Stress and trauma: BDNF control of dendritic-spine formation and regression. Prog Neurobiol. 2014;112:80-99. [PMID: 24211850 DOI: 10.1016/j.pneurobio.2013.10.005]

Hepatic kynurenic acid mediates phosphorylation of Nogo-A in the medial prefrontal cortex to regulate chronic stress-induced anxiety-like behaviors in mice

Exercise training effectively relieves anxiety disorders via modulating specific brain networks. The role of post-translational modification of proteins in this process, however, has been underappreciated. Here we performed a mouse study in which chronic restraint stress-induced anxiety-like behaviors can be attenuated by 14-day persistent treadmill exercise, in association with dramatic changes of protein phosphorylation patterns in the medial prefrontal cortex (mPFC). In particular, exercise was proposed to modulate the phosphorylation of Nogo-A protein, which drives the ras homolog family member A (RhoA)/ Rho-associated coiled-coil-containing protein kinases 1(ROCK1) signaling cascade. Further mechanistic studies found that liver-derived kynurenic acid (KYNA) can affect the kynurenine metabolism within the mPFC, to modulate this RhoA/ROCK1 pathway for conferring stress resilience. In sum, we proposed that circulating KYNA might mediate stress-induced anxiety-like behaviors via protein phosphorylation modification within the mPFC, and these findings shed more insights for the liver-brain communications in responding to both stress and physical exercise.

Protective role of TRPV2 in synaptic plasticity through the ERK1/2-CREB-BDNF pathway in chronic unpredictable mild stress rats

PURPOSE

Chronic stress is a significant risk factor for mood disorders such as depression, where synaptic plasticity plays a central role in pathogenesis. Transient Receptor Potential Vanilloid Type-2 (TRPV2) Ion Channels are implicated in hypothalamic-pituitary-adrenal axis disorders. Previous proteomic analysis indicated a reduction in TRPV2 levels in the chronic unpredictable mild stress (CUMS) rat model, yet its role in synaptic plasticity during depression remains to be elucidated. This study aims to investigate TRPV2's role in depression and its underlying mechanisms.

METHODS

In vivo and in vitro experiments were conducted using the TRPV2-specific agonist probenecid and ERK1/2 inhibitors SCH772984. In vivo, rats underwent six weeks of CUMS before probenecid administration. Depressive-like behaviors were assessed through behavioral tests. ELISA kits measured 5-HT, DA, NE levels in rat hippocampal tissues. Hippocampal morphology was examined via Nissl staining. In vitro, rat hippocampal neuron cell lines were treated with ERK1/2 inhibitors SCH772984 and probenecid. Western blot, immunofluorescence, immunohistochemical staining, and RT-qPCR assessed TRPV2 expression, neurogenesis-related proteins, synaptic markers, and ERK1/2-CREB-BDNF signaling proteins.

RESULTS

Decreased hippocampal TRPV2 levels were observed in CUMS rats. Probenecid treatment mitigated depressive-like behavior and enhanced hippocampal 5-HT, NE, and DA levels in CUMS rats. TRPV2 activation countered CUMS-induced synaptic plasticity inhibition. Probenecid activated the ERK1/2-CREB-BDNF pathway, suggesting TRPV2's involvement in this pathway via ERK1/2.

CONCLUSION

These findings indicate that TRPV2 activation offers protective effects against depressive-like behaviors and enhances hippocampal synaptic plasticity in CUMS rats via the ERK1/2-CREB-BDNF pathway. TRPV2 emerges as a potential therapeutic target for depression.

Targeting the postsynaptic scaffolding protein PSD-95 enhances BDNF signaling to mitigate depression-like behaviors in mice

Signaling mediated by brain-derived neurotrophic factor (BDNF), which is supported by the postsynaptic scaffolding protein PSD-95, has antidepressant effects. Conversely, clinical depression is associated with reduced BDNF signaling. We found that peptidomimetic compounds that bind to PSD-95 promoted signaling by the BDNF receptor TrkB in the hippocampus and reduced depression-like behaviors in mice. The compounds CN2097 and Syn3 both bind to the PDZ3 domain of PSD-95, and Syn3 also binds to an α-helical region of the protein. Syn3 reduced depression-like behaviors in two mouse models of stress-induced depression; CN2097 had similar but less potent effects. In hippocampal neurons, application of Syn3 enhanced the formation of TrkB-Gαi1/3-PSD-95 complexes and potentiated downstream PI3K-Akt-mTOR signaling. In mice subjected to chronic mild stress (CMS), systemic administration of Syn3 reversed the CMS-induced, depression-associated changes in PI3K-Akt-mTOR signaling, dendrite complexity, spine density, and autophagy in the hippocampus and reduced depression-like behaviors. Knocking out Gαi1/3 in hippocampal neurons prevented the therapeutic effects of Syn3, indicating dependence of these effects on the TrkB pathway. The findings suggest that compounds that induce the formation of PSD-95-TrkB complexes have therapeutic potential to alleviate depression.

Synergistic effects of citicoline and silymarin nanomicelles in restraint stress-exposed mice

This study evaluated the effects of citicoline and silymarin nanomicelles (SMnm) in repeated restraint stress (RRS).

METHOD

Mice were exposed to RRS for four consecutive days, 2 hrs. daily. On day 5 of the study, SMnm (25 and 50 mg/kg, i.p.) and citicoline (25 and 75 mg/kg), and a combination of them (25 mg/kg, i.p.) were initiated. On day 18, anxiety-like behavior, behavioral despair, and exploratory behavior were evaluated. The prefrontal cortex (PFC) and the hippocampus were dissected measuring brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), and tumor necrosis factor-alpha (TNF-α) through Western Blot and ELISA, respectively.

RESULTS

In RR-exposed mice, anxiety-like behavior in the elevated plus maze (EPM) was enhanced by reductions in open arm time (OAT%) P < 0.001, and open arm entry (OAE%) P < 0.001. In the forced swimming test (FST), the immobility increased P < 0.001 while the swimming and climbing reduced P < 0.001. In the open field test (OFT), general motor activity was raised P < 0.05. Further, body weights reduced P < 0.001, and tissue BDNF and pCREB expressions decreased P < 0.001 while TNF-α increased P < 0.001. Conversely, SMnm, citicoline and their combination could reduce anxiety-like behavior P < 0.001. The combination group reduced the depressive-like behaviors P < 0.001. Moreover, body weights were restored P < 0.001. Besides, BDNF and pCREB expressions increased while TNF-α reduced, P < 0.001.

CONCLUSION

The combination synergistically improved emotion-like behaviors, alleviating the inflammation and upregulating the hippocampal BDNF-mediated CREB signaling pathway.

The genomic landscape of mammal domestication might be orchestrated by selected transcription factors regulating brain and craniofacial development

Domestication transforms once wild animals into tamed animals that can be then exploited by humans. The process entails modifications in the body, cognition, and behavior that are essentially driven by differences in gene expression patterns. Although genetic and epigenetic mechanisms were shown to underlie such differences, less is known about the role exerted by trans-regulatory molecules, notably transcription factors (TFs) in domestication. In this paper, we conducted extensive in silico analyses aimed to clarify the TF landscape of mammal domestication. We first searched the literature, so as to establish a large list of genes selected with domestication in mammals. From this list, we selected genes experimentally demonstrated to exhibit TF functions. We also considered TFs displaying a statistically significant number of targets among the entire list of (domestication) selected genes. This workflow allowed us to identify 5 candidate TFs (SOX2, KLF4, MITF, NR3C1, NR3C2) that were further assessed in terms of biochemical and functional properties. We found that such TFs-of-interest related to mammal domestication are all significantly involved in the development of the brain and the craniofacial region, as well as the immune response and lipid metabolism. A ranking strategy, essentially based on a survey of protein-protein interactions datasets, allowed us to identify SOX2 as the main candidate TF involved in domestication-associated evolutionary changes. These findings should help to clarify the molecular mechanics of domestication and are of interest for future studies aimed to understand the behavioral and cognitive changes associated to domestication.

Occupational stress is associated with sex and subregion specific modifications of the amygdala volumes

Background: Despite the rapid increase in reports of exhaustion syndrome (ES) due to daily occupational stress, the mechanisms underlying ES are unknown. In the present study, we investigated whether occupational ES is associated with specific modifications of the subfields of the amygdala and hippocampus resembling those described in other chronic stress conditions. Special focus was paid to possible sex differences.Methods: As a follow up to our previous studies of occupational ES, we carried out MRI-based subfield segmentation of the hippocampus and amygdala volumes in 58 patients with occupational ES (22 males) and 65 age-matched controls (27 males) (age range 30-46 years).Results: There was a significant and bilateral enlargement of the lateral, basal and central nucleus of the amygdala in patients with ES (corrected for the total intracranial volume (ICV)). These differences were detected only in females. Higher values in the right central and right basal amygdala remained when the whole amygdala volume was used as reference, instead of the ICV. Notably, in female patients the volumes of these specific nuclei were positively correlated with the degree of perceived stress. No changes in the hippocampus subfields were detected in female or male patients.Conclusions: The findings underline that ES is a chronic stress condition, suggesting that not only extreme forms of stress, but also the everyday stress is associated with localized differences from controls in the amygdala. The absence of significant alterations among men with ES despite a similar degree of perceived stress supports the notion that women seem more susceptible to stress-related cerebral changes, and may explain the higher prevalence of ES among women.

Effect of consumption of blue maize tortilla on anxiety-like behaviour, learning, memory and hippocampal BDNF expression in a chronic stress model in rats

BACKGROUND

Pigmented maize consumption is of much interest because of its high anthocyanin content and multiple health benefits.

OBJETIVES

This study was aimed to assess the effect of consuming blue maize tortillas on the anxiolytic capacity, preserve emotional memory, and the expression of brain-derived neurotrophic factor (BDNF) in rats subjected to chronic stress.

METHODS

Sixty-four 3-month-old male Wistar rats were used, divided into eight groups (n = 8). Four groups were subjected to chronic stress by movement restriction (7 h/daily/7 consecutive days) and the remaining four groups were subjected to standard management. The treatments were commercial food, blue tortilla, anthocyanin extract, or white tortilla, administered for nine weeks to stressed or unstressed animals. In the eighth week, the animals were subjected to the restraint stress model. Subsequently, anxiety-like behaviour was assessed using the elevated plus-maze, and memory and emotional learning were evaluated by the step-down passive avoidance test. The animals were then sacrificed to quantify the relative expression of hippocampal BDNF by RT-qPCR.

RESULTS

The consumption of anthocyanin extract or tortilla made with blue corn decreased anxiety-like behaviours, additionally, it improved the ability to retain emotionally relevant information, and it upregulated BDNF mRNA expression.

PERSPECTIVE

Thus, the analyse of the impact of blue tortilla consumption on the nervous system is now necessary to guarantee the nutraceutical value of this food.

DNA methylation and the opposing NMDAR dysfunction in schizophrenia and major depression disorders: a converging model for the therapeutic effects of psychedelic compounds in the treatment of psychiatric illness

Psychedelic compounds are being increasingly explored as a potential therapeutic option for treating several psychiatric conditions, despite relatively little being known about their mechanism of action. One such possible mechanism, DNA methylation, is a process of epigenetic regulation that changes gene expression via chemical modification of nitrogenous bases. DNA methylation has been implicated in the pathophysiology of several psychiatric conditions, including schizophrenia (SZ) and major depressive disorder (MDD). In this review, we propose alterations to DNA methylation as a converging model for the therapeutic effects of psychedelic compounds, highlighting the N-methyl D-aspartate receptor (NMDAR), a crucial mediator of synaptic plasticity with known dysfunction in both diseases, as an example and anchoring point. We review the established evidence relating aberrant DNA methylation to NMDAR dysfunction in SZ and MDD and provide a model asserting that psychedelic substances may act through an epigenetic mechanism to provide therapeutic effects in the context of these disorders.

Cannabidiol Modulates Emotional Function and Brain-Derived Neurotrophic Factor Expression in Middle-Aged Female Rats Exposed to Social Isolation

Aging is associated with changes in cognitive and emotional function. Cannabidiol (CBD) has been reported to attenuate stress and anxiety in human and animal studies. In this study, we aimed to assess the therapeutic potential of CBD among middle-aged female rats exposed to social isolation (SI) and the potential involvement of brain-derived neurotrophic factor (BDNF) in these effects. Thirteen-month-old female rats were group-housed (GH) or exposed to social isolation (SI) and treated with vehicle or CBD (10 mg/kg). CBD restored the SI-induced immobility in the forced swim test and the SI-induced decrease in the expression of BDNF protein levels in the nucleus accumbens (NAc). CBD also increased the time that rats spent in the center in an open field, improved spatial training, and increased BDNF expression in the medial prefrontal cortex (mPFC) and basolateral amygdala (BLA). BDNF expression was found to be correlated with an antidepressant (in the NAc) and an anxiolytic (in the mPFC, BLA, NAc) phenotype, and with learning improvement in the PFC. Together, our results suggest that CBD may serve as a beneficial agent for wellbeing in old age and may help with age-related cognitive decline.

Interpersonal early adversity demonstrates dissimilarity from early socioeconomic disadvantage in the course of human brain development: A meta-analysis

It has been established that early-life adversity impacts brain development, but the role of development itself has largely been ignored. We take a developmentally-sensitive approach to examine the neurodevelopmental sequelae of early adversity in a preregistered meta-analysis of 27,234 youth (birth to 18-years-old), providing the largest group of adversity-exposed youth to date. Findings demonstrate that early-life adversity does not have an ontogenetically uniform impact on brain volumes, but instead exhibits age-, experience-, and region-specific associations. Relative to non-exposed comparisons, interpersonal early adversity (e.g., family-based maltreatment) was associated with initially larger volumes in frontolimbic regions until ∼10-years-old, after which these exposures were linked to increasingly smaller volumes. By contrast, socioeconomic disadvantage (e.g., poverty) was associated with smaller volumes in temporal-limbic regions in childhood, which were attenuated at older ages. These findings advance ongoing debates regarding why, when, and how early-life adversity shapes later neural outcomes.

Amygdala subfield and prefrontal cortex abnormalities in patients with functional seizures

BACKGROUND

Functional seizures (FS) are paroxysmal episodes, resembling epileptic seizures, but without underlying epileptic abnormality. The aetiology and neuroanatomic associations are incompletely understood. Recent brain imaging data indicate cerebral changes, however, without clarifying possible pathophysiology. In the present study, we specifically investigated the neuroanatomic changes in subregions of the amygdala and hippocampus in FS.

METHODS

T1 MRI scans of 37 female patients with FS and 37 age-matched female seizure naïve controls (SNC) were analyzed retrospectively in FreeSurfer version 7.1. Seizure naïve controls included patients with depression and anxiety disorders. The analysis included whole-brain cortical thickness, subcortical volumes, and subfields of the amygdala and hippocampus. Group comparisons were carried out using multivariable linear models.

RESULTS

The FS and SNC groups did not differ in the whole hippocampus and amygdala volumes. However, patients had a significant reduction of the right lateral amygdala volume (p = 0.00041), an increase of the right central amygdala, (p = 0.037), and thinning of the left superior frontal gyrus (p = 0.024). Additional findings in patients were increased volumes of the right medial amygdala (p = 0.031), left anterior amygdala (p = 0.017), and left dentate gyrus of the hippocampus (p = 0.035).

CONCLUSIONS

The observations from the amygdala and hippocampus segmentation affirm that there are neuroanatomic associations of FS. The pattern of these changes aligned with some of the cerebral changes described in chronic stress conditions and depression. The pattern of detected changes further study, and may, after validation, provide biomarkers for diagnosis and treatment.

(2R,6R)-hydroxynorketamine improves PTSD-associated behaviors and structural plasticity via modulating BDNF-mTOR signaling in the nucleus accumbens

BACKGROUND

Post-traumatic stress disorder (PTSD) is a mental illness caused by either experiencing or observing a traumatic event that is perceived to pose a serious risk to one's life. (2R,6R)-HNK has an alleviating effect on negative emotions, nevertheless, the mechanism of (2R,6R)-HNK action is unclear.

METHODS

In this study, the single prolonged stress and electric foot shock (SPS&S) method was used to establish a rat model of PTSD. After determining the validity of the model, (2R,6R)-HNK was administered to the NAc by microinjection using a concentration gradient of 10, 50, and 100 μM, and the effects of the drug in the SPS&S rat model were evaluated. Moreover, our study measured changes in related proteins in the NAc (BDNF, p-mTOR/mTOR, and PSD95) and synaptic ultrastructure.

RESULTS

In the SPS&S group, the protein expression of brain-derived neurotrophic factor (BDNF), mammalian target of rapamycin (mTOR), and PSD95 was reduced and synaptic morphology was damaged in the NAc. In contrast, after the administration of 50 μM (2R,6R)-HNK, SPS&S-treated rats improved their exploration and depression-linked behavior, while protein levels and synaptic ultrastructure were also restored in the NAc. With the administration of 100 μM (2R,6R)-HNK, locomotor behavior, and social interaction improved in the PTSD model.

LIMITATIONS

The mechanism of BDNF-mTOR signaling after (2R,6R)-HNK administration was not explored.

CONCLUSION

(2R,6R)-HNK may ameliorate negative mood and social avoidance symptoms in PTSD rats by regulating BDNF/mTOR-mediated synaptic structural plasticity in the NAc, providing new targets for the development of anti-PTSD drugs.

The Role of BDNF as a Biomarker in Cognitive and Sensory Neurodegeneration

Brain-derived neurotrophic factor (BDNF) has a crucial function in the central nervous system and in sensory structures including olfactory and auditory systems. Many studies have highlighted the protective effects of BDNF in the brain, showing how it can promote neuronal growth and survival and modulate synaptic plasticity. On the other hand, conflicting data about BDNF expression and functions in the cochlear and in olfactory structures have been reported. Several clinical and experimental research studies showed alterations in BDNF levels in neurodegenerative diseases affecting the central and peripheral nervous system, suggesting that BDNF can be a promising biomarker in most neurodegenerative conditions, including Alzheimer's disease, shearing loss, or olfactory impairment. Here, we summarize current research concerning BDNF functions in brain and in sensory domains (olfaction and hearing), focusing on the effects of the BDNF/TrkB signalling pathway activation in both physiological and pathological conditions. Finally, we review significant studies highlighting the possibility to target BDNF as a biomarker in early diagnosis of sensory and cognitive neurodegeneration, opening new opportunities to develop effective therapeutic strategies aimed to counteract neurodegeneration.

Associations of psychiatric disease and ageing with FKBP5 expression converge on superficial layer neurons of the neocortex

Identification and characterisation of novel targets for treatment is a priority in the field of psychiatry. FKBP5 is a gene with decades of evidence suggesting its pathogenic role in a subset of psychiatric patients, with potential to be leveraged as a therapeutic target for these individuals. While it is widely reported that FKBP5/FKBP51 mRNA/protein (FKBP5/1) expression is impacted by psychiatric disease state, risk genotype and age, it is not known in which cell types and sub-anatomical areas of the human brain this occurs. This knowledge is critical to propel FKBP5/1-targeted treatment development. Here, we performed an extensive, large-scale postmortem study (n = 1024) of FKBP5/1, examining neocortical areas (BA9, BA11 and ventral BA24/BA24a) derived from subjects that lived with schizophrenia, major depression or bipolar disorder. With an extensive battery of RNA (bulk RNA sequencing, single-nucleus RNA sequencing, microarray, qPCR, RNAscope) and protein (immunoblot, immunohistochemistry) analysis approaches, we thoroughly investigated the effects of disease state, ageing and genotype on cortical FKBP5/1 expression including in a cell type-specific manner. We identified consistently heightened FKBP5/1 levels in psychopathology and with age, but not genotype, with these effects strongest in schizophrenia. Using single-nucleus RNA sequencing (snRNAseq; BA9 and BA11) and targeted histology (BA9, BA24a), we established that these disease and ageing effects on FKBP5/1 expression were most pronounced in excitatory superficial layer neurons of the neocortex, and this effect appeared to be consistent in both the granular and agranular areas examined. We then found that this increase in FKBP5 levels may impact on synaptic plasticity, as FKBP5 gex levels strongly and inversely correlated with dendritic mushroom spine density and brain-derived neurotrophic factor (BDNF) levels in superficial layer neurons in BA11. These findings pinpoint a novel cellular and molecular mechanism that has potential to open a new avenue of FKBP51 drug development to treat cognitive symptoms in psychiatric disorders.

Treatment response with ketamine in chronic suicidality: An open label functional connectivity study

BACKGROUND

Ketamine has recently been proposed as a treatment option for suicidality. Whilst its mechanism of action has been explored at molecular levels, the effect on the brain at the organ level remains unclear. Here we investigate immediate post-treatment and prolonged large-scale resting-state neural network changes to elucidate the neuronal underpinnings associated with ketamine's therapeutic effects.

METHODS

Twenty-eight adults (aged 22-72 years) participated in the Oral Ketamine Trial On Suicidality, which is an open-label trial of weekly sub-anaesthetic doses of oral ketamine over 6 weeks. MRI was acquired at baseline, post-treatment, and follow-up. Functional connectivity changes at post-treatment and follow-up were examined using seed based and independent component analysis.

RESULTS

The seed-based connectivity analysis revealed significantly reduced connectivity at post-treatment from the right hippocampus to both right and left superior frontal gyrus, from the left anterior parahippocampus to right superior frontal gyrus, left superior frontal gyrus, right middle frontal gyrus, and left frontal operculum cortex. Compared with baseline, the ICA showed reduced anterior default mode network connectivities to bilateral posterior cingulate cortex, middle and anterior cingulate cortex, lingual gyrus, and cuneus and increased connectivity of the frontoparietal network to the right superior parietal lobule at post-treatment.

LIMITATIONS

Open label pilot study.

CONCLUSIONS

We have shown sub-anaesthetic doses of ketamine alters connectivity in networks which have been shown to be aberrantly hyper-connected in numerous psychiatric conditions. These neurocircuitry changes are supported by significant reductions in suicide ideation. Our results provide support for the use of ketamine as a treatment for suicidality.

Involvement of brain-derived neurotrophic factor methylation in the prefrontal cortex and hippocampus induced by chronic unpredictable mild stress in male mice

Early life stress alters brain-derived neurotrophic factor (BDNF) promoter IV methylation and BDNF expression, which is closely related to the pathophysiological process of depression. However, the role of abnormal methylation of BDNF induced by stress during adolescence due to depression has not yet been clarified. In this study, adolescent mice were exposed to chronic unpredictable mild stress (CUMS). Depression-like behaviors, BDNF promoter IV methylation, expression of DNA methyltransferases (DNMTs), demethylation machinery enzymes, BDNF protein levels, and neuronal development in the prefrontal cortex (PFC) and hippocampus (HIP) were assessed in adolescent and adult mice. The DNMT inhibitor, 5-Aza-2-deoxycytidine (5-AzaD), was used as an intervention. Stress in adolescence induces behavioral dysfunction, elevated methylation levels of BDNF promoter IV, changes in the expression of DNMT, and demethylation machinery enzymes in adolescent and adult mice. Additionally, the stress in adolescence induced lower levels of BDNF and abnormal hippocampal doublecortin (DCX) expression in adolescent and adult mice. However, DNMT inhibitor treatment in adolescent-stressed mice relieved the abnormal behaviors, normalized the methylation level of BDNF promoter IV, BDNF protein expression, expression of DNMTs, and demethylation machinery enzymes, and improved the neuronal development of adult mice. These results suggest that stress in adolescence induces short- and long-term hypermethylation of BDNF promoter IV, which is regulated by DNMTs, and leads to the development of depression.

Interpersonal early adversity demonstrates dissimilarity from early socioeconomic disadvantage in the course of human brain development: A meta-analysis

It has been established that early-life adversity impacts brain development, but the role of development itself has largely been ignored. We take a developmentally-sensitive approach to examine the neurodevelopmental sequelae of early adversity in a preregistered meta-analysis of 27,234 youth (birth to 18-years-old), providing the largest group of adversity-exposed youth to date. Findings demonstrate that early-life adversity does not have an ontogenetically uniform impact on brain volumes, but instead exhibits age-, experience-, and region-specific associations. Relative to non-exposed comparisons, interpersonal early adversity (e.g., family-based maltreatment) was associated with initially larger volumes in frontolimbic regions until ~10-years-old, after which these exposures were linked to increasingly smaller volumes. By contrast, socioeconomic disadvantage (e.g., poverty) was associated with smaller volumes in temporal-limbic regions in childhood, which were attenuated at older ages. These findings advance ongoing debates regarding why, when, and how early-life adversity shapes later neural outcomes.

Targeting Shank3 deficiency and paresthesia in autism spectrum disorder: A brief review

Autism spectrum disorder (ASD) includes a group of multifactorial neurodevelopmental disorders characterized by impaired social communication, social interaction, and repetitive behaviors. Several studies have shown an association between cases of ASD and mutations in the genes of SH3 and multiple ankyrin repeat domain protein 3 (SHANK3). These genes encode many cell adhesion molecules, scaffold proteins, and proteins involved in synaptic transcription, protein synthesis, and degradation. They have a profound impact on all aspects of synaptic transmission and plasticity, including synapse formation and degeneration, suggesting that the pathogenesis of ASD may be partially attributable to synaptic dysfunction. In this review, we summarize the mechanism of synapses related to Shank3 in ASD. We also discuss the molecular, cellular, and functional studies of experimental models of ASD and current autism treatment methods targeting related proteins.

Reduced BDNF expression in the auditory cortex contributed to neonatal pain-induced hearing impairment and dendritic pruning deficiency in mice

INTRODUCTION

Procedural pain in neonates is associated with impaired neurodevelopment. Whether hearing development is impaired, however, remains unknown. This study examined potential cause-and-effect relationship between neonatal pain and subsequent hearing loss in mice.

METHODS

Male C57BL/6J mouse pups received an intra-plantar injection of complete Freund's adjuvant on postnatal day 7 or repetitive needle prick stimuli from postnatal days 0-7. Mechanical and thermal pain thresholds were tested between postnatal days 14 and 49. The auditory brainstem response test was used to determine hearing thresholds. The inner ear structures and dendritic morphology in auditory cortex were assessed using immunofluorescence and Golgi-staining. The effects of oxycodone, tropomyosin receptor kinase B agonists and antagonists were tested.

RESULTS

Neonatal pain resulted in impaired hearing in adulthood of both pain models No damage or synapse loss was found in the cochlea but increased dendritic spine density and reduced brain-derived neurotrophic factor level were found in auditory cortex in neonatal pain group. Oxycodone attenuated hearing loss and the associated changes in dendritic spine density and brain-derived neurotrophic factor changes in auditory cortex. A tropomyosin receptor kinase B agonist reversed neonatal pain-induced hearing impairment and decreased caspase 3 expression in auditory cortex. Administration of tropomyosin receptor kinase B antagonist in naïve mouse pups impaired hearing development suppressed phosphorylated-AKT, and increased caspase 3 expression.

CONCLUSION

Chronic pain during the neonatal period resulted in impaired hearing in adulthood in mice, possibly via the brain-derived neurotrophic factor signaling pathway and dendritic spine pruning deficiency in auditory cortex.

Hippocampus: Molecular, Cellular, and Circuit Features in Anxiety

Anxiety disorders are currently a major psychiatric and social problem, the mechanisms of which have been only partially elucidated. The hippocampus serves as a major target of stress mediators and is closely related to anxiety modulation. Yet so far, its complex anatomy has been a challenge for research on the mechanisms of anxiety regulation. Recent advances in imaging, virus tracking, and optogenetics/chemogenetics have permitted elucidation of the activity, connectivity, and function of specific cell types within the hippocampus and its connected brain regions, providing mechanistic insights into the elaborate organization of the hippocampal circuitry underlying anxiety. Studies of hippocampal neurotransmitter systems, including glutamatergic, GABAergic, cholinergic, dopaminergic, and serotonergic systems, have contributed to the interpretation of the underlying neural mechanisms of anxiety. Neuropeptides and neuroinflammatory factors are also involved in anxiety modulation. This review comprehensively summarizes the hippocampal mechanisms associated with anxiety modulation, based on molecular, cellular, and circuit properties, to provide tailored targets for future anxiety treatment.

Neural Plasticity in the Ventral Tegmental Area, Aversive Motivation during Drug Withdrawal and Hallucinogenic Therapy

Aberrant glutamatergic signaling has been closely related to several pathologies of the central nervous system. Glutamatergic activity can induce an increase in neural plasticity mediated by brain-derived neurotrophic factor (BDNF) in the ventral tegmental area (VTA), a nodal point in the mesolimbic dopamine system. Recent studies have related BDNF dependent plasticity in the VTA with the modulation of aversive motivation to deal with noxious environmental stimuli. The disarray of these learning mechanisms would produce an abnormal augmentation in the representation of the emotional information related to aversion, sometimes even in the absence of external environmental trigger, inducing pathologies linked to mood disorders such as depression and drug addiction. Recent studies point out that serotonin (5-hydroxytryptamine, 5-HT) receptors, especially the 2a (5-HT2a) subtype, play an important role in BDNF-related neural plasticity in the VTA. It has been observed that a single administration of a 5HT2a agonist can both revert an animal to a nondependent state from a drug-dependent state (produced by the chronic administration of a substance of abuse). The 5HT2a agonist also reverted the BDNF-induced neural plasticity in the VTA, suggesting that the administration of 5-HT2a agonists could be used as effective therapeutic agents to treat drug addiction. These findings could explain the neurobiological correlate of the therapeutic use of 5HT2a agonists, which can be found in animals, plants and fungi during traditional medicine ceremonies and rituals to treat mood related disorders.

Habit Formation and the Effect of Repeated Stress Exposures on Cognitive Flexibility Learning in Horses

Horse training exposes horses to an array of cognitive and ethological challenges. Horses are routinely required to perform behaviours that are not aligned to aspects of their ethology, which may delay learning. While horses readily form habits during training, not all of these responses are considered desirable, resulting in the horse being subject to retraining. This is a form of cognitive flexibility and is critical to the extinction of habits and the learning of new responses. It is underpinned by complex neural processes which can be impaired by chronic or repeated stress. Domestic horses may be repeatedly exposed to multiples stressors. The potential contribution of stress impairments of cognitive flexibility to apparent training failures is not well understood, however research from neuroscience can be used to understand horses’ responses to training. We trained horses to acquire habit-like responses in one of two industry-style aversive instrumental learning scenarios (moving away from the stimulus-instinctual or moving towards the stimulus-non-instinctual) and evaluated the effect of repeated stress exposures on their cognitive flexibility in a reversal task. We measured heart rate as a proxy for noradrenaline release, salivary cortisol and serum Brain Derived Neurotrophic Factor (BDNF) to infer possible neural correlates of the learning outcomes. The instinctual task which aligned with innate equine escape responses to aversive stimuli was acquired significantly faster than the non-instinctual task during both learning phases, however contrary to expectations, the repeated stress exposure did not impair the reversal learning. We report a preliminary finding that serum BDNF and salivary cortisol concentrations in horses are positively correlated. The ethological salience of training tasks and cognitive flexibility learning can significantly affect learning in horses and trainers should adapt their practices where such tasks challenge innate equine behaviour.

Protein tyrosine phosphatase 1B (PTP1B) as a potential therapeutic target for neurological disorders

Protein tyrosine phosphatase 1B (PTP1B) is a typical member of the PTP family, considered a direct negative regulator of several receptor and receptor-associated tyrosine kinases. This widely localized enzyme has been involved in the pathophysiology of several diseases. More recently, PTP1B has attracted attention in the field of neuroscience, since its activation in brain cells can lead to schizophrenia-like behaviour deficits, anxiety-like effects, neurodegeneration, neuroinflammation and depression. Conversely, PTP1B inhibition has been shown to prevent microglial activation, thus exerting a potent anti-inflammatory effect and has also shown potential to increase the cognitive process through the stimulation of hippocampal insulin, leptin and BDNF/TrkB receptors. Notwithstanding, most research on the clinical efficacy of targeting PTP1B has been developed in the field of obesity and type 2 diabetes mellitus (TD2M). However, despite the link existing between these metabolic alterations and neurodegeneration, no clinical trials assessing the neurological advantages of PTP1B inhibition have been performed yet. Preclinical studies, though, have provided strong evidence that targeting PTP1B could allow to reach different pathophysiological mechanisms at once. herefore, specific interventions or trials should be designed to modulate PTP1B activity in brain, since it is a promising strategy to decelerate or prevent neurodegeneration in aged individuals, among other neurological diseases. The present paper fails to include all neurological conditions in which PTP1B could have a role; instead, it focuses on those which have been related to metabolic alterations and neurodegenerative processes. Moreover, only preclinical data is discussed, since clinical studies on the potential of PTP1B inhibition for treating neurological diseases are still required.

The Neurobiological Links between Stress and Traumatic Brain Injury: A Review of Research to Date

Neurological dysfunctions commonly occur after mild or moderate traumatic brain injury (TBI). Although most TBI patients recover from such a dysfunction in a short period of time, some present with persistent neurological deficits. Stress is a potential factor that is involved in recovery from neurological dysfunction after TBI. However, there has been limited research on the effects and mechanisms of stress on neurological dysfunctions due to TBI. In this review, we first investigate the effects of TBI and stress on neurological dysfunctions and different brain regions, such as the prefrontal cortex, hippocampus, amygdala, and hypothalamus. We then explore the neurobiological links and mechanisms between stress and TBI. Finally, we summarize the findings related to stress biomarkers and probe the possible diagnostic and therapeutic significance of stress combined with mild or moderate TBI.

Neurobiological Features of Posttraumatic Stress Disorder (PTSD) and Their Role in Understanding Adaptive Behavior and Stress Resilience

Posttraumatic stress disorder (PTSD) has been impacting the functioning of a large number of people in military activities and victims of violence for many generations. However, investments in research aiming to understand the neurobiological aspects of the disorder started relatively late, around the last third of the 20th century. The development of neuroimaging methods has greatly supported further understanding of the structural and functional changes in the re-organization processes of brains with PTSD. This helps to better explain the severity and evolution of behavioral symptoms, and opens the possibilities for identifying individual preexisting structural characteristics that could increase symptom severity and the risk of development. Here, we review the advances in neuroanatomical research on these adaptations in PTSD and discuss how those modifications in prefrontal and anterior cingulate circuitry impact the severity and development of the disorder, detaching the research from an amygdalocentric perspective. In addition, we investigate existing and contradictory evidence regarding the preexisting neurobiological features found mostly in twin studies and voxel-based morphometry (VBM) reports.

Experience-driven plasticity and the emergence of psychopathology: A mechanistic framework integrating development and the environment into the Research Domain Criteria (RDoC) model

Despite the clear importance of a developmental perspective for understanding the emergence of psychopathology across the life-course, such a perspective has yet to be integrated into the Research Domain Criteria (RDoC) model. In this paper, we articulate a framework that incorporates developmentally specific learning mechanisms that reflect experience-driven plasticity as additional units of analysis in the existing RDoC matrix. These include both experience-expectant learning mechanisms that occur during sensitive periods of development and experience-dependent learning mechanisms that may exhibit substantial variation across development. Incorporating these learning mechanisms allows for clear integration not only of development but also environmental experience into the RDoC model. We demonstrate how individual differences in environmental experiences-such as early life adversity-can be leveraged to identify experience-driven plasticity patterns across development and apply this framework to consider how environmental experience shapes key biobehavioral processes that comprise the RDoC model. This framework provides a structure for understanding how affective, cognitive, social, and neurobiological processes are shaped by experience across development and ultimately contribute to the emergence of psychopathology. We demonstrate how incorporating an experience-driven plasticity framework is critical for understanding the development of many processes subsumed within the RDoC model, which will contribute to greater understanding of developmental variation in the etiology of psychopathology and can be leveraged to identify potential windows of heightened developmental plasticity when clinical interventions might be maximally efficacious. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The etiology of poststroke-depression: a hypothesis involving HPA axis

Approximately, one in three ischemic stroke survivors suffered from depression, namely, post-stroke depression (PSD). PSD affects functional rehabilitation and may lead to poor quality of life of patients. There are numerous explanations about the etiologies of PSD. Here, we speculated that PSD are likely to be the result of specific changes in brain pathology. We hypothesized that the stroke-induced hyperactivity of hypothalamic-pituitary-adrenal (HPA) axis plays an important role in PSD. Stroke initiates a complex sequence of events in neuroendocrine system including HPA axis. The HPA axis is involved in the pathophysiology of depression, especially, the overactivity of the HPA axis occurs in major depressive disorder. This review summarizes the possible etiologies of PSD, focusing on the stroke-induced activation of HPA axis, mainly including the stress followed by severe brain damage and the proinflammatory cytokines release. The role of hyperactive of HPA axis in PSD was discussed in detail, which includes the role of high level corticotropin-releasing hormone in PSD, the effects of glucocorticoids on the alterations in specific brain structures, the expression of enzymes, excitotoxicity, the change in intestinal permeability, and the activation of microglia. The relationship between neuroendocrine regulation and inflammation was also described. Finally, the therapy of PSD by regulating HPA axis, neuroendocrine, and immunity was discussed briefly. Nevertheless, the change of HPA axis and the occurring of PSD maybe interact and promote on each other, and future investigations should explore this hypothesis in more depth.

Regulating DNA methylation could reduce neuronal ischemia response and apoptosis after ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion injury (IRI) is an important pathophysiological condition that can cause cell injury and large-scale tissue injury in the nervous system. Previous studies have shown that epigenetic regulation may play a role in the pathogenesis of IRI.

METHODS

In this study, we isolated mouse cortical neurons and constructed an oxygen-glucose deprivation/reoxygenation (OGD) model to explore the change in DNA methylation and its effect on the expression of corresponding genes.

RESULTS

We found that DNA methylation in neurons increased with hypoxia duration and that hypermethylation of numerous promoters and 3'-untranslated regions increased. We performed Gene Ontology enrichment analysis to study gene function and Kyoto Encyclopedia of Genes and Genomes pathway analysis to identify the pathways associated with gene regulation. The results showed that hypermethylation-related genes expressed after OGD were related to physiological pathways such as neuronal projection, ion transport, growth and development, while hypomethylation-related genes were related to pathological pathways such as the external apoptosis signaling pathway, neuronal death regulation, and regulation of oxidative stress. However, the changes in DNA methylation were specific for certain genes and may have been related to OGD-induced neuronal damage. Importantly, we integrated transcription and DNA methylation data to identify several candidate target genes, including hypomethylated Apoe, Pax6, Bmp4, and Ptch1 and hypermethylated Adora2a, Crhr1, Stxbp1, and Tac1. This study further indicated the effect of DNA methylation on gene function in brain IRI from the perspective of epigenetics, and the identified genes may become new targets for achieving neuroprotection in the brain after IRI.

Alteration of Cortical Volume and Thickness in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Myalgic Encephalomyelitis/Chronic fatigue syndrome (ME/CFS) patients suffer from neurocognitive impairment. In this study, we investigated cortical volumetric and thickness changes in ME/CFS patients and healthy controls (HC). We estimated mean surface-based cortical volume and thickness from 18 ME/CFS patients who met International Consensus Criteria (ICC) and 26 HC using FreeSurfer. Vertex-wise analysis showed significant reductions in the caudal middle frontal gyrus (p = 0.0016) and precuneus (p = 0.013) thickness in ME/CFS patients compared with HC. Region based analysis of sub-cortical volumes found that amygdala volume (p = 0.002) was significantly higher in ME/CFS patients compared with HC. We also performed interaction-with-group regressions with clinical measures to test for cortical volume and thickness correlations in ME/CFS with opposite slopes to HC (abnormal). ME/CFS cortical volume and thickness regressions with fatigue, heart-rate variability, heart rate, sleep disturbance score, respiratory rate, and cognitive performance were abnormal. Our study demonstrated different cortical volume and thickness in ME/CFS patients and showed abnormal cortical volume and thickness regressions with key symptoms of ME/CFS patients.

Oral ketamine reduces the experience of stress in people with chronic suicidality

BACKGROUND

Stress is prevalent in people experiencing suicidality and is a major contributor to the development of mental disorders. Evidence suggests ketamine shows capacity to reverse stress-induced brain changes. Though stress and ketamine have been explored individually for suicidality, this study is the first to examine ketamine treatment for self-reported stress in adults with chronic suicidality, building on pre-clinical evidence of ketamine's capacity to normalize stress-induced responses and contributing to our understanding of oral ketamine in clinical populations.

METHODS

Thirty two adult participants (22-72 years; 17 female) with chronic suicidality completed 6 weeks of active treatment, receiving low (0.5 mg/kg - 3.0 mg/kg) doses of oral ketamine once per week, with a 4-week follow-up phase, to assess the effect of ketamine on their perceived stress. Stress was measured via self-report utilizing the Depression Anxiety Stress Scale-21(DASS-21), and analysed at pre-treatment (week 0), post-treatment (week 6) and at follow-up (week 10).

RESULTS

Repeated measures ANOVA showed a significant reduction in stress (p<.001) post-treatment and Reliable Change Index calculations confirmed this to be clinically significant. Furthermore, those classified as 'prolonged responders' demonstrated a sustained reduction in stress at follow-up (i.e. after 4 weeks of nil ketamine).

LIMITATIONS

Small sample size, open label design, expectancy, secondary analysis CONCLUSIONS: Ketamine showed the capacity to produce a robust and sustained improvement in stress symptoms, in people with chronic suicidality. Future larger, controlled studies examining treatment suitability in a range of stress related disorders are warranted.

Human cytomegalovirus IE2 may impair the cognitive ability of the hippocampus through the GluNRs/CaMKIIα/CREB signaling pathway in the Rosa26-LSL-IE2/Cre mouse

Nowadays, there are few studies in vivo to explore the effects of Human Cytomegalovirus (HCMV) single gene such as immediate early protein 2 (IE2) on the nervous system, let alone the mechanism that IE2 causes cognitive impairment. In this study, the Rosa26-LSL-IE2/Cre mouse was used to show the effects of IE2 on the cognitive ability and the GluNRs/CaMKIIα/CREB signaling pathway in the hippocampus. We divided the mice into experimental and control groups based on the results of PCR firstly. After that, the cognitive abilities of the two groups were compared through new object recognition (NOR) and Morris water maze (MWM) tests. The results of the behavioral tests showed that the cognitive ability of the experimental mice was lower than that of the control group. It is known that changes in the expression levels of N-methyl D-aspartate receptor 1, 2A, and 2B (GluN1, GluN2A, GluN2B) affect synaptic plasticity and cause cognitive changes. Finally, we analyzed the expression levels of GluN1, GluN2A, GluN2B, and related signaling pathway molecules by qPCR and western blot. We found that the expression levels of the GluNRs/CaMKIIα/CREB signaling pathway were decreased in the experimental group. These results indicated that IE2 could affect the expression levels of GluNRs/CaMKIIα/CREB signaling pathway, which was closely related to the cognitive impairment of the experimental group. In summary, we used this novel mouse model to show that IE2 could cause cognitive impairment in the hippocampus, which might be related to the GluNRs/CaMKIIα/CREB signaling pathway. It is helpful to further understand the mechanism of the cognitive impairment induced by HCMV IE2.

Administration of brain-derived neurotrophic factor in the ventral tegmental area produces a switch from a nicotine nondependent D1R-mediated motivational state to a nicotine dependent-like D2R-mediated motivational state

Brain-derived neurotrophic factor (BDNF) has been implicated in the transition from a nondependent motivational state to a drug-dependent and -withdrawn motivational state. Chronic nicotine can increase BDNF in the rodent brain and is associated with smoking severity in humans; however, it is unknown whether this increased BDNF is linked functionally to the switch from a nicotine-nondependent to a nicotine-dependent state. We used a place conditioning paradigm to measure the conditioned responses to nicotine, showing that a dose of acute nicotine that nondependent male mice find aversive is found rewarding in chronic nicotine-treated mice experiencing withdrawal. A single BDNF injection in the ventral tegmental area (in the absence of chronic nicotine treatment) caused mice to behave as if they were nicotine-dependent and in withdrawal, switching the neurobiological substrate mediating the conditioned motivational effects from dopamine D1 receptors to D2 receptors. Quantification of gene expression of BDNF and its receptor, tropomyosin-receptor-kinase B (TrkB), revealed an increase in TrkB mRNA but not BDNF mRNA in the VTA in nicotine-dependent and -withdrawn mice. These results suggest that BDNF signaling in the VTA is a critical neurobiological substrate for the transition to nicotine dependence. The modulation of BDNF signaling may be a promising new pharmacological avenue for the treatment of addictive behavior.

Early-Life Stress Reprograms Stress-Coping Abilities in Male and Female Juvenile Rats

Prenatal stress (PS) is a major risk factor for the development of emotional disorders in adulthood that may be mediated by an altered hypothalamic-pituitary-adrenal axis response to stress. Although the early onset of stress-related disorders is recognized as a major public health problem, to date, there are relatively few studies that have examined the incidence of early-life stressors in younger individuals. In this study, we assessed PS impact on the stress-coping response of juvenile offspring in behavioral tests and in the induced molecular changes in the hippocampus. Furthermore, we assessed if pregnancy stress could be driving changes in patterns of maternal behavior during early lactation. We found that PS modified stress-coping abilities of both sex offspring. In the hippocampus, PS increased the expression of bdnf-IV and crfr1 and induced sex difference changes on glucocorticoids and BDNF mRNA receptor levels. PS changed the hippocampal epigenetic landscape mainly in male offspring. Stress during pregnancy enhanced pup-directed behavior of stressed dams. Our study indicates that exposure to PS, in addition to enhanced maternal behavior, induces dynamic neurobehavioral variations at juvenile ages of the offspring that should be considered adaptive or maladaptive, depending on the characteristics of the confronting environment. Our present results highlight the importance to further explore risk factors that appear early in life that will be important to allow timely prevention strategies to later vulnerability to stress-related disorders.

Neuroplasticity and Multilevel System of Connections Determine the Integrative Role of Nucleus Accumbens in the Brain Reward System

A growing body of evidence suggests that nucleus accumbens (NAc) plays a significant role not only in the physiological processes associated with reward and satisfaction but also in many diseases of the central nervous system. Summary of the current state of knowledge on the morphological and functional basis of such a diverse function of this structure may be a good starting point for further basic and clinical research. The NAc is a part of the brain reward system (BRS) characterized by multilevel organization, extensive connections, and several neurotransmitter systems. The unique role of NAc in the BRS is a result of: (1) hierarchical connections with the other brain areas, (2) a well-developed morphological and functional plasticity regulating short- and long-term synaptic potentiation and signalling pathways, (3) cooperation among several neurotransmitter systems, and (4) a supportive role of neuroglia involved in both physiological and pathological processes. Understanding the complex function of NAc is possible by combining the results of morphological studies with molecular, genetic, and behavioral data. In this review, we present the current views on the NAc function in physiological conditions, emphasizing the role of its connections, neuroplasticity processes, and neurotransmitter systems.

Chronic Stress Weakens Connectivity in the Prefrontal Cortex: Architectural and Molecular Changes

Chronic exposure to uncontrollable stress causes loss of spines and dendrites in the prefrontal cortex (PFC), a recently evolved brain region that provides top-down regulation of thought, action, and emotion. PFC neurons generate top-down goals through recurrent excitatory connections on spines. This persistent firing is the foundation for higher cognition, including working memory, and abstract thought. However, exposure to acute uncontrollable stress drives high levels of catecholamine release in the PFC, which activates feedforward calcium-cAMP signaling pathways to open nearby potassium channels, rapidly weakening synaptic connectivity to reduce persistent firing. Chronic stress exposures can further exacerbate these signaling events leading to loss of spines and resulting in marked cognitive impairment. In this review, we discuss how stress signaling mechanisms can lead to spine loss, including changes to BDNF-mTORC1 signaling, calcium homeostasis, actin dynamics, and mitochondrial actions that engage glial removal of spines through inflammatory signaling. Stress signaling events may be amplified in PFC spines due to cAMP magnification of internal calcium release. As PFC dendritic spine loss is a feature of many cognitive disorders, understanding how stress affects the structure and function of the PFC will help to inform strategies for treatment and prevention.

Brain-derived neurotrophic factor upregulates synaptic GluA1 in the amygdala to promote depression in response to psychological stress

Psychological stress impairs neuronal structure and function and leads to emotional disorders, but the underlying mechanisms have not yet been fully elucidated. The amygdala is closely correlated with emotional regulation. In the present study, we analyzed whether the amygdala plasticity is regulated by psychological stress and explored their regulatory mechanism. We established a mouse psychological stress model using an improved communication box, wherein mice were exposed to chronic fear and avoided physical stress interference. After the 14-day psychological stress paradigm, mice exhibited significantly increased depressive behaviors (decreased sucrose consumption in the sucrose preference test and longer immobility time in the forced swimming test). HPLC, ELISA, and molecular and morphological evidences showed that psychological stress increased the content of glutamate and the expression of glutamatergic neurons, upregulated the content of the stress hormone corticosterone, and activated the CREB/BDNF pathway in the amygdala. Furthermore, psychological stress induced an increased density of dendritic spines and LTD impairment in the amygdala. Importantly, virus-mediated silencing of BDNF in the basolateral amygdala (BLA) nuclei reversed the depression-like behaviors and the increase of synaptic GluA1 and its phosphorylation at Ser831 and Ser845 sites in psychologically stressed mice. This process was likely achieved through mTOR signaling activation. Finally, we treated primary amygdala neurons with corticosterone to mimic psychological stress; corticosterone-induced upregulation of GluA1 was prevented by BDNF and mTOR antagonists. Thus, activation of the CREB/BDNF pathway in the amygdala following psychological stress upregulates synaptic GluA1 via mTOR signaling, which dysregulates synaptic plasticity of the amygdala, eventually promoting depression.

Brain Amygdala Volume Increases in Veterans and Active-Duty Military Personnel With Combat-Related Posttraumatic Stress Disorder and Mild Traumatic Brain Injury

OBJECTIVE

To identify amygdalar volumetric differences associated with posttraumatic stress disorder (PTSD) in individuals with comorbid mild traumatic brain injury (mTBI) compared with those with mTBI-only and to examine the effects of intracranial volume (ICV) on amygdala volumetric measures.

SETTING

Marine Corps Base and VA Healthcare System.

PARTICIPANTS

A cohort of veterans and active-duty military personnel with combat-related mTBI (N = 89).

DESIGN

Twenty-nine participants were identified with comorbid PTSD and mTBI. The remaining 60 formed the mTBI-only control group. Structural images of brains were obtained with a 1.5-T MRI scanner using a T1-weighted 3D-IR-FSPGR pulse sequence. Automatic segmentation was performed in Freesurfer.

MAIN MEASURES

Amygdala volumes with/without normalizations to ICV.

RESULTS

The comorbid mTBI/PTSD group had significantly larger amygdala volumes, when normalized to ICV, compared with the mTBI-only group. The right and left amygdala volumes after normalization to ICV were 0.122% ± 0.012% and 0.118% ± 0.011%, respectively, in the comorbid group compared with 0.115% ± 0.012% and 0.112% ± 0.009%, respectively, in the mTBI-only group (corrected P < .05).

CONCLUSIONS

The ICV normalization analysis performed here may resolve previous literature discrepancies. This is an intriguing structural finding, given the role of the amygdala in the challenging neuroemotive symptoms witnessed in casualties of combat-related mTBI and PTSD.

Therapeutic effects of saffron extract on different memory types, anxiety, and hippocampal BDNF and TNF-α gene expressions in sub-chronically stressed rats

Objective: While stress reportedly impairs memory, saffron enhances it. This study investigated the therapeutic effects of saffron extract on different memory types, anxiety-like behavior, and expressions of BDNF and TNF-α genes in sub-chronically stressed rats.Methods: Rats were randomly assigned to control, restraint stress (6 h/day/7 days), two 7-days saffron treatments with 30 and 60 mg/kg, and two stress-saffron groups (30 and 60 mg/kg/7 post-stress days). Serum cortisol level and hippocampal BDNF and TNF-α gene expressions were measured. Open field, passive avoidance, novel object recognition, and object location tests were performed to assess anxiety-like behavior and avoidance as well as cognitive and spatial memories, respectively.Results: The low saffron dose in the sub-chronic stressed group led to a significant increase in passive avoidance latency from day 3 onward whereas this effect was observed after 7 days under the high-dose treatment that simultaneously led to a significant decline in serum cortisol level. While the low saffron dose led to a sharp drop in hippocampal TNF-α gene expression, the high dose significantly increased the hippocampal BDNF gene expression in the sub-chronic stress group. Finally, both saffron doses reduced anxiety in the stressed groups.Conclusion: Compared to the low saffron dose, the high dose had a latent but long-lasting impact. Cognitive and spatial memories remained unaffected by either stress or saffron treatment. In addition, only the high saffron dose reversed anxiety in the sub-chronically stressed group. These findings suggest that various doses of saffron act differently on different brain functions under sub-chronic stress conditions.Abbreviations: Brain derived neurotrophic factor (BDNF), tumor necrosis factor-α (TNF-α), hypothalamic-pituitary-adrenal axis (HPA), novel object recognition task (NORT), novel object location task (NOLT), open field test (OFT), passive avoidance (PA).

Amygdala Circuit Substrates for Stress Adaptation and Adversity

Brain systems that promote maintenance of homeostasis in the face of stress have significant adaptive value. A growing body of work across species demonstrates a critical role for the amygdala in promoting homeostasis by regulating physiological and behavioral responses to stress. This review focuses on an emerging body of evidence that has begun to delineate the contribution of specific long-range amygdala circuits in mediating the effects of stress. After summarizing the major anatomical features of the amygdala and its connectivity to other limbic structures, we discuss recent findings from rodents showing how stress causes structural and functional remodeling of amygdala neuronal outputs to defined cortical and subcortical target regions. We also consider some of the environmental and genetic factors that have been found to moderate how the amygdala responds to stress and relate the emerging preclinical literature to the current understanding of the pathophysiology and treatment of stress-related neuropsychiatric disorders. Future effort to translate these findings to clinics may help to develop valuable tools for prevention, diagnosis, and treatment of these diseases.

Loss of Calretinin in L5a impairs the formation of the barrel cortex leading to abnormal whisker-mediated behaviors

The rodent whisker-barrel cortex system has been established as an ideal model for studying sensory information integration. The barrel cortex consists of barrel and septa columns that receive information input from the lemniscal and paralemniscal pathways, respectively. Layer 5a is involved in both barrel and septa circuits and play a key role in information integration. However, the role of layer 5a in the development of the barrel cortex remains unclear. Previously, we found that calretinin is dynamically expressed in layer 5a. In this study, we analyzed calretinin KO mice and found that the dendritic complexity and length of layer 5a pyramidal neurons were significantly decreased after calretinin ablation. The membrane excitability and excitatory synaptic transmission of layer 5a neurons were increased. Consequently, the organization of the barrels was impaired. Moreover, layer 4 spiny stellate cells were not able to properly gather, leading to abnormal formation of barrel walls as the ratio of barrel/septum size obviously decreased. Calretinin KO mice exhibited deficits in exploratory and whisker-associated tactile behaviors as well as social novelty preference. Our study expands our knowledge of layer 5a pyramidal neurons in the formation of barrel walls and deepens the understanding of the development of the whisker-barrel cortex system.

Cognitive reserve and Alzheimer's biological continuum: clues for prediction and prevention of dementia

Cognitive reserve is originally an epidemiological concept that encompasses individual abilities to cope with changes. It is considered the result of a balance between processes of cellular damage and repair, and its description raised much interest in predicting and preventing cognitive decline in aging and Alzheimer's disease (AD). In this study, we discussed the concept of cognitive reserve considering the recent definition of AD as a biological continuum and suggest that the protection of cognitive reserve may result from efficient synaptic plasticity mechanisms. Despite pathological changes of AD appearing very early during life, long before the onset of cognitive symptoms, different variables act together to keep repair mechanisms effective guaranteeing successful aging if environmental enrichment is maintained.

BDNF Protein and BDNF mRNA Expression of the Medial Prefrontal Cortex, Amygdala, and Hippocampus during Situational Reminder in the PTSD Animal Model

Whether BDNF protein and BDNF mRNA expression of the medial prefrontal cortex (mPFC; cingulated cortex area 1 (Cg1), prelimbic cortex (PrL), and infralimbic cortex (IL)), amygdala, and hippocampus (CA1, CA2, CA3, and dentate gyrus (DG)) was involved in fear of posttraumatic stress disorder (PTSD) during the situational reminder of traumatic memory remains uncertain. Footshock rats experienced an inescapable footshock (3 mA, 10 s), and later we have measured fear behavior for 2 min in the footshock environment on the situational reminder phase. In the final retrieval of situational reminder, BDNF protein and mRNA levels were measured. The results showed that higher BDNF expression occurred in the Cg1, PrL, and amygdala. Lower BDNF expression occurred in the IL, CA1, CA2, CA3, and DG. BDNF mRNA levels were higher in the mPFC and amygdala but lower in the hippocampus. The neural connection analysis showed that BDNF protein and BDNF mRNA exhibited weak connections among the mPFC, amygdala, and hippocampus during situational reminders. The present data did not support the previous viewpoint in neuroimaging research that the mPFC and hippocampus revealed hypoactivity and the amygdala exhibited hyperactivity for PTSD symptoms. These findings should be discussed with the previous evidence and provide clinical implications for PTSD.

Robustly High Hippocampal BDNF levels under Acute Stress in Mice Lacking the Full-length p75 Neurotrophin Receptor

BACKGROUND

Brain-derived neurotrophic factor (BDNF) exerts its effects on neural plasticity via 2 distinct receptor types, the tyrosine kinase TrkB and the p75 neurotrophin receptor (p75NTR). The latter can promote inflammation and cell death while TrkB is critically involved in plasticity and memory, particularly in the hippocampus. Acute and chronic stress have been associated with suppression of hippocampal BDNF expression and impaired hippocampal plasticity. We hypothesized that p75NTR might be involved in the hippocampal stress response, in particular in stress-induced BDNF suppression, which might be accompanied by increased neuroinflammation.

METHOD

We assessed hippocampal BDNF protein concentrations in wild-type mice compared that in mice lacking the long form of the p75NTR (p75NTR^ExIII-/-) with or without prior exposure to a 1-hour restraint stress challenge. Hippocampal BDNF concentrations were measured using an optimized ELISA. Furthermore, whole-brain mRNA expression of pro-inflammatory interleukin-6 (Il6) was assessed with RT-PCR.

RESULTS

Deletion of full-length p75NTR was associated with higher hippocampal BDNF protein concentration in the stress condition, suggesting persistently high hippocampal BDNF levels in p75NTR-deficient mice, even under stress. Stress elicited increased whole-brain Il6 mRNA expression irrespective of genotype; however, p75NTR^ExIII-/- mice showed elevated baseline Il6 expression and thus a lower relative increase.

CONCLUSIONS

Our results provide evidence for a role of p75NTR signaling in the regulation of hippocampal BDNF levels, particularly under stress. Furthermore, p75NTR signaling modulates baseline but not stress-related Il6 gene expression in mice. Our findings implicate p75NTR signaling as a potential pathomechanism in BDNF-dependent modulation of risk for neuropsychiatric disorders.

Family-effects in the epigenomic response of red blood cells to a challenge test in the European sea bass (Dicentrarchus labrax, L.)

Abstract

Background

In fish, minimally invasive blood sampling is widely used to monitor physiological stress with blood plasma biomarkers. As fish blood cells are nucleated, they might be a source a potential new markers derived from ‘omics technologies. We modified the epiGBS (epiGenotyping By Sequencing) technique to explore changes in genome-wide cytosine methylation in the red blood cells (RBCs) of challenged European sea bass (Dicentrarchus labrax), a species widely studied in both natural and farmed environments.

Results

We retrieved 501,108,033 sequencing reads after trimming, with a mean mapping efficiency of 73.0% (unique best hits). Minor changes in RBC methylome appeared to manifest after the challenge test and a family-effect was detected. Only fifty-seven differentially methylated cytosines (DMCs) close to 51 distinct genes distributed on 17 of 24 linkage groups (LGs) were detected between RBCs of pre- and post-challenge individuals. Thirty-seven of these genes were previously reported as differentially expressed in the brain of zebrafish, most of them involved in stress coping differences. While further investigation remains necessary, few DMC-related genes associated to the Brain Derived Neurotrophic Factor, a protein that favors stress adaptation and fear memory, appear relevant to integrate a centrally produced stress response in RBCs.

Conclusion

Our modified epiGBS protocol was powerful to analyze patterns of cytosine methylation in RBCs of D. labrax and to evaluate the impact of a challenge using minimally invasive blood samples. This study is the first approximation to identify epigenetic biomarkers of exposure to stress in fish.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07420-9.

Repeated exposure to propofol in the neonatal period impairs hippocampal synaptic plasticity and the recognition function of rats in adulthood

Anesthesia of neonates with propofol induces persistent behavioral abnormalities in adulthood. Although propofol-triggered apoptosis of neurons in the developing brain may contribute to the development of cognitive deficits, the mechanism of neurotoxicity induced by neonatal exposure to propofol remains unclear. In this study, the effects of neonatal propofol anesthesia on synaptic plasticity and neurocognitive function were investigated. Postnatal day 7 (PND-7) Sprague-Dawley rats were intraperitoneally injected with fat emulsion or 20, 40 or 60 mg/kg propofol for three consecutive days. The expression of brain-derived neurotrophic factor (BDNF), tropomyosin-related kinase B (TrkB) and postsynaptic density protein 95 (PSD-95) in the rat hippocampus at PND-10 and PND-12 was measured by Western blotting. The number of dendritic branches, total dendritic length and dendritic spine density were observed by Golgi-Cox staining 24 h and 72 h after the last propofol administration. Long-term potentiation (LTP) was measured electrophysiologically in hippocampus of PND-60 rats to evaluate the synaptic function. The learning and memory abilities of rats were evaluated by Morris water maze (MWM) experiments, Novel object recognition test (NORT) and Object location test (OLT) at PND-60. Our results showed that neonatal exposure to propofol significantly inhibited the expression of BDNF, TrkB and PSD-95 in the rat hippocampus. The number of dendritic branches, total dendritic length and dendritic spine density of neurons in the rat hippocampus were markedly reduced after neonatal propofol anesthesia. LTP was significantly diminished in hippocampus of PND-60 rats after repeated exposure to propofol in the neonatal period. Morris water maze experiments showed that repeated neonatal exposure to propofol significantly prolonged the escape latency and decreased the time spent in the target quadrant and the number of platform crossings. NORT and OLT showed that repeated neonatal exposure to propofol markedly reduced the Investigation Time for novel object or location. All of the results above indicate that repeated exposure to propofol in the neonatal period can impair hippocampal synaptic plasticity and the recognition function of rats in adulthood.

The Antidepressant Effects of Resveratrol are Accompanied by the Attenuation of Dendrite/Dendritic Spine Loss and the Upregulation of BDNF/p-cofilin1 Levels in Chronic Restraint Mice

Depression afflicts more than 300 million people worldwide, but there is currently no universally effective drug in clinical practice. In this study, chronic restraint stress (CRS)-induced mice depression model was used to study the antidepressant effects of resveratrol and its mechanism. Our results showed that resveratrol significantly attenuated depression-like behavior in mice. Consistent with behavioral changes, resveratrol significantly attenuated CRS-induced reduction in the density of dendrites and dendritic spines in both hippocampus and medial prefrontal cortex (mPFC). Meanwhile, in hippocampus and mPFC, resveratrol consistently alleviated CRS-induced cofilin1 activation by increasing its ser3 phosphorylation. In addition, cofilin1 immunofluorescence distribution in neuronal inner peri-membrane in controls, and cofilin1 diffusely distribution in the cytoplasm in CRS group were common in hippocampus. However, the distribution of cofilin1 in mPFC was reversed. Pearson's correlation analysis revealed that there was a significant positive correlation found between the sucrose consumption in sucrose preference test and the dendrite density in multiple sub-regions of hippocampus and mPFC, and a significant negative correlation between the immobility time in tail suspension test and the dendrite/dendritic spine density in several different areas of hippocampus and mPFC. P-cofilin1 was significantly positively correlated with the overall dendritic spine density in mPFC as well as with the overall dendrite density or BDNF in the hippocampus. Our results suggest that the BDNF/cofilin1 pathway, in which cofilin1 may be activated in a brain-specific manner, was involved in resveratrol's attenuating the dendrite and dendritic spine loss and behavioral abnormality.

Gender dysphoria: prejudice from childhood to adulthood, but no impact on inflammation. A cross-sectional controlled study

INTRODUCTION

Gender dysphoria (GD) is characterized by a marked incongruence between experienced gender and one's gender assigned at birth. Transsexual individuals present a higher prevalence of psychiatric disorders when compared to non-transsexual populations, and it has been proposed that minority stress, i.e., discrimination or prejudice, has a relevant impact on these outcomes. Transsexuals also show increased chances of having experienced maltreatment during childhood. Interleukin (IL)-1β, IL-6, IL-10 and tumor necrosis factor-alpha (TNF-α) are inflammatory cytokines that regulate our immune system. Imbalanced levels in such cytokines are linked to history of childhood maltreatment and psychiatric disorders. We compared differences in IL-1β, IL-6, IL-10 and TNF-α levels and exposure to traumatic events in childhood and adulthood in individuals with and without GD (DSM-5).

METHODS

Cross-sectional controlled study comparing 34 transsexual women and 31 non-transsexual men. They underwent a thorough structured interview, assessing sociodemographic information, mood and anxiety symptoms, childhood maltreatment, explicit discrimination and suicidal ideation. Inflammatory cytokine levels (IL-1β, IL-6, IL-10 and TNF-α) were measured by multiplex immunoassay.

RESULTS

Individuals with GD experienced more discrimination (p = 0.002) and childhood maltreatment (p = 0.046) than non-transsexual men. Higher suicidal ideation (p < 0.001) and previous suicide attempt (p = 0.001) rates were observed in transsexual women. However, no differences were observed in the levels of any cytokine.

CONCLUSIONS

These results suggest that transsexual women are more exposed to stressful events from childhood to adulthood than non-transsexual men and that GD per se does not play a role in inflammatory markers.

A CRHR1 antagonist prevents synaptic loss and memory deficits in a trauma-induced delirium-like syndrome

Older patients with severe physical trauma are at high risk of developing neuropsychiatric syndromes with global impairment of cognition, attention, and consciousness. We employed a thoracic trauma (TxT) mouse model and thoroughly analyzed age-dependent spatial and temporal posttraumatic alterations in the central nervous system. Up to 5 days after trauma, we observed a transient 50% decrease in the number of excitatory synapses specifically in hippocampal pyramidal neurons accompanied by alterations in attention and motor activity and disruption of contextual memory consolidation. In parallel, hippocampal corticotropin-releasing hormone (CRH) expression was highly upregulated, and brain-derived neurotrophic factor (BDNF) levels were significantly reduced. In vitro experiments revealed that CRH application induced neuronal autophagy with rapid lysosomal degradation of BDNF via the NF-κB pathway. The subsequent synaptic loss was rescued by BDNF as well as by specific NF-κB and CRH receptor 1 (CRHR1) antagonists. In vivo, the chronic application of a CRHR1 antagonist after TxT resulted in reversal of the observed histological, molecular, and behavioral alterations. The data suggest that neuropsychiatric syndromes (i.e., delirium) after peripheral trauma might be at least in part due to the activation of the hippocampal CRH/NF-κB/BDNF pathway, which results in a dramatic loss of synaptic contacts. The successful rescue by stress hormone receptor antagonists should encourage clinical trials focusing on trauma-induced delirium and/or other posttraumatic syndromes.

The adenosine A(2A) receptor agonist CGS 21680 alleviates auditory sensorimotor gating deficits and increases in accumbal CREB in rats neonatally treated with quinpirole

RATIONALE AND OBJECTIVE

The adenosine A(2A) receptor forms a mutually inhibitory heteromer with the dopamine D₂ receptor, and A(2A) agonists decrease D₂ signaling. This study analyzed whether an adenosine A(2A) agonist would alleviate deficits in sensorimotor gating and increases in cyclic-AMP response element binding protein (CREB) in the nucleus accumbens (NAc) in the neonatal quinpirole model of schizophrenia (SZ).

METHODS

Male and female Sprague-Dawley rats were neonatally treated with saline (NS) or quinpirole HCl (NQ; 1 mg/kg) from postnatal days (P) 1-21. Animals were raised to P44 and behaviorally tested on auditory sensorimotor gating as measured through prepulse inhibition (PPI) from P44 to P48. Approximately 15 min before each session, animals were given an ip administration of saline or the adenosine A(2A) agonist CGS 21680 (0.03 or 0.09 mg/kg). One day after PPI was complete on P49, animals were administered a locomotor activity test in the open field after saline or CGS 21680 treatment, respectively. On P50, the nucleus accumbens (NAc) was evaluated for CREB protein.

RESULTS

NQ-treated rats demonstrated a deficit in PPI that was alleviated to control levels by either dose of CGS 21680. The 0.03 mg/kg dose of CGS 21680 increased startle amplitude in males. The 0.09 mg/kg dose of CGS 21680 resulted in an overall decrease in locomotor activity. NQ treatment significantly increased NAc CREB that was attenuated to control levels by either dose of CGS 21680.

CONCLUSIONS

This study revealed that an adenosine A(2A) receptor agonist was effective to alleviate PPI deficits in the NQ model of SZ in both male and female rats.