Electroacupuncture alleviates anxiety and modulates amygdala CRH/CRHR1 signaling in single prolonged stress mice.

BACKGROUND: Post-traumatic stress disorder (PTSD) is an anxiety-related psychiatric disorder, manifesting high comorbidity with anxiety disorders. Its underlying neurobiological mechanisms have been associated with hypothalamic-pituitary-adrenal (HPA) axis dysfunction and stress hormones. Corticotropin-releasing hormone (CRH) is a primary stress hormone, expressed in the hypothalamus and amygdala. Electroacupuncture (EA) can improve mood disorders, but its mechanisms have not been fully elucidated. The aim of this study was to observe the effect of EA on PTSD and explore the related mechanisms. METHODS: We used single prolonged stress (SPS) mice to establish a PTSD model, and EA was performed after SPS or 7 days later for a week. Then we observed their fear and anxiety-like behavior through cue-induced fear condition tests, open field test and the elevated zero maze. CRH and CRH receptor 1 (CRHR1) protein levels in the amygdala were measured in SPS mice after EA intervention. RESULTS: We found that EA at ST36 and GV20 improved fear and anxiety behavior in SPS mice. The amygdala CRH and CRHR1 protein levels increased in the SPS mice, and this effect was reversed by the EA intervention. CRHR1 inhibition by the CRHR1 antagonist NBI 27914 alleviated anxiety behavior in SPS mice. CONCLUSION: CRH/CRHR1 signaling in the amygdala may contribute to the anxiolytic effect of EA in SPS mice.

A honokiol-enriched Magnolia officinalis Rehder & E.H. Wilson. bark extract possesses anxiolytic-like activity with neuroprotective effect through the modulation of CB1 receptor.

OBJECTIVES: The exposure of neurons to an excessive excitatory stimulation induces the alteration of the normal neuronal function. Mood disorders are among the first signs of alterations in the central nervous system function. Magnolia officinalis bark extract has been extensively used in the traditional medicine systems of several countries, showing several pharmacological activities. Honokiol, the main constituent of M. officinalis, is a GABA modulator and a CB1 agonist, which is deeply investigated for its role in modulating mood disorders. METHODS: Thus, we evaluated the possible neuroprotective effect of a standardized M. officinalis bark extract (MOE), enriched in honokiol, and its effect on animal mood behavioural tests and in an in vitro model of excitotoxicity. KEY FINDINGS: MOE showed neuroprotective effect using SH-SY5Y cells, by normalizing brain-derived neurotrophic factor release. Then, we tested the effect of MOE in different behavioural tests evaluating anxiety and depression and we observed a selective anxiolytic-like effect. Finally, we confirmed the involvement of CB1 in the final effect of MOE by the co-administration of the CB1 antagonist, AM251. CONCLUSION: These results suggest that MOE could be considered an effective and safe anxiolytic candidate with neuroprotective activity.

Cannabidiol as a Potential Treatment for Anxiety and Mood Disorders: Molecular Targets and Epigenetic Insights from Preclinical Research.

Cannabidiol (CBD) is the most abundant non-psychoactive component of cannabis; it displays a very low affinity for cannabinoid receptors, facilitates endocannabinoid signaling by inhibiting the hydrolysis of anandamide, and stimulates both transient receptor potential vanilloid 1 and 2 and serotonin type 1A receptors. Since CBD interacts with a wide variety of molecular targets in the brain, its therapeutic potential has been investigated in a number of neuropsychiatric diseases, including anxiety and mood disorders. Specifically, CBD has received growing attention due to its anxiolytic and antidepressant properties. As a consequence, and given its safety profile, CBD is considered a promising new agent in the treatment of anxiety and mood disorders. However, the exact molecular mechanism of action of CBD still remains unknown. In the present preclinical review, we provide a summary of animal-based studies that support the use of CBD as an anxiolytic- and antidepressant-like compound. Next, we describe neuropharmacological evidence that links the molecular pharmacology of CBD to its behavioral effects. Finally, by taking into consideration the effects of CBD on DNA methylation, histone modifications, and microRNAs, we elaborate on the putative role of epigenetic mechanisms in mediating CBD's therapeutic outcomes.

A GABAergic neural circuit in the ventromedial hypothalamus mediates chronic stress-induced bone loss.

Homeostasis of bone metabolism is regulated by the central nervous system, and mood disorders such as anxiety are associated with bone metabolism abnormalities, yet our understanding of the central neural circuits regulating bone metabolism is limited. Here, we demonstrate that chronic stress in crewmembers resulted in decreased bone density and elevated anxiety in an isolated habitat mimicking a space station. We then used a mouse model to demonstrate that GABAergic neural circuitry in the ventromedial hypothalamus (VMH) mediates chronic stress-induced bone loss. We show that GABAergic inputs in the dorsomedial VMH arise from a specific group of somatostatin neurons in the posterior region of the bed nucleus of the stria terminalis, which is indispensable for stress-induced bone loss and is able to trigger bone loss in the absence of stressors. In addition, the sympathetic system and glutamatergic neurons in the nucleus tractus solitarius were employed to regulate stress-induced bone loss. Our study has therefore identified the central neural mechanism by which chronic stress-induced mood disorders, such as anxiety, influence bone metabolism.

Effects of Paeonia lactiflora Extract on Estrogen Receptor ß, TPH2, and SERT in Rats with PMS Anxiety.

This study is to investigate the effect of Paeonia lactiflora extract on PMS anxiety and on expression of estrogen receptor ß (ERß), tryptophan hydroxylase-2 (TPH2), and serotonin transporter (SERT) in the premenstrual syndrome (PMS) anxiety model rats. The vaginal smear and open field test were used to screen rats in nonreception phase of estrus cycle with similar macroscopic behaviors and regular estrus cycle. PMS anxiety model rats were prepared by electrical stimulation. RT-PCR and immunofluorescence were used to measure the expression of ERß, TPH2, and SERT. Compared with normal rats, the total distance in the open field test of the model rats was significantly increased (P < 0.05). The model rats showed nervous alertness, irritability, and sensitivity to external stimuli. After treatment with the Paeonia lactiflora extract, the total distance of rats was significantly reduced (P < 0.05). In reception stage, there was no significant difference in the mRNA and protein expression of ERß, TPH2, and SERT. In nonreception stage, the expression of ERß and TPH2 in the model group was significantly decreased (P < 0.05) as compared with the control group, but not SERT. Abnormal changes of the above indicators were reversed after the administration of the Paeonia lactiflora extract. In conclusion, Paeonia lactiflora extract can increase the expression of ERß and TPH2 and decrease SERT in PMS model rats, which may be one of the mechanisms underlying the effect of Paeonia lactiflora extract on PMS.

Stress peptides sensitize fear circuitry to promote passive coping.

Survival relies on optimizing behavioral responses through experience. Animals often react to acute stress by switching to passive behavioral responses when coping with environmental challenge. Despite recent advances in dissecting mammalian circuitry for Pavlovian fear, the neuronal basis underlying this form of non-Pavlovian anxiety-related behavioral plasticity remains poorly understood. Here, we report that aversive experience recruits the posterior paraventricular thalamus (PVT) and corticotropin-releasing hormone (CRH) and sensitizes a Pavlovian fear circuit to promote passive responding. Site-specific lesions and optogenetic manipulations reveal that PVT-to-central amygdala (CE) projections activate anxiogenic neuronal populations in the CE that release local CRH in response to acute stress. CRH potentiates basolateral (BLA)-CE connectivity and antagonizes inhibitory gating of CE output, a mechanism linked to Pavlovian fear, to facilitate the switch from active to passive behavior. Thus, PVT-amygdala fear circuitry uses inhibitory gating in the CE as a shared dynamic motif, but relies on different cellular mechanisms (postsynaptic long-term potentiation vs. presynaptic facilitation), to multiplex active/passive response bias in Pavlovian and non-Pavlovian behavioral plasticity. These results establish a framework promoting stress-induced passive responding, which might contribute to passive emotional coping seen in human fear- and anxiety-related disorders.

Association of high-fat diet with neuroinflammation, anxiety-like defensive behavioral responses, and altered thermoregulatory responses in male rats.

Overweight and obesity are a worldwide pandemic affecting billions of people. These conditions have been associated with a chronic low-grade inflammatory state that is recognized as a risk factor for a range of somatic diseases as well as neurodevelopmental disorders, anxiety disorders, trauma- and stressor-related disorders, and affective disorders. We previously reported that the ingestion of a high-fat diet (HFD; 45% fat kcal/g) for nine weeks was capable of inducing obesity in rats in association with increased reactivity to stress and increased anxiety-related defensive behavior. In this study, we conducted a nine-week diet protocol to induce obesity in rats, followed by investigation of anxiety-related defensive behavioral responses using the elevated T-maze (ETM), numbers of FOS-immunoreactive cells after exposure of rats to the avoidance or escape task of the ETM, and neuroinflammatory cytokine expression in hypothalamic and amygdaloid nuclei. In addition, we investigated stress-induced cutaneous thermoregulatory responses during exposure to an open-field (OF). Here we demonstrated that nine weeks of HFD intake induced obesity, in association with increased abdominal fat pad weight, increased anxiety-related defensive behavioral responses, and increased proinflammatory cytokines in hypothalamic and amygdaloid nuclei. In addition, HFD exposure altered avoidance- or escape task-induced FOS-immunoreactivity within brain structures involved in control of neuroendocrine, autonomic, and behavioral responses to aversive stimuli, including the basolateral amygdala (BLA) and dorsomedial (DMH), paraventricular (PVN) and ventromedial (VMH) hypothalamic nuclei. Furthermore, rats exposed to HFD, relative to control diet-fed rats, responded with increased tail skin temperature at baseline and throughout exposure to an open-field apparatus. These data are consistent with the hypothesis that HFD induces neuroinflammation, alters excitability of brain nuclei controlling neuroendocrine, autonomic, and behavioral responses to stressful stimuli, and enhances stress reactivity and anxiety-like defensive behavioral responses.

Augmentation of Extinction and Inhibitory Learning in Anxiety and Trauma-Related Disorders.

Although the fear response is an adaptive response to threatening situations, a number of psychiatric disorders feature prominent fear-related symptoms caused, in part, by failures of extinction and inhibitory learning. The translational nature of fear conditioning paradigms has enabled us to develop a nuanced understanding of extinction and inhibitory learning based on the molecular substrates to systems neural circuitry and psychological mechanisms. This knowledge has facilitated the development of novel interventions that may augment extinction and inhibitory learning. These interventions include nonpharmacological techniques, such as behavioral methods to implement during psychotherapy, as well as device-based stimulation techniques that enhance or reduce activity in different regions of the brain. There is also emerging support for a number of psychopharmacological interventions that may augment extinction and inhibitory learning specifically if administered in conjunction with exposure-based psychotherapy. This growing body of research may offer promising novel techniques to address debilitating transdiagnostic fear-related symptoms.

Effects of 5-HT7 receptor antagonists on behaviors of mice that detect drugs used in the treatment of anxiety, depression, or schizophrenia.

5-HT7 receptors have been suggested to play a role in the regulation of psychiatric disorders. The experimental literature however is not fully consistent on this possibility. Two selective 5-HT7 receptor antagonists, DR-4004 and SB-269970, were evaluated in mouse models used to detect drugs used to treat anxiety, depression, or schizophrenia. A 5-HT-induced hypothermia assay was used to define the doses of DR-4004 and SB-269970 predicted to impact 5-HT7 receptors in the brain in vivo. 5-HT produced hypothermia in wildtype mice by either i.p. or i.c.v. routes but did not in 5-HT7 receptor knockout mice. 5-HT-induced hypothermia was not attenuated by drugs selectively blocking alpha1 or 5-HT1A receptors. Doses of DR-4004 and SB-269970 that blocked 5-HT-induced hypothermia, did not display significant anxiolytic-like (elevated plus maze; vogel conflict) or antidepressant-like efficacy (tail-suspension test) in mouse models. These compounds did demonstrate some antipsychotic-like properties in the PCP-induced hyperactivity assay and anxiolytic/anti-stress effects in the stress-induced cGMP assay. Negative findings were substantiated by positive control drugs that were active in each assay system. We conclude that 5-HT-induced hypothermia can be used to estimate blockade of central 5-HT7 receptors. Effects of DR-4004 and SB-269970 in animal models are generally consistent with the experimental literature that the evidence is mixed or not robust regarding the potential efficacy of 5-HT7 receptor antagonism in the treatment of anxiety, depression, or schizophrenia.

Psychedelics and Personality.

In the past decade, an increasing number of clinical trials are reporting evidence that psychedelics or serotonergic hallucinogens (such as lysergic acid diethylamide, psilocybin, and ayahuasca/dimethyltryptamine) could be effective in the treatment of mood, anxiety, and substance use disorders. The mechanisms responsible for these effects are not fully understood but seem to involve changes in bran dynamics in areas rich in serotonergic 5-HT2A receptors and in personality. In the present text, we present a brief and critical overview of the current research in this field, pointing out both promises and limitations of these studies.

The Interrelated Physiological and Psychological Effects of EcoMeditation.

This study investigated changes in psychological and physiological markers during a weekend meditation workshop (N = 34). Psychological symptoms of anxiety, depression, posttraumatic stress disorder (PTSD) and happiness were assessed. Physiological markers included cortisol, salivary immunoglobulin A (SigA), heart rate variability (HRV), blood pressure (BP), and resting heart rate (RHR). On posttest, significant reductions were found in cortisol (-29%, P < .0001), RHR (-5%, P = .0281), and pain (-43%, P = .0022). Happiness increased significantly (+11%, P = .0159) while the increase in SigA was nonsignificant (+27%, P = .6964). Anxiety, depression, and PTSD all declined (-26%, P = .0159; -32%, P = .0197; -18%, P = .1533), though changes in PTSD did not reach statistical significance. No changes were found in BP, HRV, and heart coherence. Participants were assessed for psychological symptoms at 3-month follow-up, but the results were nonsignificant due to inadequate sample size (n = 17). EcoMeditation shows promise as a stress-reduction method.

An exploratory study of salivary cortisol changes during chamomile extract therapy of moderate to severe generalized anxiety disorder.

OBJECTIVES: Dysfunctions in stress biology are hypothesized to contribute to anxiety disorders, and to be ameliorated during successful treatment, but limited clinical data exist to support this hypothesis. We evaluated whether increases in morning cortisol and the diurnal cortisol slope, markers of stress biology, are associated with clinical response to chamomile therapy among subjects with generalized anxiety disorder (GAD). METHODS: Among 45 subjects with DSM-IV diagnosed GAD in an open-label clinical trial of chamomile, salivary cortisol was assessed for three days each pre- and post-treatment, at 8am, 12pm, 4pm, and 8pm. Mixed model analyses assessed whether GAD symptom change predicted the degree to which cortisol levels changed during treatment. RESULTS: Symptom improvement during treatment was significantly associated with pre-to-post treatment changes in cortisol. Subjects who experienced more symptomatic improvement experienced significant increases in their morning salivary cortisol (ß = 0.48, p < 0.001), and a greater decrease in cortisol from morning to the rest of the day (ß = 0.55, p < 0.001). In addition, at baseline a lower cortisol level (ß = -0.24, p = 0.023) and a lesser decrease in cortisol after morning (ß = 0.30, p = 0.003) were associated with greater symptomatic improvement. CONCLUSION: Increases in morning salivary cortisol and the diurnal cortisol slope are associated with symptom improvement in chamomile treatment of GAD. Response to treatment for GAD could partially stem from normalization of stress biology dysfunction, but further work involving establishing abnormalities within-sample, ruling out of confounds (e.g., sleep), and a placebo control is necessary to conclude an amelioration effect. REGISTRATION CODE: NCT01072344. URL: https://clinicaltrials.gov/ct2/show/NCT01072344.

The psychoneuroimmunology of pregnancy.

Pregnancy is associated with a number of significant changes in maternal physiology. Perhaps one of the more notable changes is the significant alteration in immune function that occurs during pregnancy. This change in immune function is necessary to support a successful pregnancy, but also creates a unique period of life during which a female is susceptible to disease and, as we'll speculate here, may also contribute to mental health disorders associated with pregnancy and the postpartum period. Here, we review the known changes in peripheral immune function that occur during pregnancy and the postpartum period, while highlighting the impact of hormones during these times on immune function, brain or neural function, as well as behavior. We also discuss the known and possible impact of pregnancy-induced immune changes on neural function during this time and briefly discuss how these changes might be a risk factor for perinatal anxiety or mood disorders.

The Phytoestrogen Genistein Produces Similar Effects as 17ß-Estradiol on Anxiety-Like Behavior in Rats at 12 Weeks after Ovariectomy.

The phytoestrogen genistein produces anxiolytic-like effects in ovariectomized rats, which highlights its potential therapeutic effect in ameliorating anxiety in surgical menopausal women. However, no studies have directly compared the effects of identical doses of genistein and 17ß-estradiol, the main estrogen used in hormone replacement therapy in menopausal women. The present study evaluated the anxiolytic-like effects of identical doses of genistein and 17ß-estradiol (0.045, 0.09, and 0.18 mg/kg/7 days, s.c.) in a surgical menopause model in rats in the elevated plus maze and locomotor activity tests at 12 weeks after ovariectomy. Additionally, the participation of estrogen receptor-ß in the anxiolytic-like effect of genistein and 17ß-estradiol was explored by previous administration of the 5 mg/kg tamoxifen antagonist. Genistein and 17ß-estradiol (0.09 and 0.18 mg/kg) similarly reduced anxiety-like behavior in the elevated plus maze and also increased the time spent grooming and rearing, without affecting crossing in locomotor activity test. These effects were blocked by tamoxifen. Present results indicate that the phytoestrogen genistein has a similar behavioral profile as 17ß-estradiol in rats at 12 weeks after ovariectomy through action at the estrogen receptor-ß. Thus genistein has potential for reducing anxiety-like behavior associated with low concentrations of ovarian hormones, which normally occurs during natural and surgical menopause.

Terminalia arjuna bark extract attenuates picrotoxin-induced behavioral changes by activation of serotonergic, dopaminergic, GABAergic and antioxidant systems.

Stress and emotion are associated with several illnesses from headaches to heart diseases and immune deficiencies to central nervous system. Terminalia arjuna has been referred as traditional Indian medicine for several ailments. The present study aimed to elucidate the effect of T. arjuna bark extract (TA) against picrotoxin-induced anxiety. Forty two male Balb/c mice were randomly divided into six experimental groups (n = 7): control, diazepam (1.5 mg·kg-1), picrotoxin (1 mg·kg-1) and three TA treatemt groups (25, 50, and 100 mg/kg). Behavioral paradigms and PCR studies were performed to determine the effect of TA against picrotoxin-induced anxiety. The results showed that TA supplementation increased locomotion towards open arm (EPM) and illuminated area (light-dark box test), and increased rearing frequency (open field test) in a dose dependent manner, compared to picrotoxin (P < 0.05). Furthermore, TA increased number of licks and shocks in Vogel's conflict. PCR studies showed an up-regulation of several genes, such as BDNF, IP3, D2L, CREB, GABAA, SOD, GPx, and GR in TA administered groups. In conclusion, alcoholic extract of TA bark showed protective activity against picrotoxin in mice by modulation of genes related to synaptic plasticity, neurotransmitters, and antioxidant enzymes.

Distribution of corticotropin-releasing factor receptor 1 in the developing mouse forebrain: A novel sex difference revealed in the rostral periventricular hypothalamus.

Corticotropin-releasing factor (CRF) signaling through CRF receptor 1 (CRFR1) regulates autonomic, endocrine and behavioral responses to stress and has been implicated in the pathophysiology of several disorders including anxiety, depression, and addiction. Using a validated CRFR1 reporter mouse line (bacterial artificial chromosome identified by green fluorescence protein (BAC GFP-CRFR1)), we investigated the distribution of CRFR1 in the developing mouse forebrain. Distribution of CRFR1 was investigated at postnatal days (P) 0, 4, and 21 in male and female mice. CRFR1 increased with age in several regions including the medial amygdala, arcuate nucleus, paraventricular hypothalamus, medial septum, CA1 hippocampal area, and the lateral habenula. Regions showing decreased CRFR1 expression with increased age include the intermediate portion of the periventricular hypothalamic nucleus, and CA3 hippocampal area. We report a sexually dimorphic expression of CRFR1 within the rostral portion of the anteroventral periventricular nucleus of the hypothalamus (AVPV/PeN), a region known to regulate ovulation, reproductive and maternal behaviors. Females had a greater number of CRFR1-GFP-ir cells at all time points in the AVPV/PeN and CRFR1-GFP-ir was nearly absent in males by P21. Overall, alterations in CRFR1-GFP-ir distribution based on age and sex may contribute to observed age- and sex-dependent differences in stress regulation.

Upregulation of Mineralocorticoid Receptor in the Hypothalamus Associated with a High Anxiety-like Level in Apolipoprotein E4 Transgenic Mice.

Anxiety symptoms occur in a large portion of Alzheimer's disease (AD) patients. ApolipoproteinE-4 (ApoE ε4 allele), a risk factor for AD, has been recognized as an important contributor to psychiatric disorders. In the present study, we aimed to investigate the corticosterone level in relation to anxiety-like behavior changes in transgenic male mice with different glial fibrillary acidic protein (GFAP)-ApoE isoforms. GFAP-ApoE4 transgenic mice aged 3 months showed higher anxiety-like behavior in open field, light-dark box and elevated plus maze tasks compared with that of age-matched GFAP-ApoE3 mice. However, corticotropin releasing factor levels in the hypothalamus and plasma corticosterone secretion were similar in GFAP-ApoE3 and GFAP-ApoE4 transgenic male mice. Additionally, increased expression of the mineralocorticoid receptor (MR) and unchanged expression of the glucocorticoid receptor were observed in the hypothalamus of GFAP-ApoE4 mice. However, no significant differences were found in the expression levels of the MR in GFAP-ApoE3 and GFAP-ApoE4 mice at postnatal day 2. In conclusion, we found that MR upregulation rather than corticosterone level changes in the early stage of adulthood was associated with the higher anxiety-like level measured in GFAP-ApoE4 mice.

Ethnopharmacological approaches in mood and anxiety disorders. The relevance of the oxidative stress status.

Neurodegenerative diseases and psychiatric disorders are one of the most important pathologies that lead to increased morbidity in populations. Both mood and anxiety disorders include mental disorders not caused by detectable organic abnormalities of the brain. At the molecular level, affective spectrum symptomatology is due to neurotransmitter dysregulation including receptor or transporter impairments and also due to faulty intracellular signaling that generally leads to impaired neurotransmission. Also, recent studies have shown the relationship between oxidative stress and the development of affective disorders. Since classical medication can cause major side effects and alternative approaches tend to be more and more trusted, it seems that plant extracts-based complementary therapies may offer superior yielding and safety compared to traditional medication.

Working memory dysfunction associated with brain functional deficits and cellular metabolic changes in patients with generalized anxiety disorder.

Generalized anxiety disorder (GAD) is associated with brain functional and morphological changes in connected with emotional dysregulation and cognitive deficit. This study dealt with the neural functional deficits and metabolic abnormalities in working memory (WM) task with emotion-inducing distractors in patients with GAD. Fourteen patients with GAD and 14 healthy controls underwent functional magnetic resonance imaging (fMRI) and proton magnetic resonance spectroscopy ((1)H-MRS) at 3T. In response to the emotional distractors in WM tasks, the patients concurrently showed higher activity in the hippocampus and lower activities in the superior occipital gyrus, superior parietal gyrus, dorsolateral prefrontal cortex (DLPFC) and precentral gyrus compared to the controls. MRS revealed significantly lower choline/creatine (Cho/Cr) and choline/N-acetylaspartate (Cho/NAA) ratios in the DLPFC. In particular, the Cho ratios were positively correlated with the brain activities based on blood oxygenation level-dependent signal change in the DLPFC. This study provides the first evidence for the association between the metabolic alterations and functional deficit in WM processing with emotion-inducing distractors in GAD. These findings will be helpful to understand the neural dysfunction in connection with WM impairment in GAD.

Chronic activation of NPFFR2 stimulates the stress-related depressive behaviors through HPA axis modulation.

Neuropeptide FF (NPFF) is a morphine-modulating peptide that regulates the analgesic effect of opioids, and also controls food consumption and cardiovascular function through its interaction with two cognate receptors, NPFFR1 and NPFFR2. In the present study, we explore a novel modulatory role for NPFF-NPFFR2 in stress-related depressive behaviors. In a mouse model of chronic mild stress (CMS)-induced depression, the expression of NPFF significantly increased in the hypothalamus, hippocampus, medial prefrontal cortex (mPFC) and amygdala. In addition, transgenic (Tg) mice over-expressing NPFFR2 displayed clear depression and anxiety-like behaviors with hyperactivity in the hypothalamic-pituitary-adrenal (HPA) axis, reduced expression of glucocorticoid receptor (GR) and neurogenesis in the hippocampus. Furthermore, acute treatment of NPFFR2 agonists in wild-type (WT) mice enhanced the activity of the HPA axis, and chronic administration resulted in depressive and anxiety-like behaviors. Chronic stimulation of NPFFR2 also decreased the expression of hippocampal GR and led to persistent activation of the HPA axis. Strikingly, bilateral intra-paraventricular nucleus (PVN) injection of NPFFR2 shRNA predominately inhibits the depressive-like behavior in CMS-exposed mice. Antidepressants, fluoxetine and ketamine, effectively relieved the depressive behaviors of NPFFR2-Tg mice. We speculate that persistent NPFFR2 activation, in particular in the hypothalamus, up-regulates the HPA axis and results in long-lasting increases in circulating corticosterone (CORT), consequently damaging hippocampal function. This novel role of NPFFR2 in regulating the HPA axis and hippocampal function provides a new avenue for combating depression and anxiety-like disorder.