobility and exploratory behavior of the animals in the OFT mainly on day 14. PET imaging and the NOR test did not show any significant effects on microglia activation and memory, respectively. BDNF protein concentrations in the hippocampus and frontal cortex were not significantly affected by either RSD or harmine treatment.

DISCUSSION

Harmine was not able to reverse the acute effects of RSD on anxiety and anhedonia and even aggravated the effect of RSD on bodyweight loss. Moreover, harmine treatment caused unexpected side effects on general locomotion, both in RSD and control animals, but did not influence glial activation status and BDNF concentrations in the brain. In this model, RSD-induced stress was not strong enough to induce long-term effects on the behavior, neuroinflammation, or BDNF protein concentration. Thus, the efficacy of harmine treatment on these delayed parameters needs to be further evaluated in more severe models of chronic stress.

Use of Selective Serotonin Reuptake Inhibitors and Outcomes in Stroke Rehabilitation: A Prospective Observational Pilot Cohort Study

Purpose

The aim of this study was to examine the association between selective serotonin reuptake inhibitor (SSRI) therapy and rehabilitation outcomes, specifically disability and quality of life (QOL), in a real-world setting of multi-ethnic Asian patients with first-ever stroke.

Methods

In this prospective observational pilot cohort study, we included patients with first-ever stroke admitted to two inpatient rehabilitation centres in Singapore between January and July 2018. Outcomes were measured using Functional Independence Measure (FIM)-motor scale, modified Barthel Index (MBI) and the Stroke and Aphasia Quality of Life Scale-39 generic (SAQOL-39g) questionnaire. Linear regression was used to assess the association between SSRI therapy and outcomes. Regression coefficients and 95% confidence intervals (CIs) were reported.

Results

Among 57 patients included for analyses, 38.6% received SSRIs. Although SSRI therapy was significantly associated with gains in MBI (coefficient 11.35; 95% CI 0.21–22.50) and SAQOL-39g overall score (coefficient 0.45; 95% CI 0.05–0.85) based on simple linear regression, no significant association between SSRI therapy and any of the investigated outcomes was found after adjustment for confounders. However, an increase in the mean number of physiotherapy and occupational therapy (PT/OT) sessions per day significantly improved FIM-motor (coefficient 16.86; 95% CI 2.64–31.07) and MBI (coefficient 22.79; 95% CI 2.35–43.23) scores.

Conclusion

SSRI therapy did not improve disability and QOL in multi-ethnic Asian patients with first-ever stroke undergoing rehabilitation.

Electronic supplementary material

The online version of this article (10.1007/s40268-019-00287-y) contains supplementary material, which is available to authorized users.

GSK3β: A Master Player in Depressive Disorder Pathogenesis and Treatment Responsiveness

Glycogen synthase kinase 3β (GSK3β), originally described as a negative regulator of glycogen synthesis, is a molecular hub linking numerous signaling pathways in a cell. Specific GSK3β inhibitors have anti-depressant effects and reduce depressive-like behavior in animal models of depression. Therefore, GSK3β is suggested to be engaged in the pathogenesis of major depressive disorder, and to be a target and/or modifier of anti-depressants’ action. In this review, we discuss abnormalities in the activity of GSK3β and its upstream regulators in different brain regions during depressive episodes. Additionally, putative role(s) of GSK3β in the pathogenesis of depression and the influence of anti-depressants on GSK3β activity are discussed.

NMDAR-independent, cAMP-dependent antidepressant actions of ketamine

Ketamine produces rapid and robust antidepressant effects in depressed patients within hours of administration, often when traditional antidepressant compounds have failed to alleviate symptoms. We hypothesized that ketamine would translocate Gα_s from lipid rafts to non-raft microdomains, similarly to other antidepressants but with a distinct, abbreviated treatment duration. C6 glioma cells were treated with 10 µM ketamine for 15 min, which translocated Gα_s from lipid raft domains to non-raft domains. Other NMDA antagonist did not translocate Gα_s from lipid raft to non-raft domains. The ketamine-induced Gα_s plasma membrane redistribution allows increased functional coupling of Gα_s and adenylyl cyclase to increase intracellular cyclic adenosine monophosphate (cAMP). Moreover, increased intracellular cAMP increased phosphorylation of cAMP response element-binding protein (CREB), which, in turn, increased BDNF expression. The ketamine-induced increase in intracellular cAMP persisted after knocking out the NMDA receptor indicating an NMDA receptor-independent effect. Furthermore, 10 µM of the ketamine metabolite (2R,6R)-hydroxynorketamine (HNK) also induced Gα_s redistribution and increased cAMP. These results reveal a novel antidepressant mechanism mediated by acute ketamine treatment that may contribute to ketamine's powerful antidepressant effect. They also suggest that the translocation of Gα_s from lipid rafts is a reliable hallmark of antidepressant action that might be exploited for diagnosis or drug development.

Antidepressant-like effect induced by P2X7 receptor blockade in FSL rats is associated with BDNF signalling activation

BACKGROUND

P2X7 receptors (P2X7R) are ligand-gated ion channels activated by adenosine 5'-triphosphate (ATP), which are involved in processes that are dysfunctional in stress response and depression, such as neurotransmitter release, and neuroimmune response. Genetic and pharmacological inhibition of the P2X7R induce antidepressant-like effects in animals exposed to stress. However, the effect of P2X7R antagonism in an animal model of depression based on selective breeding has not previously been studied, and the mechanism underling the antidepressant-like effect induced by the P2X7R blockade remains unknown.

AIMS

The present study aimed to: (1) determine whether P2X7R blockade induces antidepressant-like effects in the Flinders Sensitive Line (FSL) rats and, (2) investigate whether brain-derived neurotrophic factor (BDNF) signalling in the frontal cortex and hippocampus is involved in this effect.

METHODS

FSL and the control Flinders Resistant Line (FRL) rats were treated with vehicle or the P2X7R antagonist A-804598 (3, 10 or 30 mg/Kg/day) for 1 or 7 days before being exposed to the forced swim test (FST). After the behavioural test, animals were decapitated, their brains were removed and the frontal cortex, ventral and dorsal hippocampus were dissected for BDNF signalling analysis.

RESULTS

We found that repeated treatment with A-804598 (30 mg/Kg) reduced the immobility time in the FST and activated the BDNF signalling in the ventral hippocampus of FSL rats.

CONCLUSIONS

P2X7R blockade induces an antidepressant-like effect associated with increased levels of BDNF-AKT-p70 S6 kinase in the ventral hippocampus, which may be mediated by tropomyosin-related kinase B (TRKB) receptor activation supporting the notion of P2X7R antagonism as a potential new antidepressant strategy.

On the Involvement of BDNF Signaling in Memory Reconsolidation

When retrieval occurs concomitantly with novelty detection, mismatch perception or reactivation of conflicting information, consolidated memories can enter into a labile state, and to persist, must be restabilized through a protein synthesis-dependent reconsolidation process during which their strength and content can be modified. Extensive literature implicates brain-derived neurotrophic factor (BDNF), a key regulator of synaptogenesis and synaptic plasticity, in the acquisition, consolidation and extinction of several memory types. However, the participation of BDNF in memory reconsolidation has been less studied. In this review, we discuss recent reports supporting the involvement of BDNF signaling in reactivation-induced memory updating.

Activation of the TRKB receptor mediates the panicolytic-like effect of the NOS inhibitor aminoguanidine

Nitric oxide (NO) triggers escape reactions in the dorsal periaqueductal gray matter (dPAG), a core structure mediating panic-associated response, and decreases the release of BDNF in vitro. BDNF mediates the panicolytic effect induced by antidepressant drugs and produces these effects per se when injected into the dPAG. Based on these findings, we hypothesize that nitric oxide synthase (NOS) inhibitors would have panicolytic properties associated with increased BDNF signaling in the dPAG. We observed that the repeated (7 days), but not acute (1 day), systemic administration of the NOS inhibitor aminoguanidine (AMG; 15 mg/kg/day) increased the latency to escape from the open arm of the elevated T-maze (ETM) and inhibited the number of jumps in hypoxia-induced escape reaction in rats, suggesting a panicolytic-like effect. Repeated, but not acute, AMG administration (15 mg/kg) also decreased nitrite levels and increased TRKB phosphorylation at residues Y706/7 in the dPAG. Notwithstanding the lack of AMG effect on total BDNF levels in this structure, the microinjection of the TRK antagonist K252a into the dPAG blocked the anti-escape effect of this drug in the ETM. Taken together our data suggest that the inhibition of NO production by AMG increases the levels of pTRKB, which is required for the panicolytic-like effect observed.

Influence of Tacrolimus on Depressive-Like Behavior in Diabetic Rats Through Brain-Derived Neurotrophic Factor Regulation in the Hippocampus

The neurotoxicity of immunosuppressive agents and diabetes mellitus are known risk factors of neurological complications in kidney transplant recipients. The aim of the present study was to investigate the influence of tacrolimus on brain-derived neurotrophic factor (BDNF), the critical protein for maintenance of neuronal functions, in the hippocampus in a diabetic condition. A diabetic rat model was established by a single streptozotocin injection (60 mg/kg). Control and diabetic rats then received daily tacrolimus (1.5 mg/kg per day) injections for 6 weeks. BDNF expression in the hippocampus was examined in the dentate gyrus (DG) and CA3 region using immunohistochemistry. There was a significant decrease of BDNF expression in the DG and CA3 region in tacrolimus-treated and diabetic rats compared with that of the control group injected with vehicle only. However, there was no difference in BDNF expression between the two experimental groups. Tacrolimus treatment in diabetic rats further decreased the BDNF expression level in the DG and CA3 region. Interestingly, mossy fiber sprouting, demonstrated by prominent punctate immunolabeling of BDNF with synaptoporin, was observed in the diabetic group treated with tacrolimus, which localized at the stratum oriens of the CA3 region. These data suggest that tacrolimus treatment or a diabetic condition decreases BDNF expression in the hippocampus, and that tacrolimus treatment in the diabetic condition further injures the CA3 region of the hippocampus. In addition to BDNF expression, decreased locomotor activity and evident depressive behavior were observed in tacrolimus-treated diabetic rats. Moreover, there were significant decreases of the mRNA levels of γ-aminobutyric acid and serotonin receptors in the diabetic hippocampus with tacrolimus treatment. This finding suggests that tacrolimus treatment may cause further psychiatric and neurological complications for patients with diabetes, and should thus be used with caution.

The possible beneficial effects of creatine for the management of depression

Depression, a highly prevalent neuropsychiatric disorder worldwide, causes a heavy burden for the society and is associated with suicide risk. The treatment of this disorder remains a challenge, since currently available antidepressants provide a slow and, often, incomplete response and cause several side effects that contribute to diminish the adhesion of patients to treatment. In this context, several nutraceuticals have been investigated regarding their possible beneficial effects for the management of this neuropsychiatric disorder. Creatine stands out as a supplement frequently used for ergogenic purpose, but it also is a neuroprotective compound with potential to treat or mitigate a broad range of central nervous systems diseases, including depression. This review presents preclinical and clinical evidence that creatine may exhibit antidepressant properties. The focus is given on the possible molecular mechanisms underlying its effects based on the results obtained with different animal models of depression. Finally, evidence obtained in animal models of depression addressing the possibility that creatine may produce rapid antidepressant effect, similar to ketamine, are also presented and discussed.

Repeated fluoxetine treatment induces long-lasting neurotrophic changes in the medial prefrontal cortex of adult rats

Fluoxetine (Flx), a selective serotonin reuptake inhibitor, is extensively used to treat mood and anxiety disorders. Previous animal studies have shown that early-life exposure to Flx results in long-lasting behavioral alterations and neuroplasticity in the hippocampus and cortex, which may persist into adulthood. It remains unclear whether repeated Flx treatment in normal adult animals can induce lasting neuroplasticity and behavioral alterations persisting long beyond the treatment period. In this study, young adult rats (about 9 weeks old) were treated with Flx (10 mg/kg body weight, twice daily) for 15 consecutive days, and the effects of Flx on medial prefrontal cortex (mPFC) neuroplasticity and mPFC-related behaviors were assessed 20 days after the last injection. It was observed that the mPFC of Flx-treated rats had significant increases in the number of 5-bromodeoxyuridine-positive (BrdU⁺) cells, dendritic complexity/spine density in layer II/III pyramidal neurons, and brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) expression levels, as well as a significant decrease in the number of parvalbumin-positive (PV⁺) interneurons. The Flx-treated rats exhibited higher motivation to explore new environments, evidenced by a significantly increased number of entries into the novel arm in the Y-maze test. However, they did not show any significant changes in the anhedonia and anxiety levels measured by sucrose preference and elevated plus maze tests respectively. In conclusion, repeated Flx treatment, with the paradigm used, induces long-lasting neuroplastic changes in the mPFC of normal adult rats; such changes and related behavioral manifestations may persist up to 20 days after the last dose.

Molecular aspects of depression: A review from neurobiology to treatment

Major depressive disorder (MDD), also known as unipolar depression, is one of the leading causes of disability and disease worldwide. The signs and symptoms are low self‑esteem, anhedonia, feeling of worthlessness, sense of rejection and guilt, suicidal thoughts, among others. This review focuses on studies with molecular-based approaches involving MDD to obtain an integrated, more detailed and comprehensive view of the brain changes produced by this disorder and its treatment and how the Central Nervous System (CNS) produces neuroplasticity to orchestrate adaptive defensive behaviors. This article integrates affective neuroscience, psychopharmacology, neuroanatomy and molecular biology data. In addition, there are two problems with current MDD treatments, namely: 1) Low rates of responsiveness to antidepressants and too slow onset of therapeutic effect; 2) Increased stress vulnerability and autonomy, which reduces the responses of currently available treatments. In the present review, we encourage the prospection of new bioactive agents for the development of treatments with post-transduction mechanisms, neurogenesis and pharmacogenetics inducers that bring greater benefits, with reduced risks and maximized access to patients, stimulating the field of research on mood disorders in order to use the potential of preclinical studies. For this purpose, improved animal models that incorporate the molecular and anatomical tools currently available can be applied. Besides, we encourage the study of drugs that do not present "classical application" as antidepressants, (e.g., the dissociative anesthetic ketamine and dextromethorphan) and drugs that have dual action mechanisms since they represent potential targets for novel drug development more useful for the treatment of MDD.

The effect of exercise on resting concentrations of peripheral brain-derived neurotrophic factor (BDNF) in major depressive disorder: A meta-analysis

Exercise interventions have been shown to successfully improve depression in patients with major depressive disorder (MDD), but like other forms of antidepressant treatment, exercise is not effective in all patients and its mechanisms of action have not been fully elucidated. Brain-derived neurotrophic factor (BDNF), a key mediator of neurogenesis and neuronal survival, has been shown to be decreased in individuals with MDD. One potential mechanism by which exercise alleviates depression is through an increase in BDNF. In order to evaluate this hypothesis, we conducted a meta-analysis of studies that assessed the effects of a chronic (multi-week) exercise intervention on BDNF concentrations in MDD patients. MEDLINE, Embase, PsycINFO, SPORTDiscus, Rehabilitation & Sports Medicine Source, and CINAHL databases were searched for original, peer-reviewed reports of peripheral blood BDNF concentrations before and after a chronic exercise intervention in MDD patients. Standardized mean differences (SMDs) were generated from random effects models. Potential sources of heterogeneity were explored in meta-regression analyses. In six studies that met inclusion criteria, resting blood concentrations of BDNF were not significantly higher after a chronic exercise intervention (SMD = 0.43, 95% CI: -0.06-0.92, p = 0.09) in MDD patients. This meta-analysis did not find evidence that a chronic aerobic exercise intervention increases resting concentrations of BDNF in the blood of MDD patients; however, there is a lack of studies in this area making it difficult to reach a definitive conclusion. Future studies on this topic with larger sample sizes and longer durations are needed to draw more robust conclusions.

Serotonin Reuptake Inhibitors in Obstructive Sleep Apnea: Associations in People with and without Epilepsy

Purpose

Positive airway pressure remains the gold-standard treatment for OSA, but many are intolerant. The neurotransmitter serotonin is involved in respiratory control. Evidence exists for SRIs in reducing OSA severity in the general population and ictal hypoxemia and seizure-induced respiratory arrest in people with epilepsy (PWE). However, the association between SRIs and OSA severity has not been studied in populations consisting of both groups. This study aims to determine if SRIs are associated with OSA severity in both PWE and people without epilepsy (PWO) and whether differences exist between the two groups.

Methods

A retrospective study of adults with OSA was conducted. Subjects were categorized as PWE or PWO and for the use (+SRI) or absence (-SRI) of an SRI. The primary outcome was OSA severity relative to SRI status. OSA severity as a function of SRI status was also compared between PWE and PWO and within the PWE and PWO cohorts. Oxygen saturation nadir was a secondary outcome measure. Statistical adjustment of pertinent characteristics was performed.

Results

There were 125 subjects (57 PWE, 68 PWO, 80 –SRI, and 45 +SRI). +SRI was associated with reduced odds of severe compared to moderate OSA, in unadjusted and adjusted analysis. Compared to PWO, PWE demonstrated a more robust association between OSA severity and +SRI. When analyzed as separate cohorts, only PWE demonstrated reduced OSA severity, with adjustment for age (OR:0.140, CI:0.021-1.116, and p=0.042). Oxygen saturation nadir was not significant in any model.

Conclusions

SRIs represent a potential treatment option for OSA and may demonstrate a more robust association with reduced OSA severity in PWE compared to PWO.

Computational Model of Antidepressant Response Heterogeneity as Multi-pathway Neuroadaptation

Current hypotheses cannot fully explain the clinically observed heterogeneity in antidepressant response. The therapeutic latency of antidepressants suggests that therapeutic outcomes are achieved not by the acute effects of the drugs, but rather by the homeostatic changes that occur as the brain adapts to their chronic administration. We present a computational model that represents the known interactions between the monoaminergic neurotransmitter-producing brain regions and associated non-monoaminergic neurotransmitter systems, and use the model to explore the possible ways in which the brain can homeostatically adjust to chronic antidepressant administration. The model also represents the neuron-specific neurotransmitter receptors that are known to adjust their strengths (expressions or sensitivities) in response to chronic antidepressant administration, and neuroadaptation in the model occurs through sequential adjustments in these receptor strengths. The main result is that the model can reach similar levels of adaptation to chronic administration of the same antidepressant drug or combination along many different pathways, arriving correspondingly at many different receptor strength configurations, but not all of those adapted configurations are also associated with therapeutic elevations in monoamine levels. When expressed as the percentage of adapted configurations that are also associated with elevations in one or more of the monoamines, our modeling results largely agree with the percentage efficacy rates of antidepressants and antidepressant combinations observed in clinical trials. Our neuroadaptation model provides an explanation for the clinical reports of heterogeneous outcomes among patients chronically administered the same antidepressant drug regimen.

Brain-Derived Neurotrophic Factor, Depression, and Physical Activity: Making the Neuroplastic Connection

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that is vital to the survival, growth, and maintenance of neurons in key brain circuits involved in emotional and cognitive function. Convergent evidence indicates that neuroplastic mechanisms involving BDNF are deleteriously altered in major depressive disorder (MDD) and animal models of stress. Herein, clinical and preclinical evidence provided that stress-induced depressive pathology contributes to altered BDNF level and function in persons with MDD and, thereby, disruptions in neuroplasticity at the regional and circuit level. Conversely, effective therapeutics that mitigate depressive-related symptoms (e.g., antidepressants and physical activity) optimize BDNF in key brain regions, promote neuronal health and recovery of function in MDD-related circuits, and enhance pharmacotherapeutic response. A greater knowledge of the interrelationship between BDNF, depression, therapeutic mechanisms of action, and neuroplasticity is important as it necessarily precedes the derivation and deployment of more efficacious treatments.

Acute and Chronic Noradrenergic Effects on Cortical Excitability in Healthy Humans

Background

Noradrenaline is a major neuromodulator in the central nervous system, and it is involved in the pathophysiology of diverse neuropsychiatric diseases. Previous transcranial magnetic stimulation studies suggested that acute application of selective noradrenaline reuptake inhibitors enhances cortical excitability in the human brain. However, other, such like clinical effects, usually require prolonged noradrenaline reuptake inhibitor treatment, which might go along with different physiological effects.

Methods

The purpose of this study was to investigate the acute and chronic effects of the selective noradrenaline reuptake inhibitor reboxetine on cortical excitability in healthy humans in a double-blind, placebo-controlled, randomized crossover study. Sixteen subjects were assessed with different transcranial magnetic stimulation measurements: motor thresholds, input-output curve, short-latency intracortical inhibition and intracortical facilitation, I-wave facilitation, and short-interval afferent inhibition before and after placebo or reboxetine (8 mg) single-dose administration. Afterwards, the same subjects took reboxetine (8 mg/d) consecutively for 21 days. During this period (subjects underwent 2 experimental sessions with identical transcranial magnetic stimulation measures under placebo or reboxetine), transcranial magnetic stimulation measurements were assessed before and after drug intake.

Results

Both single-dose and chronic administration of reboxetine increased cortical excitability; increased the slope of the input-output curve, intracortical facilitation, and I-wave facilitation; but decreased short-latency intracortical inhibition and short-interval afferent inhibition. Moreover, chronic reboxetine showed a larger enhancement of intracortical facilitation and I-wave facilitation compared with single-dose application.

Conclusions

The results show physiological mechanisms of noradrenergic enhancement possibly underlying the functional effects of reboxetine regarding acute and chronic application.

The involvement of BDNF-CREB signaling pathways in the pharmacological mechanism of combined SSRI- antipsychotic treatment in schizophrenia

Previous studies into the mechanism of SSRI-antipsychotic synergism in our laboratory identified unique changes in the brain, particularly in the γ-aminobutyric acid (GABA)-A receptor and its modulators. This study examined the role of brain derived neurotrophic factor (BDNF)-cAMP response element binding (CREB) protein signaling pathways, including protein kinase B (AKT), glycogen synthase kinase (GSK)-3β and related molecules in the molecular response to haloperidol, fluvoxamine, combined haloperidol+fluvoxamine and clozapine treatments in rat frontal cortex, hippocampus and primary cortical neuronal cultures. The effect of fluvoxamine augmentation on BDNF-CREB pathways in peripheral mononuclear cells (PMC׳s) of medicated schizophrenia patients was also studied. Chronic haloperidol (1mg/kg) +fluvoxamine (10mg/kg) treatment increased TrkB receptor and BDNF expression levels, and the phosphorylation of AKT/CREB/GSK-3β, compared to the individual drugs in rat brain. In addition, haloperidol+fluvoxamine treatment improved cognitive functions in rats, indicating that the molecular changes may have a role in behavioral improvement. In primary neuronal cell cultures, pretreatment with a selective PI3K inhibitor abolished the haloperidol+fluvoxamine-induced phosphorylation of AKT and GSK-3β, but did not affect the upregulation of CREB phosphorylation. In the clinic, PMC׳s of treated patients showed upregulation of mRNA expression and protein levels of BDNF, CREB and AKT after addition of fluvoxamine. Analyses of PMC genes and proteins showed significant inter-correlations and some gene changes correlated with improvement in negative and cognitive symptoms. Our study provides new knowledge of the molecular mechanisms of symptom amelioration in schizophrenia and may advance development of new drugs for this disease and other neuropsychiatric disorders.

Acute and chronic effects of noradrenergic enhancement on transcranial direct current stimulation-induced neuroplasticity in humans

KEY POINTS

Chronic administration of the selective noradrenaline reuptake inhibitor (NRI) reboxetine (RBX) increased and prolonged the long-term potentiation-like plasticity induced by anodal transcranial direct current stimulation (tDCS) for over 24 h. Chronic administration of RBX converted cathodal tDCS-induced long-term depression-like plasticity into facilitation for 120 min. Chronic noradrenergic activity enhancement on plasticity of the human brain might partially explain the delayed therapeutic impact of selective NRIs in depression and other neuropsychiatric diseases.

ABSTRACT

Noradrenaline affects cognition and motor learning processes via its impact on long-term potentiation (LTP) and depression (LTD). We aimed to explore the impact of single dose and chronic administration of the selective noradrenaline reuptake inhibitor (NRI) reboxetine (RBX) on plasticity induced by transcranial direct current stimulation (tDCS) in healthy humans via a double-blinded, placebo-controlled, randomized crossover study. Sixteen healthy volunteers received placebo or single dose RBX (8 mg) before anodal or cathodal tDCS of the primary motor cortex. Afterwards, the same subjects took RBX (8 mg day-1 ) consecutively for 21 days. During this period, two additional interventions were performed (RBX with anodal or cathodal tDCS), to explore the impact of chronic RBX treatment on plasticity. Plasticity was monitored by motor-evoked potential amplitudes elicited by transcranial magnetic stimulation. Chronic administration of RBX increased and prolonged the LTP-like plasticity induced by anodal tDCS for over 24 h. Chronic RBX significantly converted cathodal tDCS-induced LTD-like plasticity into facilitation, as compared to the single dose condition, for 120 min after stimulation. The results show a prominent impact of chronic noradrenergic enhancement on plasticity of the human brain that might partially explain the delayed therapeutic impact of selective NRIs in depression and other neuropsychiatric diseases.

Electroacupuncture Alleviates Depressive-Like Symptoms and Modulates BDNF Signaling in 6-Hydroxydopamine Rats

Previous studies have identified the beneficial effects of electroacupuncture (EA) on motor behaviors in Parkinson's disease (PD). However, the role and potential mechanisms of EA in PD-associated depression remain unclear. In the present study, a rat model of PD with unilateral 6-hydroxydopamine (6-OHDA) lesions in the medial forebrain bundle was treated using EA for 4 weeks. We found that 100 Hz EA improved several motor phenotypes. In addition, tyrosine hydroxylase (TH) immunohistochemical analysis showed that EA had a minimal impact on the TH-positive profiles of the ipsilateral ventral tegmental area. Compared with the 6-OHDA group, long-term EA stimulation significantly increased sucrose solution consumption and decreased immobility time in the forced swim test. EA treatment did not alter dopamine, norepinephrine, and serotonin levels in the striatum and hippocampus. Noticeably, EA treatment reversed the 6-OHDA-induced abnormal expression of brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) in the midbrain and hippocampus. These results demonstrate that EA at 100-Hz possesses the ability to improve depressive-like symptoms in PD rats, which is, at least in part, due to the distinct effect of EA on the mesostriatal and mesocorticolimbic dopaminergic pathways. Moreover, BDNF seems to participate in the effect of EA in PD.

Brain-derived neurotrophic factor in mood disorders and antidepressant treatments

Levels of brain-derived neurotrophic factor (BDNF) are reduced in the brain and serum of depressed patients and at least the reduction in serum levels is reversible upon successful treatment. These data, together with a wealth of reports using different animal models with depression-like behavior or manipulation of expression of BDNF or its receptor TrkB have implicated BDNF in the pathophysiology of depression as well as in the mechanism of action of antidepressant treatments. Recent findings have shown that posttranslational processing of BDNF gene product can yield different molecular entities that differently influence signaling through BNDF receptor TrkB and the pan-neurotrophin receptor p75^NTR. We will here review these data and discuss new insights into the possible pathophysiological roles of those new BDNF subtypes as well as recent findings on the role of BDNF mediated neuronal plasticity in mood disorders and their treatments.

Different interventions for post-ischaemic stroke depression in different time periods: a single-blind randomized controlled trial with stratification by time after stroke

OBJECTIVE

To determine the appropriate treatments for post-ischaemic stroke depression at different times after stroke.

DESIGN

A single-blind, randomized, controlled trial that compared three intervention groups, with subgroups stratified by time after stroke.

SETTING

Outpatient clinic.

SUBJECTS

Eligible patients were recruited at discharge ( n = 73) and three ( n = 67), six ( n = 65), and nine months ( n = 69) after discharge, and patients completed mood questionnaires.

INTERVENTIONS

Patients were randomly distributed into three groups: Group A received placebos and participated in general discussions; Group B, received citalopram and participated in general discussions; and Group C, received placebos and underwent cognitive behavioural therapy. All three groups participated in rehabilitation during three months of follow-up.

MAIN MEASURES

Outcome was assessed three months after baseline using the 17-item Hamilton Depression Scale (HAMD₁₇) and the Bech-Rafaelsen Melancholia Scale (MES). During treatment, the Udvalg for Kliniske Undersogelser side-effect scale was also administered.

RESULTS

When stratification was not considered, the scores of Group B on the Melancholia Scale were lower than those of Group A ( P = 0.02); when the four time-based subgroups were analysed, significant differences were observed between Groups A and B (P_MES = 0.02, P_HAMD17 = 0.02) in the group recruited six months after discharge and between Groups A and C (P_MES = 0.01) in the last time period nine months after discharge.

CONCLUSIONS

The effects of citalopram or cognitive behavioural therapy is similar to the effect of rehabilitation alone for early-onset post-ischaemic depression; rehabilitation and citalopram for delayed-onset post-ischaemic depression; and rehabilitation and cognitive behavioural therapy for late-onset post-ischaemic depression are more effective than rehabilitation alone.

Venlafaxine treatment after endothelin-1-induced cortical stroke modulates growth factor expression and reduces tissue damage in rats

Neuromodulators, such as antidepressants, may contribute to neuroprotection by modulating growth factor expression to exert anti-inflammatory effects and to support neuronal plasticity after stroke. Our objective was to study whether early treatment with venlafaxine, a serotonin-norepinephrine reuptake inhibitor, modulates growth factor expression and positively contributes to reducing the volume of infarcted brain tissue resulting in increased functional recovery. We studied the expression of BDNF, FGF2 and TGF-β1 by examining their mRNA and protein levels and cellular distribution using quantitative confocal microscopy at 5 days after venlafaxine treatment in control and infarcted brains. Venlafaxine treatment did not change the expression of these growth factors in sham rats. In infarcted rats, BDNF mRNA and protein levels were reduced, while the mRNA and protein levels of FGF2 and TGF-β1 were increased. Venlafaxine treatment potentiated all of the changes that were induced by cortical stroke alone. In particular, increased levels of FGF2 and TGF-β1 were observed in astrocytes at 5 days after stroke induction, and these increases were correlated with decreased astrogliosis (measured by GFAP) and increased synaptophysin immunostaining at twenty-one days after stroke in venlafaxine-treated rats. Finally, we show that venlafaxine reduced infarct volume after stroke resulting in increased functional recovery, which was measured using ladder rung motor tests, at 21 days after stroke. Our results indicate that the early oral administration of venlafaxine positively contributes to neuroprotection during the acute and late events that follow stroke.

Vortioxetine promotes early changes in dendritic morphology compared to fluoxetine in rat hippocampus

Preclinical studies reveal that the multimodal antidepressant vortioxetine enhances long-term potentiation and dendritic branching compared to a selective serotonin reuptake inhibitor (SSRI). In the present study, we investigated vortioxetine׳s effects on spines and dendritic morphology in rat hippocampus at two time points compared to the SSRI, fluoxetine. Rats were dosed for 1 and 4 weeks with vortioxetine and fluoxetine at doses relevant for antidepressant activity. Dendritic morphology of pyramidal neurons (i.e., dendritic length, dendritic branch, spine number and density, and Sholl analysis) was examined in Golgi-stained sections from hippocampal CA1. After 1 week of treatment, vortioxetine significantly increased spine number (apical and basal dendrites), spine density (only basal), dendritic length (only apical), and dendritic branch number (apical and basal), whereas fluoxetine had no effect. After 4 weeks of treatment, vortioxetine significantly increased all measures of dendritic spine morphology as did fluoxetine except for spine density of basal dendrites. The number of intersections in the apical and basal dendrites was also significantly increased for both treatments after 4 weeks compared to control. In addition, 4 weeks of vortioxetine treatment, but not fluoxetine, promoted a decrease in spine neck length. In conclusion, 1-week vortioxetine treatment induced changes in spine number and density and dendritic morphology, whereas an equivalent dose of fluoxetine had no effects. Decreased spine neck length following 4-week vortioxetine treatment suggests a transition to mature spine morphology. This implies that vortioxetine׳s effects on spine and dendritic morphology are mediated by mechanisms that go beyond serotonin reuptake inhibition.

Changes in serotonin (5-HT) and brain-derived neurotrophic factor (BDFN) expression in frontal cortex and hippocampus of aged rat treated with high tryptophan diet

Age-related cognitive decline is accompanied by an alteration in neurotransmitter synthesis and a dysregulation of neuroplasticity-related molecules such as serotonin (5-HT) and brain-derived neurotrophic factor (BDFN). It has been previously demonstrated that hyperserotonemia induced by l-Tryptophan (TrP) enriched diet protect against memory deficits during physiological aging. Since 5-HT is closely associated to BDNF, we aimed to investigate the effect of high TrP diet on 5-HT levels and BDNF expression in Frontal Cortex (FC) and Hippocampus (Hp) of aged rats. We found that the raising of systemic 5-HT levels by chronic diet (1 month) containing high TrP significantly prevents age-related decline of BDNF protein expression in both brain areas as indicated by ELISA and Western Blot analyses. Interestingly, immunohistochemical analyses confirmed that high TrP diet significantly elevates the number of 5-HT immunoreactive fibers in both brain areas tested and this correlated with BDNF increase in the FC and hippocampal regions CA1, CA2, CA3 and a strikingly down-regulation of neurotrophin levels in the dentate gyrus (DG) of aged rats. Altogether, these finding provide evidence that enhanced TrP intake and the consequent increase in 5-HT neurotransmission may act as a modulator of BDNF system suggesting a possible mechanism for the protective role of serotonergic system on memory impairment occurring along normal aging process.

Effects of doxepin on brain-derived neurotrophic factor, tumor necrosis factor alpha, mitogen-activated protein kinase 14, and AKT1 genes expression in rat hippocampus

BACKGROUND

It has been suggested that doxepin in addition to enhancement of noradrenaline and serotonin levels may have neuroprotective effects. Therefore, this study investigated the effect of doxepin on gene expression of brain-derived neurotrophic factor (BDNF), tumor necrosis factor alpha (TNF-α), mitogen-activated protein kinase 14 (MAPK14), and serine-threonine protein kinase AKT1 in rat hippocampus.

MATERIALS AND METHODS

Male rats were divided randomly into three groups: Control, doxepin 1 mg/kg, and doxepin 5 mg/kg. Rats received an i.p injection of doxepin for 21 days. Then the hippocampi were dissected for the measurement of the expression of BDNF, TNF-α, MAPK14, and AKT1 genes.

RESULTS

Our results showed no significant effects of doxepin on gene expression of BDNF, TNF-α, MAPK14, and AKT1 genes in the hippocampus.

CONCLUSIONS

These results did not show significant effects of doxepin on the genes that affect the neuronal survival in intact animals. However, more studies need to be done, especially in models associated with neuronal damage.

Epigenetic mechanisms underlying the role of brain-derived neurotrophic factor in depression and response to antidepressants

Major depressive disorder (MDD) is a devastating neuropsychiatric disorder encompassing a wide range of cognitive and emotional dysfunctions. The prevalence of MDD is expected to continue its growth to become the second leading cause of disease burden (after HIV) by 2030. Despite an extensive research effort, the exact etiology of MDD remains elusive and the diagnostics uncertain. Moreover, a marked inter-individual variability is observed in the vulnerability to develop depression, as well as in response to antidepressant treatment, for nearly 50% of patients. Although a genetic component accounts for some cases of MDD, it is now clearly established that MDD results from strong gene and environment interactions. Such interactions could be mediated by epigenetic mechanisms, defined as chromatin and DNA modifications that alter gene expression without changing the DNA structure itself. Some epigenetic mechanisms have recently emerged as particularly relevant molecular substrates, promoting vulnerability or resilience to the development of depressive-like symptoms. Although the role of brain-derived neurotrophic factor (BDNF) in the pathophysiology of MDD remains unclear, its modulation of the efficacy of antidepressants is clearly established. Therefore, in this review, we focus on the epigenetic mechanisms regulating the expression of BDNF in humans and in animal models of depression, and discuss their role in individual differences in vulnerability to depression and response to antidepressant drugs.

The FOCUS, AFFINITY and EFFECTS trials studying the effect(s) of fluoxetine in patients with a recent stroke: a study protocol for three multicentre randomised controlled trials

Background

Several small trials have suggested that fluoxetine improves neurological recovery from stroke. FOCUS, AFFINITY and EFFECTS are a family of investigator-led, multicentre, parallel group, randomised, placebo-controlled trials that aim to determine whether routine administration of fluoxetine (20 mg daily) for 6 months after acute stroke improves patients’ functional outcome.

Methods/Design

The three trial investigator teams have collaboratively developed a core protocol. Minor variations have been tailored to the national setting in the UK (FOCUS), Australia and New Zealand (AFFINITY) and Sweden (EFFECTS). Each trial is run and funded independently and will report its own results. A prospectively planned individual patient data meta-analysis of all three trials will subsequently provide the most precise estimate of the overall effect of fluoxetine after stroke and establish whether any effects differ between trials and subgroups of patients.

The trials include patients ≥18 years old with a clinical diagnosis of stroke, persisting focal neurological deficits at randomisation between 2 and 15 days after stroke onset. Patients are randomised centrally via web-based randomisation systems using a common minimisation algorithm. Patients are allocated fluoxetine 20 mg once daily or matching placebo capsules for 6 months. Our primary outcome measure is the modified Rankin scale (mRS) at 6 months. Secondary outcomes include the Stroke Impact Scale, EuroQol (EQ5D-5 L), the vitality subscale of the Short-Form 36, diagnosis of depression, adherence to medication, adverse events and resource use. Outcomes are collected at 6 and 12 months. The methods of collecting these data are tailored to the national setting. If FOCUS, AFFINITY and EFFECTS combined enrol 6000 participants as planned, they would have 90 % power (alpha 5 %) to detect a common odds ratio of 1.16, equivalent to a 3.7 % absolute difference in percentage with mRS 0–2 (44.0 % to 47.7 %). This is based on an ordinal analysis of mRS adjusted for baseline variables included in the minimisation algorithm.

Discussion

If fluoxetine is safe and effective in promoting functional recovery, it could be rapidly, widely and affordably implemented in routine clinical practice and reduce the burden of disability due to stroke.

Trial registration

FOCUS: ISRCTN83290762 (23/05/2012), AFFINITY: ACTRN12611000774921 (22/07/2011). EFFECTS: ISRCTN13020412 (19/12/2014).

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-015-0864-1) contains supplementary material, which is available to authorized users.