Prefrontal cortex circuits in depression and anxiety: contribution of discrete neuronal populations and target regions

The N-methyl-d-aspartate receptor hypothesis of ketamine's antidepressant action: evidence and controversies

Substantial clinical evidence has unravelled the superior antidepressant efficacy of ketamine: in comparison to traditional antidepressants targeting the monoamine systems, ketamine, as an N-methyl-d-aspartate receptor (NMDAR) antagonist, acts much faster and more potently. Surrounding the antidepressant mechanisms of ketamine, there is ample evidence supporting an NMDAR-antagonism-based hypothesis. However, alternative arguments also exist, mostly derived from the controversial clinical results of other NMDAR inhibitors. In this article, we first summarize the historical development of the NMDAR-centred hypothesis of rapid antidepressants. We then classify different NMDAR inhibitors based on their mechanisms of inhibition and evaluate preclinical as well as clinical evidence of their antidepressant effects. Finally, we critically analyse controversies and arguments surrounding ketamine's NMDAR-dependent and NMDAR-independent antidepressant action. A better understanding of ketamine's molecular targets and antidepressant mechanisms should shed light on the future development of better treatment for depression. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.

Co-decoction of Lilii bulbus and Radix Rehmannia Recens and its key bioactive ingredient verbascoside inhibit neuroinflammation and intestinal permeability associated with chronic stress-induced depression via the gut microbiota-brain axis

BACKGROUND

Gut microbiota plays a critical role in the pathogenesis of depression and are a therapeutic target via maintaining the homeostasis of the host through the gut microbiota-brain axis (GMBA). A co-decoction of Lilii bulbus and Radix Rehmannia Recens (LBRD), in which verbascoside is the key active ingredient, improves brain and gastrointestinal function in patients with depression. However, in depression treatment using verbascoside or LBRD, mechanisms underlying the bidirectional communication between the intestine and brain via the GMBA are still unclear.

PURPOSE

This study aimed to examine the role of verbascoside in alleviating depression via gut-brain bidirectional communication and to study the possible pathways involved in the GMBA.

METHODS

Key molecules and compounds involved in antidepressant action were identified using HPLC and transcriptomic analyses. The antidepressant effects of LBRD and verbascoside were observed in chronic stress induced depression model by behavioural test, neuronal morphology, and synaptic dendrite ultrastructure, and their neuroprotective function was measured in corticosterone (CORT)-stimulated nerve cell injury model. The causal link between the gut microbiota and the LBRD and verbascoside antidepressant efficacy was evaluate via gut microbiota composition analysis and faecal microbiota transplantation (FMT).

RESULTS

LBRD and Verbascoside administration ameliorated depression-like behaviours and synaptic damage by reversing gut microbiota disturbance and inhibiting inflammatory responses as the result of impaired intestinal permeability or blood-brain barrier leakiness. Furthermore, verbascoside exerted neuroprotective effects against CORT-induced cytotoxicity in an in vitro depression model. FMT therapy indicated that verbascoside treatment attenuated gut inflammation and central nervous system inflammatory responses, as well as eliminated neurotransmitter and brain-gut peptide deficiencies in the prefrontal cortex by modulating the composition of gut microbiota. Lactobacillus, Parabacteroides, Bifidobacterium, and Ruminococcus might play key roles in the antidepressant effects of LBRD via the GMBA.

CONCLUSION

The current study elucidates the multi-component, multi-target, and multi-pathway therapeutic effects of LBRD on depression by remodeling GMBA homeostasis and further verifies the causality between gut microbiota and the antidepressant effects of verbascoside and LBRD.

The 5-HT7 receptor antagonist SB 269970 ameliorates maternal fluoxetine exposure-induced impairment of synaptic plasticity in the prefrontal cortex of the offspring female mice

The use of a selective serotonin reuptake inhibitor fluoxetine in depression during pregnancy and the postpartum period might increase the risk of affective disorders and cognitive symptoms in progeny. In animal models, maternal exposure to fluoxetine throughout gestation and lactation negatively affects the behavior of the offspring. Little is known about the effects of maternal fluoxetine on synaptic transmission and plasticity in the offspring cerebral cortex. During pregnancy and lactation C57BL/6J mouse dams received fluoxetine (7.5 mg/kg/day) with drinking water. Female offspring mice received intraperitoneal injections of the selective 5-HT7 receptor antagonist SB 269970 (2.5 mg/kg) for 7 days. Whole-cell and field potential electrophysiological recordings were performed in the medial prefrontal cortex (mPFC) ex vivo brain slices. Perinatal exposure to fluoxetine resulted in decreased field potentials and impaired long-term potentiation (LTP) in layer II/III of the mPFC of female young adult offspring. Neither the intrinsic excitability nor spontaneous excitatory postsynaptic currents were altered in layer II/III mPFC pyramidal neurons. In mPFC slices obtained from fluoxetine-treated mice that were administered SB 269970 both field potentials and LTP magnitude were restored and did not differ from controls. Treatment of fluoxetine-exposed mice with a selective 5-HT7 receptor antagonist, SB 269970, normalizes synaptic transmission and restores the potential for plasticity in the mPFC of mice exposed in utero and postnatally to fluoxetine.

Chronic restraint stress induces depression-like behaviors and alterations in the afferent projections of medial prefrontal cortex from multiple brain regions in mice

INTRODUCTION

The medial prefrontal cortex (mPFC) forms output pathways through projection neurons, inversely receiving adjacent and long-range inputs from other brain regions. However, how afferent neurons of mPFC are affected by chronic stress needs to be clarified. In this study, the effects of chronic restraint stress (CRS) on the distribution density of mPFC dendrites/dendritic spines and the projections from the cortex and subcortical brain regions to the mPFC were investigated.

METHODS

In the present study, C57BL/6 J transgenic (Thy1-YFP-H) mice were subjected to CRS to establish an animal model of depression. The infralimbic (IL) of mPFC was selected as the injection site of retrograde AAV using stereotactic technique. The effects of CRS on dendrites/dendritic spines and afferent neurons of the mPFC IL were investigaed by quantitatively assessing the distribution density of green fluorescent (YFP) positive dendrites/dendritic spines and red fluorescent (retrograde AAV recombinant protein) positive neurons, respectively.

RESULTS

The results revealed that retrograde tracing virus labeled neurons were widely distributed in ipsilateral and contralateral cingulate cortex (Cg1), second cingulate cortex (Cg2), prelimbic cortex (PrL), infralimbic cortex, medial orbital cortex (MO), and dorsal peduncular cortex (DP). The effects of CRS on the distribution density of mPFC red fluorescence positive neurons exhibited regional differences, ranging from rostral to caudal or from top to bottom. Simultaneously, CRS resulted a decrease in the distribution density of basal, proximal and distal dendrites, as well as an increase in the loss of dendritic spines of the distal dendrites in the IL of mPFC. Furthermore, varying degrees of red retrograde tracing virus fluorescence signals were observed in other cortices, amygdala, hippocampus, septum/basal forebrain, hypothalamus, thalamus, mesencephalon, and brainstem in both ipsilateral and contralateral brain. CRS significantly reduced the distribution density of red fluorescence positive neurons in other cortices, hippocampus, septum/basal forebrain, hypothalamus, and thalamus. Conversely, CRS significantly increased the distribution density of red fluorescence positive neurons in amygdala.

CONCLUSION

Our results suggest a possible mechanism that CRS leads to disturbances in synaptic plasticity by affecting multiple inputs to the mPFC, which is characterized by a decrease in the distribution density of dendrites/dendritic spines in the IL of mPFC and a reduction in input neurons of multiple cortices to the IL of mPFC as well as an increase in input neurons of amygdala to the IL of mPFC, ultimately causing depression-like behaviors.

Transcriptomic Evaluation of a Stress Vulnerability Network using Single Cell RNA-Seq in mouse Prefrontal Cortex

BACKGROUND

Increased vulnerability to stress is a major risk factor for several mood disorders, including major depressive disorder (MDD). Although cellular and molecular mechanisms associated with depressive behaviors following stress have been identified, little is known about the mechanisms conferring vulnerability that predisposes individuals to future damage from chronic stress.

METHODS

We used multi-site in vivo neurophysiology in freely behaving male and female C57BL/6 mice (n=12) to measure electrical brain network activity previously identified as indicating a latent stress vulnerability brain state. We combined this neurophysiological approach with single-cell RNA sequencing (scRNA-Seq) of the prefrontal cortex (PFC) to identify distinct transcriptomic differences between groups of mice with inherent high and low stress vulnerability.

RESULTS

We identified hundreds of differentially expressed genes (padj <0.05) across five major cell types between animals with high and low stress vulnerability brain network activity. This unique analysis revealed that GABAergic neuron gene expression contributes most to the network activity of the stress vulnerability brain state. Upregulation of mitochondrial and metabolic pathways also distinguished high and low vulnerability brain states, especially in inhibitory neurons. Importantly, genes that were differentially regulated with vulnerability network activity significantly overlapped (above chance) with those identified by genome-wide association studies (GWAS) as having SNPs significantly associated with depression as well as genes more highly expressed in post-mortem PFC of patients with MDD.

CONCLUSIONS

This is the first study to identify cell types and genes involved in a latent stress vulnerability state in the brain.

Two polygenic mouse models of major depressive disorders identify TMEM161B as a potential biomarker of disease in humans

Treatments are only partially effective in major depressive disorders (MDD) but no biomarker exists to predict symptom improvement in patients. Animal models are essential tools in the development of antidepressant medications, but while recent genetic studies have demonstrated the polygenic contribution to MDD, current models are limited to either mimic the effect of a single gene or environmental factor. We developed in the past a model of depressive-like behaviors in mice (H/Rouen), using selective breeding based on behavioral reaction after an acute mild stress in the tail suspension test. Here, we propose a new mouse model of depression (H-TST) generated from a more complex genetic background and based on the same selection process. We first demonstrated that H/Rouen and H-TST mice had similar phenotypes and were more sensitive to glutamate-related antidepressant medications than selective serotonin reuptake inhibitors. We then conducted an exome sequencing on the two mouse models and showed that they had damaging variants in 174 identical genes, which have also been associated with MDD in humans. Among these genes, we showed a higher expression level of Tmem161b in brain and blood of our two mouse models. Changes in TMEM161B expression level was also observed in blood of MDD patients when compared with controls, and after 8-week treatment with duloxetine, mainly in good responders to treatment. Altogether, our results introduce H/Rouen and H-TST as the two first polygenic animal models of MDD and demonstrate their ability to identify biomarkers of the disease and to develop rapid and effective antidepressant medications.

Acute manipulation of Drd1 neurons in the prefrontal cortex bidirectionally regulates anxiety and depression-like behaviors

BACKGROUND CONTEXT

The medial prefrontal cortex (mPFC) has been implicated in modulating anxiety and depression. Manipulation of Drd1 neurons in the mPFC resulted in variable neuronal activity and, consequently, strikingly different behaviors. The acute regulation of anxiety- and depression-like behaviors by Drd1 neurons, a major neuronal subtype in the mPFC, has not yet been investigated.

PURPOSE

The purpose of this study was to investigate whether acute manipulation of Drd1 neurons in the mPFC affects anxiety- and depression-like behaviors.

STUDY DESIGN

Male Drd1-Cre mice were injected with an adeno-associated virus (AAV) expressing hM3DGq or hM4DGi. Clozapine-n-oxide (CNO, 1 mg/kg, i.p.) was injected 30 min before the behavioral tests.

METHODS

Male Drd1-Cre mice were injected with AAV-Ef1α-DIO-hM4DGi-mCherry-WPRE-pA, AAV-Ef1α-DIO-hM3DGq-mCherry-WPRE-pA or AAV-Ef1α-DIO-mCherry-WPRE-pA. Three weeks later, whole-cell recordings after CNO (5 μM) were applied to the bath were used to validate the functional expression of hM4DGi and hM3DGq. Four groups of mice underwent all the behavioral tests, and after each of the tests, the mice were allowed to rest for 3-4 days. CNO (1 mg/kg) was injected intraperitoneally 30 min before the behavior test. Anxiety-like behaviors were evaluated by the open field test (OFT), the elevated plus maze test (EPMT), and the novelty-suppressed feeding test (NSFT). Depression-like behaviors were evaluated by the sucrose preference test (SPT) and force swimming test (FST). For all experiments, coronal sections of the targeted brain area were used to confirm virus expression.

RESULTS

Whole-cell recordings from brain slices demonstrated that infusions of CNO (5 µM) into mPFC slices dramatically increased the firing activity of hM3DGq-mCherry+ neurons and abolished the firing activity of hM4DGi-mCherry+ neurons. Acute chemogenetic activation of Drd1 neurons in the mPFC increased the time spent in the central area in the OFT, increased the time spent in the open arms in the EMPT, decreased the latency to bite the food in the NSFT, increased the sucrose preference in the SPT, and decreased the immobility time in the FST. Acute chemogenetic inhibition of Drd1 neurons in the mPFC decreased the time spent in the central area in the OFT, decreased the time spent in the open arms in the EMPT, increased the latency to bite the food in the NSFT, decreased the sucrose preference in the SPT, and increased the immobility time in the FST.

CONCLUSIONS

The present study showed that acute activation of Drd1 neurons in the mPFC produced rapid anxiolytic- and antidepressant-like effects, and acute inhibition had the opposite effect, revealing that Drd1 neurons in the mPFC bidirectionally regulate anxiety- and depression-like behaviors.

CLINICAL SIGNIFICANCE

The findings of the present study regarding the acute effects of stimulating Drd1 neurons in the mPFC on anxiety and depression suggest that Drd1 neurons in the mPFC are a focus for the treatment of anxiety disorders and depression.

1,2-Dichloroethane causes anxiety and cognitive dysfunction in mice by disturbing GABA metabolism and inhibiting the cAMP-PKA-CREB signaling pathway

1,2-Dichloroethane (1,2-DCE) is a powerfully toxic neurotoxin, which is a common environmental pollutant. Studies have indicated that 1,2-DCE long-term exposure can result in adverse effects. Nevertheless, the precise mechanism remains unknown. In this study, behavioral results revealed that 1,2-DCE long-term exposure could cause anxiety and learning and memory ability impairment in mice. The contents of γ-aminobutyric acid (GABA) and glutamine (Gln) in mice's prefrontal cortex decreased, whereas that of glutamate (Glu) increased. With the increase in dose, the activities of glutamate decarboxylase (GAD) decreased and those of GABA transaminase (GABA-T) increased. The protein and mRNA expressions of GABA transporter-3 (GAT-3), vesicular GABA transporter (VGAT), GABA A receptor α2 (GABAARα2), GABAARγ2, K-Cl cotransporter isoform 2 (KCC2), GABA B receptor 1 (GABABR1), GABABR2, protein kinase A (PKA), cAMP-response element binding protein (CREB), p-CREB, brain-derived neurotrophic factor (BDNF), c-fos, c-Jun and the protein of glutamate dehydrogenase (GDH) and PKA-C were decreased, while the expression levels of GABA transporter-1 (GAT-1) and Na-K-2Cl cotransporter isoform 1 (NKCC1) were increased. However, there was no significant change in the protein content of succinic semialdehyde dehydrogenase (SSADH). The expressions of adenylate cyclase (AC) and cyclic adenosine monophosphate (cAMP) contents were also reduced. In conclusion, the results of this study show that exposure to 1,2-DCE could lead to anxiety and cognitive impairment in mice, which may be related to the disturbance of GABA metabolism and its receptors along with the cAMP-PKA-CREB pathway.

Antidepressant effects of activation of infralimbic cortex via upregulation of BDNF and β-catenin in an estradiol withdrawal model

RATIONALE

Clinical and preclinical studies have demonstrated that estradiol withdrawal after delivery is one of important factors involved in the pathogenesis of postpartum depression (PPD). The infralimbic cortex (IL) is related to anxiety and mood disorders. Whether IL neurons mediate PPD is still unclear.

OBJECTIVES

This study was to observe the antidepressant effect and expression of BDNF and β-catenin in IL by allopregnanolone (ALLO) treatment or the selective activation or inhibition of IL neurons using a chemogenetic approach in a pseudopregnancy model of PPD.

METHODS

Administration of estradiol combined with progesterone and the abrupt withdrawal of estradiol simulated the pregnancy and early postpartum periods to induce depression in ovariectomized rats. The relative expression levels of β-catenin and BDNF were observed by western blotting.

RESULTS

Immobility time was significantly increased in the forced swim test and open-arm movement was reduced in the elevated plus maze test in the estradiol-withdrawn rats. After ALLO treatment, the immobility time were lower and open-arm traveling times higher than those of the estradiol-withdrawn rats. Meanwhile, the expression level of BDNF or β-catenin in the IL was reduced significantly in estradiol-withdrawn rats, which was prevented by treatment with ALLO. The hM3Dq chemogenetic activation of pyramidal neurons in the IL reversed the immobility and open-arm travel time trends in the estradiol-withdrawal rat model, but chemogenetic inhibition of IL neurons failed to affect this. Upregulated BDNF and β-catenin expression and increased c-Fos in the basolateral amygdala were found following IL neuron excitation in model rats.

CONCLUSIONS

Our results demonstrated that pseudopregnancy and estradiol withdrawal produced depressive-like behavior and anxiety. ALLO treatment or specific excitement of IL pyramidal neurons relieved abnormal behaviors and upregulated BDNF and β-catenin expression in the IL in the PPD model, suggesting that hypofunction of IL neurons may be involved in the pathogenesis of PPD.

Brain-derived neurotrophic factor from microglia regulates neuronal development in the medial prefrontal cortex and its associated social behavior

Microglia and brain-derived neurotrophic factor (BDNF) are essential for the neuroplasticity that characterizes critical developmental periods. The experience-dependent development of social behaviors-associated with the medial prefrontal cortex (mPFC)-has a critical period during the juvenile period in mice. However, whether microglia and BDNF affect social development remains unclear. Herein, we aimed to elucidate the effects of microglia-derived BDNF on social behaviors and mPFC development. Mice that underwent social isolation during p21-p35 had increased Bdnf in the microglia accompanied by reduced adulthood sociability. Additionally, transgenic mice overexpressing microglial Bdnf-regulated using doxycycline at different time points-underwent behavioral, electrophysiological, and gene expression analyses. In these mice, long-term overexpression of microglial BDNF impaired sociability and excessive mPFC inhibitory neuronal circuit activity. However, administering doxycycline to normalize BDNF from p21 normalized sociability and electrophysiological function in the mPFC, whereas normalizing BDNF from later ages (p45-p50) did not normalize electrophysiological abnormalities in the mPFC, despite the improved sociability. To evaluate the possible role of BDNF in human sociability, we analyzed the relationship between adverse childhood experiences and BDNF expression in human macrophages, a possible proxy for microglia. Results show that adverse childhood experiences positively correlated with BDNF expression in M2 but not M1 macrophages. In summary, our study demonstrated the influence of microglial BDNF on the development of experience-dependent social behaviors in mice, emphasizing its specific impact on the maturation of mPFC function, particularly during the juvenile period. Furthermore, our results propose a translational implication by suggesting a potential link between BDNF secretion from macrophages and childhood experiences in humans.

Sex-specific effects of ketogenic diet on anxiety-like behavior and neuroimmune response in C57Bl/6J mice

The ketogenic diet (KD) has been shown to reduce anxiety and enhance cognitive functions in neurological diseases. However, the sex-specific effects of KD on anxiety-like behavior in healthy individuals and the underlying molecular mechanisms contributing to these effects, including neuroinflammation, are unelucidated. This study investigated the sex-specific effects of KD on anxiety-like behavior and the neuroimmune response in the prefrontal cortex (PFC) and hippocampus of healthy C57BL/6J male and female mice. Animals were fed either a control diet (CD- 17% fat, 65% carb, 18% protein) or a KD (80% fat, 5% carb, 15% protein) for 4 weeks. KD increased the levels of circulating β-hydroxybutyrate (BHB) both in males and females. However, PFC BHB levels were found to be elevated only in KD males. Moreover, KD did not affect the behavior of females but improved motor abilities and reduced anxiety levels in males. KD suppressed the mRNA expression of the pan microglial markers (Cd68, P2ry12) and induced morphological changes in the male PFC microglia. A sex-specific decrease in IL1β and an increase in IL-10 levels was found in the PFC of KD males. A similar trend was observed in the hippocampus of males where KD reduced the mRNA expression of P2ry12, Il1β, and cFos. Additionally, BHB increased the production of IL-10 whereas it decreased the production of IL1β from human microglia in in-vitro conditions. In summary, these results demonstrate that the anxiolytic and motor function enhancement abilities of KD are male-specific. Reduced pro-inflammatory and improved anti-inflammatory factors in the male PFC and hippocampus may underlie these effects.

C3aR in the medial prefrontal cortex modulates the susceptibility to LPS-induced depressive-like behaviors through glutamatergic neuronal excitability

Complement activation and prefrontal cortical dysfunction both contribute to the pathogenesis of major depressive disorder (MDD), but their interplay in MDD is unclear. We here studied the role of complement C3a receptor (C3aR) in the medial prefrontal cortex (mPFC) and its influence on depressive-like behaviors induced by systematic lipopolysaccharides (LPS) administration. C3aR knockout (KO) or intra-mPFC C3aR antagonism confers resilience, whereas C3aR expression in mPFC neurons makes KO mice susceptible to LPS-induced depressive-like behaviors. Importantly, the excitation and inhibition of mPFC neurons have opposing effects on depressive-like behaviors, aligning with increased and decreased excitability by C3aR deletion and activation in cortical neurons. In particular, inhibiting mPFC glutamatergic (mPFCGlu) neurons, the main neuronal subpopulation expresses C3aR, induces depressive-like behaviors in saline-treated WT and KO mice, but not in LPS-treated KO mice. Compared to hypoexcitable mPFCGlu neurons in LPS-treated WT mice, C3aR-null mPFCGlu neurons display hyperexcitability upon LPS treatment, and enhanced excitation of mPFCGlu neurons is anti-depressant, suggesting a protective role of C3aR deficiency in these circumstances. In conclusion, C3aR modulates susceptibility to LPS-induced depressive-like behaviors through mPFCGlu neuronal excitability. This study identifies C3aR as a pivotal intersection of complement activation, mPFC dysfunction, and depression and a promising therapeutic target for MDD.

An empirical analysis of structural neuroimaging profiles in a staging model of depression

We examine structural brain characteristics across three diagnostic categories: at risk for serious mental illness; first-presenting episode and recurrent major depressive disorder (MDD). We investigate whether the three diagnostic groups display a stepwise pattern of brain changes in the cortico-limbic regions. Integrated clinical and neuroimaging data from three large Canadian studies were pooled (total n = 622 participants, aged 12-66 years). Four clinical profiles were used in the classification of a clinical staging model: healthy comparison individuals with no history of depression (HC, n = 240), individuals at high risk for serious mental illness due to the presence of subclinical symptoms (SC, n = 80), first-episode depression (FD, n = 82), and participants with recurrent MDD in a current major depressive episode (RD, n = 220). Whole-brain volumetric measurements were extracted with FreeSurfer 7.1 and examined using three different types of analyses. Hippocampal volume decrease and cortico-limbic thinning were the most informative features for the RD vs HC comparisons. FD vs HC revealed that FD participants were characterized by a focal decrease in cortical thickness and global enlargement in amygdala volumes. Greater total amygdala volumes were significantly associated with earlier onset of illness in the FD but not the RD group. We did not confirm the construct validity of a tested clinical staging model, as a differential pattern of brain alterations was identified across the three diagnostic groups that did not parallel a stepwise clinical staging approach. The pathological processes during early stages of the illness may fundamentally differ from those that occur at later stages with clinical progression.

Prefrontal cortical synaptoproteome profile combined with machine learning predicts resilience towards chronic social isolation in rats

Chronic social isolation (CSIS) of rats serves as an animal model of depression and generates CSIS-resilient and CSIS-susceptible phenotypes. We aimed to investigate the prefrontal cortical synaptoproteome profile of CSIS-resilient, CSIS-susceptible, and control rats to delineate biochemical pathways and predictive biomarker proteins characteristic for the resilient phenotype. A sucrose preference test was performed to distinguish rat phenotypes. Class separation and machine learning (ML) algorithms support vector machine with greedy forward search and random forest were then used for discriminating CSIS-resilient from CSIS-susceptible and control rats. CSIS-resilient compared to CSIS-susceptible rat proteome analysis revealed, among other proteins, downregulated glycolysis intermediate fructose-bisphosphate aldolase C (Aldoc), and upregulated clathrin heavy chain 1 (Cltc), calcium/calmodulin-dependent protein kinase type II (Cam2a), synaptophysin (Syp) and fatty acid synthase (Fasn) that are involved in neuronal transmission, synaptic vesicular trafficking, and fatty acid synthesis. Comparison of CSIS-resilient and control rats identified downregulated mitochondrial proteins ATP synthase subunit beta (Atp5f1b) and citrate synthase (Cs), and upregulated protein kinase C gamma type (Prkcg), vesicular glutamate transporter 1 (Slc17a7), and synaptic vesicle glycoprotein 2 A (Sv2a) involved in signal transduction and synaptic trafficking. The combined protein differences make the rat groups linearly separable, and 100% validation accuracy is achieved by standard ML models. ML algorithms resulted in four panels of discriminative proteins. Proteomics-data-driven class separation and ML algorithms can provide a platform for accessing predictive features and insight into the molecular mechanisms underlying synaptic neurotransmission involved in stress resilience.

Prefrontal Regulation of Social Behavior and Related Deficits: Insights From Rodent Studies

The prefrontal cortex (PFC) is well known as the executive center of the brain, combining internal states and goals to execute purposeful behavior, including social actions. With the advancement of tools for monitoring and manipulating neural activity in rodents, substantial progress has been made in understanding the specific cell types and neural circuits within the PFC that are essential for processing social cues and influencing social behaviors. Furthermore, combining these tools with translationally relevant behavioral paradigms has also provided novel insights into the PFC neural mechanisms that may contribute to social deficits in various psychiatric disorders. This review highlights findings from the past decade that have shed light on the PFC cell types and neural circuits that support social information processing and distinct aspects of social behavior, including social interactions, social memory, and social dominance. We also explore how the PFC contributes to social deficits in rodents induced by social isolation, social fear conditioning, and social status loss. These studies provide evidence that the PFC uses both overlapping and unique neural mechanisms to support distinct components of social cognition. Furthermore, specific PFC neural mechanisms drive social deficits induced by different contexts.

Brain-Targeted Black Phosphorus-Based Nanotherapeutic Platform for Enhanced Hypericin Delivery in Depression

Depression is a significant global health concern that remains inadequately treated due to the limited effectiveness of conventional drug therapies. One potential therapeutic agent, hypericin (HYP), is identified as an effective natural antidepressant. However, its poor water solubility, low bioavailability, and limited ability to penetrate the brain parenchyma have hindered its clinical application. To address these shortcomings and enhance the therapeutic efficacy of HYP, it is loaded onto black phosphorus nanosheets (BP) modified with the neural cell-targeting peptide RVG29 to synthesize a nanoplatform named BP-RVG29@HYP (BRH). This platform served as a nanocarrier for HYP and integrated the advantages of BP with advanced delivery methods and precise targeting strategies. Under the influence of 808 nm near-infrared irradiation (NIR), BRH effectively traversed an in vitro BBB model. In vivo experiments validated these findings, demonstrating that treatment with BRH significantly alleviated depressive-like behaviors and oxidative stress in mice. Importantly, BRH exhibited an excellent safety profile, causing minimal adverse effects, which highlighted its potential as a promising therapeutic agent. In brief, this novel nanocarrier holds great promise in the development of antidepressant drugs and can create new avenues for the treatment of depression.

Discrete prefrontal neuronal circuits determine repeated stress-induced behavioral phenotypes in male mice

Chronic stress is a major risk factor for psychiatric disorders, including depression. Although depression is a highly heterogeneous syndrome, it remains unclear how chronic stress drives individual differences in behavioral responses. In this study, we developed a subtyping-based approach wherein stressed male mice were divided into four subtypes based on their behavioral patterns of social interaction deficits and anhedonia, the core symptoms of psychiatric disorders. We identified three prefrontal cortical neuronal projections that regulate repeated stress-induced behavioral phenotypes. Among them, the medial prefrontal cortex (mPFC)→anterior paraventricular thalamus (aPVT) pathway determines the specific behavioral subtype that exhibits both social deficits and anhedonia. Additionally, we identified the circuit-level molecular mechanism underlying this subtype: KDM5C-mediated epigenetic repression of Shisa2 transcription in aPVT projectors in the mPFC led to social deficits and anhedonia. Thus, we provide a set of biological aspects at the cellular, molecular, and epigenetic levels that determine distinctive stress-induced behavioral phenotypes.

TREK-1 inhibition promotes synaptic plasticity in the prelimbic cortex

Synaptic plasticity is one of the putative mechanisms involved in the maturation of the prefrontal cortex (PFC) during postnatal development. Early life stress (ELS) affects the shaping of cortical circuitries through impairment of synaptic plasticity supporting the onset of mood disorders. Growing evidence suggests that dysfunctional postnatal maturation of the prelimbic division (PL) of the PFC might be related to the emergence of depression. The potassium channel TREK-1 has attracted particular interest among many factors that modulate plasticity, concerning synaptic modifications that could underlie mood disorders. Studies have found that ablation of TREK-1 increases the resilience to depression, while rats exposed to ELS exhibit higher TREK-1 levels in the PL. TREK-1 is regulated by multiple intracellular transduction pathways including the ones activated by metabotropic receptors. In the hippocampal neurons, TREK-1 interacts with the serotonergic system, one of the main factors involved in the action of antidepressants. To investigate possible mechanisms related to the antidepressant role of TREK-1, we used brain slice electrophysiology to evaluate the effects of TREK-1 pharmacological blockade on synaptic plasticity at PL circuitry. We extended this investigation to animals subjected to ELS. Our findings suggest that in non-stressed animals, TREK-1 activity is required for the reduction of synaptic responses mediated by the 5HT1A receptor activation. Furthermore, we demonstrate that TREK-1 blockade promotes activity-dependent long-term depression (LTD) when acting in synergy with 5HT1A receptor stimulation. On the other hand, in ELS animals, TREK-1 blockade reduces synaptic transmission and facilitates LTD expression. These results indicate that TREK-1 inhibition stimulates synaptic plasticity in the PL and this effect is more pronounced in animals subjected to ELS during postnatal development.

An integrative view on the cell-type-specific mechanisms of ketamine's antidepressant actions

Over the past six decades, the use of ketamine has evolved from an anesthetic and recreational drug to the first non-monoaminergic antidepressant approved for treatment-resistant major depressive disorder (MDD). Subanesthetic doses of ketamine and its enantiomer (S)-ketamine (esketamine) directly bind to several neurotransmitter receptors [including N-methyl-d-aspartic acid receptor (NMDAR), κ and μ opioid receptor (KOR and MOR)] widely distributed in the brain and across different cell types, implicating several potential molecular mechanisms underlying the action of ketamine as an antidepressant. This review examines preclinical studies investigating cell-type-specific mechanisms underlying the effects of ketamine on behavior and synapses. Cell-type-specific approaches are crucial for disentangling the critical mechanisms involved in the therapeutic effect of ketamine.

Transcriptomic Similarity Informs Neuromorphic Deviations in Depression Biotypes

BACKGROUND

Major depressive disorder (MDD) is complicated by population heterogeneity, motivating the investigation of biotypes through imaging-derived phenotypes. However, neuromorphic heterogeneity in MDD remains unclear, and how the correlated gene expression (CGE) connectome constrains these neuromorphic anomalies in MDD biotypes has not yet been studied.

METHODS

Here, we related cortical thickness deviations in MDD biotypes to a pattern of CGE connectome. Cortical thickness was estimated from 3-dimensional T1-weighted magnetic resonance images in 2 independent cohorts (discovery cohort: N = 425; replication cohort: N = 217). The transcriptional activity was measured according to Allen Human Brain Atlas. A density peak-based clustering algorithm was used to identify MDD biotypes.

RESULTS

We found that patients with MDD were clustered into 2 replicated biotypes based on single-patient regional deviations from healthy control participants across 2 datasets. Biotype 1 mainly exhibited cortical thinning across the brain, whereas biotype 2 mainly showed cortical thickening in the brain. Using brainwide gene expression data, we found that deviations of transcriptionally connected neighbors predicted regional deviation for both biotypes. Furthermore, putative CGE-informed epicenters of biotype 1 were concentrated on the cognitive control circuit, whereas biotype 2 epicenters were located in the social perception circuit. The patterns of epicenter likelihood were separately associated with depression- and anxiety-response maps, suggesting that epicenters of MDD biotypes may be associated with clinical efficacies.

CONCLUSIONS

Our findings linked the CGE connectome and neuromorphic deviations to identify distinct epicenters in MDD biotypes, providing insight into how microscale gene expressions informed MDD biotypes.

Gray matter biomarkers for major depressive disorder and manic disorder using logistic regression

The study investigates morphometric changes using surface-based measures and logistic regression in Major depressive-disorder (MDD) and Manic-disorder patients as compared to controls. MDD (n = 21) and manic (n = 20) subjects were recruited from psychiatric clinics, along with 19 healthy-controls from local population, after structured and semi-structured clinical interview (DSM-IV, brief Psychotic-Rating Scale (BPRS), Young Mania Rating Scale (YMRS), Hamilton depression rating scale (HDRS), cognitive function by postgraduate Institute Battery of Brain Dysfunction (PGIBBD)). Using 3D T1-weighted images, gray matter (GM) cortical thickness and GM-based morphometric signatures (using logistic regression) were compared among MDD, manic disorder and controls using analysis of covariance (ANCOVA). No significant difference was found between the MDD and manic disorder patients. When compared to controls, cortical thinning was observed in bilateral rostral middle frontal gyrus and parsopercularis, right lateral occipital cortex, right lingual gyrus in MDD; and bilateral rostral middle frontal and superior frontal gyrus, right middle temporal gyrus, left supramarginal and left precentral gyrus in Manic disorders. Logistic regression analysis exhibited GM cortical thinning in the bilateral parsopercularis, right lateral occipital cortex and lingual gyrus in MDD; and bilateral rostral middle, superior frontal gyri, right middle temporal gyrus in Manic with a sensitivity and specificity of 85.7 % and 94.7 % and 90.0 % and 94.7 %, respectively in comparison with controls. Both groups exhibited GM loss in bilateral rostral middle frontal gyrus brain regions compared to controls. Multivariate analysis revealed common changes in GM in MDD and manic disorders associated with mood temperament, but differences when compared to controls.

An epigenetic mechanism of social isolation stress in adolescent female mice

Social isolation during adolescence can increase the risk of mental disorders. Epigenetic changes induced by chronic social isolation may serve as a mechanism underlying emotional disturbances. To test this, we exposed female mice to a post-weaning 6-week social isolation (SI) stress. We found the significantly increased methylation of histone H3 at lysine 9 (H3K9), a histone mark linked to gene repression, as well as the increased H3K9 methyltransferases SUV39H1 and SETDB1, in prefrontal cortex (PFC) of SI females. To find out potential downstream genes affected by this epigenetic alteration, we examined genes linked to neuronal and synaptic functions. Activity-dependent genes, including Arc, c-Fos and Npas4, were significantly reduced in PFC of SI females, correlated with the increased H3K9me2 occupancy around Arc enhancer. Treatment of SI females with UNC0642, a selective inhibitor of H3K9 methylation, significantly attenuated the anxiety-like behavior and elevated Arc expression. These results have revealed an epigenetic mechanism and intervention avenue for anxiety induced by chronic social isolation.

Structural and Functional Brain Changes After Glucocorticoid Therapy in Thyroid-Associated Ophthalmopathy

OBJECTIVE

To investigate the brain structural and functional alterations in patients with thyroid-associated ophthalmopathy (TAO) before and after glucocorticoid therapy, using voxel-based morphometry (VBM) as well as resting-state functional magnetic resonance imaging (MRI) with amplitude of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo).

METHODS

Between 2019 and 2022, 32 patients with TAO and 23 healthy controls underwent pre-therapy MRI in Nanjing, China. Intravenous glucocorticoid therapy was administered to all patients. At 3 months after end of therapy, 26 patients were available for rescanned MRI. VBM, ALFF, and ReHo were used to evaluate the brain structural and functional differences.

RESULTS

Before therapy, TAO patients showed significantly decreased gray matter volume (GMV) in the left orbital part of superior frontal gyrus (ORBsup) and medial superior frontal gyrus (SFGmed) than healthy controls. Patients had higher ALFF values in bilateral gyrus rectus and olfactory cortex and lower values in bilateral cuneus. Patients also showed decreased ReHo values in bilateral lingual gyrus. After therapy, increased GMV in the left anterior cingulate gyrus and SFGmed, increased ALFF values in bilateral cuneus and superior occipital gyrus, and increased ReHo values in bilateral SFGmed were found in TAO patients compared to the pre-therapy cohort. Compared to controls, decreased GMV in left ORBsup was observed in post-therapy TAO patients.

CONCLUSION

Our results indicated that TAO might cause functional and structural deficits in the visual and emotional regions of the brain, with recovery in the former and partial restoration in the latter after effective glucocorticoid therapy. These findings may lead to deeper understanding of the pathophysiological mechanism behind TAO.

Lateralization of the 5-HT1A receptors in the basolateral amygdala in metabolic and anxiety responses to chronic restraint stress

Behavioral and functional studies describe hemispheric asymmetry in anxiety and metabolic behaviors in responses to stress. However, no study has reported serotonergic receptor (the 5-HT1A receptor) lateralization in the basolateral amygdala (BLA) in vivo on anxiety and metabolic behaviors under stress. In the present study, the effect of unilateral and bilateral suppression of the 5-HT1A receptor in the BLA on anxiety, and metabolic responses to chronic restraint stress was assessed. Male Wistar rats 7 days after cannulation into the BLA received chronic restraint stress for 14 consecutive days. 20 minutes before induction of stress, WAY-100-635 (selective 5-HT1A antagonist) or sterile saline (vehicle) was administered either uni- or bi-laterally into the BLA. Behavioral (elevated plus maze; EPM, and open field test), and metabolic parameter studies were performed. Results showed that stress causes a significant increase in weight gain compared to control. In the non-stress condition, the left and bilaterally, and in the stress condition the right, left, and both sides, inhibition of 5-HT1A in the BLA reduced weight gain. In the restraint stress condition, only inhibition of the 5-HT1A receptor in the left BLA led to decreased food intake compared to the control group. In stress conditions, inhibition of the 5-HT1A receptor on the right, left, and bilateral BLA increased water intake compared to the stress group. Inhibition of the 5-HT1A receptor on the left side of the BLA by WAY-100-635 induced anxiety-like behaviors in stressed rats. Similarly, WAY-100-635 on the left BLA effectively caused anxiety-like behaviors in both EPM and open field tests in the control animals. In conclusion, it seems that 5-HT1A receptors in the left BLA are more responsible for anxiety-like behaviors and metabolic changes in responses to stress.

Effects of childhood maltreatment and major depressive disorder on functional connectivity in hippocampal subregions

Major Depressive Disorder (MDD) with childhood maltreatment is a prevalent clinical phenotype. Prior studies have observed abnormal hippocampal activity in MDD patients, considering the hippocampus as a single nucleus. However, there is limited research investigating the static and dynamic changes in hippocampal subregion functional connectivity (FC) in MDD patients with childhood maltreatment. Therefore, we employed static and dynamic FC analyses using hippocampal subregions, including the anterior hippocampus and posterior hippocampus, as seed regions to investigate the neurobiological alterations associated with MDD resulting from childhood maltreatment. This study involved four groups: MDD with (n = 48) and without childhood maltreatment (n = 30), as well as healthy controls with (n = 57) and without (n = 46) childhood maltreatment. Compared to MDD patients without childhood maltreatment, those with childhood maltreatment exhibit altered FC between the hippocampal subregion and multiple brain regions, including the anterior cingulate gyrus, superior frontal gyrus, putamen, calcarine gyrus, superior temporal gyrus, angular gyrus, and supplementary motor area. Additionally, dynamic FC between the right medial-2 hippocampal head and the right calcarine gyrus shows a positive correlation with childhood maltreatment across all its subtypes. Moreover, dFC between the right hippocampal tail and the left angular gyrus moderates the relationship between childhood maltreatment and the depression severity. Our findings of distinct FC patterns within hippocampal subregions provide new clues for understanding the neurobiological basis of MDD with childhood maltreatment.

Choline metabolism in regulating inflammatory bowel disease-linked anxiety disorders: A multi-omics exploration of the gut-brain axis

Anxiety and depression caused by inflammatory bowel disease (IBD) negatively affect the mental health of patients. Emerging studies have demonstrated that the gut-brain axis (GBA) mediates IBD-induced mood disorders, but the underlying mechanisms of these findings remain unknown. Therefore, it's vital to conduct comprehensive research on the GBA in IBD. Multi-omics studies can provide an understanding of the pathological mechanisms of the GBA in the development of IBD, helping to uncover the mechanisms underlying the onset and progression of the disease. Thus, we analyzed the prefrontal cortex (PFC) of Dextran Sulfate Sodium Salt (DSS)-induced IBD mice using transcriptomics and metabolomics. We observed increased mRNA related to acetylcholine synthesis and secretion, along with decreased phosphatidylcholine (PC) levels in the PFC of DSS group compared to the control group. Fecal metagenomics also revealed abnormalities in the microbiome and lipid metabolism in the DSS group. Since both acetylcholine and PC are choline metabolites, we posited that the DSS group may experience choline deficiency and choline metabolism disorders. Subsequently, when we supplemented CDP-choline, IBD mice exhibited improvements, including decreased anxiety-like behaviors, reduced PC degradation, and increased acetylcholine synthesis in the PFC. In addition, administration of CDP-choline can restore imbalances in the gut microbiome and disruptions in lipid metabolism caused by DSS treatment. This study provides compelling evidence to suggest that choline metabolism plays a crucial role in the development and treatment of mood disorders in IBD. Choline and its metabolites appear to have a significant role in maintaining the stability of the GBA.

Dissociation and other trauma symptomatology are linked to imbalance in the competing neurobehavioral decision systems

Objective

Dissociation is a conscious state characterized by alterations in sensation and perception and is thought to arise from traumatic life experiences. Previous research has demonstrated that individuals with high levels of dissociation show impairments in cognitive-emotional processes. Therefore, using the Competing Neurobehavioral Decisions System (CNDS) theory, we used statistical modeling to examine whether dissociative experience and trauma symptoms are independently predicted by impulsivity, risk-seeking, affective state (i.e., anxiety, depression, stress, and negative affect), and trauma history.

Method

In this cross-sectional study design, data were collected via Amazon Mechanical Turk from a total of n = 557 English-speaking participants in the United States. Using Qualtrics, participants answered a series of self-reported questionnaires and completed several neurocognitive tasks. Three independent multiple linear regression models were conducted to assess whether impulsivity, risk seeking, affective state, and trauma history predict depersonalization, trauma symptoms, and PTSD symptoms.

Results

As hypothesized, we found that depersonalization and other trauma symptoms are associated with heightened impulsivity, increased risk-seeking, impaired affective states, and a history of traumatic experiences.

Conclusion

We demonstrate that an imbalanced CNDS (i.e., hyperimpulsive/hypoexecutive), as evidenced by decreased future valuation, increased risk seeking, and impaired affective states, predicts heightened depersonalization and other trauma and PTSD symptomatology. This is the first time that dissociation has been connected to delay discounting (i.e., the tendency to place more value on rewards received immediately compared to farther in the future). Interventions that positively impact areas of the CNDS, such as episodic future thinking or mindfulness meditation, may be a target to help decrease dissociative symptoms.

Social environment enrichment alleviates anxiety-like behavior in mice: Involvement of the dopamine system

Rearing environment plays a vital role in maintaining physical and mental health of both animals and humans. Plenty of studies have proved that physical environment enrichment in adolescence has protective effects on emotion, social behavior, learning and memory deficits. However, the following effects of social environment enrichment in adolescence remain largely elusive. Using the paradigm of companion rotation (CR), the present study found that social environment enrichment reduced anxiety-like behaviors of early adult male C57BL/6J mice. CR group also showed significantly higher expression of tyrosine hydroxylase in the ventral tegmental area and dopamine 1 receptor mRNA in the nucleus accumbens shell than control group. Taken together, these findings demonstrate that CR from adolescence to early adulthood can suppress the level of anxiety and upregulate dopaminergic neuron activity in early adult male C57BL/6J mice.

Transcranial direct current stimulation of the prefrontal cortex improves depression-like behaviors in rats with Parkinson's disease

Depression associated with Parkinson's disease (PD) seriously affects patients, and there is a lack of effective treatments. Transcranial direct current stimulation (tDCS) is increasingly used as a new non-invasive neuromodulation technique in the treatment of neuropsychiatric diseases. However, there is a paucity of research on tDCS for PD-related depression. Our study used PD model rats established with unilateral destruction of the medial forebrain bundle (MFB) to observe the modulatory effects of tDCS acting on the mPFC on depression-like behaviors. We found that tDCS acting on the mPFC improved depression-like behaviors in PD model rats by increasing sucrose intake in sucrose preference test (n = 7-10 rats/group) and shortening immobility time in forced swimming test (n = 7-8 rats/group). Meanwhile, tDCS decreased the expression of c-Fos protein (n = 8-11 rats/group) and the excitation of glutamatergic neurons (n = 6-8 rats/group) in the PrL and LHb of PD model rats. Western blots showed that tDCS decreased the overexpression of serine 845 phosphorylation site of AMPA receptor GluR1 (p-GluR1-S845) in the PrL and LHb of PD model rats (n = 8-11 rats/group), and the overexpression of p-GluR1-S831 in the LHb (n = 8-11 rats/group). The results of this study show that tDCS acting on the mPFC helps to improve PD-related depression, which involves the modulation of excitability and AMPA receptor phosphorylation on the PrL and LHb neurons.

Effect of salidroside on neuroprotection and psychiatric sequelae during the COVID-19 pandemic: A review

The coronavirus disease 2019 (COVID-19) pandemic has affected the mental health of individuals worldwide, and the risk of psychiatric sequelae and consequent mental disorders has increased among the general population, health care workers and patients with COVID-19. Achieving effective and widespread prevention of pandemic-related psychiatric sequelae to protect the mental health of the global population is a serious challenge. Salidroside, as a natural agent, has substantial pharmacological activity and health effects, exerts obvious neuroprotective effects, and may be effective in preventing and treating psychiatric sequelae and mental disorders resulting from stress stemming from the COVID-19 pandemic. Herein, we systematically summarise, analyse and discuss the therapeutic effects of salidroside in the prevention and treatment of psychiatric sequelae as well as its roles in preventing the progression of mental disorders, and fully clarify the potential of salidroside as a widely applicable agent for preventing mental disorders caused by stress; the mechanisms underlying the potential protective effects of salidroside are involved in the regulation of the oxidative stress, neuroinflammation, neural regeneration and cell apoptosis in the brain, the network homeostasis of neurotransmission, HPA axis and cholinergic system, and the improvement of synaptic plasticity. Notably, this review innovatively proposes that salidroside is a potential agent for treating stress-induced health issues during the COVID-19 pandemic and provides scientific evidence and a theoretical basis for the use of natural products to combat the current mental health crisis.

Reviving: restoring depression-like behaviour through glial cell-derived neurotrophic factor treatment in the medial prefrontal cortex

BACKGROUND

Depression is a prevalent nonmotor symptom in Parkinson disease and can greatly reduce the quality of life for patients; the dopamine receptors found in glutamatergic pyramidal cells in the medial prefrontal cortex (mPFC) play a role in regulating local field activity, which in turn affects behavioural and mood disorders. Given research showing that glial cell-derived neurotrophic factor (GDNF) may have an antidepressant effect, we sought to evaluate the impact of exogenous GDNF on depression-like behaviour in mouse models of Parkinson disease.

METHODS

We used an established subacute model of Parkinson disease in mice involving intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), followed by brain stereotaxic injection of GDNF into the mPFC region. Subsequently, we assessed depression-like behaviour using the sucrose preference test, forced swimming test and tail suspension test, while also evaluating protein expression in the mPFC.

RESULTS

We included 60 mice, divided into 3 groups, including a control group (saline injection), an MPTP plus saline injection group and an MPTP plus GDNF injection group. We found that exogenous GDNF injection into the mPFC led to an increase in dopamine receptor D1 (DRD1) protein levels. We also observed that activating the protein kinase A pathway through DRD1 produced a prolonged antidepressant response. Under GDNF stimulation, the expression of dopamine receptor D2 (DRD2) remained constant, suggesting that the DRD2 signal was ineffective in alleviating depression-like symptoms. Moreover, our investigation involved Golgi staining and Western blot techniques, which found enhanced synaptic plasticity, including increased dendritic branches, dendritic spines and retrograde protection after GDNF treatment in Parkinson disease models.

LIMITATIONS

A subtle motor phenotype became evident only toward the conclusion of the behavioural testing period. The study exclusively involved male mice, and no separate control group receiving only GDNF treatment was included in the experimental design.

CONCLUSION

Our findings support a positive effect of exogenous GDNF on synaptic plasticity, mediated by DRD1 signalling in the mPFC, which could facilitate depression remission in Parkinson disease.

Prediction of anxious depression using multimodal neuroimaging and machine learning

Anxious depression is a common subtype of major depressive disorder (MDD) associated with adverse outcomes and severely impaired social function. It is important to clarify the underlying neurobiology of anxious depression to refine the diagnosis and stratify patients for therapy. Here we explored associations between anxiety and brain structure/function in MDD patients. A total of 260 MDD patients and 127 healthy controls underwent three-dimensional T1-weighted structural scanning and resting-state functional magnetic resonance imaging. Demographic data were collected from all participants. Differences in gray matter volume (GMV), (fractional) amplitude of low-frequency fluctuation ((f)ALFF), regional homogeneity (ReHo), and seed point-based functional connectivity were compared between anxious MDD patients, non-anxious MDD patients, and healthy controls. A random forest model was used to predict anxiety in MDD patients using neuroimaging features. Anxious MDD patients showed significant differences in GMV in the left middle temporal gyrus and ReHo in the right superior parietal gyrus and the left precuneus than HCs. Compared with non-anxious MDD patients, patients with anxious MDD showed significantly different GMV in the left inferior temporal gyrus, left superior temporal gyrus, left superior frontal gyrus (orbital part), and left dorsolateral superior frontal gyrus; fALFF in the left middle temporal gyrus; ReHo in the inferior temporal gyrus and the superior frontal gyrus (orbital part); and functional connectivity between the left superior temporal gyrus(temporal pole) and left medial superior frontal gyrus. A diagnostic predictive random forest model built using imaging features and validated by 10-fold cross-validation distinguished anxious from non-anxious MDD with an AUC of 0.802. Patients with anxious depression exhibit dysregulation of brain regions associated with emotion regulation, cognition, and decision-making, and our diagnostic model paves the way for more accurate, objective clinical diagnosis of anxious depression.

Dose-dependent action of cordycepin on the microbiome-gut-brain-adipose axis in mice exposed to stress

The high risk for anxiety and depression among individuals with stress has become a growing concern globally. Stress-related mental disorders are often accompanied by symptoms of metabolic dysfunction. Cordycepin is a Chinese herbal medicine commonly used for its metabolism-enhancing effects. We aimed to investigate the dose-dependent effects of cordycepin on psycho-metabolic disorders induced by stress. Our behavioral tests revealed that 12.5 mg/kg cordycepin by oral gavage significantly attenuated the anxiety- and depression-like behaviors induced by stress in mice. At 25 mg/kg, cordycepin restored the reduced weight and cell size of adipose tissues caused by stress. Besides ameliorating the metabolic dysbiosis of gut microbiota due to stress, cordycepin significantly reduced the elevated contents of 5-hydroxyindoleacetic acid in the serum and prefrontal cortex at 12.5 mg/kg and reversed the decrease in adipose induced by stress at 25 mg/kg. Correlation analyses further revealed that 12.5 mg/kg cordycepin reversed stress-induced changes in the intestinal microbiome of NK4A214_group and decreased serum Myristic acid and PC(15:0/18:1(11Z)) and cytokines, such as IFN-γ and IL-1β. 25 mg/kg cordycepin reversed stress-induced changes in the abundances of Prevoteaceae_UCG-001 and Desulfovibrio, increased serum L-alanine level, and decreased serum Inosine-5'-monophosphate level. Cordycepin thereby ameliorated the anxiety- and depression-like behaviors as well as disturbances in the adipose metabolism of mice exposed to stress. Overall, these findings offer evidence indicating that the prominent effects of cordycepin in the brain and adipose tissues are dose dependent, thus highlight the importance of evaluating the precise therapeutic effects of different cordycepin doses on psycho-metabolic diseases.

Corticotropin-releasing factor signaling and its potential role in the prefrontal cortex-dependent regulation of anxiety

A large body of literature has highlighted the significance of the corticotropin-releasing factor (CRF) system in the regulation of neuropsychiatric diseases. Anxiety disorders are among the most common neuropsychiatric disorders. An increasing number of studies have demonstrated that the CRF family mediates and regulates the development and maintenance of anxiety. Thus, the CRF family is considered to be a potential target for the treatment of anxiety disorders. The prefrontal cortex (PFC) plays a role in the occurrence and development of anxiety, and both CRF and CRF-R1 are widely expressed in the PFC. This paper begins by reviewing CRF-related signaling pathways and their different roles in anxiety and related processes. Then, the role of the CRF system in other neuropsychiatric diseases is reviewed and the potential role of PFC CRF signaling in the regulation of anxiety disorders is discussed. Although other signaling pathways are potentially involved in the process of anxiety, CRF in the PFC primarily modulates anxiety disorders through the activation of corticotropin-releasing factor type1 receptors (CRF-R1) and the excitation of the cAMP/PKA signaling pathway. Moreover, the main signaling pathways of CRF involved in sex differentiation in the PFC appear to be different. In summary, this review suggests that the CRF system in the PFC plays a critical role in the occurrence of anxiety. Thus, CRF signaling is of great significance as a potential target for the treatment of stress-related disorders in the future.

Decoding anxiety-impulsivity subtypes in preadolescent internalising disorders: findings from the Adolescent Brain Cognitive Development study

BACKGROUND

Internalising disorders are highly prevalent emotional dysregulations during preadolescence but clinical decision-making is hampered by high heterogeneity. During this period impulsivity represents a major risk factor for psychopathological trajectories and may act on this heterogeneity given the controversial anxiety-impulsivity relationships. However, how impulsivity contributes to the heterogeneous symptomatology, neurobiology, neurocognition and clinical trajectories in preadolescent internalising disorders remains unclear.

AIMS

The aim was to determine impulsivity-dependent subtypes in preadolescent internalising disorders that demonstrate distinct anxiety-impulsivity relationships, neurobiological, genetic, cognitive and clinical trajectory signatures.

METHOD

We applied a data-driven strategy to determine impulsivity-related subtypes in 2430 preadolescents with internalising disorders from the Adolescent Brain Cognitive Development study. Cross-sectional and longitudinal analyses were employed to examine subtype-specific signatures of the anxiety-impulsivity relationship, brain morphology, cognition and clinical trajectory from age 10 to 12 years.

RESULTS

We identified two distinct subtypes of patients who internalise with comparably high anxiety yet distinguishable levels of impulsivity, i.e. enhanced (subtype 1) or decreased (subtype 2) compared with control participants. The two subtypes exhibited opposing anxiety-impulsivity relationships: higher anxiety at baseline was associated with higher lack of perseverance in subtype 1 but lower sensation seeking in subtype 2 at baseline/follow-up. Subtype 1 demonstrated thicker prefrontal and temporal cortices, and genes enriched in immune-related diseases and glutamatergic and GABAergic neurons. Subtype 1 exhibited cognitive deficits and a detrimental trajectory characterised by increasing emotional/behavioural dysregulations and suicide risks during follow-up.

CONCLUSIONS

Our results indicate impulsivity-dependent subtypes in preadolescent internalising disorders and unify past controversies about the anxiety-impulsivity interaction. Clinically, individuals with a high-impulsivity subtype exhibit a detrimental trajectory, thus early interventions are warranted.

[Ketamine: a neuropsychotropic drug with an innovative mechanism of action]

Ketamine, a non-competitive antagonist of the N-methyl-D-aspartate-glutamate receptor (R-NMDA), has a rapid (from 24 h post-dose) and prolonged (up to one week) antidepressant effect in treatment resistant depression and in rodent models of anxiety/depression. Arguments regarding its cellular and molecular mechanisms underlying its antidepressant activity mainly come from animal studies. However, debates still persist on the structural remodeling of frontocortical/hippocampal neurons and the role of excitatory/inhibitory neurotransmitters involved in its behavioral effect. Neurochemical and behavioral changes are maintained 24 h after administration of ketamine, well beyond its plasma elimination half-life. The glutamatergic pyramidal cells of the medial prefrontal cortex are primarily implicated in the therapeutic effects of ketamine. Advances in knowledge of the consequences of R-NMDA blockade allowed to specify the underlying mechanisms involving the activation of AMPA glutamate receptors, which triggers a cascade of intracellular events dependent on the mechanistic target of rapamycin, brain-derived neurotrophic factor, and synaptic protein synthesis facilitating synaptic plasticity (number of dendritic spines, synaptogenesis). This review focuses on abnormalities of neurotransmitter systems involved in major depressive disorders, their potential impact on neural circuitry and beneficial effects of ketamine. Recent preclinical data pave the way for future studies to better clarify the mechanism of action of fast-acting antidepressant drugs for the development of novel, more effective therapies.

TET2 deficiency promotes anxiety and depression-like behaviors by activating NLRP3/IL-1β pathway in microglia of allergic rhinitis mice

BACKGROUND

Anxiety and depression-like behaviors in allergic rhinitis (AR) are attracting attention, while the precise mechanism has not been clearly elucidated. Recent evidence shows that neuroinflammation in anterior cingulate cortex (ACC) may be the core of these neuropsychiatric symptoms in AR. Here, we investigated the molecular link between the anxiety and depression-like behaviors and neuroinflammation in ACC.

METHODS

Mice were sensitized and challenged with ovalbumin (OVA) to induce AR. Nasal inflammation levels were assessed by H&E staining and PAS staining. Anxiety and depression-like behaviors were evaluated by behavioral experiments including open field test, forced swimming test, and sucrose preference test. Neuronal impairment was characterized via Nissl staining and 18FDG-PET. The role of ten-eleven translocation 2 (TET2) in AR-related anxiety and depression was assessed by Tet2-/- mice. In addition, the murine BV2 microglial cell line was utilized to explore the molecular mechanisms by which TET2 mediates neuroinflammation. The levels of TET2, NLRP3 and their downstream molecules were detected by immunohistochemistry, Western blot, Dot blot and ELISA. The effects of metformin on depression-like behaviors in AR mice were also evaluated.

RESULTS

AR mice showed significant anxiety and depression-like behaviors, which associated with the activation of ACC. Loss of TET2 activated the NLRP3/IL-1β pathway of microglia in AR mice, further accelerating the anxiety and depression-like behaviors. In addition, knockdown of TET2 activated the NLRP3/IL-1β pathway in BV2 cells. Metformin improved the neuropsychiatric symptoms of AR mice by reducing the activation of NLRP3/IL-1β pathway after upregulating TET2.

CONCLUSION

TET2 deficiency activates the NLRP3/IL-1β pathway of microglia in the ACC, promoting the pathological process of anxiety and depression-like behavior in AR. Metformin could be effective in treating neuroinflammation by regulating microglia via TET2 up-regulation, indicating that metformin is a potential way to treat anxiety and depression-like behaviors in AR.

Distinct Neural Representations and Cognitive Behaviors Attributable to Naturally Developed Active Avoidance or Reactive Escape Strategies in the Male Rat

BACKGROUND

The high individual variability in coping with stress is often attributed to genetic background differences, sustained environmental conditions, or a combination of both. However, the neural mechanisms underlying coping style variability are still poorly understood.

METHODS

Here we examined the impact of a single extended emotional challenge on coping style variability and the associated involvement of the hippocampus, medial prefrontal cortex (mPFC), and periaqueductal gray (PAG). Male Sprague-Dawley rats (n = 170) were trained in an extended 2-way shuttle avoidance (eTWSA) task for 7 days, and daily avoidance rates were measured. Forced swim test, elevated plus maze, or Morris water maze was tested before or after eTWSA exposure. Excitotoxic lesion of the hippocampal dentate gyrus (DG) was performed by Ibotenic infusion. Transient pharmacological blocking of DG, mPFC, or PAG was performed by muscimol or CNQX+TTX infusion.

RESULTS

Exposing rats to eTWSA was found to lead to naturally developing dichotomous, not continuous, coping styles, which we termed active avoidance (AA) or reactive escape (RE). Prior emotional responses did not predict the developing coping style. AA was associated with beneficial outcomes, including reduced behavioral despair and improved spatial learning. RE led to impaired spatial retrieval. AA was abolished by lesioning or pharmacological blocking of the DG. RE was prevented by blocking mPFC or PAG.

CONCLUSION

The results indicate that a single exposure to a significant emotional challenge can lead, in otherwise healthy individuals, to dichotomous development of an active or reactive coping style with distinctive neural correlates and subsequent behavioral significance.

The neural basis underlying female vulnerability to depressive disorders

Depressive disorders are more prevalent and severe in women; however, our knowledge of the underlying factors contributing to female vulnerability to depression remains limited. Additionally, females are notably underrepresented in studies seeking to understand the mechanisms of depression. Various animal models of depression have been devised, but only recently have females been included in research. In this comprehensive review, we aim to describe the sex differences in the prevalence, pathophysiology, and responses to drug treatment in patients with depression. Subsequently, we highlight animal models of depression in which both sexes have been studied, in the pursuit of identifying models that accurately reflect female vulnerability to depression. We also introduce explanations for the neural basis of sex differences in depression. Notably, the medial prefrontal cortex and the nucleus accumbens have exhibited sex differences in previous studies. Furthermore, other brain circuits involving the dopaminergic center (ventral tegmental area) and the serotonergic center (dorsal raphe nucleus), along with their respective projections, have shown sex differences in relation to depression. In conclusion, our review covers the critical aspects of sex differences in depression, with a specific focus on female vulnerability in humans and its representation in animal models, including the potential underlying mechanisms. Employing suitable animal models that effectively represent female vulnerability would benefit our understanding of the sex-dependent pathophysiology of depression.

In vivo labeling and quantitative imaging of neuronal populations using MRI

The study of neural circuits, which underlies perception, cognition, emotion, and behavior, is essential for understanding the mammalian brain, a complex organ consisting of billions of neurons. To study the structure and function of the brain, in vivo neuronal labeling and imaging techniques are crucial as they provide true physiological information that ex vivo methods cannot offer. In this paper, we present a new strategy for in vivo neuronal labeling and quantification using MRI. We demonstrate the efficacy of this method by delivering the oatp1a1 gene to the target neurons using rAAV2-retro virus. OATP1A1 protein expression on the neuronal membrane increased the uptake of a specific MRI contrast agent (Gd-EOB-DTPA), leading to hyperintense signals on T1W images of labeled neuronal populations. We also used dynamic contrast enhancement-based methods to obtain quantitative information on labeled neuronal populations in vivo.

Medial prefrontal cortical PPM1F alters depression-related behaviors by modifying p300 activity via the AMPK signaling pathway

AIMS

Protein phosphatase Mg2+/Mn2+-dependent 1F (PPM1F) is a serine/threonine phosphatase, and its dysfunction in depression in the hippocampal dentate gyrus has been previously identified. Nevertheless, its role in depression of another critical emotion-controlling brain region, the medial prefrontal cortex (mPFC), remains unclear. We explored the functional relevance of PPM1F in the pathogenesis of depression.

METHODS

The gene expression levels and colocalization of PPM1F in the mPFC of depressed mice were measured by real-time PCR, western blot and immunohistochemistry. An adeno-associated virus strategy was applied to determine the impact of knockdown or overexpression of PPM1F in the excitatory neurons on depression-related behaviors under basal and stress conditions in both male and female mice. The neuronal excitability, expression of p300 and AMPK phosphorylation levels in the mPFC after knockdown of PPM1F were measured by electrophysiological recordings, real-time PCR and western blot. The depression-related behavior induced by PPM1F knockdown after AMPKα2 knockout or the antidepressant activity of PPM1F overexpression after inhibiting acetylation activity of p300 was evaluated.

RESULTS

Our results indicate that the expression levels of PPM1F were largely decreased in the mPFC of mice exposed to chronic unpredictable stress (CUS). Behavioral alterations relevant to depression emerged with short hairpin RNA (shRNA)-mediated genetic knockdown of PPM1F in the mPFC, while overexpression of PPM1F produced antidepressant activity and ameliorated behavioral responses to stress in CUS-exposed mice. Molecularly, PPM1F knockdown decreased the excitability of pyramidal neurons in the mPFC, and restoring this low excitability decreased the depression-related behaviors induced by PPM1F knockdown. PPM1F knockdown reduced the expression of CREB-binding protein (CBP)/E1A-associated protein (p300), a histone acetyltransferase (HAT), and induced hyperphosphorylation of AMPK, resulting in microglial activation and upregulation of proinflammatory cytokines. Conditional knockout of AMPK revealed an antidepressant phenotype, which can also block depression-related behaviors induced by PPM1F knockdown. Furthermore, inhibiting the acetylase activity of p300 abolished the beneficial effects of PPM1F elevation on CUS-induced depressive behaviors.

CONCLUSION

Our findings demonstrate that PPM1F in the mPFC modulates depression-related behavioral responses by regulating the function of p300 via the AMPK signaling pathway.

Predictors for delayed awakening in adult glioma patients receiving awake craniotomy under monitored anesthesia care

PURPOSE

Delayed awakening after anesthetic discontinuation during awake craniotomy is associated with somnolence during functional brain mapping. However, predictors of delayed awakening in patients receiving monitored anesthesia care for awake craniotomy are unknown.

METHODS

This retrospective cohort study analyzed 117 adult patients with supratentorial glioma in or near eloquent areas who received monitored anesthesia care for awake craniotomy between July 2020 and January 2023 at Linkou Chang Gung Memorial Hospital. These patients were divided into two groups according to their time to awakening (ability to speak their names) after propofol cessation: longer or shorter than 20 min (median duration). Because propofol was solely used anesthetic from skin incision to dural opening, parameters in Schnider model for propofol target-controlled infusion, such as age, sex, and BMI, were adjusted or propensity-matched to compare their anesthetic, surgical, and histopathological profiles.

RESULTS

After propensity-matched comparisons of age and BMI, significant predictors of delayed awakening included IDH1 wild-type tumors and repeated craniotomies. Subgroup analysis revealed that older age and larger T2 volume were predictors in patients undergoing the first craniotomy, while lower preoperative Karnofsky performance scale scores and depression were predictors in repeated craniotomy cases. Delayed awakening was also associated with somnolence and a lower gross total resection rate.

CONCLUSION

Our retrospective analysis of patients receiving monitored anesthesia care for awake craniotomy revealed that delayed awakening after propofol discontinuation occurred more often in patients with IDH1 wild-type tumors and repeated craniotomies. Also, delayed awakening was associated with somnolence during functional mapping and a lower gross total resection rate.

Anxiety, aggression, reward sensitivity, and forebrain dopamine receptor expression in a laboratory rat model of early-life disadvantage

Despite early-life disadvantage (ELD) in humans being a highly heterogenous construct, it consistently predicts negative neurobehavioral outcomes. The numerous environmental contributors and neural mechanisms underlying ELD remain unclear, though. We used a laboratory rat model to evaluate the effects of limited resources and/or heavy metal exposure on mothers and their adult male and female offspring. Dams and litters were chronically exposed to restricted (1-cm deep) or ample (4-cm deep) home cage bedding postpartum, with or without lead acetate (0.1%) in their drinking water from insemination through 1-week postweaning. Restricted-bedding mothers showed more pup-directed behaviors and behavioral fragmentation, while lead-exposed mothers showed more nestbuilding. Restricted bedding-raised male offspring showed higher anxiety and aggression. Either restricted bedding or lead exposure impaired goal-directed performance in a reinforcer devaluation task in females, whereas restricted bedding alone disrupted it in males. Lead exposure, but not limited bedding, also reduced sucrose reward sensitivity in a progressive ratio task in females. D1 and D2 receptor mRNA in the medial prefrontal cortex and nucleus accumbens (NAc) were each affected by the early-life treatments and differently between the sexes. Most notably, adult males (but not females) exposed to both early-life treatments had greatly increased D1 receptor mRNA in the NAc core. These results illuminate neural mechanisms through which ELD threatens neurobehavioral development and highlight forebrain dopamine as a factor.

Effective connectivity between deep brain stimulation targets in individuals with treatment-resistant depression

The therapeutic effect of deep brain stimulation on patients with treatment-resistant depression is strongly dependent on the connectivity of the stimulation region with other regions associated with depression. The aims of this study are to characterize the effective connectivity between the brain regions playing important roles in depression and further investigate the underlying pathophysiological mechanisms of treatment-resistant depression and the mechanisms involving deep brain stimulation. Thirty-three individuals with treatment-resistant depression and 29 healthy control subjects were examined. All subjects underwent resting-state functional MRI scanning. The coupling parameters reflecting the causal interactions among deep brain stimulation targets and medial prefrontal cortex were estimated using spectral dynamic causal modelling. Our results showed that compared to the healthy control subjects, in the left hemisphere of treatment-resistant depression patients, the nucleus accumbens was inhibited by the inferior thalamic peduncle and excited the ventral caudate and the subcallosal cingulate gyrus, which in turn excited the lateral habenula. In the right hemisphere, the lateral habenula inhibited the ventral caudate and the nucleus accumbens, both of which inhibited the inferior thalamic peduncle, which in turn inhibited the cingulate gyrus. The ventral caudate excited the lateral habenula and the cingulate gyrus, which excited the medial prefrontal cortex. Furthermore, these effective connectivity links varied between males and females, and the left and right hemispheres. Our findings suggest that intrinsic excitatory/inhibitory connections between deep brain stimulation targets are impaired in treatment-resistant depression patients, and that these connections are sex dependent and hemispherically lateralized. This knowledge can help to better understand the underlying mechanisms of treatment-resistant depression, and along with tractography, structural imaging, and other relevant clinical information, may assist to determine the appropriate region for deep brain stimulation therapy in each treatment-resistant depression patient.

Research trends in chemogenetics for neuroscience in recent 14 years: A bibliometric study in CiteSpace

BACKGROUND

Chemogenetics has been widely adopted in Neuroscience. Neuroscience has become a hot research topic for scientists. Therefore, the purpose of this study is to explore the current status and trends in the global application of chemogenetics in neuroscience over the last 14 years via CiteSpace.

METHODS

Publications related to chemogenetics in neuroscience were retrieved from the Science Citation Index-Extended Web of Science from 2008 to 2021. We used CiteSpace to analyze publications, citations, cited journals, countries, institutions, authors, cited authors, cited references, and keywords.

RESULTS

A total of 947 records were retrieved from 2008 to 2021 on February 21, 2022. The number and rate of publications and citations increased significantly. Journal of Neuroscience was the most cited journal, and BRAIN RES BULL ranked first in the centrality of cited journals. The United States of America (USA) had the highest number of publications among the countries. Takashi Minamoto was the most prolific author and Armbruster BN ranked the first among authors cited. The first article in the frequency ranking of the references cited was published by Roth BL. The keyword of "nucleus accumben (NAc)" had the highest frequency. The top 3 keywords with the strongest citation bursts include "transgenic mice," "cancer," and "blood-brain barrier."

CONCLUSION

The period 2008 to 2021 has seen a marked increase in research on chemogenetics in neuroscience. The application of chemogenetics is indispensable for research in the field of neuroscience. This bibliometrics study provides the current situation and trend in chemogenetic methods in neuroscience in recent 14 years, which may help researchers to identify the hot topics and frontiers for future studies in this field.

Retrovirus-Derived RTL/SIRH: Their Diverse Roles in the Current Eutherian Developmental System and Contribution to Eutherian Evolution

Eutherians have 11 retrotransposon Gag-like (RTL)/sushi-ichi retrotransposon homolog (SIRH) genes presumably derived from a certain retrovirus. Accumulating evidence indicates that the RTL/SIRH genes play a variety of roles in the current mammalian developmental system, such as in the placenta, brain, and innate immune system, in a eutherian-specific manner. It has been shown that the functional role of Paternally Expressed 10 (PEG10) in placental formation is unique to the therian mammals, as are the eutherian-specific roles of PEG10 and PEG11/RTL1 in maintaining the fetal capillary network and the endocrine regulation of RTL7/SIRH7 (aka Leucine Zipper Down-Regulated in Cancer 1 (LDOCK1)) in the placenta. In the brain, PEG11/RTL1 is expressed in the corticospinal tract and hippocampal commissure, mammalian-specific structures, and in the corpus callosum, a eutherian-specific structure. Unexpectedly, at least three RTL/SIRH genes, RTL5/SIRH8, RTL6/SIRH3, and RTL9/SIRH10, play important roles in combating a variety of pathogens, namely viruses, bacteria, and fungi, respectively, suggesting that the innate immunity system of the brain in eutherians has been enhanced by the emergence of these new components. In this review, we will summarize the function of 10 out of the 11 RTL/SIRH genes and discuss their roles in eutherian development and evolution.

Decoding Depression Severity From Intracranial Neural Activity

BACKGROUND

Disorders of mood and cognition are prevalent, disabling, and notoriously difficult to treat. Fueling this challenge in treatment is a significant gap in our understanding of their neurophysiological basis.

METHODS

We recorded high-density neural activity from intracranial electrodes implanted in depression-relevant prefrontal cortical regions in 3 human subjects with severe depression. Neural recordings were labeled with depression severity scores across a wide dynamic range using an adaptive assessment that allowed sampling with a temporal frequency greater than that possible with typical rating scales. We modeled these data using regularized regression techniques with region selection to decode depression severity from the prefrontal recordings.

RESULTS

Across prefrontal regions, we found that reduced depression severity is associated with decreased low-frequency neural activity and increased high-frequency activity. When constraining our model to decode using a single region, spectral changes in the anterior cingulate cortex best predicted depression severity in all 3 subjects. Relaxing this constraint revealed unique, individual-specific sets of spatiospectral features predictive of symptom severity, reflecting the heterogeneous nature of depression.

CONCLUSIONS

The ability to decode depression severity from neural activity increases our fundamental understanding of how depression manifests in the human brain and provides a target neural signature for personalized neuromodulation therapies.

Age-related changes in glutamic acid decarboxylase 1 gene expression in the medial prefrontal cortex and ventral hippocampus of fear-potentiated rats subjected to isolation stress

Gamma-aminobutyric acid (GABA) plays a crucial role as a neurotransmitter in anxiety circuits, prominently in the hippocampus, amygdala, and prefrontal cortex. The synthesis of GABA in the central nervous system is primarily governed by glutamic acid decarboxylase 67 (GAD67). Aging is associated with emotional alterations, and isolation stress has been linked to increased anxiety. This study aimed to investigate the impact of aging on the gene expression of GAD67 (Gad1) in the medial prefrontal cortex (m PC) and ventral hippocampus (v Hip) of fear-potentiated rats subjected to isolation stress. To conduct the study, Wistar rats of different age groups 21-day-old (immature), 42-day-old (peri-adolescent), and 365-day-old (mature adult) were utilized. Each age level was categorized into four groups: 1) Control group - no pre-stressor, no maze, no drug, 2) Innate fear group (M) - no pre-stressor, maze, no drug, 3) Fear-potentiated group (IM) - isolation pre-stressor for 120 min, maze, no drug, and 4) Diazepam-treated group (IMD) - isolation pre-stressor for 120 min, maze, and diazepam administration. Following the tests, the (m PC) and (v Hip) regions were dissected, and Gad1 gene expression changes were assessed using Real-time PCR technique. The results revealed that, across all age groups, Gad1 expression in both the (m PC) and (v Hip) was significantly higher in the fear-potentiated groups (IM) compared to the control and innate fear (M) groups. Notably, in aged 365-day-old rats from the innate fear group (M), the expression of Gad1 in (v Hip) was also higher than that in the control group. Additionally, aged fear-potentiated rats exhibited elevated Gad1 gene expression in both structures compared to other age groups. These findings suggest that isolation stress before exposure to the elevated plus maze (EPM) can elevate Gad1 gene expression in both the (v Hip) and (m PC), and age may play a role in modulating its expression.

β-Arrestins: Structure, Function, Physiology, and Pharmacological Perspectives

The two β-arrestins, β-arrestin-1 and -2 (systematic names: arrestin-2 and -3, respectively), are multifunctional intracellular proteins that regulate the activity of a very large number of cellular signaling pathways and physiologic functions. The two proteins were discovered for their ability to disrupt signaling via G protein-coupled receptors (GPCRs) via binding to the activated receptors. However, it is now well recognized that both β-arrestins can also act as direct modulators of numerous cellular processes via either GPCR-dependent or -independent mechanisms. Recent structural, biophysical, and biochemical studies have provided novel insights into how β-arrestins bind to activated GPCRs and downstream effector proteins. Studies with β-arrestin mutant mice have identified numerous physiologic and pathophysiological processes regulated by β-arrestin-1 and/or -2. Following a short summary of recent structural studies, this review primarily focuses on β-arrestin-regulated physiologic functions, with particular focus on the central nervous system and the roles of β-arrestins in carcinogenesis and key metabolic processes including the maintenance of glucose and energy homeostasis. This review also highlights potential therapeutic implications of these studies and discusses strategies that could prove useful for targeting specific β-arrestin-regulated signaling pathways for therapeutic purposes. SIGNIFICANCE STATEMENT: The two β-arrestins, structurally closely related intracellular proteins that are evolutionarily highly conserved, have emerged as multifunctional proteins able to regulate a vast array of cellular and physiological functions. The outcome of studies with β-arrestin mutant mice and cultured cells, complemented by novel insights into β-arrestin structure and function, should pave the way for the development of novel classes of therapeutically useful drugs capable of regulating specific β-arrestin functions.

Sex-specific association between prenatal androgenization (second-to-fourth digit length ratio) and frontal brain volumes in adolescents

Prenatal androgenization associates sex-dependently with behavior and mental health in adolescence and adulthood, including risk-taking, emotionality, substance use, and depression. However, still little is known on how it affects underlying neural correlates, like frontal brain control regions. Thus, we tested whether prenatal androgen load is sex-dependently related to frontal cortex volumes in a sex-balanced adolescent sample. In a cross-sectional magnetic resonance imaging study, we examined 61 adolescents (28 males, 33 females; aged 14 or 16 years) and analyzed associations of frontal brain region volumes with the second-to-fourth digit length ratio (2D:4D), an established marker for prenatal androgenization, using voxel-based morphometry in a region-of-interest approach. Lower 2D:4D (indicative of higher prenatal androgen load) correlated significantly with smaller volumes of the right anterior cingulate cortex (r-ACC; β = 0.45) in male adolescents and with larger volumes of the left inferior frontal gyrus orbital part (l-IFGorb; β = - 0.38) in female adolescents. The regression slopes of 2D:4D on the r-ACC also differed significantly between males and females. The study provides novel evidence that prenatal androgenization may influence the development of the frontal brain in a sex- and frontal brain region-specific manner. These effects might contribute to the well-known sex differences in risk-taking, emotionality, substance use, and depression. Future research is needed to elucidate the role of prenatal androgenization within the biopsychosocial model.