Corticotropin-releasing hormone neurons control trigeminal neuralgia-induced anxiodepression via a hippocampus-to-prefrontal circuit

Enhancing mPFC to BLA information transmission through chemical genetics to improve exploratory behavior in chronic stress rats

The pathogenesis of depression is fundamentally linked to the dysregulation of neural circuit structure and function. Notably, the medial prefrontal cortex (mPFC) and basolateral amygdala (BLA) are critical brain regions in the regulation of depression-related behaviors. Depressed rats exhibited attenuated messaging between the mPFC and BLA, along with abnormally enhanced theta oscillations in the BLA during the execution of an exploratory task. However, whether specific activation of the mPFC improves exploratory behavior in rats and whether recovery of exploratory behavior is mediated by the mPFC-BLA neural circuitry is unknown. We modeled depression in rats using chronic unpredictable mild stimulation (CUMS) and employed chemogenetic approaches to selectively activate mPFC glutamatergic neurons in depressed rats. Through simultaneous monitoring of behavioral patterns and local field potentials (LFPs) in both mPFC and BLA during open-field exploration, we conducted comparative analyses between chemogenetically activated and sham-stimulated groups. Our investigation focused on theta oscillation dynamics, network connectivity strength, and interregional information transfer between mPFC and BLA during exploratory behavior. The results demonstrated that chemogenetic activation of mPFC not only ameliorated exploratory deficits in depressed rats but also enhanced mPFC-to-BLA information transfer while attenuating BLA theta oscillations. These findings suggest that the restoration of mPFC-to-BLA information flow may play a crucial role in improving exploratory behavior, thereby revealing a potential neural mechanism underlying depressive state modulation.

Enhanced Rap1 small GTPase activity in the ventral hippocampus drives stress-induced anxiety

Chronic stress exposure is a primary contributor to the development of anxiety disorders, closely associated with hippocampal dysfunction. However, the underlying molecular mechanism remains poorly understood. Here, using a mouse model of chronic restraint stress (CRS), we observed a notable increase in the activity, rather than its overall expression level, of hippocampal Rap1, a small guanosine triphosphatase belonging to the Ras superfamily. Pharmacological inhibition of Rap1 activity in the ventral hippocampus (vHPC) effectively mitigated CRS-induced anxiety. Cell type-specific manipulation of Rap1 activity revealed that Rap1 dysfunction in vHPC pyramidal neurons (PNs), but not in astrocytes or interneurons, contributed to CRS-induced anxiety-like behaviors. Mechanistically, the heightened Rap1 activity in vHPC PNs augmented their intrinsic excitability through Kv4.2 phosphorylation at the Thr607 site, which contributes to the onset of anxiety-like behaviors in mice following CRS. Overall, our study reveals a previously undescribed anxiogenic effect of Rap1 and highlights it as a potential target for therapeutic intervention in stress-related mental disorders.

Lysophosphatidic acid receptor 5 in insular cortex as a potential analgesic target in neuropathic pain

Neuropathic pain remains a significant clinical challenge and existing treatments have limited efficacy and often over rely on opioids. Pharmacological inhibition and genetic knockout of lysophosphatidic acid receptor 5 (LPA5) lead to an analgesic effect on nerve injury-induced nociceptive hypersensitivity in rodents. However, the specific pain-associated regions where LPA5 is required for neuropathic pain remain unidentified. Here, we demonstrate a site-specific increase in the levels of Lpa5 mRNA and LPA5 protein in the contralateral insular cortex and hippocampus 3-14 days after chronic constriction injury (CCI) of the unilateral sciatic nerve in mice. Blocking this time-dependent increase through microinjection of adeno-associated virus 5 (AAV5) expressing Lpa5 shRNA (AAV5-LPA5 shRNA) into insular cortex mitigated CCI-induced development of nociceptive hypersensitivities. This effect was not seen after microinjection of AAV5-LPA5 shRNA into the hippocampus. Mimicking this increase through microinjection of AAV5 expressing full-length Lpa5 mRNA into the insular cortex augmented responses to mechanical, heat and cold stimuli and induced ongoing pain in naïve mice. Moreover, systemic administration of selective LPA5 antagonist RLPA-76 alleviated CCI-induced mechanical allodynia and heat hyperalgesia. All treated mice displayed normal locomotor activities. Altogether, these findings suggest that LPA5 in the insular cortex plays a critical role in neuropathic pain genesis and support LPA5 as a potential target for neuropathic pain treatment.

Role of Prefrontal Cortex Circuitry in Maintaining Social Homeostasis

Homeostasis is a fundamental concept in biology and ensures the stability of life by maintaining the constancy of physiological processes. Recent years have witnessed a surge in research interest in these physiological processes, with a growing focus on understanding the mechanisms underlying social homeostasis. This shift in focus underscores our increasing understanding of the importance of social interactions and their impact on individual well-being. In this review, we explore the interconnected research across 3 primary categories: understanding the neural mechanisms influencing set points, defining contemporary factors that can disrupt social homeostasis, and identifying the potential contributions of social homeostatic failure in the development of psychiatric diseases. We also delve into the role of the prefrontal cortex and its circuitry in regulating social behavior, decision-making processes, and the manifestation of neuropsychiatric disorders, such as depression and anxiety. Finally, we examine the influence of more recent factors such as growing social media exposure and the COVID-19 pandemic on mental health, highlighting their disruptive effects. We also identify gaps in current literature through the analysis of research trends and propose future research directions to advance our understanding of social homeostasis, with implications for mental health interventions.

A long-term mixed eosinophilic and neutrophilic chronic rhinosinusitis C57BL/6 mouse model with neuroinflammation, olfactory dysfunction and anxiety-like behaviors

BACKGROUND

Chronic rhinosinusitis (CRS) is a heterogeneous condition characterized by persistent inflammation and high recurrence rates. The mixed granulocytic endotype, marked by increased eosinophils and neutrophils, is particularly refractory and prone to relapse.

OBJECTIVE

This study aimed to evaluate the papain-induced mouse model for investigating the more refractory mixed granulocytic CRS endotype, characterized by elevated eosinophils and neutrophils.

METHODS

Male C57BL/6 mice were intranasally administered papain for 11 days to induce CRS. Cytokine profiles, nasal tissue histology, olfactory bulb analysis, assessments of olfactory function, cognition, anxiety-like and depression-like behaviors were performed at 30, 60, and 90 days post-treatment.

RESULTS

A long-term mixed eosinophilic and neutrophilic CRS model was successfully established, showing elevated IgE, IL-4, IL-5, IL-13, IL-33, TSLP, and TNF-α in nasal lavage fluid, alongside infiltration of eosinophils and neutrophils in both olfactory and respiratory regions. Chronic pathology included increased mast cells, goblet cells, basal cells, mucus hyperproduction, and epithelial damage, persisting up to 90 days, with partial improvement observed at the 60-day mark. Brain analysis revealed ongoing neuroinflammation, olfactory dysfunction, and anxiety-like behaviors in CRS mice, without signs of cognitive impairment or depression-like behaviors.

CONCLUSIONS

This study phenotypically delineated a long-term mixed eosinophilic and neutrophilic CRS mouse model, demonstrating sustained neuroinflammation, olfactory dysfunction, and anxiety-like behaviors following short-term papain exposure. These findings highlighted the role of mixed inflammation in CRS and provided a time-efficient platform for further exploration of its pathogenesis and mind-brain-body interactions.

Association between mental disorders and trigeminal neuralgia: a cohort study and Mendelian randomization analysis

BACKGROUND

Clinical observational evidence suggests a close association between Trigeminal Neuralgia (TN) and Mental disorders (MDs). However, the causal relationship between the two remains unclear. This study aims to observe and analyse the associations between depression, anxiety, insomnia, and TN through clinical research. It also employs Mendelian randomization (MR) analysis to verify the potential genetic correlation between TN and various mental disorders. offering new insights for the diagnosis, prevention, and intervention strategies for TN.

METHODS

In the cohort study section, clinical data were collected from 154 patients with TN, all of whom were excluded from preoperative use of psychotropic drugs such as carbamazepine. The PHQ-9, GAD-7, and ISI scales were used to assess preoperative symptoms of depression, anxiety, and insomnia. Multivariable linear regression models were used to identify factors associated with questionnaire scores, with model performance evaluated by adjusted R², AIC, BIC, and p-values. Patients with significant positive symptoms preoperatively were followed up one-year after surgery, and non-parametric tests were employed to examine changes in mental disorder symptoms after pain relief. In MR analysis section, the main MR analysis methods include Inverse Variance Weighted (IVW), MR Egger, Weighted Median, Simple Mode, and Weighted Mode. The Benjamini-Hochberg (BH) method was used to adjust the p -values ​​and control the false discovery rate (FDR). Subsequent sensitivity analyses involved Cochran's Q test, MR-Egger regression intercept, MR-pleiotropy residual sum and outlier test (MR-PRESSO).

RESULTS

Multiple linear regression analyses revealed that longer disease duration and greater involvement of trigeminal branches were consistently associated with higher PHQ-9, GAD-7, and ISI scores, while demographic factors and baseline BNI scores showed no significant predictive value. MR analysis indicated that autism (OR = 0.697, 95% CI [0.494-0.982], P = 0.039), schizophrenia (OR = 0.910, 95% CI [0.831-0.997], P = 0.042), and ADHD combined with OCD (OR = 0.175, 95% CI [0.044-0.693], P = 0.013) reduced the risk of TN. Conversely, bipolar disorder (OR = 1.249, 95% CI [1.016-1.535], P = 0.034), depression (OR = 2.375, 95% CI [1.043-5.409], P = 0.039), anxiety (OR = 1.174, 95% CI [1.008-1.368], P = 0.039), and insomnia (OR = 2.036, 95% CI [1.074-3.861], P = 0.029)increased the risk of TN. TN also elevated the risk of anxiety (OR = 1.43, 95% CI [1.04-1.96], P = 0.034), depression (OR = 1.00305, 95% CI [1.00036-1.00549], P = 0.013), and insomnia (OR = 1.00918, 95% CI [1.00236-1.01605], P = 0.008).

CONCLUSIONS

Longer disease duration and broader trigeminal nerve involvement were independently associated with increased severity of depressive, anxiety, and insomnia symptoms, highlighting the importance of early clinical intervention in patients with TN. And results of MR analysis provide evidence supporting a causal relationship between MDs and TN. In contrast to the traditional view that pain causes mood changes such as anxiety and depression, a variety of MDs such as anxiety, depression, and insomnia also alter the risk of developing TN.

CD38-mediated oxytocin signaling in paraventricular nucleus contributes to empathic pain

Empathy plays a crucial role in social communication and the perception of affective states and behavioral processes. In this study, we observed that empathic interaction with a mouse experiencing pain resulted in decreased mechanical pain thresholds and anxiety-like behaviors in its bystander, though the underlying mechanisms remain unknown. We demonstrated that CD38 expression in the paraventricular nucleus (PVN) was upregulated during empathic pain, and the pain and emotions of CD38 knockout (CD38KO) mice as bystanders were not affected. Furthermore, fiber photometry recordings indicated that calcium activities of PVN neurons were increased during empathic pain. Interestingly, direct chemogenetic inhibition of PVN neurons attenuated the hyperalgesia and anxiety-like behaviors associated with empathic pain. In contrast, activating PVN neurons through chemogenetics in CD38KO mice induced hyperalgesia and anxiety-like effects in empathic pain. Oxytocin levels in PVN were upregulated during empathic pain, while CD38KO mice inhibit the upregulation in OXT levels, confirming that CD38 is involved in releasing brain OXT and that the CD38-OXT system in the PVN plays a role in empathic pain. Collectively, CD38-mediated oxytocin signaling in PVN is closely linked to empathic pain through its effect on the activation of PVN neurons, and it could be viable targets for novel empathic behavior interventions.

Chronic Pain and Comorbid Emotional Disorders: Neural Circuitry and Neuroimmunity Pathways

Chronic pain is a multidimensional experience that not only involves persistent nociception but is also frequently accompanied by significant emotional disorders, such as anxiety and depression, which complicate its management and amplify its impact. This review provides an in-depth exploration of the neurobiological mechanisms underlying the comorbidity of chronic pain and emotional disturbances. Key areas of focus include the dysregulation of major neurotransmitter systems (serotonin, gamma-aminobutyric acid, and glutamate) and the resulting functional remodeling of critical neural circuits implicated in pain processing, emotional regulation, and reward. Given the contribution of neuroimmune mechanisms to pain chronicity and mood disorders, we further conducted an in-depth investigation into the role of neuroimmune factors, including resident immune cells, infiltrating immune cells, and the release of inflammatory mediators. This review further discusses current therapeutic strategies, encompassing pharmacological interventions, neuromodulation, and integrative approaches, and emphasizes the necessity of targeted treatments that address both pain and emotional components. Finally, it identifies gaps in the current understanding and outlines future research directions aimed at elucidating the complex interplay between chronic pain and emotional disorders, thereby laying the foundation for more effective and holistic treatment paradigms.

Ginsenoside Rg1 promotes non-rapid eye movement sleep via inhibition of orexin neurons of the lateral hypothalamus and corticotropin-releasing hormone neurons of the paraventricular hypothalamic nucleus

OBJECTIVE

This study investigates the sleep-modulating effects of ginsenoside Rg1 (Rg1, C42H72O14), a key bioactive component of ginseng, and elucidates its underlying mechanisms.

METHODS

C57BL/6J mice were intraperitoneally administered doses of Rg1 ranging from 12.5 to 100 mg/kg. Sleep parameters were assessed to determine the average duration of each sleep stage by monitoring the electrical activity of the brain and muscles. Further, orexin neurons in the lateral hypothalamus (LH) and corticotropin-releasing hormone (CRH) neurons in the paraventricular hypothalamic nucleus (PVH) were ablated using viral vector surgery and electrode embedding. The excitability of LHorexin and PVHCRH neurons was evaluated through the measurement of cellular Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog (c-Fos) expression.

RESULTS

Rg1 (12.5-100 mg/kg) augmented the duration of non-rapid eye movement (NREM) sleep phases, while reducing the duration of wakefulness, in a dose dependent manner. The reduced latency from wakefulness to NREM sleep indicates an accelerated sleep initiation time. We found that these sleep-promoting effects were weakened in the LHorexin and PVHCRH neuron ablation groups, and disappeared in the orexin and CRH double-ablation group. Decreased c-Fos protein expression in the LH and PVH confirmed that Rg1 promoted NREM sleep by inhibiting orexin and CRH neurons.

CONCLUSION

Rg1 increases the duration of NREM sleep, underscoring the essential roles of LHorexin and PVHCRH neurons in facilitating the sleep-promoting effects of Rg1. Please cite this article as: Wang YY, Wu Y, Yu KW, Xie HY, Gui Y, Chen CR, Wang NH. Ginsenoside Rg1 promotes non-rapid eye movement sleep via inhibition of orexin neurons of the lateral hypothalamus and corticotropin-releasing hormone neurons of the paraventricular hypothalamic nucleus. J Integr Med. 2024; 22(6): 721-730.

Progress in research of corticotropin-releasing hormone receptor 2 in inflammatory bowel disease

Members of the corticotropin-releasing hormone family and their receptors are widely distributed in central and peripheral tissues and are involved in the regulation of the cardiovascular system, metabolism, immune function, and inflammatory response in the body. Corticotropin-releasing hormone receptor 2 (CRHR2), one of specific receptors for corticotropin releasing factor, attenuates stress-induced intestinal hypersensitivity, influences intestinal microbial composition and diversity, has strong anti-inflammatory capacity, and regulates the proliferation, migration, and apoptosis of intestinal epithelial cells, and promotes intestinal mucosal repair. In recent years, studies have shown that the levels of CRHR2 in the colon tissue of patients with inflammatory bowel disease (IBD) are significantly different from those in normal human intestinal tissue, and it has been suggested that CRHR2 may be a potential therapeutic target for IBD. This paper reviews the physiological functions of CRHR2 and its clinical relevance to IBD, with the aim of exploring its specific mechanism of action and potential clinical application in the treatment of IBD, so as to provide a basis for the development of more effective therapeutic means for IBD in the future.

Identification and experimental validation of hub genes underlying depressive-like behaviors induced by chronic social defeat stress

Introduction: Major depressive disorder (MDD), characterized by severe neuropsychiatric symptoms and significant cognitive deficits, continues to present both etiological and therapeutic challenges. However, the specific underlying mechanisms and therapeutic targets remain unclear. Methods: We analyzed human postmortem dorsolateral prefrontal cortex (dlPFC) samples from MDD patients using datasets GSE53987 and GSE54568, identifying three key genes: AGA, FBXO38, and RGS5. To model depressive-like behavior, we employed chronic social defeat stress (CSDS) and subsequently measured the expression of AGA, FBXO38, and RGS5 in the dlPFC using qPCR and Western blot analysis following CSDS exposure. Results: CSDS significantly induced depressive-like behavior, and both the protein and transcriptional expression levels of AGA, FBXO38, and RGS5 in the dlPFC of mice were markedly reduced after stress, consistent with findings from datasets GSE53987 and GSE54568. Conclusion: Our research suggests that AGA, FBXO38, and RGS5 are potential biomarkers for MDD and could serve as valuable targets for MDD risk prediction.

Chronic Neuropathic Pain and Comorbid Depression Syndrome: From Neural Circuit Mechanisms to Treatment

Chronic neuropathic pain and comorbid depression syndrome (CDS) is a major worldwide health problem that affects the quality of life of patients and imposes a tremendous socioeconomic burden. More than half of patients with chronic neuropathic pain also suffer from moderate or severe depression. Due to the complex pathogenesis of CDS, there are no effective therapeutic drugs available. The lack of research on the neural circuit mechanisms of CDS limits the development of treatments. The purpose of this article is to provide an overview of the various circuits involved in CDS. Notably, activating some neural circuits can alleviate pain and/or depression, while activating other circuits can exacerbate these conditions. Moreover, we discuss current and emerging pharmacotherapies for CDS, such as ketamine. Understanding the circuit mechanisms of CDS may provide clues for the development of novel drug treatments for improved CDS management.

Propofol Alleviates Anxiety-Like Behaviors Associated with Pain by Inhibiting the Hyperactivity of PVNCRH Neurons via GABAA Receptor β3 Subunits

Pain, a comorbidity of anxiety disorders, causes substantial clinical, social, and economic burdens. Emerging evidence suggests that propofol, the most commonly used general anesthetic, may regulate psychological disorders; however, its role in pain-associated anxiety is not yet described. This study investigates the therapeutic potential of a single dose of propofol (100 mg kg-1) in alleviating pain-associated anxiety and examines the underlying neural mechanisms. In acute and chronic pain models, propofol decreased anxiety-like behaviors in the elevated plus maze (EPM) and open field (OF) tests. Propofol also reduced the serum levels of stress-related hormones including corticosterone, corticotropin-releasing hormone (CRH), and norepinephrine. Fiber photometry recordings indicated that the calcium signaling activity of CRH neurons in the paraventricular nucleus (PVNCRH) is reduced after propofol treatment. Interestingly, artificially activating PVNCRH neurons through chemogenetics interfered with the anxiety-reducing effects of propofol. Electrophysiological recordings indicated that propofol decreases the activity of PVNCRH neurons by increasing spontaneous inhibitory postsynaptic currents (sIPSCs). Further, reducing the levels of γ-aminobutyric acid type A receptor β3 (GABAAβ3) subunits in PVNCRH neurons diminished the anxiety-relieving effects of propofol. In conclusion, this study provides a mechanistic and preclinical rationale to treat pain-associated anxiety-like behaviors using a single dose of propofol.