Neurocan regulates vulnerability to stress and the anti-depressant effect of ketamine in adolescent rats

Neurocan regulates axon initial segment organization and neuronal activity

The neural extracellular matrix (ECM) accumulates in the form of perineuronal nets (PNNs), particularly around fast-spiking GABAergic interneurons in the cortex and hippocampus, but also around synapses and in association with the axon initial segments (AIS) and nodes of Ranvier. Increasing evidence highlights the role of Neurocan (Ncan), a brain-specific component of ECM, in the pathophysiology of neuropsychiatric disorders like bipolar disorder and schizophrenia. Ncan localizes at PNNs, perisynaptically, and at the nodes of Ranvier and the AIS, highlighting its potential role in regulating axonal excitability. Here, we used knockdown and knockout approaches in mouse primary cortical neurons in combination with immunocytochemistry, Western blotting and electrophysiological techniques to characterize the role of Ncan in the organization of PNNs and AISs and regulation of neuronal activity. We found that reduced Ncan levels led to remodeling of PNNs around neurons via upregulation of aggrecan mRNA and protein levels, increased expression of activity-dependent c-Fos and FosB genes and elevated spontaneous synaptic activity. The latter correlated with increased levels of ankyrin-G in the AIS, particularly in excitatory neurons, and with the elevated expression of Nav1.6 channels. Our results suggest that Ncan regulates the expression of key proteins in PNNs and AISs and provide new insights into its role in fine-tuning neuronal functions.

Prelimbic cortex perineuronal net expression and social behavior: Impact of adolescent intermittent ethanol exposure

Adolescent intermittent ethanol (AIE) exposure in rats leads to social deficits. Parvalbumin (PV) expressing fast-spiking interneurons in the prelimbic cortex (PrL) contribute to social behavior, and perineuronal nets (PNNs) within the PrL preferentially encompass and regulate PV interneurons. AIE exposure increases PNNs, but it is unknown if this upregulation contributes to AIE-induced social impairments. The current study was designed to determine the effect of AIE exposure on PNN expression in the PrL and to assess whether PNN dysregulation contributes to social deficits elicited by AIE. cFos-LacZ male and female rats were exposed every other day to tap water or ethanol (4 g/kg, 25% w/v) via intragastric gavage between postnatal day (P) 25-45. We evaluated neuronal activation by β-galactosidase expression and PNN levels either at the end of the exposure regimen on P45 and/or in adulthood on P70. In addition, we used Chondroitinase ABC (ChABC) to deplete PNNs following adolescent exposure (P48) and allowed for PNN restoration before social testing in adulthhod. AIE exposure increased PNN expression in the PrL of adult males, but decreased PNNs immediately following AIE. Vesicular glutamate transporter 2 (vGlut2) and vesicular GABA transporter (vGat) near PNNs were downregulated only in AIE-exposed females. Gene expression of PNN components was largely unaffected by AIE exposure. Removal and reestablishment of PrL PNNs by ChABC led to upregulation of PNNs and social impairments in males, regardless of adolescent exposure. These data suggest that AIE exposure in males upregulates PrL PNNs that likely contribute to social impairments induced by AIE.

Perineuronal Nets: From Structure to Neurological Disorders

Perineuronal nets (PNN) is condensed extracellular matrix (ECM) in the central nervous system (CNS), which surrounds cell soma, axon initial segments, and synapses. In the brain, most neurons surrounded by PNN are interneurons, especially the parvalbumin-expressing interneurons (PVI). The formation of PNN is involved in the PVI maturation as well as the onset and closure of critical periods for developmental plasticity end. Dysfunction of PVI can lead to some neurological disorders, such as schizophrenia, bipolar depression, and Alzheimer's disease. Similarly, PNN assembling abnormalities are often observed in human patients and animal disease models. PNN is thought to have a neuroprotective effect and interact with signaling molecules to regulate synaptic plasticity and neuronal activity. In this review, we provide an overview of the composition, structure, and functions of PNN. In addition, we highlight abnormal changes in PNN components in pathological conditions. Understanding the roles of different components of PNN will bring us a new perspective on brain plasticity and neurological disorders.

A disinhibitory microcircuit of the orbitofrontal cortex mediates cocaine preference in mice

Both clinical and animal studies showed that the impaired functions of the orbitofrontal cortex (OFC) underlie the compulsive drug-seeking behavior of drug addiction. However, the functional changes of the microcircuit in the OFC and the underlying molecular mechanisms in drug addiction remain elusive, and little is known for whether microcircuits in the OFC contributed to drug addiction-related behaviors. Utilizing the cocaine-induced conditioned-place preference model, we found that the malfunction of the microcircuit led to disinhibition in the OFC after cocaine withdrawal. We further showed that enhanced Somatostatin-Parvalbumin (SST-PV) inhibitory synapse strength changed microcircuit function, and SST and PV inhibitory neurons showed opposite contributions to the drug addiction-related behavior of mice. Brevican of the perineuronal nets of PV neurons regulated SST-PV synapse strength, and the knockdown of Brevican alleviated cocaine preference. These results reveal a novel molecular mechanism of the regulation of microcircuit function and a novel circuit mechanism of the OFC in gating cocaine preference.

Degradation of Perineuronal Nets in the Ventral Hippocampus of Adult Rats Recreates an Adolescent-Like Phenotype of Stress Susceptibility

Background

Psychiatric disorders often emerge during late adolescence/early adulthood, a period with increased susceptibility to socioenvironmental factors that coincides with incomplete parvalbumin interneuron (PVI) development. Stress during this period causes functional loss of PVIs in the ventral hippocampus (vHip), which has been associated with dopamine system overdrive. This vulnerability persists until the appearance of perineuronal nets (PNNs) around PVIs. We assessed the long-lasting effects of adolescent or adult stress on behavior, ventral tegmental area dopamine neuron activity, and the number of PVIs and their associated PNNs in the vHip. Additionally, we tested whether PNN removal in the vHip of adult rats, proposed to reset PVIs to a juvenile-like state, would recreate an adolescent-like phenotype of stress susceptibility.

Methods

Male rats underwent a 10-day stress protocol during adolescence or adulthood. Three to 4 weeks poststress, we evaluated behaviors related to anxiety, sociability, and cognition, ventral tegmental area dopamine neuron activity, and the number of PV+ and PNN+ cells in the vHip. Furthermore, adult animals received intra-vHip infusion of ChABC (chondroitinase ABC) to degrade PNNs before undergoing stress.

Results

Unlike adult stress, adolescent stress induced anxiety responses, reduced sociability, cognitive deficits, ventral tegmental area dopamine system overdrive, and decreased PV+ and PNN+ cells in the vHip. However, intra-vHip ChABC infusion caused the adult stress to produce changes similar to the ones observed after adolescent stress.

Conclusions

Our findings underscore adolescence as a period of heightened vulnerability to the long-lasting impact of stress and highlight the protective role of PNNs against stress-induced damage in PVIs.

Clemastine improves emotional and social deficits in adolescent social isolation mice by reversing demyelination

Adolescence is a critical period for social experience-dependent oligodendrocyte maturation and myelination. Adolescent stress predisposes to cause irreversible changes in brain structure and function with lasting effects on adulthood or beyond. However, the molecular mechanisms linking adolescent social isolation stress with emotional and social competence remain largely unknown. In our study, we found that social isolation during adolescence leads to anxiety-like behaviors, depression-like behaviors, impaired social memory and altered patterns of social ultrasonic vocalizations in mice. In addition, adolescent social isolation stress induces demyelination in the prefrontal cortex and hippocampus of mice, with decreased myelin-related gene expression and disrupted myelin structure. More importantly, clemastine was sufficient to rescue the impairment of emotional and social memory by promoting remyelination. These findings reveal the demyelination mechanism of emotional and social deficits caused by social isolation stress in adolescence, and provides potential therapeutic targets for treating stress-related mental disorders.

Perineuronal net structure as a non-cellular mechanism contributing to affective state: A scoping review

Affective state encompasses emotional responses to our physiology and influences how we perceive and respond within our environment. In affective disorders such as depression, cognitive adaptability is challenged, and structural and functional brain changes have been identified. However, an incomplete understanding persists of the molecular and cellular mechanisms at play in affective state. An exciting area of newly appreciated importance is perineuronal nets (PNNs); a specialised component of extracellular matrix playing a critical role in neuroprotection and synaptic plasticity. A scoping review found 24 studies demonstrating that PNNs are still a developing field of research with a promising general trend for stress in adulthood to increase the intensity of PNNs, whereas stress in adolescence reduced (potentially developmentally delayed) PNN numbers and intensity, while antidepressants correlated with reduced PNN numbers. Despite promising trends, limited research underscores the need for further exploration, emphasizing behavioral outcomes for validating affective states. Understanding PNNs' role may offer therapeutic insights for depression and inform biomarker development, advancing precision medicine and enhancing well-being.

Perineuronal Nets Alterations Contribute to Stress-Induced Anxiety-Like Behavior

Anxiety disorder is one of the most common mental disorders worldwide, affecting nearly 30% of adults. However, its underlying molecular mechanisms are still unclear. Here we subjected mice to chronic restraint stress (CRS), a paradigm known to induce anxiety-like behavior in mice. CRS mice exhibited anxiety-like behavior and reduced synaptic transmission in the medial prefrontal cortex (mPFC). Notably, Wisteria Floribunda agglutinin (WFA) staining showed a reduction of perineuronal nets (PNNs) expression in the mPFC of CRS mice. And the mRNA and protein levels of aggrecan (ACAN), a core component of PNNs, were also reduced. Parallelly, enzymatic digestion of PNNs in the mPFC by injecting Chondroitinase ABC (chABC) resulted in anxiety-like behavior in mice. Fluoxetine (FXT) is a clinically prescribed antidepressant/anxiolytic drug. FXT treatment in CRS mice not only ameliorated their deficits in behavior and synaptic transmissions, but also prevented CRS-induced reduction of PNNs and ACAN expressions. This study demonstrates that proper PNNs level is critical to brain functions, and their decline may serve as a pathological mechanism of anxiety disorders.

Electroacupuncture promotes the repair of the damaged spinal cord in mice by mediating neurocan-perineuronal net

AIMS

This study aimed to investigate the effect of perineuronal net (PNN) and neurocan (NCAN) on spinal inhibitory parvalbumin interneuron (PV-IN), and the mechanism of electroacupuncture (EA) in promoting spinal cord injury (SCI) repair through neurocan in PNN.

METHODS

A mouse model of SCI was established. Sham-operated mice or SCI model mice were treated with chondroitin sulfate ABC (ChABC) enzyme or control vehicle for 2 weeks (i.e., sham+veh group, sham+ChABC group, SCI+veh group, and SCI+ChABC group, respectively), and then spinal cord tissues were taken from the T10 lesion epicenter for RNA sequencing (RNA-seq). MSigDB Hallmark and C5 databases for functional analysis, analysis strategies such as differential expression gene analysis (DEG), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set enrichment analysis (GSEA), and protein-protein interaction (PPI). According to the results of RNA-seq analysis, the expression of NCAN was knocked down or overexpressed by virus intervention, or/and EA intervention. Polymerase chain reaction (PCR), immunofluorescence, western blot, electrophysiological, and behavioral tests were performed.

RESULTS

After the successful establishment of SCI model, the motor dysfunction of lower limbs, and the expression of PNN core glycan protein at the epicenter of SCI were reduced. RNA-seq and PCR showed that PNN core proteoglycans except NCAN showed the same expression trend in normal and injured spinal cord treated with ChABC. KEGG and GSEA showed that PNN is mainly associated with inhibitory GABA neuronal function in injured spinal cord tissue, and PPI showed that NCAN in PNN can be associated with inhibitory neuronal function through parvalbumin (PV). Calcium imaging showed that local parvalbumin interneuron (PV-IN) activity decreased after PNN destruction, whether due to ChABC treatment or surgical bruising of the spinal cord. Overexpression of neurocan in injured spinal cord can enhance local PV-IN activity. PCR and western blot suggested that overexpression or knockdown of neurocan could up-regulate or down-regulate the expression of GAD. At the same time, the activity of PV-IN in the primary motor cortex (M1) and the primary sensory cortex of lower (S1HL) extremity changed synchronously. In addition, overexpression of neurocan improved the electrical activity of the lower limb and promoted functional repair of the paralyzed hind limb. EA intervention reversed the down-regulation of neurocan, enhanced the expression of PNN in the lesioned area, M1 and S1HL.

CONCLUSION

Neurocan in PNN can regulate the activity of PV-IN, and EA can promote functional recovery of mice with SCI by upregulating neurocan expression in PNN.

Enhanced TARP-γ8-PSD-95 coupling in excitatory neurons contributes to the rapid antidepressant-like action of ketamine in male mice

Ketamine produces rapid antidepressant effects at sub-anesthetic dosage through early and sustained activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), however, the exact molecular mechanism still remains unclear. Transmembrane AMPAR regulatory protein-γ8 (TARP-γ8) is identified as one of AMPAR auxiliary subunits, which controls assemblies, surface trafficking and gating of AMPARs. Here, we show that ketamine rescues both depressive-like behaviors and the decreased AMPARs-mediated neurotransmission by recruitment of TARP-γ8 at the postsynaptic sites in the ventral hippocampus of stressed male mice. Furthermore, the rapid antidepressant effects of ketamine are abolished by selective blockade of TARP-γ8-containing AMPAR or uncoupling of TARP-γ8 from PSD-95. Overexpression of TARP-γ8 reverses chronic stress-induced depressive-like behaviors and attenuation of AMPARs-mediated neurotransmission. Conversely, knockdown of TARP-γ8 in excitatory neurons prevents the rapid antidepressant effects of ketamine.

Deep brain stimulation of ventromedial prefrontal cortex reverses depressive-like behaviors via BDNF/TrkB signaling pathway in rats

AIM

Deep brain stimulation (DBS) is currently under investigation as a potential therapeutic approach for managing major depressive disorder (MDD) and ventromedial prefrontal cortex (vmPFC) is recognized as a promising target region. Therefore, the present study aimed to investigate a preclinical paradigm of bilateral vmPFC DBS and examine the molecular mechanisms underlying its antidepressant-like effects using chronic unpredictable stress (CUS) model in rats.

MAIN METHODS

Male rats were subjected to stereotaxic surgery and deep brain stimulation paradigm in non-stressed and CUS rats respectively, and the therapeutic effect of DBS were assessed by a series of behavioral tests including sucrose preference test, open field test, elevated plus maze test, and forced swim test. The potential involvement of the BDNF/TrkB signaling pathway and its downstream effects in this process were also investigated using western blot.

KEY FINDINGS

We identified that a stimulation protocol consisting of 130 Hz, 200 μA, 90 μs pulses administered for 5 h per day over a period of 7 days effectively mitigated CUS-induced depressive-like and anxiety-like behaviors in rats. These therapeutic effects were associated with the enhancement of the BDNF/TrkB signaling pathway and its downstream ERK1/2 activity.

SIGNIFICANCE

These findings provide valuable insights into the potential clinical utility of vmPFC DBS as an approach of improving the symptoms experienced by individuals with MDD. This evidence contributes to our understanding of the neurobiological basis of depression and offers promise for the development of more effective treatments.

Possible Involvement of Perineuronal Nets in Anti-Depressant Effects of Electroacupuncture in Chronic-Stress-Induced Depression in Rats

Acupuncture can alleviate depression-like behaviors. However, the neural mechanisms behind the anti-depressive effect remain unknown. Perineuronal net (PNN) abnormalities have been reported in multiple psychiatric disorders. This study investigated the modulation and neural mechanism of PNNs in the anti-depressant process of electroacupuncture (EA) at Baihui (GV20) and Yintang (GV29) points. A rat depression model was induced by chronic unpredicted mild stress (CUMS). The results revealed that CUMS, applied for four weeks, specifically reduces PNNs around parvalbumin (PV). In addition, EA and fluoxetine treatments reverse the decrease in PNNs+ cell density and the ratio of PV and PNN double-positive cells to PV+ neurons in the medial prefrontal cortex (mPFC) after CUMS. Furthermore, EA treatment can reverse the decrease in the protein expression of PNN components (aggrecan and brevican) in the mPFC caused by stress. After EA treatment, the decreased expression of GAD67, GLuA1, and PSD95 in the mPFC induced by CUMS for four weeks was also reversed. PNN degradation in mPFC brain areas potentially interferes with the anti-depressant benefits of EA in rats with depression induced by CUMS. EA treatment did not increase PNNs+ cell density and the ratio of PV and PNN double-positive cells to PV+ neurons after PNNs degradation in the mPFC brain region of rats. This finding indicated that the mechanism of acupuncture's anti-depressant effect may be based on reversing the CUMS-induced decline in PNN expression, the functional impairment of γ-aminobutyric acid (GABA) neurons, and the regulation of excitatory synaptic proteins expression.

Involvement of brain cell phenotypes in stress-vulnerability and resilience

Stress-related disorders' prevalence is epidemically increasing in modern society, leading to a severe impact on individuals' well-being and a great economic burden on public resources. Based on this, it is critical to understand the mechanisms by which stress induces these disorders. The study of stress made great progress in the past decades, from deeper into the hypothalamic-pituitary-adrenal axis to the understanding of the involvement of a single cell subtype on stress outcomes. In fact, many studies have used state-of-the-art tools such as chemogenetic, optogenetic, genetic manipulation, electrophysiology, pharmacology, and immunohistochemistry to investigate the role of specific cell subtypes in the stress response. In this review, we aim to gather studies addressing the involvement of specific brain cell subtypes in stress-related responses, exploring possible mechanisms associated with stress vulnerability versus resilience in preclinical models. We particularly focus on the involvement of the astrocytes, microglia, medium spiny neurons, parvalbumin neurons, pyramidal neurons, serotonergic neurons, and interneurons of different brain areas in stress-induced outcomes, resilience, and vulnerability to stress. We believe that this review can shed light on how diverse molecular mechanisms, involving specific receptors, neurotrophic factors, epigenetic enzymes, and miRNAs, among others, within these brain cell subtypes, are associated with the expression of a stress-susceptible or resilient phenotype, advancing the understanding/knowledge on the specific machinery implicate in those events.

Effect of esketamine on postoperative depressive symptoms in patients undergoing thoracoscopic lung cancer surgery: A randomized controlled trial

Background

Depressive symptoms are common among patients with lung cancer. We aimed to assess the effects of esketamine on postoperative depressive symptoms after thoracoscopic lung cancer surgery.

Methods

In this randomized, double-blind, placebo-controlled trial, 156 patients undergoing thoracoscopic lung cancer surgery were randomly allocated in a 1:1 ratio to receive intravenous esketamine (intraoperatively and in patient-controlled analgesia until 48 h postoperatively) or normal saline placebo. The primary outcome was the proportion of patients with depressive symptoms at 1 month postoperatively, assessed using the Beck Depression Inventory-II (BDI-II). Secondary outcomes included depressive symptoms at 48 h postoperatively, hospital discharge and 3 months postoperatively, BDI-II scores, anxious symptoms, Beck Anxiety Inventory scores, Quality of Recovery-15 (QoR-15) scores, and 1- and 3-month mortality.

Main results

A total of 151 patients (75 in the esketamine group and 76 in the normal saline group) completed the 1-month follow-up. The esketamine group had a significantly lower incidence of depressive symptoms at 1 month compared to the normal saline group (1.3% vs. 11.8%; risk difference = −10.5, 95%CI = −19.6% to −0.49%; p = 0.018). After excluding patients without lung cancer diagnosis, the incidence of depressive symptoms was also lower in the esketamine group (1.4% vs. 12.2%; risk difference = −10.8, 95%CI = −20.2% to −0.52%; p = 0.018). The secondary outcomes were similar between groups, except that the esketamine group had higher QoR-15 scores at 1 month postoperatively (median difference = 2; 95%CI = 0 to 5; p = 0.048). The independent risk factors for depressive symptoms were hypertension (odds ratio = 6.75, 95%CI = 1.13 to 40.31; p = 0.036) and preoperative anxious symptoms (odds ratio = 23.83, 95%CI = 3.41 to 166.33; p = 0.001).

Conclusion

Perioperative administration of esketamine reduced the incidence of depressive symptoms at 1 month after thoracoscopic lung cancer surgery. History of hypertension and preoperative anxious symptoms were independent risk factors for depressive symptoms.

Clinical trial registration: Chinese Clinical Trial Registry http://www.chictr.org.cn, Identifier (ChiCTR2100046194).

Effects of chronic fluoxetine treatment on anxiety- and depressive-like behaviors in adolescent rodents - systematic review and meta-analysis

Background

Drugs prescribed for psychiatric disorders in adolescence should be studied very extensively since they can affect developing and thus highly plastic brain differently than they affect the adult brain. Therefore, we aimed to summarize animal studies reporting the behavioral consequences of chronic exposure to the most widely prescribed antidepressant drug among adolescents i.e., fluoxetine.

Methods

Electronic databases (Medline via Pubmed, Web of Science Core Collection, ScienceDirect) were systematically searched until April 12, 2022, for published, peer-reviewed, controlled trials concerning the effects of chronic fluoxetine administration vs. vehicle on anxiety and depression measures in naïve and stress-exposed adolescent rodents. All of the relevant studies were selected and critically appraised, and a meta-analysis of eligible studies was performed.

Results

A total of 18 studies were included in the meta-analysis. In naïve animals, chronic adolescent fluoxetine administration showed dose-related anxiogenic-like effects, measured as a reduction in time spent in the open arms of the elevated plus maze. No significant effects of chronic adolescent fluoxetine on depression-like behavior were reported in naïve animals, while in stress-exposed rodents chronic adolescent fluoxetine significantly decreased immobility time in the forced swim test compared to vehicle.

Conclusions

These results suggest that although chronic fluoxetine treatment proves positive effects in animal models of depression, it may simultaneously increase anxiety in adolescent animals in a dose-related manner. Although the clinical implications of the data should be interpreted with extreme caution, adolescent patients under fluoxetine treatment should be closely monitored.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-022-00420-w.

Effects of 3-methylmethcathinone on conditioned place preference and anxiety-like behavior: Comparison with methamphetamine

3-Methylmethcathinone (3-MMC), a drug belonging to synthetic cathinones family, raised public attention due to its harmful health effects and abuse potential. Although it has similar properties to other cathinone derivatives, the behavioral effects of 3-MMC remain largely unknown. In the present research, we evaluated the rewarding effect of 3-MMC using conditioned place preference (CPP) paradigm and its effect on anxiety-like behavior using elevated plus maze (EPM) and compared with methamphetamine (METH). Then, we performed a whole-brain c-Fos mapping to identify the specific brain regions in response to 3-MMC exposure and explored the changes of synaptic transmission in nucleus accumbens (NAc) using patch-clamp recording after chronic 3-MMC and METH exposure. 3-MMC induced CPP at higher doses of 3 or 10 mg/kg in rats and acute exposure of 3 mg/kg 3-MMC to rats produced anxiolytic-like effect, while anxiety-like behavior was increased after 7 days of injection with 3-MMC. Whole-brain immunostaining revealed increased c-Fos expression in anterior cingulate cortex (ACC), NAc and ventral tegmental area (VTA) after chronic 3-MMC injection compared with saline, which was similar to METH. Especially, 3-MMC induced more neural activation of VTA compared with METH. Finally, we found that amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs) in NAc was decreased after chronic 3-MMC injection, while frequency of sIPSCs and spontaneous excitatory postsynaptic currents (sEPSCs) were not affected. Taken together, our results revealed the addictive potential of 3-MMC and its effect on anxiety-like behavior, which warn the risks of 3-MMC abuse and justify the control of synthetic cathinones. And 3-MMC selectively inhibit inhibitory but not excitatory transmission onto neurons in NAc, which may contribute to its effects.

Impact of stress on inhibitory neuronal circuits, our tribute to Bruce McEwen

This manuscript is dedicated to the memory of Bruce S. McEwen, to commemorate the impact he had on how we understand stress and neuronal plasticity, and the profound influence he exerted on our scientific careers. The focus of this review is the impact of stressors on inhibitory circuits, particularly those of the limbic system, but we also consider other regions affected by these adverse experiences. We revise the effects of acute and chronic stress during different stages of development and lifespan, taking into account the influence of the sex of the animals. We review first the influence of stress on the physiology of inhibitory neurons and on the expression of molecules related directly to GABAergic neurotransmission, and then focus on specific interneuron subpopulations, particularly on parvalbumin and somatostatin expressing cells. Then we analyze the effects of stress on molecules and structures related to the plasticity of inhibitory neurons: the polysialylated form of the neural cell adhesion molecule and perineuronal nets. Finally, we review the potential of antidepressants or environmental manipulations to revert the effects of stress on inhibitory circuits.