The role of 5-HT receptors in depression

Feasibility of Using Serum, Plasma, and Platelet 5-hydroxytryptamine as Peripheral Biomarker for the Depression Diagnosis and Response Evaluation to Antidepressants: Animal Experimental Study

Objective

Whether peripheral blood 5-hydroxytrptamine (5-HT) levels serve as biomarker for depression diagnosis/response evaluation has not been well determined. This work was explored to address this inconclusive issue.

Methods

Animals were randomized into normal control group (NC, n = 10) and chronic unpredictable mild stress model group (CUMS-model, n = 20), respectively. Animals in CUMS-model group were subjected to chronic stress, then they were randomly subdivided into CUMS subgroup and CUMS + fluoxetine subgroup (CUMS + FLX). After FLX treatment, blood and tissues were collected. 5-HT and relevant protein expression were measured.

Results

In mice model, there was a significant increase in serum and a significant reduction in plasma 5-HT levels in CUMS-model group versus NC group, while platelet 5-HT levels change little. After FLX treatment, serum and platelet 5-HT levels were significantly decreased in CUMS + FLX subgroup, while plasma 5-HT levels had not much change versus CUMS subgroup. Chronic stress enhanced colon and platelet serotonin transporter (SERT) expression and FLX treatment mitigated SERT expression. In rats' model, there was a significant increase in serum 5-HT levels while plasma and platelet 5-HT levels showed little change in CUMS group versus NC group. After FLX treatment, serum, plasma and platelet 5-HT levels were significantly decreased in CUMS + FLX subgroup versus CUMS subgroup. The profile of relevant proteins expression changed by FLX were like those in mice.

Conclusion

Serum 5-HT levels might serve as a potential biomarker for depression diagnosis, meanwhile serum and platelet 5-HT levels might respond to antidepressant treatment.

Yeast Extract Peptides Alleviate Depression in Chronic Restraint Stress Rats by Alleviating Hippocampal Neuronal Apoptosis and Dysbiosis of the Gut Microbiota

SCOPE

Depression as a global neurological disorder, and hippocampal neuronal apoptosis and disorders of the gut microbiota are closely related to it. This study aims to expose the ameliorative effect of enzyme peptides (AP) from brewer's yeast on depressive behavior caused by chronic restraint stress (CRS) in rats.

METHODS AND RESULTS

After 4 weeks of AP intervention, a significant alleviation of depressive behavior in the sucrose preference test (SPT), forced swim test (FST), and light-dark test (LDT) is observed in depressed rats. AP ameliorates neuronal damage with increased the expression of the key CREB/BDNF/TrkB/Akt signaling pathway, which increases the levels of the monoamine neurotransmitters 5-hydroxytryptamine (5-HT) and norepinephrine (NE) in the hippocampus, buffering hyperactivity of the hypothalamo-pituitary-adrenal axis (HPA), and decreasing the serum cortisol (CORT) and adrenocorticotropic hormone (ACTH) levels in rats. In addition, AP modulates the disruption of the rat gut microbiota by chronic restraint stress (CRS), and the changes in the abundance of Lactobacillus animalis and Lactobacillus johnsonii are probably the key for AP performing antidepressant benefits. A strong correlation is found between gut microbiota and biochemical markers of depression.

CONCLUSION

AP, as a natural and safe active substance, has a positive effect in the treatment of depression.

Ghrelin in Depression: A Promising Therapeutic Target

Depression is a widespread disease affecting over 300 million individuals of various ethnicities and socioeconomic backgrounds globally. It frequently strikes early in life and becomes a chronic or recurring lifelong illness. Out of the various hypotheses for the pathophysiology of depression, the gut-brain axis and stress hypothesis are the ones that need to be researched, as psychological stress impairs one or more pathways of the brain-gut axis and is likely to cause brain-gut axis dysfunction and depression. A dysfunctional reciprocal gut-brain relationship may contribute to many diseases, including inflammatory disorders, abnormal stress responses, impaired behavior, and metabolic changes. The hormone ghrelin is a topic of interest concerning the gut-brain axis as it interacts with the gut-brain axis indirectly via the central nervous system or via crossing the blood-brain barrier. Ghrelin release is also affected by the gut microbes, which has also been discussed in the review. This review elaborates on Ghrelin's role in depression and its effect on various aspects like neurogenesis, HPA axis, and neuroinflammation. Furthermore, this review focuses on ghrelin as a potential target for alleviation of depressive symptoms.

The dorsal raphe-to-ventral hippocampal projection modulates reactive aggression through 5-HT1B receptors

Maladaptive reactive aggression is a core symptom of neuropsychiatric disorders such as schizophrenia. While uncontrolled aggression dampens societal safety, there is a limited understanding of the neural regulation involved in reactive aggression and its treatment. High levels of aggression have been linked to low serotonin (5-HT) levels. Additionally, post-weaning socially isolated (SI) mice exhibit outbursts of aggression following encountering acute stress, and hyperactivated ventral hippocampus (vHip) involves this stress-provoked escalated aggression. Here, we investigated the potential role of the raphe nucleus projecting to the vHip in modulating aggressive behavior. Chemogenetically activating the dorsal raphe nucleus (DRN) soma projecting the vHip or DRN nerve terminals in the vHip reduced reactive aggression. The reduction of attack behavior was abolished by the pretreatment of 5-HT1B receptor antagonist SB-224289. However, activating the median raphe nucleus (MRN)-to-vHip pathway ameliorated depression-like behavior but did not affect reactive aggression. DRN→vHip activation suppressed the vHip downstream area, the ventromedial hypothalamus (VMH), which is a core aggression area. Intra-vHip infusion of 5-HT1B receptor agonists (anpirtoline, CP-93129) suppressed reactive aggression and decreased c-Fos levels in the vHip neurons projecting to the VMH, suggesting an inhibition mechanism. Our findings indicate that activating the DRN projecting to the vHip is sufficient to inhibit reactive aggression in a 5-HT1B receptor-dependent manner. Thus, targeting 5-HT1B receptor could serve as a promising therapeutic approach to ameliorate symptoms of reactive aggression.

Association between chronic disease status and transitions in depressive symptoms among middle-aged and older Chinese population: Insights from a Markov model-based cohort study

BACKGROUND

The relationship between chronic disease status (CDS) and transitions in depressive symptoms (DS) remains unclear. This study explores the association between CDS and DS transitions.

METHODS

This cohort study analyzed data from 8175 participants aged 45+, sourced from China Family Panel Studies (2016, 2018, 2020). DS were assessed using a brief version of Center for Epidemiologic Studies Depression Scale (CES-D). CDS was categorized into healthy, single disease, and multimorbidity. Markov models were used to estimate state transition intensities, mean sojourn times and hazard ratios (HRs).

RESULTS

DS transitions occurred between adjacent and non-adjacent states, but transition intensity between adjacent states was higher than among non-adjacent states. Self-transition intensities of severe-DS, mild-DS, and non-DS progressively increased, with average durations of 1.365, 1.482, and 7.854 years, respectively. Both single disease and multimorbidity were significantly associated with an increased risk of transitioning from non-DS to mild-DS, with multimorbidity showing a stronger association. In contrast, HRs for single diseases transitioning from mild-DS to severe-DS were significantly lower than 1. Furthermore, their HRs were almost <1 in recovery transitions but not statistically significant.

LIMITATIONS

Specific chronic diseases and their combinations were not analyzed.

CONCLUSIONS

The progression of DS exhibits various pathways. CDS is associated with DS transitions, but the roles of single disease and multimorbidity may differ across different DS progression stages. Both conditions were significantly linked to the risk of new-onset DS, with multimorbidity posing a greater association. However, this relationship is not observed in other progression stages. These findings could provide insights for early prevention and intervention for DS.

Deciphering the role of siRNA in anxiety and depression

Anxiety and depression are central nervous system illnesses that are among the most prevalent medical concerns of the twenty-first century. Patients with this condition and their families bear psychological, financial, and societal hardship. There are currently restrictions when utilizing the conventional course of treatment. RNA interference is expected to become an essential approach in anxiety and depression due to its potent and targeted gene silencing. Silencing of genes by post-transcriptional modification is the mechanism of action of small interfering RNA (siRNA). The suppression of genes linked to disease is typically accomplished by siRNA molecules in an efficient and targeted manner. Unfavourable immune responses, off-target effects, naked siRNA instability, nuclease vulnerability, and the requirement to create an appropriate delivery method are some of the challenges facing the clinical application of siRNA. This review focuses on the use of siRNA in the treatment of anxiety and depression.

Serotonin in depression and Alzheimer's disease: Focus on SSRI's beneficial effects

Depression is a complex and pervasive mental health disorder affecting millions globally. Serotonin, a critical neurotransmitter, plays a central role in the pathophysiology of depression. This review explores serotonin's multifaceted role in depression, focusing on its synthesis, bioavailability, receptor interactions, and the impact of various factors, including diet, stress, and gender differences. This review aims to provide a comprehensive understanding of serotonin's role in depression by examining its synthesis and structure, its bioavailability and dietary influences, and its interactions with stress and immune responses. Additionally, it investigates the influence of age, socioeconomic status, and gender on depression, and integrates findings from animal research to elucidate serotonin's impact on mood disorders and cognitive decline. A literature review was conducted using PubMed, Google Scholar, and Embase databases. Key focus areas included serotonin synthesis and receptor interactions, dietary effects on serotonin bioavailability, and the relationship between serotonin, immune responses, and stress. Gender differences, age-related factors, and socioeconomic influences on depression were also examined. Studies were thematically categorized and analyzed to provide a cohesive overview. Our review highlights that serotonin synthesis involves a complex enzymatic process, with recent structural studies revealing intricate receptor interactions. Dietary factors significantly impact serotonin levels, with interventions potentially modulating mood disorders. Stress and immune responses are linked to serotonin dynamics, with chronic stress exacerbating mood disorders and influencing cognitive decline. Animal studies underscore serotonin's role in mood regulation and cognitive function, while human research reveals how age, gender, and socioeconomic factors affect depression. The findings emphasize the need for a multidimensional approach to understanding and treating depression. Various factors, including diet, stress, and immune responses, influence serotonin's role in mood disorders. The review suggests potential therapeutic pathways involving dietary interventions and stress management. Furthermore, gender-specific considerations and the impact of age and socioeconomic status on depression outcomes highlight the need for tailored treatment strategies.

Evaluation of 4 quantification methods for monitoring 16 antidepressant drugs and their metabolites in human plasma by LC-MS/MS

BACKGROUND

Therapeutic drug monitoring for antidepressants (ADs) is vital due to the potentially serious consequences and disputes related to medical events. Therefore, we created a quick and convenient analysis way for separation and quantification of ADs.

METHODS

To ensure quantitative stability, we divided the 16 ADs or their metabolites into 4 pools (AD1-AD4), considering the hospital frequency that the clinician prescribed, the physicochemical properties of medicines, and the calibration range of selected ADs. After precipitation with methanol, the analytes were eluted for at least 3.5 min on a BEH C18 analytical column by different gradient elution methods.

RESULTS

The LLOQ and LOD were 1.25-10 ng/mL and 0.42-5 ng/mL, respectively. High precision (<12 %) and accuracy (87.07-111.47 %) were demonstrated by quality control samples both within and between days. All the compounds were stable at room temperature and within -80 °C.

CONCLUSION

The method is of wide clinical and laboratory interest due to simpler sample cleanup, shorter chromatographic run times, and wider calibration range compared to other methods.

Dorsal raphe dopaminergic neurons target CaMKII+ neurons in dorsal bed nucleus of the stria terminalis for mediating depression-related behaviors

Dopamine (DA) neurons play a crucial role in the development and manifestation of depression, as well as in response to antidepressant treatments. While the function of the predominantly distributed DA neurons in the ventral tegmental area (VTA) is well established, the contribution of a small fraction of DA neurons in the dorsal raphe nucleus (DRN) during depression remains unclear. In this study, we found that chronic unpredictable stress (CUS) induces depression-related behaviors and decreases spontaneous firing rates, excitatory and inhibitory postsynaptic currents of DA neurons in the DRN associated with reduced excitatory synaptic transmission in male and female mice. The chemogenetic inhibition of DA neurons in the DRN produces depressive phenotypes. Conversely, their activation completely reversed the anhedonic and despair behaviors induced by CUS. Furthermore, we showed that a DRN dopaminergic projecting to the dorsal bed nucleus of the stria terminalis (dBNST) selectively controls depressive behaviors by influencing the neural activity and N-methyl-D-aspartate receptor (NMDAR) mediating EPSC of calcium/calmodulin-dependent protein kinase II+ (CaMKII+) target neurons by regulating dopamine neurotransmitter and dopamine receptor 2 (DR2) in the dBNST. Overall, these findings highlight the essential role of the DRNDA → dBNSTCaMKII+ neural circuit in bi-directionally mediating stress-induced depression-related behaviors. Our findings indicate that DRN DA neurons are a key component of the neural circuitry involved in regulating depression-related behaviors, making them a potential therapeutic target for depression.

Serotonergic neuromodulation of synaptic plasticity

Synaptic plasticity constitutes a fundamental process in the reorganization of neural networks that underlie memory, cognition, emotional responses, and behavioral planning. At the core of this phenomenon lie Hebbian mechanisms, wherein frequent synaptic stimulation induces long-term potentiation (LTP), while less activation leads to long-term depression (LTD). The synaptic reorganization of neuronal networks is regulated by serotonin (5-HT), a neuromodulator capable of modify synaptic plasticity to appropriately respond to mental and behavioral states, such as alertness, attention, concentration, motivation, and mood. Lately, understanding the serotonergic Neuromodulation of synaptic plasticity has become imperative for unraveling its impact on cognitive, emotional, and behavioral functions. Through a comparative analysis across three main forebrain structures-the hippocampus, amygdala, and prefrontal cortex, this review discusses the actions of 5-HT on synaptic plasticity, offering insights into its role as a neuromodulator involved in emotional and cognitive functions. By distinguishing between plastic and metaplastic effects, we provide a comprehensive overview about the mechanisms of 5-HT neuromodulation of synaptic plasticity and associated functions across different brain regions.

The interplay of serotonin 5-HT1A and 5-HT7 receptors in chronic stress

Serotonin regulates multiple physiological and pathological processes in the brain, including mood and cognition. The serotonin receptors 5-HT1AR (also known as HTR1A) and 5-HT7R (also known as HTR7) have emerged as key players in stress-related disorders, particularly depression. These receptors can form heterodimers, which influence their functions. Here, we explored the developmental dynamics of 5-HT1AR and 5-HT7R expression and validated heterodimerization levels in the brain of control and stressed mice. In control animals, we found that there was an increase in 5-HT1AR expression over 5-HT7R in the prefrontal cortex (PFC) and hippocampus during development. Using a chronic unpredictable stress as a depression model, we found an increase in 5-HT7R expression exclusively in the PFC of resilient animals, whereas no changes in 5-HT1AR expression between control and anhedonic mice were obtained. Quantitative in situ analysis of heterodimerization revealed the PFC as the region exhibiting the highest abundance of 5-HT1AR-5-HT7R heterodimers. More importantly, upon chronic stress, the amount of heterodimers was significantly reduced only in PFC of anhedonic mice, whereas it was not affected in resilient animals. These results suggest an important role of brain-region-specific 5-HT1AR-5-HT7R heterodimerization for establishing depressive-like behaviour and for development of resiliency.

Monoamine alterations in Alzheimer's disease and their implications in comorbid neuropsychiatric symptoms

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by relentless cognitive decline and the emergence of profoundly disruptive neuropsychiatric symptoms. As the disease progresses, it unveils a formidable array of neuropsychiatric manifestations, including debilitating depression, anxiety, agitation, and distressing episodes of psychosis. The intricate web of the monoaminergic system, governed by serotonin, dopamine, and norepinephrine, significantly influences our mood, cognition, and behavior. Emerging evidence suggests that dysregulation and degeneration of this system occur early in AD, leading to notable alterations in these critical neurotransmitters' levels, metabolism, and receptor function. However, how the degeneration of monoaminergic neurons and subsequent compensatory changes contribute to the presentation of neuropsychiatric symptoms observed in Alzheimer's disease remains elusive. This review synthesizes current findings on monoamine alterations in AD and explores how these changes contribute to the neuropsychiatric symptomatology of the disease. By elucidating the biological underpinnings of AD-related psychiatric symptoms, we aim to underscore the complexity and inform innovative approaches for treating neuropsychiatric symptoms in AD.

Reactive Astrocytosis-A Potential Contributor to Increased Suicide in Long COVID-19 Patients?

BACKGROUND

Long COVID-19 is an emerging chronic illness of significant public health concern due to a myriad of neuropsychiatric sequelae, including increased suicidal ideation (SI) and behavior (SB).

METHODS

This review provides a concise synthesis of clinical evidence that points toward the dysfunction of astrocytes, the most abundant glial cell type in the central nervous system, as a potential shared pathology between SI/SB and COVID-19.

RESULTS

Depression, a suicide risk factor, and SI/SB were both associated with reduced frequencies of various astrocyte subsets and complex proteomic/transcriptional changes of astrocyte-related markers in a brain-region-specific manner. Astrocyte-related circulating markers were increased in depressed subjects and, to a less consistent extent, in COVID-19 patients. Furthermore, reactive astrocytosis was observed in subjects with SI/SB and those with COVID-19.

CONCLUSIONS

Astrocyte dysfunctions occurred in depression, SI/SB, and COVID-19. Reactive-astrocyte-mediated loss of the blood-brain barrier (BBB) integrity and subsequent neuroinflammation-a factor previously linked to SI/SB development-might contribute to increased suicide in individuals with long COVID-19. As such, the formulation of new therapeutic strategies to restore astrocyte homeostasis, enhance BBB integrity, and mitigate neuroinflammation may reduce SI/SB-associated neuropsychiatric manifestations among long COVID-19 patients.

Association of the Serotonin and Kynurenine Pathways as Possible Therapeutic Targets to Modulate Pain in Patients with Fibromyalgia

Fibromyalgia (FM) is a disorder characterized by widespread chronic pain, significant depression, and various neural abnormalities. Recent research suggests a reciprocal exacerbation mechanism between chronic pain and depression. In patients with FM, dysregulation of tryptophan (Trp) metabolism has been identified. Trp, an essential amino acid, serves as a precursor to serotonin (5-HT), a neuromodulator that influences mood, appetite, sleep, and pain perception through the receptors 5-HT1, 5-HT2, and 5-HT3. Additionally, Trp is involved in the kynurenine pathway, a critical route in the immune response, inflammation, and production of neuroactive substances and nicotinamide adenine dinucleotide (NAD+). The activation of this pathway by pro-inflammatory cytokines, such as tumor necrosis factor α (TNF-α) and interferon gamma (IFN-γ), leads to the production of kynurenic acid (KYNA), which has neuroprotective properties, and quinolinic acid (QA), which is neurotoxic. These findings underscore the crucial balance between Trp metabolism, 5-HT, and kynurenine, where an imbalance can contribute to the dual burden of pain and depression in patients with FM. This review proposes a novel therapeutic approach for FM pain management, focusing on inhibiting QA synthesis while co-administering selective serotonin reuptake inhibitors to potentially increase KYNA levels, thus dampening pain perception and improving patient outcomes.

A comparison of ondansetron in preventing postoperative nausea and vomiting for patients with or without preoperative anxiety with painless egg retrieval: a prospective, randomized, controlled trial

Background

Patients undergoing painless egg retrieval are prone to preoperative anxiety, and whether preoperative anxiety induces postoperative nausea and vomiting (PONV) is debated. The primary objective of this prospective, randomized, controlled study was to compare the clinical effect of ondansetron in preventing PONV for patients with and without preoperative anxiety. The secondary objective was to investigate whether preoperative anxiety was associated with PONV.

Methods

The self-rating anxiety scale (SAS) was used to assess the anxiety patients undergoing painless egg retrieval. Patients with a SAS standard score of 50-60 were selected to the anxiety group (n=105); and patients with a SAS standard score of 25-35 were assigned to the non-anxiety group (n=104). Venous blood samples of both groups of patients were obtained during admission and 1 hour after surgery, and all serotonin (5-HT) levels were tested using an enzyme-linked immunosorbent assay. The anxiety group was then randomly assigned into two subgroups: ondansetron (AO group, n=53) and placebo saline (AS group, n=52). Similarly, patients in the non-anxiety group were also randomly assigned to one of two subgroups: ondansetron (NO group, n=51) and placebo saline (NS group, n=53). The AO and NO groups received 8 mg (4 mL) of intravenous ondansetron 15 minutes before surgery, while the AS and NS groups received an equivalent volume (4 mL) of normal saline. We then analyzed the vital signs, risk factors for nausea and vomiting, intraoperative anesthetic doses, incidences of nausea and vomiting in 24 hours after surgery, serum 5-HT level before and after surgery, other adverse responses, pain scores, and satisfaction.

Results

A total of 200 patients eventually completed this study. The serum 5-HT values in the anxiety group were higher before and after surgery than in the non-anxiety group (P<0.05), but there was no significant difference in serum 5-HT before and after surgery in the same group (P>0.05). The incidence of PONV was more significant in the AS group than in the NS group (P<0.05). The incidence of PONV was also higher in the AS group than in the AO group (P<0.05). Still, there was no statistically significant difference between the NO and NS groups (P>0.05). There were no significant differences between the four groups in vital signs, risk factors for nausea and vomiting, intraoperative anesthetic doses, other adverse responses and pain scores (P>0.05). Patients in the AS group had lower satisfaction scores than those in the other three groups (P<0.05).

Conclusions

Patients experiencing preoperative anxiety have a greater risk of PONV following painless egg retrieval compared to those without preoperative anxiety. Ondansetron can reduce the occurrence of PONV in patients with preoperative anxiety, but it has no discernible preventative effect in non-anxious patients.

Trial Registration

Chinese Clinical Trial Registry ChiCTR2400079504.

Obstructive Sleep Apnea and Serotoninergic Signalling Pathway: Pathomechanism and Therapeutic Potential

Obstructive Sleep Apnea (OSA) is a disorder characterized by repeated upper airway collapse during sleep, leading to apneas and/or hypopneas, with associated symptoms like intermittent hypoxia and sleep fragmentation. One of the agents contributing to OSA occurrence and development seems to be serotonin (5-HT). Currently, the research focuses on establishing and interlinking OSA pathogenesis and the severity of the disease on the molecular neurotransmitter omnipresent in the human body-serotonin, its pathway, products, receptors, drugs affecting the levels of serotonin, or genetic predisposition. The 5-HT system is associated with numerous physiological processes such as digestion, circulation, sleep, respiration, and muscle tone-all of which are considered factors promoting and influencing the course of OSA because of correlations with comorbid conditions. Comorbidities include obesity, physiological and behavioral disorders as well as cardiovascular diseases. Additionally, both serotonin imbalance and OSA are connected with psychiatric comorbidities, such as depression, anxiety, or cognitive dysfunction. Pharmacological agents that target 5-HT receptors have shown varying degrees of efficacy in reducing the Apnea-Hypopnea Index and improving OSA symptoms. The potential role of the 5-HT signaling pathway in modulating OSA provides a promising avenue for new therapeutic interventions that could accompany the primary treatment of OSA-continuous positive airway pressure. Thus, this review aims to elucidate the complex role of 5-HT and its regulatory mechanisms in OSA pathophysiology, evaluating its potential as a therapeutic target. We also summarize the relationship between 5-HT signaling and various physiological functions, as well as its correlations with comorbid conditions.

Phase 1, placebo-controlled, single ascending dose trial to evaluate the safety, pharmacokinetics and effect on altered states of consciousness of intranasal BPL-003 (5-methoxy-N,N-dimethyltryptamine benzoate) in healthy participants

AIMS

To investigate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of BPL-003, a novel intranasal benzoate salt formulation of 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), in healthy participants.

METHODS

In all, 44 psychedelic-naïve participants enrolled in the double-blind, placebo-controlled single ascending dose study (1-12 mg BPL-003). Concentrations of 5-MeO-DMT and its pharmacologically active metabolite, bufotenine, were determined in plasma and urine. PD endpoints included subjective drug intensity (SDI) rating, the Mystical Experience Questionnaire (MEQ-30) and the Ego Dissolution Inventory (EDI).

RESULTS

BPL-003 was well tolerated at doses up to 12 mg. There were no serious adverse events (AEs), and most AEs were mild; the most common being nasal discomfort, nausea, headache and vomiting. 5-MeO-DMT was rapidly absorbed and eliminated; the median time to peak plasma concentration was approximately 8-10 min and the mean terminal elimination half-life was <27 min. 5-MeO-DMT systemic exposure increased approximately dose-proportionally, while plasma bufotenine concentrations and urinary excretion of 5-MeO-DMT and bufotenine were negligible. The intensity of the SDI ratings was associated with plasma 5-MeO-DMT concentrations. MEQ-30 and EDI scores generally increased with the BPL-003 dose; 60% of participants had a 'complete mystical experience' at 10 and 12 mg doses. Profound and highly emotional consciousness-altering effects were observed with BPL-003, with a rapid onset and short-lasting duration.

CONCLUSION

The novel intranasal formulation of BPL-003 was well tolerated with dose-proportional increases in PK and PD effects. The short duration of action and induction of mystical experiences suggest clinical potential, warranting further trials.

CLINICAL TRIAL REGISTRATION

NCT05347849.

N-(3-((3-(trifluoromethyl)phenyl)selanyl)prop-2-yn-1-yl) benzamide induces antidepressant-like effect in mice: involvement of the serotonergic system

RATIONALE

Major Depressive Disorder (MDD) significantly impairs the quality of life for those affected. While the exact causes of MDD are not fully understood, the deficit of monoamines, especially serotonin and noradrenaline, is widely accepted. Resistance to long-term treatments and adverse effects are often observed, highlighting the need for new pharmacological therapies. Synthetic organic compounds containing selenium have exhibited pharmacological properties, including potential antidepressant effects.

OBJECTIVE

To evaluate the antidepressant-like effect of N-(3-((3-(trifluoromethyl)phenyl)selenyl)prop-2-yn-1-yl) benzamide (CF3SePB) in mice and the involvement of the serotonergic and noradrenergic systems.

METHODS

Male Swiss mice were treated with CF3SePB (1-50 mg/kg, i.g.) and 30 min later the forced swimming test (FST) or tail suspension test (TST) was performed. To investigate the involvement of the serotonergic and noradrenergic systems in the antidepressant-like effect of CF3SePB, mice were pre-treated with p-CPA (a 5-HT depletor, 100 mg/kg, i.p.) or the receptor antagonists WAY100635 (0.1 mg/kg, s.c., a 5-HT1A receptor antagonist), ketanserin (1 mg/kg, i.p., a 5-HT2A/2C receptor antagonist), ondansetron (1 mg/kg, i.p., a 5-HT3 receptor antagonist), GR110838 (0.1 mg/kg, i.p., a 5-HT4 receptor antagonist), prazosin (1 mg/kg, i.p., an α1-adrenergic receptor antagonist), yohimbine (1 mg/kg, i.p., an α2-adrenergic receptor antagonist) and propranolol (2 mg/kg, i.p., a non-selective beta-adrenergic receptor antagonist) at specific times before CF3SePB (50 mg/kg, i.g.), and after 30 min of CF3SePB administration the FST was performed.

RESULTS

CF3SePB showed an antidepressant-like effect in both FST and TST and this effect was related to the modulation of the serotonergic system, specially the 5-HT1A and 5-HT3 receptors. None of the noradrenergic antagonists prevented the antidepressant-like effect of CF3SePB. The compound exhibited a low potential for inducing acute toxicity in adult female Swiss mice.

CONCLUSION

This study pointed a new compound with antidepressant-like effect, and it could be considered for the development of new antidepressants.

HTR3A Promotes Non-small Cell Lung Cancer Through the FOXH1/Wnt3A Signaling Pathway

5-Hydroxytryptamine receptors (5-HTRs) are strongly correlated with tumor progression in various types of cancer. Despite this, the underlying mechanisms responsible for the role of 5-HTRs in non-small cell lung cancer (NSCLC) remains unclear. This study aimed to investigate the relationship between 5-hydroxytryptamine receptor 3A (HTR3A) and NSCLC development. Our findings indicated a higher distribution of HTR3A expression in NSCLC tissues when compared with normal tissues, where patients with high HTR3A levels demonstrated shorter overall survival times. In vitro analyses revealed that overexpression of HTR3A facilitated the proliferation and migration of NSCLC cell lines (A549 and NCI-H3255). Similarly, a notable acceleration of tumor growth and enhanced pulmonary tumorigenic potential were observed in HTR3A-overexpressing tumor-bearing mice. Mechanistically, upregulation of Forkhead Box H1 (FOXH1) by HTR3A led to the activation of Wnt3A/β-catenin signaling pathways, thereby promoting the development of NSCLC. Our report thus highlights the significance of the HTR3A/FOXH1 axis during tumor progression in NSCLC, proposing HTR3A as a possible diagnostic indicator and candidate target for clinical therapy.

New insights into the involvement of serotonin and BDNF-TrkB signalling in cannabidiol's antidepressant effect

Cannabidiol (CBD) is a phytocannabinoid devoid of psychostimulant properties and is currently under investigation as a potential antidepressant drug. However, the mechanisms underlying CBD's antidepressant effects are not yet well understood. CBD targets include a variety of receptors, enzymes, and transporters, with different binding-affinities. Neurochemical and pharmacological evidence indicates that both serotonin and BDNF-TrkB signalling in the prefrontal cortex are necessary for the antidepressant effects induced by CBD in animal models. Herein, we reviewed the current literature to dissect if these are independent mechanisms or if CBD-induced modulation of the serotonergic neurotransmission could mediate its neuroplastic effects through subsequent regulation of BDNF-TrkB signalling, thus culminating in rapid neuroplastic changes. It is hypothesized that: a) CBD interaction with serotonin receptors on neurons of the dorsal raphe nuclei and the resulting disinhibition of serotonergic neurons would promote rapid serotonin release in the PFC and hence its neuroplastic and antidepressant effects; b) CBD facilitates BDNF-TRKB signalling, especially in the PFC, which rapidly triggers neurochemical and neuroplastic effects. These hypotheses are discussed with perspectives for new drug development and clinical applications.

Involvement of serotonergic receptors in depressive processes and their modulation by β-arrestins: A review

Over time, several studies have been conducted to demonstrate the functions of the neurotransmitter 5-hydroxytryptamine (5-HT), better known as serotonin. This neurotransmitter is associated with the modulation of various social and physiological behaviors, and its dysregulation has consequences at the behavioral level, leading to various neurophysiological disorders. Disorders such as anxiety, depression, schizophrenia, epilepsy, sexual disorders, and eating disorders, have been closely linked to variations in 5-HT concentrations and modifications in brain structures, including the raphe nuclei (RN), prefrontal cortex, basal ganglia, hippocampus, and hypothalamus, among others. The involvement of β-arrestin proteins has been implicated in the modulation of the serotonergic receptor response, as well as the activation of different signaling pathways related to the serotonergic system, this is particularly relevant in depressive disorders. This review will cover the implications of alterations in 5-HT receptor expression in depressive disorders in one hand and how β-arrestin proteins modulate the response mediated by these receptors in the other hand.

Therapeutic potential of cannabidiol in depression

Major depressive disorder (MDD) is a widespread and debilitating condition affecting a significant portion of the global population. Traditional treatment for MDD has primarily involved drugs that increase brain monoamines by inhibiting their uptake or metabolism, which is the basis for the monoaminergic hypothesis of depression. However, these treatments are only partially effective, with many patients experiencing delayed responses, residual symptoms, or complete non-response, rendering the current view of the hypothesis as reductionist. Cannabidiol (CBD) has shown promising results in preclinical models and human studies. Its mechanism is not well-understood, but may involve monoamine and endocannabinoid signaling, control of neuroinflammation and enhanced neuroplasticity. This chapter will explore CBD's effects in preclinical and clinical studies, its molecular mechanisms, and its potential as a treatment for MDD.

Dorsal raphe neurons integrate the values of reward amount, delay, and uncertainty in multi-attribute decision-making

The dorsal raphe nucleus (DRN) is implicated in psychiatric disorders that feature impaired sensitivity to reward amount, impulsivity when facing reward delays, and risk-seeking when confronting reward uncertainty. However, it has been unclear whether and how DRN neurons signal reward amount, reward delay, and reward uncertainty during multi-attribute value-based decision-making, where subjects consider these attributes to make a choice. We recorded DRN neurons as monkeys chose between offers whose attributes, namely expected reward amount, reward delay, and reward uncertainty, varied independently. Many DRN neurons signaled offer attributes, and this population tended to integrate the attributes in a manner that reflected monkeys' preferences for amount, delay, and uncertainty. After decision-making, in response to post-decision feedback, these same neurons signaled signed reward prediction errors, suggesting a broader role in tracking value across task epochs and behavioral contexts. Our data illustrate how the DRN participates in value computations, guiding theories about the role of the DRN in decision-making and psychiatric disease.

High-dose Agomelatine Combined with Haloperidol Decanoate Improves Cognition, Downregulates MT2, Upregulates D5, and Maintains Krüppel-like Factor 9 But Alters Cardiac Electrophysiology

Haloperidol decanoate (HD) has been implicated in cognitive impairment. Agomelatine (AGO) has been claimed to improve cognition. We aimed at investigating the effects of HD + low- or high-dose AGO on cognition, verifying the melatonergic/dopaminergic to the cholinergic hypothesis of cognition and exploring relevant cardiovascular issues in adult male Wistar albino rats. HD + high-dose AGO prolonged the step-through latency by +61.47% (P < 0.0001), increased the time spent in bright light by +439.49% (P < 0.0001), reduced the time spent in dim light by -66.25% (P < 0.0001), and increased the percent of alternations by +71.25% (P < 0.0001), despite the reductions in brain acetylcholine level by -10.67% (P < 0.0001). Neurodegeneration was minimal, while the mean power frequency of the source wave was reduced by -23.39% (P < 0.05). Concurrently, the relative expression of brain melatonin type 2 receptors was reduced by -18.75% (P < 0.05), against increased expressions of dopamine type 5 receptors by +22.22% (P < 0.0001) and angiopoietin-like 4 by +119.18% (P < 0.0001). Meanwhile, electrocardiogram (ECG) demonstrated inverted P wave, reduced P wave duration by -36.15% (P < 0.0001) and PR interval by -19.91% (P < 0.0001), prolonged RR interval by +27.97% (P < 0.05), increased R wave amplitude by +523.15% (P < 0.0001), and a depressed ST segment and inverted T wave. In rats administered AGO, HD, or HD+ low-dose AGO, Alzheimer's disease (AD)-like neuropathologic features were more evident, accompanied by extensive ECG and neurochemical alterations. HD + high-dose AGO enhances cognition but alters cardiac electrophysiology. SIGNIFICANCE STATEMENT: Given the issue of cognitive impairment associated with HD and the claimed cognitive-enhancing activity of AGO, combined high-dose AGO with HD improved cognition of adult male rats, who exhibited minimal neurodegenerative changes. HD+ high-dose AGO was relatively safe regarding triggering epileptogenesis, while it altered cardiac electrophysiology. In the presence of low acetylcholine, the melatonergic/dopaminergic hypothesis, added to angiopoietin-like 4 and Krüppel-like factor 9, could offer some clue, thus offering novel targets for pharmacologic manipulation of cognition.

Approach/Avoidance Behavior to Novel Objects is Correlated with the Serotonergic and Dopaminergic Systems in the Brown Rat (Rattus norvegicus)

The brown rat (Rattus norvegicus) is known to show three types of behavioral responses to novel objects. Whereas some rats are indifferent to novel objects, neophobic and neophilic rats show avoidance and approach behavior, respectively. Here, we compared the dopaminergic, serotonergic, and noradrenergic systems immunohistochemically among these rats. Trapped wild rats and laboratory rats were first individually exposed to the novel objects in their home cage. Wild rats were divided into neophobic and indifferent rats depending on their behavioral responses. Similarly, laboratory rats were divided into neophilic and indifferent rats. Consistent with the behavioral differences, in the paraventricular nucleus of the hypothalamus, Fos expression in corticotropin-releasing hormone-containing neurons was higher in the neophobic rats than in the indifferent rats. In the anterior basal amygdala, the neophobic rats showed higher Fos expression than the indifferent rats. In the posterior basal amygdala, the neophobic and neophilic rats showed lower and higher Fos expressions than the indifferent rats, respectively. When we compared the neuromodulatory systems, in the dorsal raphe, the number of serotonergic neurons and Fos expression in serotonergic neurons increased linearly from neophobic to indifferent to neophilic rats. In the ventral tegmental area, Fos expression in dopaminergic neurons was higher in the neophilic rats than in the indifferent rats. These results demonstrate that approach/avoidance behavior to novel objects is correlated with the serotonergic and dopaminergic systems in the brown rat. We propose that the serotonergic system suppresses avoidance behavior while the dopaminergic system enhances approach behavior to novel objects.

Insulin modulates emotional behavior through a serotonin-dependent mechanism

Type-2 Diabetes (T2D) is characterized by insulin resistance and accompanied by psychiatric comorbidities including major depressive disorders (MDD). Patients with T2D are twice more likely to suffer from MDD and clinical studies have shown that insulin resistance is positively correlated with the severity of depressive symptoms. However, the potential contribution of central insulin signaling in MDD in patients with T2D remains elusive. Here we hypothesized that insulin modulates the serotonergic (5-HT) system to control emotional behavior and that insulin resistance in 5-HT neurons contributes to the development of mood disorders in T2D. Our results show that insulin directly modulates the activity of dorsal raphe (DR) 5-HT neurons to dampen 5-HT neurotransmission through a 5-HT1A receptor-mediated inhibitory feedback. In addition, insulin-induced 5-HT neuromodulation is necessary to promote anxiolytic-like effect in response to intranasal insulin delivery. Interestingly, such an anxiolytic effect of intranasal insulin as well as the response of DR 5-HT neurons to insulin are both blunted in high-fat diet-fed T2D animals. Altogether, these findings point to a novel mechanism by which insulin directly modulates the activity of DR 5-HT neurons to dampen 5-HT neurotransmission and control emotional behaviors, and emphasize the idea that impaired insulin-sensitivity in these neurons is critical for the development of T2D-associated mood disorders.

Efficacy, acceptability and side-effects of oral versus long-acting- injectables antipsychotics: Systematic review and network meta-analysis

Long-acting injectable antipsychotics (LAIs) are primarily used for relapse prevention, but in some settings and situations, they may also be useful for acute treatment of schizophrenia. We conducted a systematic review and frequentist network meta-analysis of randomized-controlled trials (RCTs), focusing on adult patients in the acute phase of schizophrenia. Interventions were risperidone, paliperidone, aripiprazole, olanzapine, and placebo, administered either orally or as LAI. We synthesized data on overall symptoms, complemented by 17 other efficacy and tolerability outcomes. Confidence in the evidence was assessed with the Confidence-in-Network-Meta-Analysis-framework (CINeMA). We included 115 RCTs with 25,550 participants. All drugs were significantly more efficacious than placebo with the following standardized mean differences and their 95 % confidence intervals: olanzapine LAI -0.66 [-1.00; -0.33], risperidone LAI -0.59[-0.73;-0.46], olanzapine oral -0.55[-0.62;-0.48], aripiprazole LAI -0.54[-0.71; -0.37], risperidone oral -0.48[-0.55;-0.41], paliperidone oral -0.47[-0.58;-0.37], paliperidone LAI -0.45[-0.57;-0.33], aripiprazole oral -0.40[-0.50; -0.31]. There were no significant efficacy differences between LAIs and oral formulations. Sensitivity analyses of the primary outcome overall symptoms largely confirmed these findings. Moreover, some side effects were less frequent under LAIs than under their oral counterparts. Confidence in the evidence was moderate for most comparisons. LAIs are efficacious for acute schizophrenia and may have some benefits compared to oral formulations in terms of side effects. These findings assist clinicians with insights to weigh the risks and benefits between oral and injectable agents when treating patients in the acute phase.

GSK4716 enhances 5-HT1AR expression by glucocorticoid receptor signaling in hippocampal HT22 cells

OBJECTIVES

The serotonin (5-hydroxytryptamine, 5-HT) receptor 1A (5-HT1AR) is closely associated with serotonergic neurotransmission in the brain, being the most prevalent and widely distributed receptor of its kind. The purpose of this study is to investigate the regulation mechanism of 5-HT1AR by GSK4716.

METHODS

To investigate the mechanism of GSK4716-mediated 5-HT1AR regulation, we used hippocampus-derived HT22 cells expressing 5-HT1AR. The expression level of 5-HT1AR and associated proteins, were detected by reporter gene assay and western blotting.

RESULTS

GSK4716, an estrogen-related receptor gamma agonist increased 5-HT1AR expression by interacting with the GR, a repressor of 5-HT1AR transcription. Dexamethasone, a GR agonist, decreased the GSK4716-induced increase in 5-HT1AR, which was associated with an alteration in nuclear GR. Furthermore, GR antagonist RU486 reversed the effects induced by dexamethasone, including the elevation of nuclear GR levels and the reduction of 5-HT1AR transcription and expression.

CONCLUSION

The results could provide insight into the potential applications of small molecules, such as GSK4716, in the regulation of 5-HT1AR expression, which plays a role in serotonergic neurotransmission.

Enrofloxacin exposure undermines gut health and disrupts neurotransmitters along the microbiota-gut-brain axis in zebrafish

The environmental prevalence of antibiotic residues poses a potential threat to gut health and may thereby disrupt brain function through the microbiota-gut-brain axis. However, little is currently known about the impacts of antibiotics on gut health and neurotransmitters along the microbiota-gut-brain axis in fish species. Taking enrofloxacin (ENR) as a representative, the impacts of antibiotic exposure on the gut structural integrity, intestinal microenvironment, and neurotransmitters along the microbiota-gut-brain axis were evaluated in zebrafish in this study. Data obtained demonstrated that exposure of zebrafish to 28-day environmentally realistic levels of ENR (6 and 60 μg/L) generally resulted in marked elevation of two intestinal integrity biomarkers (diamine oxidase (DAO) and malondialdehyde (MDA), upregulation of genes that encode inter-epithelial tight junction proteins, and histological alterations in gut as well as increase of lipopolysaccharide (LPS) in plasma, indicating an evident impairment of the structural integrity of gut. Moreover, in addition to significantly altered neurotransmitters, markedly higher levels of LPS while less amount of two short-chain fatty acids (SCFAs), namely acetic acid and valeric acid, were detected in the gut of ENR-exposed zebrafish, suggesting a disruption of gut microenvironment upon ENR exposure. Along with corresponding changes detected in gut, significant disruption of neurotransmitters in brain indicated by marked alterations in the contents of neurotransmitters, the activity of acetylcholin esterase (AChE), and the expression of neurotransmitter-related genes were also observed. These findings suggest exposure to environmental antibiotic residues may impair gut health and disrupt neurotransmitters along the microbiota-gut-brain axis in zebrafish. Considering the prevalence of antibiotic residues in environments and the high homology of zebrafish to other vertebrates including human, the risk of antibiotic exposure to the health of wild animals as well as human deserves more attention.

Marine natural products: potential agents for depression treatment

Depression is a common psychiatric disorder. Due to the disadvantages of current clinical drugs, including poor efficacy and unnecessary side effects, research has shifted to novel natural products with minimal or no adverse effects as therapeutic alternatives. The ocean is a vast ecological home, with a wide variety of organisms that can produce a large number of natural products with unique structures, some of which have neuroprotective effects and are a valuable source for the development of new drugs for depression. In this review, we analyzed preclinical and clinical studies of natural products derived from marine organisms with antidepressant potential, including the effects on the pathophysiology of depression, and the underlying mechanisms of these effects. It is expected to provide a reference for the development of new antidepressant drugs.

Sedative and hypnotic effects of Polygala tenuifolia willd. saponins on insomnia mice and their targets

ETHNOPHARMACOLOGICAL RELEVANCE

Polygala tenuifolia Willd. has been widely used in the treatment of cancer, forgetfulness, depression and other diseases.

AIM OF REVIEW

The purpose of this study was to investigate the sleep-enhancing effect and mechanism of P. tenuifolia saponins (PTS).

MATERIALS AND METHODS

The total saponin (YZ-I) and purified saponin (YZ-II) fractions were extracted and ICR mice model of insomnia was established by p-chlorophenylalanine (PCPA) induction to observe anxiety and depression behaviors. Effects of YZ-I and YZ-II on the levels of neurotransmitters, hormones, and inflammation cytokines were detected by ELISA, RT-qPCR and western blotting.

RESULTS

The results showed that YZ-I and YZ-II reduced the immobility time of mice and prolonged the sleep time of mice and significantly increased the concentrations of 5-HT, NE, PGD2, IL-1β and TNF-α. YZ-I and YZ-II regulated GABAARα2, GABAARα3, GAD65/67, 5-HT1A and 5-HT2A, while regulated the levels of inflammatory cytokines such as DPR, PGD2, iNOS and TNF-α to exert sedative and hypnotic effects.

CONCLUSION

PTS are mainly achieved sedative and hypnotic effects by altering serotonergic, GABAergic and immune systems, but the effects and mechanisms of action of YZ-I were different from YZ-II.

Offspring's own serotonin transporter genotype, independently from the maternal one, increases anxiety- and depression-like behavior and alters neuroplasticity markers in rats

INTRODUCTION

Developmental changes due to early life variations in the serotonin system affect stress-related behavior and neuroplasticity in adulthood. These outcomes can be caused both by offspring's own and maternal serotonergic genotype. We aimed to dissociate the contribution of the own genotype from the influences of mother genotype.

METHODS

Sixty-six male homozygous (5-HTT-/-) and heterozygous (5-HTT+/-) serotonin transporter knockout and wild-type rats from constant 5-HTT genotype mothers crossed with varying 5-HTT genotype fathers were subjected to tests assessing anxiety- and depression-like behaviors. Additionally, we measured plasma corticosterone levels and mRNA levels of BDNF, GABA system and HPA-axis components in the prelimbic and infralimbic cortex. Finally, we assessed the effect of paternal 5-HTT genotype on these measurements in 5-HTT+/- offspring receiving their knockout allele from their mother or father.

RESULTS

5-HTT-/- offspring exhibited increased anxiety- and depression-like behavior in the elevated plus maze and sucrose preference test. Furthermore, Bdnf isoform VI expression was reduced in the prelimbic cortex. Bdnf isoform IV and GABA related gene expression was also altered but did not survive false discovery rate (FDR) correction. Finally, 5-HTT+/- offspring from 5-HTT-/- fathers displayed higher levels of anxiety- and depression-like behavior and changes in GABA, BDNF and HPA-axis related gene expression not surviving FDR correction.

LIMITATIONS

Only male offspring was tested.

CONCLUSIONS

Offspring's own 5-HTT genotype influences stress-related behaviors and Bdnf isoform VI expression, independently of maternal 5-HTT genotype. Paternal 5-HTT genotype separately influenced these outcomes. These findings advance our understanding of the 5-HTT genotype dependent susceptibility to stress-related disorders.

Relationship between physical activity and risk of depression in a married group

BACKGROUND

Currently, there are many different findings on the relationship between physical activity and depression, and there may be differences between genders. This study therefore focused on gender differences to understand the relationship between physical activity behaviour and the risk of depression in married individuals.

METHODS

15607 married people in the China Family Panel Studies 2020 (CFPS 2020) were used to understand the relationship between physical activity and depression risk in different populations, and the chi-square test, Mann-Whitney U-test, and binary logistic regression were used to explore the relationship between physical activity and depression risk in the married population.

RESULTS

527 (6.64%) women were at high risk of depression and 365 (4.76%) men were at high risk of depression; physical activity was associated with the risk of depression in the married population, but after incorporating demographic and relevant cognitive variables, physical activity was negatively associated with the risk of depression in women (OR = 0.94, P < 0.01) but not statistically significant with the risk of depression in men (OR = 0.96, P > 0.05).

CONCLUSION

Physical activity was directly related to the risk of depression in married women, but not in married men.

Overweight during development dysregulates cellular metabolism and critical genes that control food intake in the prefrontal cortex

BACKGROUNDS AND AIMS

Childhood obesity is increasing substantially across the world. The World Obesity Federation (WOF) and World Health Organization (WHO) predicted that in 2030 > 1 billion people will be obese, and by 2035 over 4 billion will reach obesity worldwide. According to WHO, the world soon cannot afford the economic cost of obesity, and we need to act to stop obesity acceleration now. Data in the literature supports that the first 1000 days of life are essential in preventing obesity and related adversities. Therefore, using basic research, the present a study that focuses on the immediate effect of overnutrition and serotonin modulation during the lactation period.

METHODS

Using a neonatal overfeeding model, male Wistar rats were divided into four groups based on nutrition or serotonin modulation by pharmacological treatment up to 22 days of life. Cellular and mitochondrial function markers, oxidative stress biomarkers and mRNA levels of hedonic and homeostatic genes were evaluated.

RESULTS

Our data showed that overfeeding during lactation decrease NAD/NADH ratio, citrate synthase activity, and increase ROS production. Lipid and protein oxidation were increased in overfed animals, with a decrease in antioxidant defenses, we also observe a differential expression of mRNA levels of homeostatic and hedonic genes. On the contrary, serotonin modulation with selective serotonin reuptake inhibitors treatment reduces harmful effects caused by overnutrition.

CONCLUSION

Early effects of overnutrition significantly affect the prefrontal cortex at molecular and cellular level, which could mediate obesity-related neurodegenerative dysfunction.

Neuromodulator regulation and emotions: insights from the crosstalk of cell signaling

The unraveling of the regulatory mechanisms that govern neuronal excitability is a major challenge for neuroscientists worldwide. Neurotransmitters play a critical role in maintaining the balance between excitatory and inhibitory activity in the brain. The balance controls cognitive functions and emotional responses. Glutamate and γ-aminobutyric acid (GABA) are the primary excitatory and inhibitory neurotransmitters of the brain, respectively. Disruptions in the balance between excitatory and inhibitory transmission are implicated in several psychiatric disorders, including anxiety disorders, depression, and schizophrenia. Neuromodulators such as dopamine and acetylcholine control cognition and emotion by regulating the excitatory/inhibitory balance initiated by glutamate and GABA. Dopamine is closely associated with reward-related behaviors, while acetylcholine plays a role in aversive and attentional behaviors. Although the physiological roles of neuromodulators have been extensively studied neuroanatomically and electrophysiologically, few researchers have explored the interplay between neuronal excitability and cell signaling and the resulting impact on emotion regulation. This review provides an in-depth understanding of "cell signaling crosstalk" in the context of neuronal excitability and emotion regulation. It also anticipates that the next generation of neurochemical analyses, facilitated by integrated phosphorylation studies, will shed more light on this topic.

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.

Possible role of exercise therapy on depression: Effector neurotransmitters as key players

About 280 million people suffer from depression as the most common neurological disorder and the most common cause of death worldwide. Exercise with serotonin released in the brain by the 5-HT3-IGF-1 mechanism can lead to antidepressant effects. Swimming exercise has antidepressant effects by increasing the sensitivity of serotonin 5-HT2 receptors and postsynaptic 5-HT1A receptors, increasing 5-HT and 5HIAA levels, increasing TPH and serotonin, and decreasing inflammatory levels of IFN-γ and TNF-α. Anaerobic and aerobic exercises increase beta-endorphin, enkephalin, and dynorphin and have antidepressant effects. Exercise by increasing dopamine, D1R, and D2R leads to the expression of BDNF and activation of TrkB and has antidepressant behavior. Exercise leads to a significant increase in GABAAR (γ2 and α2 subunits) and reduces neurodegenerative disorders caused by GABA imbalance through anti-inflammatory pathways. By increasing glutamate and PGC1α and reducing glutamatergic neurotoxicity, exercise enhances neurogenesis and synaptogenesis and prevents neurodegeneration and the onset of depression. Irisin release during exercise shows an important role in depression by increasing dopamine, BDNF, NGF, and IGF-1 and decreasing inflammatory mediators such as IL-6 and IL-1β. In addition, exercise-induced orexin and NPY can increase hippocampal neurogenesis and relieve depression. After exercise, the tryptophan to large neutral amino acids (TRP/LNAA) ratio and the tryptophan to branched-chain amino acids (BCAA) ratio increase, which may have antidepressant effects. The expression of M5 receptor and nAChR α7 increases after exercise and significantly increases dopamine and acetylcholine and ameliorates depression. It appears that during exercise, muscarinic receptors can reduce depression through dopamine in the absence of acetylcholine. Therefore, exercise can be used to reduce depression by affecting neurotransmitters, neuromodulators, cytokines, and/or neurotrophins.

Akkermansia muciniphila modifies the association between metal exposure during pregnancy and depressive symptoms in late childhood

Emerging research suggests that exposures to metals during pregnancy and gut microbiome (GM) disruptions are associated with depressive disorders in childhood. Akkermansia muciniphila, a GM bacteria, has been studied for its potential antidepressant effects. However, its role in the influence of prenatal metal exposures on depressive symptoms during childhood is unknown. Leveraging a well-characterized pediatric longitudinal birth cohort and its microbiome substudy (n=112) and using a state-of-the-art machine-learning model, we investigated whether the presence of A.muciniphila in GM of 9-11-year-olds modifies the associations between exposure to a specific group of metals (or metal-clique) during pregnancy and concurrent childhood depressive symptoms. Among children with no A.muciniphila, a metal-clique of Zinc-Chromium-Cobalt was strongly associated with increased depression score (P<0.0001), whereas, for children with A.muciniphila, this same metal-clique was weakly associated with decreased depression score(P<0.4). Our analysis provides the first exploratory evidence hypothesizing A. muciniphila as a probiotic intervention attenuating the effect of prenatal metal-exposures-associated depressive disorders in late childhood.

Mood and microbes: a comprehensive review of intestinal microbiota's impact on depression

Depression is considered a multifaceted and intricate mental disorder of growing concern due to its significant impact on global health issues. The human gut microbiota, also known as the "second brain," has an important role in the CNS by regulating it through chemical, immunological, hormonal, and neurological processes. Various studies have found a significant bidirectional link between the brain and the gut, emphasizing the onset of depression therapies. The biological and molecular processes underlying depression and microbiota are required, as the bidirectional association may represent a novel study. However, profound insights into the stratification and diversity of the gut microbiota are still uncommon. This article investigates the emerging evidence of a bacterial relationship between the gut and the brain's neurological system and its potential pathogenicity and relevance. The interplay of microbiota, immune system, nervous system neurotransmitter synthesis, and neuroplasticity transitions is also widely studied. The consequences of stress, dietary fibers, probiotics, prebiotics, and antibiotics on the GB axis are being studied. Multiple studies revealed the processes underlying this axis and led to the development of effective microbiota-based drugs for both prevention and treatment. Therefore, the results support the hypothesis that gut microbiota influences depression and provide a promising area of research for an improved knowledge of the etiology of the disease and future therapies.

Structural and biochemical alterations in dendritic spines as key mechanisms for severe mental illnesses

Severe mental illnesses (SMI) collectively affect approximately 20% of the global population, as estimated by the World Health Organization (WHO). Despite having diverse etiologies, clinical symptoms, and pharmacotherapies, these diseases share a common pathophysiological characteristic: the misconnection of brain areas involved in reality perception, executive control, and cognition, including the corticolimbic system. Dendritic spines play a crucial role in excitatory neurotransmission within the central nervous system. These small structures exhibit remarkable plasticity, regulated by factors such as neurotransmitter tone, neurotrophic factors, and innate immunity-related molecules, and other mechanisms - all of which are associated with the pathophysiology of SMI. However, studying dendritic spine mechanisms in both healthy and pathological conditions in patients is fraught with technical limitations. This is where animal models related to these diseases become indispensable. They have played a pivotal role in elucidating the significance of dendritic spines in SMI. In this review, the information regarding the potential role of dendritic spines in SMI was summarized, drawing from clinical and animal model reports. Also, the implications of targeting dendritic spine-related molecules for SMI treatment were explored. Specifically, our focus is on major depressive disorder and the neurodevelopmental disorders schizophrenia and autism spectrum disorder. Abundant clinical and basic research has studied the functional and structural plasticity of dendritic spines in these diseases, along with potential pharmacological targets that modulate the dynamics of these structures. These targets may be associated with the clinical efficacy of the pharmacotherapy.

Discovery of a CB2 and 5-HT1A receptor dual agonist for the treatment of depression and anxiety

Cannabinoid CB2R agonists have gained considerable attention as potential novel therapies for psychiatric disorders due to their non-psychoactive nature, in contrast to CB1R agonists. In this study, we employed molecular docking to design and synthesize 23 derivatives of cannabidiol (CBD) with the aim of discovering potent CB2R agonists rather than CB2R antagonists or inverse agonists. Structure-activity relationship (SAR) investigations highlighted the critical importance of the amide group at the C-3' site and the cycloalkyl group at the C-4' site for CB2R activation. Interestingly, three CBD derivatives, namely 2o, 6g, and 6h, exhibited substantial partial agonistic activity towards the CB2 receptor, in contrast to the inverse agonistic property of CBD. Among these, 2o acted as a CB2R and 5-HT1AR dual agonist, albeit with some undesired antagonist activity for CB1R. It demonstrated significant CB2R partial agonism while maintaining a level of 5-HT1AR agonistic and CB1R antagonistic activity similar to CBD. Pharmacokinetic experiments confirmed that 2o possesses favorable pharmacokinetic properties. Behavioral studies further revealed that 2o elicits significant antidepressant-like and anxiolytic-like effects while maintaining a good safety profile.

Antidepressant-like effects of Jieyu Chufan capsules in the olfactory bulbectomy rat model

The olfactory bulbectomy (OBX) animal model of depression reproduces the behavioral and neurochemical changes observed in depressed patients. We assessed the therapeutic effects of the Jieyu Chufan (JYCF) capsule on OBX rats. JYCF ameliorated the hedonic and anxiety-like behavior of OBX rats and attenuated the cortical and hippocampal damage. JYCF enhanced the expression of neurotrophic factors, such as brain-derived neurotrophic factor (BDNF), fibroblast growth factor 2 (FGF2), and adiponectin (ADPN) in the cortex and hippocampus of OBX rats. JYCF also reduced cortisol levels and restored the levels of excitatory neurotransmitters, such as 5-hydroxytryptamine (5-HT), acetylcholine (ACH), and glutamic acid (Glu), in the brain tissue of OBX rats. Our results suggest that JYCF preserves the synaptic structure by increasing the levels of synaptophysin (SYN) and postsynaptic density protein 95 (PSD95) and alleviates the histological alterations of brain tissue by activating AKT/PKA-CREB-BDNF pathways, and by upregulating ADPN and FGF2 expression in OBX rats. JYCF exerts multiple therapeutic effects on depression, including modulating neurotransmitters, repairing neuronal damage, and maintaining synaptic integrity. These findings support the potential of JYCF as a novel antidepressant agent with therapeutic effects on depression and related neurological disorders.

Pharmacogenetics of selective serotonin reuptake inhibitors (SSRI): A serotonin reuptake transporter (SERT)-based approach

Neuropsychiatric disorders are considered to be the most common cause of disability worldwide. Serotonin and its transporter is a prominent paradigm in mood disorders. Response to selective serotonin reuptake inhibitors (SSRI) is altered due to heterogeneity in the serotonin transporter gene, SLC6A4 (solute carrier family 6 member 4). The reported polymorphisms are found to be in different regions of the transporter gene: promoter region (5-HTTLPR and various single nucleotide polymorphisms within it), intron (STin2), and exon 9 (I425V). The long and short alleles of the 5-HTTLPR gene, which are prevalent among variations, may mediate differential effects. In long allelic variant carriers, an increased response to SSRI and timely recovery is due to increased availability of SERT. Whereas, SERT availability is significantly decreased in short allelic carriers, necessitating a reduction in SSRI dosage due to the increased risk of adverse drug reactions. Thus, pharmacogenetic investigations are required to understand the impact of functional variations on the efficacy and tolerability of SSRI. Identifying the carrier variants may aid in clear-decision making of the treatment regimen, aiding the approach of personalized medication.

Dietary inulin alleviated constipation induced depression and anxiety-like behaviors: Involvement of gut microbiota and microbial metabolite short-chain fatty acid

Chronic constipation has been associated with depression-like behavior. Previous study identified the crucial role of gut microbiota in the development of constipation and depression. Dietary inulin (INU) could regulate gut microbiota. Whether INU treatment could ameliorate constipation induced depression was not clear. For this purpose, male CD-1 mice were administered diphenoxylate (20 mg/kg body weight/day) to induce constipation. We found that INU (10 % in standard diet) alleviated the diphenoxylate-induced constipation, manifested as the increase weight and moisture content of feces. Furthermore, the associated depression and anxiety-like behavior disorders were improved by inhibiting neuro-inflammation and preventing synaptic ultrastructure damage under INU treatment. Moreover, INU pretreatment improved the diphenoxylate-induced gut barrier damage by upregulating tight junction protein expression. INU also reshaped gut microbiota in constipation mice by increasing the relative abundance of Bacteroides and Proteobacteria and downregulating the abundance of Muribacalum and Melaminabacteria. The effects of INU on diphenoxylate-induced depression were abolished by gut microbiota depletion via antibiotic treatment. In addition, INU increased the concentration of short chain fatty acids (SCFAs) in feces contents. Meanwhile, supplementation of SCFAs could also partly improve diphenoxylate-induced depression. In conclusion, INU intake was a potential nutritional intervention strategy to prevent constipation induced depression via microbiota-gut-SCFAs axis.

Sex differences in a corticosterone-induced depression model in mice: Behavioral, neurochemical, and molecular insights

Depression is characterized by a significant sex disparity, with higher rates observed in women compared to men. This study aimed to investigate the impact of sex on depressive behaviors and explore the underlying mechanisms using a corticosterone (CORT)-induced depression model in mice. Behavioral tests, Nissl staining, UPLC-MS/MS, and Western blot analysis were performed to assess behavioral changes, as well as neuronal alterations, neurotransmitter levels, and protein expressions in the hippocampus. The mice in the model group exhibited sex-specific anxiety- and depression-like behaviors. Nissl staining revealed structural abnormalities in the CA3 region of the hippocampus in females. Neurotransmitter analysis indicated decreased serotonin and norepinephrine levels in both sexes, while glutamate levels were elevated in females. Furthermore, female mice demonstrated elevated serum CORT levels. Western blot analysis revealed sex-specific alterations in specific protein expression. Female mice exhibited downregulated glucocorticoid receptor and brain-derived neurotrophic factor expression, whereas male mice showed minimal changes. Additionally, female mice displayed reduced phosphorylated AKT, phosphorylated PI3K, and phosphorylated mTOR levels. These findings enhance our understanding of sex-specific differences in the CORT-induced depression model and provide insights into the underlying mechanisms of depression. This research emphasizes sex in depression studies and supports tailored interventions.

The Gut Microbiota and Major Depressive Disorder: Current Understanding and Novel Therapeutic Strategies

Major depressive disorder (MDD) is a common neuropsychiatric challenge that primarily targets young females. MDD as a global disorder has a multifactorial etiology related to the environment and genetic background. A balanced gut microbiota is one of the most important environmental factors involved in human physiological health. The interaction of gut microbiota components and metabolic products with the hypothalamic-pituitary-adrenal system and immune mediators can reverse depression phenotypes in vulnerable individuals. Therefore, abnormalities in the quantitative and qualitative structure of the gut microbiota may lead to the progression of MDD. In this review, we have presented an overview of the bidirectional relationship between gut microbiota and MDD, and the effect of pre-treatments and microbiomebased approaches, such as probiotics, prebiotics, synbiotics, fecal microbiota transplantation, and a new generation of microbial alternatives, on the improvement of unstable clinical conditions caused by MDD.

A Bibliometric and Visual Analysis of Single Nucleotide Polymorphism Studies in Depression

BACKGROUND

Genetic polymorphism has been proven to have an important association with depression, which can influence the risk of developing depression, the efficacy of medications, and adverse effects via metabolic and neurological pathways. Nonetheless, aspects of the association between single nucleotide polymorphisms and depression have not been systematically investigated by bibliometric analysis.

OBJECTIVE

The aim of this study was to analyze the current status and trends of single nucleotide polymorphism research on depression through bibliometric and visual analysis.

METHODS

The Web of Science Core Collection was used to retrieve 10,043 articles that were published between 1998 and 2021. CiteSpace (6.1 R4) was used to perform collaborative network analysis, co-citation analysis, co-occurrence analysis, and citation burst detection.

RESULTS

The most productive and co-cited journals were the Journal of Affective Disorders and Biological Psychiatry, respectively, and an analysis of the references showed that the most recent research focused on the largest thematic cluster, "5-HT", reflecting the important research base in this area. "CYP2D6" has been in the spotlight since its emergence in 2009 and has become a research hotspot since its outbreak in 2019. However, "BDNF ", "COMT ", "older adults", "loci", and "DNA methylation" are also the new frontier of research, and some of them are currently in the process of exploration.

CONCLUSION

These findings offer a useful perspective on existing research and potential future approaches in the study of the association between single nucleotide polymorphisms and depression, which may assist researchers in selecting appropriate collaborators or journals.

Functional Dimerization of Serotonin Receptors: Role in Health and Depressive Disorders

Understanding the neurobiological underpinnings of depressive disorder constitutes a pressing challenge in the fields of psychiatry and neurobiology. Depression represents one of the most prevalent forms of mental and behavioral disorders globally. Alterations in dimerization capacity can influence the functional characteristics of serotonin receptors and may constitute a contributing factor to the onset of depressive disorders. The objective of this review is to consolidate the current understanding of interactions within the 5-HT receptor family and between 5-HT receptors and members of other receptor families. Furthermore, it aims to elucidate the role of such complexes in depressive disorders and delineate the mechanisms through which antidepressants exert their effects.

Exploring the Bioactive Compounds in Some Apple Vinegar Samples and Their Biological Activities

Apple vinegar is highly recommended for nutrition due to its health benefits and bioactive components. However, the apple cultivar greatly influences the quality of the vinegar. In this research, our focus was on examining the impact of four different apple cultivars on the physicochemical attributes, chemical composition, as well as biological properties-including antidepressant and anti-inflammatory activities-of vinegar. Interestingly, the physicochemical properties of vinegar and the contents of acetic acid and polyphenols depend on the apple cultivars. HPLC chromatographic analysis showed that citric acid (820.62-193.63 mg/100 g) and gallic acid (285.70-54.40 µg/g) were mostly abundant in the vinegar samples. The in vivo results showed that administration of Golden Delicious apple vinegar (10 mL/kg) to adult Wistar rats reduced carrageenan-induced inflammation by 37.50%. The same vinegar sample exhibited a significant antidepressant effect by reducing the rats' immobility time by 31.07% in the forced swimming test. Due to its high acidity, Golden Delicious vinegar was found to be more effective against bacteria, particularly Bacillus subtilis and Candida albicans, resulting in a MIC value of 31.81 mg/mL. Furthermore, the antioxidant activity of various vinegar samples was found to be powerful, displaying optimal values of IC50 = 65.20 mg/mL, 85.83%, and 26.45 AAE/g in the DPPH, β-carotene decolorization and TAC assays, respectively. In conclusion, the apple cultivars used in this study impact the chemical composition and biological activities of vinegar, which may help demonstrate the importance of raw material selection for the production of vinegar.

Anxiety and Alzheimer's disease pathogenesis: focus on 5-HT and CRF systems in 3xTg-AD and TgF344-AD animal models

Dementia remains one of the leading causes of morbidity and mortality in older adults. Alzheimer's disease (AD) is the most common type of dementia, affecting over 55 million people worldwide. AD is characterized by distinct neurobiological changes, including amyloid-beta protein deposits and tau neurofibrillary tangles, which cause cognitive decline and subsequent behavioral changes, such as distress, insomnia, depression, and anxiety. Recent literature suggests a strong connection between stress systems and AD progression. This presents a promising direction for future AD research. In this review, two systems involved in regulating stress and AD pathogenesis will be highlighted: serotonin (5-HT) and corticotropin releasing factor (CRF). Throughout the review, we summarize critical findings in the field while discussing common limitations with two animal models (3xTg-AD and TgF344-AD), novel pharmacotherapies, and potential early-intervention treatment options. We conclude by highlighting promising future pharmacotherapies and translational animal models of AD and anxiety.