Search Results (275)

The accumulated ammonia within the recirculating aquaculture systems threaten fish health, while little is known about the influences during early fish ontogeny. Using larval and juvenile yellow catfish (Pelteobagrus fulvidraco) as a model, a comprehensive experiment exposing fish to varying total ammonia nitrogen concentrations (0, 10, 20 mg/L for larvae; 0, 25, 125 mg/L for juveniles) was conducted to evaluate the effects on gill transcriptome and microbiota along with the serotonergic regulation. First, the serotonin (5-HT) signal, which controls oxygen chemoreception and ventilation, was mainly detected in the surface of the body of the larvae, and then shifted to gill filaments of juveniles, showing a transition from cutaneous to branchial respiration. Both larval and juvenile yellow catfish exhibited reduced survival, damaged gill structure, and elevated 5-HT expression after ammonia exposure, as well as upregulated tph1b, slc6a4b, scgn and lama5 expression with the increased ammonia concentration, indicating the effects on respiratory function via serotonergic regulation. Further transcriptome analysis was conducted in juveniles to identify the differentially expressed genes (DEGs) and thus, to illustrate more detailed responses after ammonia exposure; KEGG enrichment analysis of DEGs indicated the coping strategy shifted from metabolic buffering to metabolic elimination via glutamine synthesis with the increased ammonia level. The qRT-PCR experiment also identified the increased expression of genes involved in the urea cycle—such as ass1, asl and glula—with the increased ammonia level. Considering the potential contributary role of microbiome to gill health, 16S sequencing was conducted on the gill in the control and the 125 mg/L ammonia-exposed group. Ammonia exposure at 125 mg/L induced significant variation in Simpson index and a marked decline in β diversity. Notably, the abundance of opportunistic pathogens such as Pseudomonadota increased, while the abundance of Deinococcota and Deinococcus—which were renowned for exceptional stress resistance capacity—decreased after ammonia exposure. Thus ammonia exposure disrupts the transcriptomic and microecological balance within gill mucosa, which may elevate the risk of pathogenic infection. Overall, our study provided the first evidence of serotonergic regulation on early fish respiration during ammonia exposure, and also offered new theoretical insights into the involvement of microorganisms in ammonia toxicity. Full article

Objectives: To overcome the limitations of invasive diagnostic approaches for ulcerative colitis (UC) diagnosis, this study integrates liquid chromatography–mass spectrometry (LC–MS)-based serum metabolomics with mucosal transcriptomics to elucidate the interplay between systemic metabolic perturbations and neuroendocrine signaling in UC pathogenesis. Methods: Serum metabolites and mucosal differentially expressed genes (DEGs) were identified through multi-omics profiling. Key neurotransmitter receptor-related genes (NRRGs) were prioritized using three machine learning algorithms: LASSO, Random Forest, and SVM-RFE. A three-gene diagnostic nomogram was developed and rigorously validated across multiple independent cohorts (GSE48958, GSE73661) using receiver operating characteristic (ROC) curve analysis and decision curve analysis (DCA). Results: The integrated analysis revealed 334 dysregulated metabolites and 3093 DEGs, both converging on the serotonergic synapse pathway. Specific molecular alterations were uncovered, including tryptophan depletion linked to the downregulation of SLC6A4, concomitant with abnormal serotonin accumulation and PTGS2-mediated inflammatory responses. The three-gene signature, HTR3C, RPS6KA6, and NETO2, formed a highly robust diagnostic model, achieving an area under the ROC curve (AUC) exceeding 0.96 in both the training cohort and external validation sets. Conclusions: This multi-omics study delineates a neuroimmune mechanism in UC centered on dysregulation of the serotonergic synapse. The resulting three-gene nomogram identifies a candidate biomarker signature that demonstrates strong discriminative potential; however, given the exceptionally high performance metrics, these findings should be interpreted as a preliminary diagnostic framework rather than a clinically validated tool, and its efficacy relative to standard markers like CRP or fecal calprotectin requires further investigation in prospective real-world cohorts. Nonetheless, this study provides critical mechanistic insights into gut–brain axis dysfunction in UC. Full article

Understanding how different pre-slaughter and slaughter procedures modulate physiological and neurochemical pathways in European sea bass (Dicentrarchus labrax) remains essential for welfare-oriented aquaculture. This study comparatively evaluated six procedures: clove oil and 2-phenoxyethanol anaesthesia, percussive stunning, asphyxiation in ice slurry or on solid ice, and clove oil anaesthesia followed by ice slurry, using plasma glucose and whole-brain monoaminergic indices as integrative physiological response indicators. Ninety-six fish were analysed. Ice-based asphyxiation and 2-phenoxyethanol exposure were associated with the highest plasma glucose concentrations, whereas clove oil and percussive stunning showed comparatively lower values. Dopaminergic and serotonergic turnover ratios (DOPAC/DA; 5-HIAA/5-HT) increased sharply under ice and 2-phenoxyethanol treatments, indicating increased monoaminergic activity under these procedures. Multivariate analyses (MANOVA, PCA) distinguished anaesthetic-based treatments from ice-based methods according to their combined neurochemical profiles. Although correlations between glucose and monoaminergic indices were modest, they were statistically significant and consistent with coordinated metabolic–neurochemical adjustments. Overall, DOPAC/DA and 5-HIAA/5-HT ratios emerged as sensitive and mechanistic biomarkers capable of differentiating slaughter procedures according to their relative physiological impact. These findings support the integration of metabolic and neurochemical indicators in welfare assessment and may contribute to evidence-based refinement of humane slaughter protocols in Mediterranean aquaculture systems. Full article

Serotonin is a critical morphogen in early development, yet the mechanisms regulating its homeostasis in the preimplantation embryo remain unclear, particularly under conditions of maternal antidepressant exposure. Here, we investigated embryonic serotonergic autonomy using mouse models of pharmacological transport blockade (maternal fluoxetine treatment) and in vitro treatment with the monoamine oxidase inhibitor pargyline. We employed immunofluorescence, RT-qPCR, and live-cell imaging to assess metabolic flux, gene expression, and physiological health. We demonstrate that monoamine oxidase functions as a metabolic firewall, progressively maturing from zygote to blastocyst to degrade excess amines. Paradoxically, maternal serotonin transporter blockade triggered significant intracellular serotonin hyper-accumulation in blastocysts, associated with a trend toward a compensatory upregulation of the biosynthetic gene Ddc. While this serotonin overload did not compromise morphology, mitochondrial function, or pluripotency marker expression, it induced a robust epigenetic response. Excess serotonin promoted elevated H3Q5ser immunoreactivity in both nuclear and cytoplasmic compartments via a transglutaminase-dependent mechanism. These findings reveal that the preimplantation embryo possesses a resilient, autonomous serotonergic system capable of compensatory synthesis. However, environmental fluctuations are chemically recorded via transglutaminase-mediated serotonylation, representing an epigenetic mark that warrants further long-term study within the Developmental Origins of Health and Disease (DOHaD) framework. Full article

Tramadol acts via μ-opioid receptor agonism and monoamine reuptake inhibition but is clinically limited by metabolic dependence, interindividual variability, and addiction risks. Structural modification aims to resolve these limitations. This review systematically summarizes tramadol’s structure–activity relationships and mechanisms, focusing on key strategies for structural optimization. Major advances include: (i) synergistic strategies, such as tramadol–celecoxib cocrystals (tramadol and celecoxib coexist in the supramolecular crystal network at a 1:1 molar ratio), achieving multimodal analgesia at lower doses; (ii) mechanism-balancing strategies such as tapentadol (derivatives of tramadol with a dual mechanism of action), which enhance μ-opioid agonism and norepinephrine reuptake inhibition while attenuating serotonergic effects to improve efficacy; (iii) metabolic optimization utilizing M1 analogues to circumvent CYP2D6 polymorphisms (tramadol is metabolized by this enzyme into the active metabolite M1 to exert analgesic effects); and (iv) pharmacophore optimization leveraging tramadol–morphine homology and “message–address” concepts to design selective ligands. Novel derivatives demonstrate improved potency and metabolic stability but continue to face challenges regarding opioid risks and clinical translation. Future research should integrate rational drug design, delivery systems, and personalized medicine to facilitate the development of safer next-generation analgesics. Full article

Eating disorders (EDs), including anorexia nervosa (AN), bulimia nervosa (BN), and binge-eating disorder (BED), are complex psychiatric conditions characterized by high morbidity and mortality. Increasing evidence suggests that beyond disorder-specific symptomatology, shared transdiagnostic mechanisms contribute to their onset and persistence. This narrative review synthesizes current data on neurobiological and nutritional factors implicated in EDs, with particular emphasis on trait–state interactions and starvation-induced neuroadaptations. Predisposing vulnerabilities such as heightened anxiety, cognitive rigidity, and perfectionism appear to interact with state-dependent biological alterations induced by malnutrition. Chronic dietary restriction is associated with measurable alterations in serotonergic and dopaminergic systems, altered reward processing, and persistent activation of the hypothalamic–pituitary–adrenal (HPA) axis. Experimental studies suggest that acute tryptophan depletion may transiently reduce anxiety in individuals with anorexia nervosa, suggesting that, in some individuals, food restriction may function as a biologically reinforced strategy of affect regulation. Furthermore, disturbances in leptin and ghrelin signaling, along with widespread micronutrient deficiencies—including zinc, iron, selenium, and B vitamins—may exacerbate cognitive inflexibility, mood instability, and impaired decision-making. These metabolic and endocrine adaptations may contribute to a self-perpetuating cycle in which starvation-induced neurochemical changes reinforce restrictive or dysregulated eating behaviors. Importantly, several of these mechanisms extend beyond anorexia nervosa and may represent common transdiagnostic processes across eating disorders and related mental health conditions, including anxiety, depression, and addictive behaviors. Recognition of these biological and nutritional factors has significant implications for treatment. Nutritional rehabilitation should be conceptualized not solely as weight restoration, but as a neurobiological recalibration of stress regulation, reward sensitivity, and affective processing systems. An integrative treatment approach that combines behavioral stabilization with attention to underlying neurobiological and relational mechanisms may offer a more comprehensive framework for long-term recovery. Full article

Alzheimer’s disease (AD), the leading cause of global dementia, is a multifactorial process that goes beyond the accumulation of β-amyloid (Aβ) plaques and tau protein tangles, including glia cell-mediated neuroinflammation, vascular dysfunction, metabolic alterations, and synaptic loss. Its complex etiology also involves oxidative stress and mitochondrial dysfunction. Multiple neurotransmitter systems involved in the pathogenesis and the various cognitive and non-cognitive symptoms of AD are thus altered. The cholinergic system, historically the first to be associated with AD, suffers early degeneration and loss of neurons/receptors, correlating with cognitive impairment. The glutamatergic system, the main excitatory system, exhibits excitotoxicity due to increased extracellular glutamate and alterations in NMDA/AMPA receptor distribution, exacerbating neuronal damage. The GABAergic system, the main inhibitor, shows alterations in parvalbumin-positive interneurons, leading to hyperexcitability and dysfunction of neuronal networks. Monoaminergic systems (serotonergic, dopaminergic and noradrenergic) undergo early degeneration in key nuclei such as the raphe and locus coeruleus, contributing to the apathy, depression and sleep disturbances characteristic of AD. Other less explored systems, such as histaminergic and purinergic, are also crucial in cognitive modulation and neuroinflammation. The endocannabinoid system acts as a master modulator with neuroprotective and anti-inflammatory effects. These systems do not operate in isolation; their complex interactions generate pathological circuits that amplify neuronal dysfunction. The limited efficacy of current therapies, which are primarily symptomatic, highlights the need for multimodal approaches that may transform AD treatment toward personalized and more effective interventions. Full article

Introduction: Psychotic symptoms (PS) in Alzheimer’s disease (AD) are associated with unfavorable prognosis, including accelerated functional decline and reduced survival. Multiple neurotransmitter systems have been implicated in the pathophysiology of PS, with the serotonergic system emerging as particularly relevant. Materials and Methods: Between 2010 and 2020, 120 patients with prodromal AD and 26 cognitively healthy controls underwent comprehensive evaluation, including clinical history, neurological and neuropsychological assessment, neuroimaging, and lumbar puncture. All participants underwent longitudinal clinical monitoring for a minimum of five years or until the emergence of PS. In February 2024, baseline cerebrospinal fluid (CSF) serotonin (5-HT) concentrations were quantified using competitive ELISA (FineTest, Wuhan, China). Results: CSF 5-HT levels were significantly elevated (p < 0.003) in patients who subsequently developed psychosis (n = 49) compared with those who remained free of PS during the 8-year follow-up (n = 19). A threshold of 4.89 ng/mL yielded 80% sensitivity for identifying individuals at risk. Baseline Neuropsychiatric Inventory (NPI; p < 0.001) and Unified Parkinson’s Disease Rating Scale part III (UPDRS III; p < 0.009) scores also demonstrated strong discriminative capacity. Conclusions: Measurement of CSF 5-HT and detailed clinical profiling in prodromal AD may provide predictive value for psychosis onset within 8 years of diagnosis. To our knowledge, this is the first study to report CSF 5-HT findings in AD patients. Full article

Suicidal behavior is a multifactorial and highly heritable phenotype; however, data concerning its genetic determinants in disparate ethnic groups remain limited. Genes implicated in serotonergic neurotransmission and stress response regulation are regarded as primary candidates for elucidating biological vulnerability to suicide. The objective of this study is to investigate the relationship between suicide attempts and candidate gene polymorphisms in an ethnically homogeneous Kazakh population from Astana, Kazakhstan. The study’s sample population comprised 126 patients with a documented history of suicide attempts and 120 age- and gender-matched controls without a history of suicidal behavior. A comprehensive genotyping analysis was conducted, encompassing polymorphisms in genes associated with serotonergic signaling, stress response, and neuroplasticity (TPH1, TPH2, HTR2A, MAOA, SLC6A4, ANKK1, BDNF, COMT, CXCL8, SKA2, and FKBP5). The associations were assessed across several genetic models, using odds ratios with 95% confidence intervals. A substantial correlation was identified between the HTR2A rs6311 polymorphism and suicide attempts. The CC genotype exhibited a protective effect (p = 1.36 × 10⁻⁵), while the TT genotype was associated with an elevated risk (OR = 3.16; 95% CI: 1.72–5.81). The association remained robust after stratification by sex, with an even stronger effect observed in women (OR = 4.70; 95% CI: 2.08–10.64). A nominal sex-specific association was observed for the SKA2 rs7208505 variant, suggesting a potential role in stress-response mechanisms in women; however, this association was no longer statistically significant after adjustment for multiple comparisons. These results identify HTR2A rs6311 as a potential genetic marker of suicide risk in the Kazakh population and support the involvement of serotonergic receptor regulation in the biological mechanisms underlying suicidal behavior. The results underscore the significance of sex-specific genetic influences, thereby enhancing our understanding of the polygenic underpinnings of suicidality. Full article

The neuropharmacology of psychedelics has traditionally focused on serotonergic mechanisms, particularly 5-HT2A receptor activation. However, this paradigm incompletely explains the diversity of neurobiological and therapeutic effects observed across psychedelic compounds. Non-classical psychedelics such as salvinorin A, the primary active constituent of Salvia divinorum, challenge this framework through direct kappa opioid receptor (KOR) agonism, representing a serotonin-independent pathway to altered consciousness. This review systematically examines the role of the endogenous opioid system in mediating psychedelic effects, with emphasis on salvinorin A’s unique KOR-dependent mechanisms. We synthesized preclinical and clinical evidence from in vitro studies, genetically modified animal models, optogenetic circuit dissection, and human neuroimaging trials. Salvinorin A’s selective KOR activation is characterized by pronounced β-arrestin-biased signaling, distinguishing it from endogenous dynorphins and classical KOR agonists. This produces rapid receptor desensitization, transient functional plasticity, and profound dissociative effects mediated through thalamocortical disruption, mesolimbic dopaminergic suppression, and fragmentation of large-scale brain networks. Classical serotonergic psychedelics indirectly engage opioid systems through downstream 5-HT2A signaling, contributing to analgesic and mood-regulatory effects via secondary MOR/DOR modulation. Despite being a potent opioid agonist, salvinorin A exhibits low abuse potential due to aversive phenomenology, dopaminergic suppression, and absence of positive reinforcement in animal models. Incorporating opioid receptor pharmacology into psychedelic neuroscience expands mechanistic understanding beyond serotonin-centric models, revealing multiple neurochemical pathways capable of inducing therapeutically relevant altered states. This framework enables rational development of biased KOR ligands and establishes salvinorin A as a paradigmatic model for non-serotonergic psychedelia with applications in treatment-resistant depression, addiction, and chronic pain. Full article

The origins of major depressive disorder (MDD) are complex, involving both environmental influences and a substantial genetic contribution. Genetic polymorphisms have been implicated in modulating susceptibility, disease course, and treatment response, yet findings are often modest, population-dependent, and sometimes inconsistent. This narrative review synthesizes current evidence on genetic variants associated with MDD, highlighting well-replicated results while distinguishing exploratory or emerging findings. Key systems reviewed include serotonergic (SLC6A4), neurotrophic (BDNF rs6265 and rs962369), dopaminergic and stress-response pathways (COMT, FKBP5, CRHR1), as well as additional emerging genes such as MAOA, TPH2, and FTO. We evaluate these variants in the context of their biological relevance, including neuroplasticity, neurotransmission, and hypothalamic–pituitary–adrenal (HPA) axis regulation, and discuss how polygenic and epigenetic interactions may shape clinical heterogeneity. This framework not only integrates current genetic knowledge but also outlines potential translational applications, offering perspectives for personalized approaches to diagnosis, prognosis, and treatment in MDD. Full article

Background/Objectives: As the prevalence of depression and the use of antidepressants have risen steadily in the last decade, new treatment options are needed. Aloysia gratissima var. gratissima ethanol extract has previously shown antidepressant-like activity, and the present study was conducted to identify the active fraction and clarify the possible mechanisms of action. Methods: Tail suspension (TST) and forced swimming (FST) behavioral tests were performed, and possible mechanisms of action were elucidated using serotonergic, dopaminergic, adrenergic, and GABAergic system antagonists. UPLC-DAD-MS analyses were performed to identify compounds in active fractions, and molecular docking studies were carried out to determine the binding affinities of these compounds to serotonergic and dopaminergic receptors (5-HT_1A, 5-HT_2A, 5-HT₃, and D₂R). Results: Ethyl acetate and butanol fractions were found to decrease immobility time in FST. The reduction in immobility time during the FST caused by the ethyl acetate fraction was reversed by pretreating mice with WAY100635 (5-HT_1A antagonist), ketanserin (a 5-HT_2A antagonist, ondansetron (5-HT₃ antagonist), or haloperidol (D₂ antagonist). UPLC-DAD-MS analysis revealed a similar composition for the ethyl acetate and butanol fractions of A. gratissima var. gratissima. Pharmacokinetic predictions suggest that only a few of the identified compounds have the potential to permeate the blood–brain barrier, and molecular docking simulations showed that compounds such as 13-oxooctadecadienoic acid, ferulic acid, and coumaric acid have binding affinities to the druggable site of serotonergic and dopaminergic receptors. Conclusions: These results suggest that the Agg ethyl acetate fraction possesses antidepressant-like activities, altering dopaminergic and serotonergic system functions. Computational simulations also suggest that some of the identified compounds have binding affinities to the 5-HT_1A, 5-HT_2A, 5-HT₃, and D₂R receptors. Full article

Burnout syndrome is increasingly recognized as a significant occupational health issue, characterized by emotional exhaustion, depersonalization, and a reduced sense of personal accomplishment. It predominantly arises from chronic work-related stress, but recent research has highlighted the role of genetic and epigenetic factors in determining individual vulnerability to burnout. This review aims to synthesize findings regarding the genetic footprints of burnout, focusing on genes related to stress regulation, including the 5-HTT (serotonin transporter) gene, BDNF (brain-derived neurotrophic factor) gene, and NR3C1 (glucocorticoid receptor) gene. Twin studies reveal that burnout is moderately heritable, with genetic factors accounting for 33–36% of the variability in burnout-related traits, such as emotional exhaustion and performance-based self-esteem. However, burnout risk seems highly driven by non-shared environmental factors, such as work stress, lack of social support, and personal coping mechanisms. Specific genetic polymorphisms in the serotonergic system (5-HTT) and HPA axis genes (NR3C1, FKBP5) have been linked to increased burnout susceptibility, particularly in individuals exposed to chronic job strain or early-life stressful situations. Variations in 5-HTT rs6354 and HTR2A rs6313 are associated with altered stress reactivity, while polymorphisms in NR3C1 and FKBP5 contribute to dysregulation of the HPA axis, which influences cortisol secretion patterns in response to stress. Increased methylation in genes like BDNF and SLC6A4 has been observed in individuals with burnout, suggesting that environmental stressors may lead to lasting changes in gene expression, contributing to the syndrome’s development. Studies on telomere length have shown that burnout is associated with accelerated cellular aging, with individuals exhibiting shorter telomeres, particularly during high-stress periods. These findings hold particular relevance for professionals within the forensic and justice systems, including law enforcement, the judiciary, and forensic experts, who operate under chronic, high-stakes stress. We examine how understanding the biological basis of burnout can inform more objective ‘fitness-for-duty’ evaluations and provide a scientific framework for distinguishing physiological exhaustion from professional negligence in legal contexts. Full article

Modern advances in artificial intelligence have accelerated the development of computational tools for protein–ligand structure prediction, yet their real-world performance remains uneven across receptor classes and ligand chemotypes. Recently published cryo-EM structures of several different psychedelics bound to the serotonin 5HT_2A receptor provide a unique opportunity to explore how modern AI-based modeling performs in a pharmacologically important GPCR system. Here, we compare three major approaches: AI-based protein–ligand cofolding (Boltz-2), a leading AI-driven docking module (Uni-Mol Docking v2), and a widely used classical physics-based docking pipeline (AutoDock Vina) across a series of tryptamine and phenethylamine psychedelics. Predicted binding poses were comparatively assessed through structural alignment with these newly available cryo-EM complexes. Additionally, calcium-mobilization assays were performed to provide a coarse functional readout for comparison with computationally predicted binding affinities. This study integrates methodological review with exploratory benchmarking to illustrate how different modeling paradigms behave on a shared receptor–ligand test set. Our results highlight substantial variation between modeling strategies, with AI-based cofolding often producing global binding orientations more closely resembling experimental structures, and classical docking showing greater variability across ligands, while still outperforming AI-driven docking on average. These observations underscore both the growing utility and current limitations of AI-assisted structure prediction in serotonergic drug discovery, and emphasize the importance of careful, experimentally anchored evaluation as such tools continue to advance. Full article

Background: Ketamine and magnesium sulfate are commonly used perioperatively to prevent shivering, a frequent and clinically relevant complication of spinal and general anesthesia. Although their hypothermic effects are well documented, the neurotransmitter mechanisms underlying these effects remain insufficiently understood. This study examines whether serotonergic, adrenergic (α₂), and GABAergic (GABA_A) systems contribute to hypothermia induced by ketamine and a ketamine–magnesium sulfate combination. Methods: Body temperature was measured in Wistar rats after administration of ketamine (10 mg/kg) or the ketamine (5 mg/kg)–magnesium sulfate (5 mg/kg) combination. To assess neurotransmitter involvement, animals received yohimbine (α₂ antagonist), methysergide (non-selective 5-HT antagonist), or bicuculline (GABA_A antagonist) prior to ketamine or the drug combination. Data were analyzed using two-way repeated measures ANOVA followed by Tukey’s post hoc test. Results: Yohimbine at 0.5 and 1 mg/kg significantly potentiated ketamine-induced hypothermia, while only 3 mg/kg enhanced the effect of the ketamine–magnesium sulfate combination. Methysergide had a bidirectional influence: 1 mg/kg methysergide deepened ketamine-induced hypothermia, whereas 0.5 mg/kg methysergide attenuated the hypothermic effect of the ketamine–magnesium sulfate combination. Bicuculline (1–2 mg/kg) did not alter the hypothermic responses to ketamine or the combination. Conclusions: These findings indicate that ketamine- and ketamine–magnesium sulfate-induced hypothermia is primarily modulated by serotonergic and adrenergic mechanisms, whereas GABA_A receptor-dependent pathways do not appear to play a major role under the experimental conditions used. These results provide new mechanistic insights into NMDA antagonist–related thermoregulation and may help inform anesthetic strategies for shivering prevention and maintenance of perioperative thermal stability. Full article