The expanded biology of serotonin

Calcitonin gene-related peptide (CGRP) exerts membrane, cellular and synaptic actions on serotonergic dorsal raphe neurons ex vivo: Functional implications for a role in dorsal raphe-controlled functions

Serotonin (5-HT) plays a role in limbic-controlled behaviors and is implicated in migraine, which is often co-morbid with cognitive-based affective disorders. The neuropeptide calcitonin gene-related peptide (CGRP) regulates vascular tone. Serotonin-acting drugs and CGRP receptor antagonists have proved therapeutic in management of migraine. Clinical interactions between the two systems have been shown, however, whether CGRP exerts direct actions on serotonergic Dorsal Raphe (DR) neurons is unknown. To fully understand the role of CGRP in control of behavior and to predict how CGRP targeted therapies (i.e. CGRP receptor antagonists) could alter DR neuronal activity, investigation of whether CGRP can directly affect 5-HT DR activity was conducted. Patch clamp electrophysiology and single photon calcium imaging in DR brain slices revealed that CGRP (10-6 M) elicited postsynaptically mediated, potassium-involved outward currents in the majority of 5-HT DR cells. Miniature excitatory synaptic events were reduced in frequency. Further, intracellular calcium was reduced in the majority of neurons, which did not involve actions on the L-type calcium channel. The CGRP agonist SAX replicated effects on the membrane and intracellular calcium. In contrast, the CGRP receptor antagonist MK-3207 blocked the effects on outward current and attenuated the action of CGRP on reducing intracellular calcium. Despite inhibitory membrane and synaptic effects, no change was noted in firing rate. Our findings raise the intriguing possibility that the CGRP system plays a role in mediating limbic-controlled behaviors, at least in part, through direct actions on serotonergic DR neurons, however the effect of CGRP on DR 5-HT output remains to be investigated.

Knockout of 5-HT7 receptor in the mouse mildly modifies the structure and function of dorsal raphe neurons

The serotonin (5-HT) type 7 receptor (5-HT7R) mediates numerous physiological actions of 5-HT in the brain. Mice with a targeted disruption of the 5-HT7R-coding gene are characterized by an altered behavioral phenotype. Modifications of the serotonergic modulation of brain development and of the activity of the 5-HT system in adulthood that are related to ablation of functional 5-HT7Rs might, potentially, underlie the behavioral phenotype described in the literature. The present study was aimed at finding the consequences of 5-HT7R deficiency for the structure and function of single 5-HT neurons of the midline region of the dorsal raphe nucleus (DRN). It was found that while the amplitude of spontaneous excitatory postsynaptic currents recorded from tryptophan hydroxylase-immunoreactive DRN neurons was elevated in 5-HT7R-deficient animals, the excitability of these cells was mildly reduced. A lack of 5-HT7Rs was accompanied by a minor modification of DRN 5-HT neuron morphology. Our findings support the hypothesis that ablation of the 5-HT7R results in an alteration of the function of mouse DRN projection neurons. Further experiments are needed to fully elucidate the effects of the knockout of the 5-HT7R coding gene on the brain 5-HT system.

Ecotoxicological implications of increased antidepressant concentrations in the Laurentian Great Lakes Basin, 2018-2023

Antidepressants are only partially metabolized and then eliminated in urine and feces. Since waste water treatment plants are not designed to remove pharmaceuticals, antidepressants and their metabolites eventually reach the environment. Antidepressants are among the most prescribed drugs in the world, and their prescription rates increased dramatically following the onset of the COVID-19 pandemic. Our aim was to compare their measured environmental concentrations (MECs) in surface water in the three years before and the three years after the pandemic onset. Nearly 1300 samples were collected from 67 sites in the Laurentian Great Lakes Basin, from streams and rivers. We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodology to measure the MECs of 7 of the most frequently used antidepressants and 3 of their metabolites. Canadian antidepressant use data was also collected via the IQVIA MIDAS® database of estimated sales data for pharmaceutical drugs (2018-2021). We found that the median MECs for 9 of the 10 substances increased between 1.5- and 7.2-fold (p < 0.05). The greatest median increases corresponded to fluvoxamine (4.8-fold) and 10-hydroxyamitriptyline (4.7-fold). Increases were concurrent with rising use rates post-COVID-onset. The highest concentrations corresponded to the metabolite O-desmethylvenlafaxine (3113.98 ng L-1) and its parent drug venlafaxine (699.59 ng L-1) in 2022. We collected and analyzed antidepressant surface water and ecotoxicological data to provide a comprehensive review to contextualize the LC-MS/MS data. We compared maximal MECs to ecotoxicological reference values and theorize a possible ecotoxicological impact when considering the overlap of maximal levels with ecotoxicological reference values cited in the scientific literature. We offer recommendations for next steps.

Past, present, and future of serotonin-targeting therapeutics for Alzheimer's disease: Perspectives from DNA methylation

With population aging, Alzheimer's disease (AD) is becoming increasingly prevalent, causing great health and economic burdens worldwide. Despite decades of research, there are still no effective disease-modifying treatments for AD, highlighting the urgent need for more in-depth understanding of the disease-causing mechanisms. The brain serotonin (5-HT) neurotransmission system undergoes structural and functional changes in aging and AD, which contributes to cognitive decline and comorbid mood disturbances. This review discusses the critical involvement of the brain 5-HT system in aging and AD. Existing findings on the changes in projection fiber innervation and receptor/transporter expression in AD are reviewed. Preclinical and clinical progress on the development of 5-HT-modulating drugs for AD and the obstacles faced by these development efforts are discussed. Epigenetic control of the brain 5-HT system and the potential of modulating 5-HT transmission via DNA methylation are also examined.

Optogenetic Stimulation of Novel Tph2-Cre Rats Advances Insight into Serotonin's Role in Locomotion, Reinforcement, and Compulsivity

Serotonin critically modulates the activity of many brain networks, including circuits that control motivation and responses to rewarding and aversive stimuli. Furthermore, the serotonin system is targeted by first-line pharmacological treatments for several psychiatric disorders, including obsessive-compulsive disorder. However, understanding the behavioral function of serotonin is hampered by methodological limitations: the (brainstem) location of serotonergic neuron cell-bodies is difficult to access, their innervation of the brain is diffuse, and they release serotonin in relatively low concentrations. Here, we advance this effort by developing novel Tph2-Cre rats, which we utilized to study serotonin in the context of motor, compulsive, and reinforced behaviors using optogenetics in both male and female rats. Specificity and sensitivity of Cre recombinase expression and Cre-dependent processes were validated immunohistochemically, and optogenetic induction of in vivo serotonin release was validated with fast-scan cyclic voltammetry. Optogenetic stimulation of serotonin neurons in the dorsal raphe nucleus did not initiate locomotion or alter aversion-induced locomotion, nor did it elicit (real-time) place preference, and it had no measurable effect on compulsive behavior in the schedule-induced polydipsia task. In contrast, this optogenetic stimulation moderately sustained ongoing spontaneous locomotion and robustly reinforced operant lever pressing for self-stimulation of serotonin neurons, which was exacerbated by food restriction. Together, this work both introduces a novel rat Cre line to study serotonin and advances our understanding of serotonin's behavioral functions. Complementing previous findings, we find that brainwide serotonin release has an overall relatively mild effect on behavior, which manifested only in the absence of natural reinforcers and was modulated by physiological state.

Transdermal Semaglutide Administration in Mice: Reduces Body Weight by Suppressing Appetite and Enhancing Metabolic Rate

BACKGROUND

Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist that shows significant efficacy in treating obesity. However, its associated side effects, including poor patient compliance and gastrointestinal inflammation, are concerning and may be largely attributed to its administration methods (e.g., injection vs. oral) and the pronounced fluctuations in systemic drug concentrations. To address these challenges, we investigated an innovative drug delivery system (Transdermal Drug Delivery System, TDDS) designed to maintain therapeutic efficacy while improving patient adherence.

RESULTS

Both transdermal and injection treatments of semaglutide decreased body weight, carcass weight, blood glucose, and triglyceride levels in male mice compared with the vehicle-treated control group. In addition, transdermal semaglutide in mice reduced the expression of feeding neuropeptides and the mass of the digestive tract, but increased brown adipose tissue (BAT) mass, metabolic rate, and physical activity, compared with the semaglutide injection group. Additionally, transdermal semaglutide had anxiolytic effects on behavior and did not alter tissue pathology in mice.

CONCLUSION

Compared with the injection paradigm, transdermal semaglutide treatment achieved superior weight loss results in two possible ways: It may reduce energy intake by decreasing the expression of feeding neuropeptides and reducing the weight of the digestive tract. It may also facilitate energy expenditure by enhancing physical activity and increasing BAT mass to boost the metabolic rate. Transdermal semaglutide treatment also has an anxiolytic effect on behavior. Together, our data suggest that TDDS treatment of GLP-1RA may have superior clinical safety and sustainability, providing a novel, efficient, and low-risk obesity treatment.

Serotonin transporter inhibits antitumor immunity through regulating the intratumoral serotonin axis

Identifying additional immune checkpoints hindering antitumor T cell responses is key to the development of next-generation cancer immunotherapies. Here, we report the induction of serotonin transporter (SERT), a regulator of serotonin levels and physiological functions in the brain and peripheral tissues, in tumor-infiltrating CD8 T cells. Inhibition of SERT using selective serotonin reuptake inhibitors (SSRIs), the most widely prescribed antidepressants, significantly suppressed tumor growth and enhanced T cell antitumor immunity in various mouse syngeneic and human xenograft tumor models. Importantly, SSRI treatment exhibited significant therapeutic synergy with programmed cell death protein 1 (PD-1) blockade, and clinical data correlation studies negatively associated intratumoral SERT expression with patient survival in a range of cancers. Mechanistically, SERT functions as a negative-feedback regulator inhibiting CD8 T cell reactivities by depleting intratumoral T cell-autocrine serotonin. These findings highlight the significance of the intratumoral serotonin axis and identify SERT as an immune checkpoint, positioning SSRIs as promising candidates for cancer immunotherapy.

Neurotransmitter modulation of human facial emotion recognition

Human facial emotion recognition (FER) is an evolutionarily preserved process that influences affiliative behaviours, approach/avoidance and fight-or-flight responses in the face of detecting threat cues, thus enhancing adaptation and survival in social groups. Here, we provide a narrative literature review on how human FER is modulated by neurotransmitters and pharmacological agents, classifying the documented effects by central neurotransmitter systems. Synthesising the findings from studies involving functional neuroimaging and FER tasks, we highlight several emerging themes; for example, noradrenaline promotes an overall positive bias in FER, while serotonin, dopamine and gamma-aminobutyric acid modulate emotions relating to self-preservation. Finally, other neurotransmitters including the cholinergic and glutamatergic systems are responsible for rather non-specific pro-cognitive effects in FER. With the ongoing accumulation of evidence further characterising the individual contributions of each neurotransmitter system, we argue that a sensible next step would be the integration of experimental neuropharmacology with computational models to infer further insights into the temporal dynamics of different neurotransmitter systems modulating FER.

Investigating potential molecular mechanisms of antiepileptic drug-induced depression through network toxicology and molecular docking

Antiepileptic drugs (AEDs) are essential for epilepsy management but frequently induce adverse effects including depression. This study employs network toxicology and molecular docking to investigate molecular mechanisms underlying AED-induced depression. After identifying eight AEDs (Topiramate, Zonisamide, Phenobarbital, Primidone, Levetiracetam, Gabapentin, Tiagabine, and Perampanel) potentially associated with depression via a literature review, further analysis integrating drug and disease target databases revealed 25 targets relevant to AED-induced depression. Gene ontology analysis conducted with DAVID, indicated that biological processes including synaptic transmission and plasticity, glutamate receptor signaling, and calcium ion regulation are critical to this phenomenon. KEGG pathway analysis demonstrated that AEDs primarily affect neuroactive ligand-receptor interactions, which are essential for synaptic transmission and plasticity, and disrupt calcium, cAMP, MAPK, and oxytocin signaling pathways. These pathways are vital for the proper functioning of the central nervous system, as neurotransmitter interactions activate crucial signaling pathways. The drug-target interaction network analysis identified 12 candidate targets that directly interact with the eight AEDs, and GeneMANIA network expansion provided deeper insights into their functional associations. Molecular docking results revealed the interactions between AEDs and their respective direct targets, with Zonisamide exhibiting significant potential to induce depression through strong binding to multiple targets. In vitro experiments demonstrated that Zonisamide treatment elevated the expression and activity of MAOA protein in the prefrontal cortex of mice, which may influence monoaminergic neurotransmission through MAO pathway regulation, potentially leading to depression. Collectively, this integrated approach elucidates the mechanisms underlying AED-induced depression, thereby establishing a foundation for future therapeutic strategies.

Study on the comorbid mechanisms of sarcopenia and late-life depression

The increasing global aging population has brought greater focus to age-related diseases, particularly muscle-brain comorbidities such as sarcopenia and late-life depression. Sarcopenia, defined by the gradual loss of muscle mass and function, is notably prevalent among older individuals, while late-life depression profoundly affects their mental health and overall well-being. Epidemiological evidence suggests a high co-occurrence of these two conditions, although the precise biological mechanisms linking them remain inadequately understood. This review synthesizes the existing body of literature on sarcopenia and late-life depression, examining their definitions, prevalence, clinical presentations, and available treatments. The goal is to clarify the potential connections between these comorbidities and offer a theoretical framework for the development of future preventive and therapeutic strategies.

TMBIM-2 links neuronal mitochondrial stress to systemic adaptation via calcium signaling

Mitochondrial function is critical for neuronal activity and systemic metabolic adaptation. In this issue, Li et al. (https://doi.org/10.1083/jcb.202408050) identify TMBIM-2 as a key regulator of calcium dynamics, coordinating the neuronal-to-intestinal mitochondrial unfolded protein response (UPRmt), pathogen-induced aversive learning, and aging.

Challenges and hopes for treatment of anxiety disorder in the autistic population

Anxiety disorders, marked by excessive fear and worry, are particularly prevalent in autism, affecting up to 45 % of individuals with the condition. Since the 1960s, advances in neuroscience, psychology, and psychopharmacology have enhanced understanding and treatment of anxiety disorders in general population. Standardized diagnostic criteria development facilitated accurate classification of anxiety disorders. Neurobiological research identified key brain regions forming the basis of the amygdala-centred fear circuit model. Pharmacological advancements introduced selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) as safer, first-line treatments. However, these medications show limited efficacy and significant side effects in autistic individuals, highlighting the need for alternative treatments. Cognitive-behavioural therapy (CBT) has gained empirical support, helping to reduce avoidance behaviours, but modifications are often needed for autistic individuals. Emerging therapies, including Mindfulness-Based Stress Reduction for Autism Spectrum Disorder (MASSI) and virtual reality-based interventions, are being explored for individuals with more treatment-resistant anxiety. Ongoing clinical trials are assessing medications used for other psychiatric disorders to determine their efficacy in anxiety treatment for autism. Recent genetic and neuroimaging research has revealed altered brain connectivity and genetic susceptibility in anxiety, promoting the development of personalized treatments. Despite these advances, challenges remain in optimizing interventions and addressing treatment resistance, necessitating continued research and innovation.

Physicochemical profiling and ranking of parkinson's disease drugs through QSPR and Fuzzy TOPSIS analysis

Parkinson's disease is a progressive neurological disorder characterized by the degeneration of the nervous system, leading to impaired motor and non-motor functions. Early symptoms include tremors, rigidity, and bradykinesia, with progressive deterioration over time. This study employs a multi-criteria decision-making approach, integrating Fuzzy TOPSIS and Quantitative Structure-Property Relationship (QSPR) analysis, to evaluate and rank 17 Parkinson's disease medications based on their physicochemical properties. Molecular structures were encoded as adjacency matrices using MATLAB 2017, and six Sombor index variants-computed via a custom Maple 2020 algorithm-served as topological descriptors for QSPR modeling. Eight critical physicochemical properties were analyzed: polarizability (P), boiling point (BP), surface tension (ST), polar surface area (PSA), flash point (FP), molar refractivity (MR), enthalpy of vaporization (EV), and molar volume (MV). The Fuzzy TOPSIS ranking revealed bromocriptine as the top-performing drug for boiling point (BP), while comparative rankings across all properties are tabulated for clinical reference. Validation metrics, including coefficient of determination, mean squared error , and mean absolute error, confirmed model robustness. Notably, surface tension (ST) and polar surface area (PSA) showed weaker correlations (R2 < 0.5, p > 0.05), highlighting limitations in their predictability via Sombor indices. This work demonstrates the utility of combining chemical graph theory, QSPR modeling, and Fuzzy TOPSIS for rational drug evaluation in neurodegenerative disorders. The methodology offers a framework for prioritizing therapeutics based on physicochemical profiles, with implications for optimizing Parkinson's disease management.

A Tetrazine-Based Synthesis for Accessing Underutilized Aza-Indole Analogues

Aza-indole functionalities fill an important role in drug discovery. While indoles are considered privileged scaffolds, aza-indoles allow for better pharmacological properties and on-target activities. Synthetic approaches to access aza-indoles are limited, with pyrazolopyridazines being some of the scarcest aza-indoles. To provide access to these underutilized cores, a synthetic approach utilizing a reaction cascade between a protected propargylhydrazine and dichlorotetrazine has been developed. In addition, a variety of methods were developed to access each position on the core for late-stage functionalization. This method offers an expedited synthetic route to a rare aza-indole scaffold with superior physiochemical properties when compared to indole analogues.

Prenatal Intake of High Multivitamins or Folic Acid With or Without Choline Contributes to Gut Microbiota-Associated Dysregulation of Serotonin in Offspring

The gut microbiota is amenable to early nutrition including micronutrients but intake above and below the recommendations commonly occur with unknown consequences. Serotonin (5-hydroxytryptamine [5-HT]) is a monoamine found centrally and peripherally with diverse functions such as food intake regulation via the hypothalamic 5-HT receptor 2C (5-HTR2C). This study determined the impact of prenatal micronutrients on the gut microbiota and serotonergic system in offspring. Pregnant Wistar rats were fed either recommended vitamins (RV), high vitamins (HV), high folic acid with recommended choline (HFRC), or high folic acid with no choline (HFNC). Offspring were fed a high-fat diet for 12 weeks postweaning. HV, HFRC, and HFNC males and females had lower hypothalamic 5-HTR2C protein expression compared to RV. Brain 5-HT concentrations were lower but colon 5-HT concentrations were higher in HV and HFNC males and females and HFRC males compared to RV. Refeeding response after 5-HTR2C agonist was negatively correlated with hypothalamic 5-HTR2C protein expression in males and with brain 5-HT concentrations in females. Random forest revealed top bacterial taxa, which Lactococcus, Ruminococcus, Bacteroides, and Oscillospira showed significant correlations with refeeding response and concentrations of brain and colon 5-HT. In conclusion, excess or imbalanced prenatal consumption of micronutrients leads to gut microbiota-associated disturbances in the serotonergic system in offspring.

2025 Seoul Consensus on Clinical Practice Guidelines for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic, disabling, and functional bowel disorder that significantly affects social functioning and reduces quality of life and increases social costs. The Korean Society of Neurogastroenterology and Motility published clinical practice guidelines on the management of IBS based on a systematic review of the literature in 2017, and planned to revise these guidelines in light of new evidence on the pathophysiology, diagnosis, and management of IBS. The current revised version of the guidelines is consistent with the previous version and targets adults diagnosed with or suspected of having IBS. These guidelines were developed using a combination of de novo and adaptation methods, with analyses of existing guidelines and discussions within the committee, leading to the identification of key clinical questions. Finally, the guidelines consisted of 22 recommendations, including 3 concerning the definition and risk factors of IBS, 4 regarding diagnostic modalities and strategies, 2 regarding general management, and 13 regarding medical treatment. For each statement, the advantages, disadvantages, and precautions were thoroughly detailed. The modified Delphi method was used to achieve expert consensus to adopt the core recommendations of the guidelines. These guidelines serve as a reference for clinicians (including primary care physicians, general healthcare providers, medical students, residents, and other healthcare professionals) and patients, helping them to make informed decisions regarding IBS management.

Context-dependent roles of 5-HT and its receptors in tumor growth and wound healing: Mechanisms and therapeutic implications

Serotonin (5-hydroxytryptamine, 5-HT), a neurotransmitter known for its roles in the central nervous system, showing dual effects in various pathological conditions, including tumor progression and wound healing. This review explores the complex and context-dependent actions of 5-HT, highlighting its contrasting roles in promoting tumor growth and facilitating wound repair. 5-HT can enhance tumor growth, survival, and metastasis via its receptors, but it also accelerates wound healing by stimulating cell proliferation, migration, and angiogenesis. This duality emphasizes the intricate balance of 5-HT and its receptors in the body. We discuss the synthesis, storage, secretion, and metabolism of 5-HT, as well as the classification and mechanisms of its receptors (5-HTRs) in different cell types under pathological conditions. We further examine the potential roles of 5-HT in both tumor progress and wound healing, proposing targeted strategies for each disease state. For tumors, "blocking therapy" involving receptor antagonists or gene silencing may inhibit tumor progression, while "activation therapy" can stimulate wound healing by enhancing receptor activation on skin cells. Challenges in clinical application, including issues related to targeting, specificity, and dosage, are addressed, alongside the promise of nanotechnology for improving targeted drug delivery. The review also explores emerging research on 5-HT's interaction with the immune system, offering insights into potential immunotherapeutic strategies for both cancer and wound healing. By balancing 5-HT's diverse effects, personalized treatments can be developed to optimize therapeutic outcomes in both contexts.

Monoamine signaling and neuroinflammation: mechanistic connections and implications for neuropsychiatric disorders

Monoamines, including norepinephrine, serotonin, and dopamine, orchestrate a broad spectrum of neurophysiological and homeostatic events. Recent research shows a pivotal role for monoaminergic signaling in modulating neuroinflammation by regulating proinflammatory cytokines and chemokines within the central nervous system. Importantly, this modulation is not unidirectional; released proinflammatory cytokines markedly "feedback" to influence the metabolism of monoamine neurotransmitters, impacting their synthesis, release, and reuptake. This bidirectional interplay significantly links monoaminergic pathways and neuroinflammatory responses. In this review, we summarize current knowledge of the dynamic interactions between monoamine signaling and neuroinflammation, as well as their critical implications for the pathophysiology of neuropsychiatric disorders, including Parkinson's Disease, Major Depressive Disorder, and Alzheimer's Disease. By integrating recent findings, we shed light on potential therapeutic targets within these interconnected pathways, providing insights into novel treatment strategies for these devastating disorders.

Effects of tianeptine on mTORC1-mediated neuronal autophagy in primary rat hippocampal neurons under nutrient deprivation

The aim of this study was to investigate the effects of the antidepressant tianeptine on the mechanistic target of rapamycin complex 1(mTORC1)-mediated autophagy pathway in primary hippocampal neurons exposed to B27-deprived conditions. When primary hippocampal neurons were treated with tianeptine at doses of 1, 10, 50, and 100 µM for 3 days under B27-deprived conditions, we observed that it activated autophagy and increased the formation of autophagosomes through the upregulation of autophagic proteins, including autophagy-activating kinase 1 (ULK1), Beclin 1, LC3B-II/I, and p62. And at a concentration of 100 µM tianeptine, the decrease in mTORC1 phosphorylation induced by B27 deprivation was significantly reversed. Changes in the expression of autophagic proteins induced by B27 deprivation were reversed by tianeptine treatment in a concentration-dependent manner, and tianeptine significantly reduced the increase in LC3B membrane number induced by B27 deprivation, an effect that was blocked by pretreatment with rapamycin. In conclusion, tianeptine attenuated the activity of mTORC1-mediated autophagy in primary rat hippocampal neurons under B27-deprived conditions. These results may suggest a novel mechanism by which tianeptine may affect autophagy in neurons.

Decoding serotonin: the molecular symphony behind depression

The serotonin (5-hydroxytryptamine) system represents a crucial neurotransmitter network that regulates mood, behavior, and cognitive functions, playing a significant role in the pathogenesis and progression of depression. Although this perspective faces significant challenges, the serotonin system continues to exert substantial modulatory effects on specific aspects of psychological functioning and actively contributes to multiple pathological processes in depression development. Therefore, this review systematically integrates interdisciplinary research advances regarding the relationship between the 5-hydroxytryptamine (5-HT) system and depression. By focusing on core biological processes including serotonin biosynthesis and metabolism, SERT gene regulatory networks, and protein molecular modifications, it aims to elucidate how 5-HT system dysregulation contributes to the development of depression, while providing novel research perspectives and therapeutic targets for innovative antidepressant drug development.

Investigating the Secondary Metabolite Profile and Neuropharmacological Activities of Ipomoea purpurea: A Multi-Method Approach Using GC-MS, In Vivo, and In Silico Techniques

Ipomoea purpurea, a traditional medicinal plant native to Mexico and Central America, was evaluated for its neuropharmacological effects. The methanol extract of I. purpurea leaves (IPML) was analyzed through in vivo and in silico approaches. The extract's secondary metabolites were identified through qualitative and gas chromatography-mass spectrometry (GC-MS) analysis. Anxiolytic effects were assessed using the elevated plus maze (EPM) and hole-board test (HBT), whereas sedative activity was evaluated through the open-field test (OFT) and hole cross test (HCT). Antidepressant properties were analyzed via the tail suspension test (TST) and forced swimming test (FST), and muscle relaxant activity was tested using the rota-rod test. IPML at 200 and 400 mg/kg showed significant anxiolytic (p < 0.001), sedative (p < 0.0001), antidepressant (p < 0.001), and muscle relaxant (p < 0.0001) effects. GC-MS analysis identified 19 bioactive compounds, and in silico molecular docking and absorption, distribution, metabolism, excretion, and toxicity (ADME/T) analysis revealed strong binding affinities, favorable pharmacokinetics, and a safe toxicological profile. Findings suggest that IPML possesses significant neuropharmacological properties, supporting its role as a natural therapeutic agent. However, further research is needed to address key concerns, such as small sample sizes, limited replication, and the necessity for extensive dose-response studies across diverse animal models.

Unraveling the Anticancer Potential of SSRIs in Prostate Cancer by Combining Computational Systems Biology and In Vitro Analyses

Selective serotonin reuptake inhibitors (SSRIs) are known to have anticancer activity against different types of cancer. In this study, an integrative informatics approach was applied to identify compound and genetic perturbations that produce similar effects to SSRIs to formulate systems biology hypotheses and identify biological pathways involved in the putative anticancer effects of SSRIs in prostate cancer. An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay assessed the antiproliferative effects of SSRIs and drug combinations. Cell death mechanisms were studied using annexin V-FITC/PI staining, and the cell cycle analysis was carried out by counterstaining with propidium iodide. Relative gene expression was assessed using a real-time polymerase chain reaction (PCR). Computational results hypothesized that SSRIs could potentially exert anticancer effects in prostate cancer cell lines by modulating apoptotic and tumorigenesis pathways and significantly inhibiting the growth of prostate cancer cells in a time and concentration-dependent manner. The combination of SSRIs with cisplatin, 5-fluorouracil, and raloxifene resulted in either synergistic or additive effects. SSRIs resulted in a significant increase in the early and late apoptotic activity in PC3 cells. Dapoxetine, paroxetine, and sertraline resulted in cell cycle arrest at the G0/G1 phase. Treatment with either dapoxetine or paroxetine decreases the expression of Bcl-2, CASP8, DR5, and VEGF. At the same time, sertraline decreases the expression of Bcl-2 and VEGF and increases the expression of CASP8 and DR5. Results revealed that SSRIs can potentially act as antiproliferative agents against prostate cancer cells, and their activity is mediated through different signaling pathways.

α2-Adrenergic Receptors in Hypothalamic Dopaminergic Neurons: Impact on Food Intake and Energy Expenditure

The adrenergic system plays an active role in modulating synaptic transmission in hypothalamic neurocircuitry. While α2-adrenergic receptors are widely distributed in various organs and are involved in various physiological functions, their specific role in the regulation of energy metabolism in the brain remains incompletely understood. Herein, we investigated the functions of α2-adrenergic receptors in the hypothalamus on energy metabolism in mice. Our study confirmed the expression of α2-adrenergic receptors in hypothalamic dopaminergic neurons and assessed metabolic phenotypes, including food intake and energy expenditure, after treatment with guanabenz, an α2-adrenergic receptor agonist. Guanabenz treatment significantly increased food intake (0.25 ± 0.03 g vs. 0.98 ± 0.05 g, p < 0.001) and body weight (-0.1 ± 0.04 g vs. 0.33 ± 0.03 g, p < 0.001) within 6 h post-treatment. Furthermore, guanabenz markedly elevated energy expenditure parameters, including respiratory exchange ratio (RER, 1.017 ± 0.007 vs. 1.113 ± 0.03, p < 0.01) and carbon dioxide production (1.512 ± 0.018 mL/min vs. 1.635 ± 0.036 mL/min, p < 0.05), compared to vehicle-treated controls. Furthermore, using chemogenetic techniques, we demonstrated that the altered metabolic phenotypes induced by guanabenz treatment were effectively reversed by inhibiting the activity of dopaminergic neurons in the hypothalamic arcuate nucleus (ARC) using a chemogenetic technique. Our findings suggest functional connectivity between hypothalamic α2-adrenergic receptor signals and dopaminergic neurons in metabolic controls.

Biogenic Amine Metabolism and Its Genetic Variations in Autism Spectrum Disorder: A Comprehensive Overview

Autism spectrum disorder (ASD) is a genetically heterogeneous syndrome characterized by repetitive, restricted, and stereotyped behaviors, along with persistent difficulties with social interaction and communication. Despite its increasing prevalence globally, the underlying pathogenic mechanisms of this complex neurodevelopmental disorder remain poorly understood. Therefore, the identification of reliable biomarkers could play a crucial role in enabling early screening and more precise classification of ASD subtypes, offering valuable insights into its physiopathology and aiding the customization of treatment or early interventions. Biogenic amines, including serotonin, histamine, dopamine, epinephrine, norepinephrine, and polyamines, are a class of organic compounds mainly produced by the decarboxylation of amino acids. A substantial portion of the genetic variation observed in ASD has been linked to genes that are either directly or indirectly involved in the metabolism of biogenic amines. Their potential involvement in ASD has become an area of growing interest due to their pleiotropic activities in the central nervous system, where they act as both neurotransmitters and neuromodulators or hormones. This review examines the role of biogenic amines in ASD, with a particular focus on genetic alterations in the enzymes responsible for their synthesis and degradation.

Dog Neuter, Yes or No? A Summary of the Motivations, Benefits, and Harms, with Special Emphasis on the Behavioral Aspect

The decision to neuter pet dogs remains a significant and ongoing debate from ethical, animal health, and animal welfare perspectives. Millions of dogs worldwide are considered integral family members, and their behavior, as well as the bond they form with their owners, play a key role in the decision to keep them as pets. When behavioral problems arise, neutering is often viewed as a potential solution. However, by removing the source of sexual hormones, neutering creates the potential for both beneficial and harmful effects on a dog's health and behavior. It is crucial for society to rely on professionals to provide informed advice about whether and when the procedure should be performed on a pet, taking into account the unique risks and benefits of each individual case. Instead, the conclusions drawn from existing research-both in terms of behavior and health aspects-remain inconclusive and sometimes conflicting. Studies have reported higher risks for developing reproductive, urinary, metabolic, and musculoskeletal disorders in neutered dogs. Additionally, some studies suggest increases in stress, fear, anxiety, and even certain types of aggression following neutering. The limitations of current research, the subjectivity of pet owners' evaluations of their dogs' behaviors, the influence of various demographic factors, and the complex relationships between sex hormones and other hormones or neurotransmitters all contribute to the challenges in this field of study. Despite these complexities, they also offer promising avenues for future research. This review aims to provide a comprehensive overview of the various effects of neutering on dogs, with a particular focus on behavioral outcomes.

Stratification of enterochromaffin cells by single-cell expression analysis

Dynamic interactions between gut mucosal cells and the external environment are essential to maintain gut homeostasis. Enterochromaffin (EC) cells transduce both chemical and mechanical signals and produce 5-hydroxytryptamine to mediate disparate physiological responses. However, the molecular and cellular basis for functional diversity of ECs remains to be adequately defined. Here, we integrated single-cell transcriptomics with spatial image analysis to identify 14 EC clusters that are topographically organized along the gut. Subtypes predicted to be sensitive to the chemical environment and mechanical forces were identified that express distinct transcription factors and hormones. A Piezo2+ population in the distal colon was endowed with a distinctive neuronal signature. Using a combination of genetic, chemogenetic, and pharmacological approaches, we demonstrated Piezo2+ ECs are required for normal colon motility. Our study constructs a molecular map for ECs and offers a framework for deconvoluting EC cells with pleiotropic functions.

Aptamer-Based Galvanic Potentiometric Sensor for Real-Time Monitoring of Serotonin Signaling Under Psychosocial Stress

Psychosocial stress, a pervasive factor in mental health disorders, is tightly linked to serotonin (5-HT) dysregulation. Real-time electrochemical monitoring of 5-HT in vivo is challenged by interference from vitamin C (Vc) and biofouling, requiring invasive pretreatments. We present a self-powered aptamer-engineered galvanic sensor (aptGRP5-HT) that integrates phosphorothioate aptamers with a redox potentiometric mechanism, achieving 21.5-fold higher selectivity and 98.3-fold enhanced sensitivity against Vc over conventional sensors while resisting electrochemical biofouling. The aptGRP5-HT operates in complex biological environments without pretreatment, enabling direct monitoring in a rodent psychosocial stress model. Using this tool, we uncover a neurochemical signature of social hierarchy: high-ranking mice exhibit elevated 5-HT release in the medial prefrontal cortex (mPFC) and dorsal raphe nucleus (DRN), with region-specific correlations to neuronal activity-reduced spontaneous firing in the mPFC and increased activity in the DRN. This work resolves long-standing challenges in neurochemical sensing and establishes aptGRP5-HT as a transformative platform for probing brain function and stress-related disorders.

Impact of prenatal phthalate exposure on newborn metabolome and infant neurodevelopment

We evaluated associations among exposure to prenatal phthalate metabolites, perturbations of the newborn metabolome, and infant neurobehavioral functioning in mother-newborn pairs enrolled in the Atlanta African American Maternal-Child Cohort during 2016-2018. We quantified eight phthalate metabolites in prenatal urine samples collected between 8- and 14-weeks' (visit 1; n = 216) and 24- and 30-weeks' gestation (visit 2; n = 145) and metabolite features in newborn dried-blood spot samples collected at delivery. Associations between phthalate metabolite concentrations and metabolic feature intensities at both visits were examined using adjusted generalized linear models (MWAS). Then, an exploratory meet-in-the-middle (MITM) analysis was conducted in a subset with NICU Neonatal Neurobehavioral Scale (NNNS) scores (visit 1 n = 81; visit 2 n = 71). In both the MWAS and MITM, many of the confirmed metabolites are involved in tyrosine and tryptophan metabolism, including tryptophan, tyrosine, thyroxine, and serine. This analysis elucidates how prenatal phthalate exposure disrupts the newborn metabolome and infant neurobehavioral outcomes.

Association between sleep quality and serum biomarkers among long-term hot spring bathers: a cross-sectional study

Previous studies investigating the influence of hot spring bathing on sleep quality have predominantly focused on the short-term effects through questionnaire surveys without blood collection for biochemical tests. Here, we undertook a comprehensive investigation of the long-term health effects of hot spring bathing among the residents of Hot Spring Village. A total of 140 participants were enrolled, and their demographic characteristics and the patterns of hot spring bathing were obtained via face-to-face interview, and sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). Moreover, the blood samples of the participants were collected for biomarker detection with the ELISA assay. Logistic regression analysis was applied to evaluate the relationship between sleep quality and serum biomarkers among long-term hot spring bathers. In individuals aged 65 and older, the results demonstrated that hot spring bathing (OR = 0.18, 95%CI: 0.05-0.68), particularly with a length of ≥ 30 min (OR = 0.10, 95%CI: 0.02-0.53) and a frequency of ≥ 3 times/week (OR = 0.07, 95%CI: 0.01-0.32) were significant protective factors for good sleep quality (P < 0.05). Furthermore, reduced TNF-α (OR = 1.03, 95% CI: 1.01-1.06) and increased 5-HT levels (OR = 0.98, 95% CI: 0.97-0.99) were associated with good sleep quality. Interestingly, for the first time, we observed that the TNF-α significantly decreased (P < 0.05) in the bathing group, along with an increasing trend of 5-HT and BDNF. Moreover, among participants in this group who reported good sleep quality, there was a notably significant decrease in TNF-α and an increase in 5-HT levels as well. These findings suggested that long-term hot spring bathing is associated with good sleep quality through the alteration of TNF-α and 5-HT levels, which could be potential biomarkers for future investigation on the health-promoting effects of bathing.

Exploring the effects of adolescent social isolation stress on the serotonin system and ethanol-motivated behaviors

RATIONALE

Alcohol is one of the most frequently used drugs of abuse and has a major impact on human health worldwide. People assigned female at birth and those with adverse childhood experiences are stress-vulnerable and more likely to report drinking as a means of "self-medication." Prior studies in our laboratory showed that adolescent social isolation stress (SIS) increases vulnerability to ethanol (EtOH) intake and consumption despite negative consequences in female rats.

OBJECTIVES

Here, we explored modulation of the dorsal raphe nucleus (DRN)-serotonin (5-HT) system, a sexually dimorphic neurotransmitter system involved in stress-reward interactions, to determine its contribution to EtOH-motivated behaviors in rats that have undergone SIS.

RESULTS

We employed electrophysiological and functional neuroanatomy strategies to show that both SIS and EtOH exposure induce persistent hypofunction of the DRN 5-HT system, particularly in females. Chemogenetic activation of DRN 5-HT neurons attenuated reward value for both EtOH and sucrose and elevated punished responding for EtOH in a stress-dependent manner.

CONCLUSIONS

Our results highlight an inverse relationship between EtOH consumption and the 5-HT system, the sex- and stress-dependent nature of this relationship, and a connection between DRN 5-HT signaling and acute responding to rewards and punishment. These data support the DRN 5-HT system as a potential target to treat aberrant alcohol consumption and drinking despite negative consequences in stress-vulnerable populations.

Association Between the Gut Microbiota and Alzheimer's Disease: An Update on Signaling Pathways and Translational Therapeutics

Alzheimer's disease (AD) is a cognitive disease with high morbidity and mortality. In AD patients, the diversity of the gut microbiota is altered, which influences pathology through the gut-brain axis. Probiotic therapy alleviates pathological and psychological consequences by restoring the diversity of the gut microbial flora. This study addresses the role of altered gut microbiota in the progression of neuroinflammation, which is a major hallmark of AD. This process begins with the activation of glial cells, leading to the release of proinflammatory cytokines and the modulation of cholinergic anti-inflammatory pathways. Short-chain fatty acids, which are bacterial metabolites, provide neuroprotective effects and maintain blood‒brain barrier integrity. Furthermore, the gut microbiota stimulates oxidative stress and mitochondrial dysfunction, which promote AD progression. The signaling pathways involved in gut dysbiosis-mediated neuroinflammation-mediated promotion of AD include cGAS-STING, C/EBPβ/AEP, RAGE, TLR4 Myd88, and the NLRP3 inflammasome. Preclinical studies have shown that natural extracts such as Ganmaidazao extract, isoorentin, camelia oil, Sparassis crispa-1, and xanthocerasides improve gut health and can delay the worsening of AD. Clinical studies using probiotics such as Bifidobacterium spp., yeast beta-glucan, and drugs such as sodium oligomannate and rifaximine have shown improvements in gut health, resulting in the amelioration of AD symptoms. This study incorporates the most current research on the pathophysiology of AD involving the gut microbiota and highlights the knowledge gaps that need to be filled to develop potent therapeutics against AD.

Global analysis of ligand-gated ion channel conservation across Platyhelminthes

Ligand-gated ion channels (LGICs) are critical for neurotransmission, mediating responses to neurotransmitters and hormones, and influencing diverse physiological processes. This study identifies and classifies LGICs across Platyhelminthes, with a particular focus on parasitic neodermatans, which impact human and animal health. Using bioinformatics tools, we analyzed LGICs from 41 neodermatan species and expanded our investigation to encompass vertebrates, other invertebrates, and non-bilaterians to trace LGIC evolutionary pathways across Metazoa. We identified 2,269 putative LGICs within neodermatan species, which we classified into the cys-loop, ASIC/Deg/ENaC, iGluR, and P2X families. Our phylogenetic and clustering analyses reveal lineage-specific patterns with distinct evolutionary trajectories for each LGIC family in neodermatans compared to free-living platyhelminths and other taxa. Notably, the ASIC/Deg/ENaC family displayed the greatest degree of neodermatan-specific divergence, while cys-loop and P2X families were more conserved across taxa. To provide insight into their potential physiological roles, we analyzed LGIC expression patterns in Schistosoma mansoni, revealing widespread expression across neuronal and muscle cell types. The distribution of acid-sensing ion channels (ASICs) in both neurons and muscles suggests a role in neuromuscular signalling, while the P2X receptor (Smp_333600) exhibited sex-specific expression, potentially indicating distinct functional roles in males and females. Additionally, several cys-loop acetylcholine and GABA receptors showed differential neuronal and muscle expression, highlighting their likely contributions to cholinergic and inhibitory neurotransmission. These findings underscore the relevance of LGICs in parasite physiology, particularly in neuromuscular and sensory processes, and suggest potential targets for antiparasitic interventions.

Plasma metabolome reveals altered oxidative stress, inflammation, and amino acid metabolism in dogs with idiopathic epilepsy

OBJECTIVE

Idiopathic epilepsy (IE) is the most common chronic neurological disease in dogs and an established natural animal model for human epilepsy types with genetic and unknown etiology. However, the metabolic pathways underlying IE remain largely unknown.

METHODS

Plasma samples of healthy dogs (n = 39) and dogs with IE (n = 49) were metabolically profiled (n = 121 known target metabolites) and fingerprinted (n = 1825 untargeted features) using liquid chromatography coupled to mass spectrometry. Dogs with IE were classified as mild phenotype (MP; n = 22) or drug-resistant (DR; n = 27). All dogs received the same standard adult maintenance diet for a minimum of 20 days (35 ± 11 days) before sampling. Data were analyzed using a combination of univariate (one-way analysis of variance or Kruskal-Wallis rank sum test), multivariate (limma, orthogonal partial least squares-discriminant analysis), and pathway enrichment statistical analysis.

RESULTS

In dogs with both DR and MP IE, a distinct plasma metabolic profile and fingerprint compared to healthy dogs was observed. Metabolic pathways involved in these alterations included oxidative stress, inflammation, and amino acid metabolism. Moreover, significantly lower plasma concentrations of vitamin B6 were found in MP (p = .001) and DR (p = .005) compared to healthy dogs.

SIGNIFICANCE

Our data provide new insights into the metabolic pathways underlying IE in dogs, further substantiating its potential as a natural animal model for humans with epilepsy, reflected by related metabolic changes in oxidative stress metabolites and vitamin B6. Even more, several metabolites within the uncovered pathways offer promising therapeutic targets for the management of IE, primarily for dogs, and ultimately for humans.

Acute decrease in the plasma tryptophan-to-large-neutral-amino-acids ratio attenuates the effects of L-tryptophan on gut hormones and energy intake in healthy males: a randomized, cross-over, exploratory trial

BACKGROUND

L-tryptophan ("Trp") and L-leucine ("Leu"), when administered intraduodenally, increase plasma cholecystokinin (CCK) and glucagon-like peptide 1 (GLP-1) and stimulate pyloric pressures, which all slow gastric emptying and suppress subsequent energy intake. The circulating Trp-to-large-neutral-amino-acids ("Trp/LNAAs") ratio is also inversely related to energy intake.

OBJECTIVES

This exploratory study characterized the impact of standardized changes in the plasma Trp/LNAAs ratio, achieved by combining a fixed-load intraduodenal infusion of Trp with increasing loads of Leu, on the appetite-inhibitory effects of enteral Trp.

METHODS

Twelve males of normal weight [mean ± standard deviation; age: 23 ± 2 y; body mass index (in kg/m2: 23±1)], received on 4 separate occasions, 90-min iso-osmotic intraduodenal infusions of 1) isotonic 0.9% saline ("control"), 2) Trp (0.15 kcal/min; "Trp"), 3) Trp + Leu (0.22 kcal/min; "Trp+Leu-0.22"), or 4) Trp + Leu (0.45 kcal/min; "Trp+Leu-0.45"), in a randomized, double-blind, cross-over fashion. Immediately postinfusion ad-libitum energy intake was quantified. Plasma CCK, GLP-1, amino acid concentrations, and antropyloroduodenal pressures were measured throughout.

RESULTS

Although there was a transient stimulation of CCK and GLP-1 by Trp + Leu - 0.45 (at t = 15 min), only Trp led to a sustained increase in plasma CCK (P = 0.04) and GLP-1 (P = 0.009) from t = 60-90 min, and stimulated pyloric pressures (P = 0.01), compared with control. Only Trp reduced energy intake [kcal (mean ± standard error of the mean); control: 1085 ± 49, Trp: 881 ± 75, Trp + Leu - 0.22: 963 ± 57, Trp + Leu - 0.45: 932 ± 60] compared with control (P = 0.008). The Trp/LNAAs ratio was dose-dependently decreased by Trp + Leu - 0.22 and Trp + Leu - 0.45, compared with Trp (all P = 0.001), and energy intake correlated inversely with the Trp/LNAAs ratio (R = -0.38; P = 0.02).

CONCLUSIONS

Acute reduction in the Trp/LNAAs ratio appears to be associated with a diminished capacity of Trp to stimulate CCK and GLP-1 and suppress energy intake. Although these observations should be interpreted with caution given the exploratory nature of the study, they attest to the complexity of the relationships between pre and postabsorptive mechanisms underlying Trp's appetite-inhibitory effect. This trial was registered at the Australian New Zealand clinical trial registry as ACTRN12620001275954.

Peripheral nerves-cancer cross-talk: the next frontier in cancer treatment

The nervous system, which regulates organogenesis, homeostasis, and plasticity of the organism during human growth and development, integrates physiological functions of all organ systems, including the immune system. Its extensive network of branches throughout the body reaches the tumor microenvironment (TME), where it secretes neurotransmitters that directly regulate or influence immune cells. This, in turn, indirectly affects the occurrence, development, and metastasis of cancer. Conversely, cancer cells are now understood to secrete neurotrophic factors that remodel the nervous system. Targeting the cross-talk between the nervous system and cancer represents a promising strategy for cancer treatment, some aspects of which have been confirmed in clinical trials. This review addresses gaps in our understanding of the interaction between peripheral nerves and various human cancers. At the intersection of neuroscience and cancer biology, new targets for neuroscience-based cancer therapies are emerging, establishing a significant new pillar in cancer treatment.

Synthesis and Biological Evaluation of Peripheral 5HT2B Antagonists for Liver Fibrosis

Liver fibrosis is characterized by an excessive accumulation of extracellular matrix components, leading to the distortion of liver architecture and function. Recent studies have shown that antagonizing 5-hydroxytryptamine receptor 2B (5HT2B) stimulates the apoptosis of activated hepatic stellate cells and inhibits their proliferation while concurrently regressing hepatocyte proliferation. In this study, we present compound 19c, which demonstrates promising efficacy both in vitro and in vivo. 19c showed robust in vitro activity with an IC50 value of 1.09 nM and limited blood-brain barrier penetration. Furthermore, 19c did not significantly inhibit hERG and cytochrome P450 enzymes. 19c markedly reduced fibrotic deposition, with a decrease in fibrosis stage and area in the CCl4-induced liver fibrosis mouse model. Additionally, treatment with 19c led to downregulation of key fibrosis-related genes, including α-SMA, Timp1, Col1a1, and Col3a1. Taken together, these results suggest that 19c has the potential to be a novel antifibrotic agent.

Characterizing serotonin expression throughout bovine mammary gland developmental stages and its relationship with 17β-estradiol at puberty

Serotonin acts in an autocrine/paracrine manner within the mammary epithelium regulating cell homeostasis during lactation and cell turnover during involution after milk stasis. However, the presence and role of mammary serotonin during the pubertal developmental stage is unknown in the bovine. Here, we characterized the serotonin receptor profile and serotonin immunolocalization in bovine mammary tissue at eight developmental stages (i.e., birth, weaning, puberty, six months gestation, early lactation, mid-lactation, early dry and late dry, n = 6/stage). Further, we investigated the effects of 5-HTP (serotonin precursor), 17β-estradiol (E2), and ICI 182780 (ERα antagonist) either alone or in various combinations (i.e., 5-HTP +  E2, 5-HTP + ICI, E2 + ICI or 5-HTP + E2 +  ICI) on cultured bovine mammary epithelial cells (MAC-T). Serotonin receptor gene expression is highly dynamic throughout mammary development, particularly highly expressed in the puberty stage expressing 12 out of the 13 serotonin receptors evaluated (5-HTR1A, -1B, -1D, -1F, -2A, -2B, -2C, -3B, -4, -5a, -6, and -7), relative to the birth stage. Following a 24-hour incubation, all treatments except ICI increased MAC-T cell proliferation. Incubation with 5-HTP +  ICI resulted in a downregulation of ESR1, ESR2, GPER1 and AREG, relative to CON. Incubation with 5-HTP and E2 alone downregulated the expression of TPH1, 5-HTR1A and 5-HTR1B, relative to CON. Overall, our data indicates serotonin is present in the juvenile developing mammary tissue and the expression of various receptors is observed suggesting an active involvement at this early stage. Additionally, serotonin might indirectly regulate mammary epithelial cell proliferation alone and concurrently with E2 during puberty through the modulation of E2 signaling genes and 5-HTR1A and -1B.

Alcohol and alcoholism associated neurological disorders: Current updates in a global perspective and recent recommendations

Alcohol use disorder (AUD) is a medical condition that impairs a person's ability to stop or manage their drinking in the face of negative social, occupational, or health consequences. AUD is defined by the National Institute on Alcohol Abuse and Alcoholism as a "severe problem". The central nervous system is the primary target of alcohol's adverse effects. It is crucial to identify various neurological disorders associated with AUD, including alcohol withdrawal syndrome, Wernicke-Korsakoff syndrome, Marchiafava-Bignami disease, dementia, and neuropathy. To gain a better understanding of the neurological environment of alcoholism and to shed light on the role of various neurotransmitters in the phenomenon of alcoholism. A comprehensive search of online databases, including PubMed, EMBASE, Web of Science, and Google Scholar, was conducted to identify relevant articles. Several neurotransmitters (dopamine, gamma-aminobutyric acid, serotonin, and glutamate) have been linked to alcoholism due to a brain imbalance. Alcoholism appears to be a complex genetic disorder, with variations in many genes influencing risk. Some of these genes have been identified, including two alcohol metabolism genes, alcohol dehydrogenase 1B gene and aldehyde dehydrogenase 2 gene, which have the most potent known effects on the risk of alcoholism. Neuronal degeneration and demyelination in people with AUD may be caused by neuronal damage, nutrient deficiencies, and blood brain barrier dysfunction; however, the underlying mechanism is unknown. This review will provide a detailed overview of the neurobiology of alcohol addiction, followed by recent studies published in the genetics of alcohol addiction, molecular mechanism and detailed information on the various acute and chronic neurological manifestations of alcoholism for the Future research.

Targeting the central and peripheral nervous system to regulate bone homeostasis: mechanisms and potential therapies

The skeleton is innervated by different types of nerves and receives signaling from the nervous system to maintain homeostasis and facilitate regeneration or repair. Although the role of peripheral nerves and signals in regulating bone homeostasis has been extensively investigated, the intimate relationship between the central nervous system and bone remains less understood, yet it has emerged as a hot topic in the bone field. In this review, we discussed clinical observations and animal studies that elucidate the connection between the nervous system and bone metabolism, either intact or after injury. First, we explored mechanistic studies linking specific brain nuclei with bone homeostasis, including the ventromedial hypothalamus, arcuate nucleus, paraventricular hypothalamic nucleus, amygdala, and locus coeruleus. We then focused on the characteristics of bone innervation and nerve subtypes, such as sensory, sympathetic, and parasympathetic nerves. Moreover, we summarized the molecular features and regulatory functions of these nerves. Finally, we included available translational approaches that utilize nerve function to improve bone homeostasis and promote bone regeneration. Therefore, considering the nervous system within the context of neuromusculoskeletal interactions can deepen our understanding of skeletal homeostasis and repair process, ultimately benefiting future clinical translation.

In Situ Recovery of Serotonin Synthesis by a Tryptophan Hydroxylase-Like Nanozyme for the Treatment of Depression

Depression is one of the most common mental disorders. The inactivation of tryptophan hydroxylase and the resulting serotonin decrease are the key factors in depression pathology. Herein, we report for the first time that Fe3O4 nanoparticles exhibit tryptophan hydroxylase-like activity and successfully verify their ability to restore serotonin synthesis in the brain for the treatment of depression. To achieve better biocompatibility and brain delivery, the Fe3O4 nanoparticles were functionalized with chitosan (CS) (Fe3O4@CS), enabling their delivery from the nose to the brain. Fe3O4@CS catalyzes the transformation of tryptophan into 5-hydroxytryptophan with the participation of high levels of endogenous ascorbic acid and hydrogen peroxide in stressed neurons, thus compensating for the deactivated tryptophan hydroxylase in the brain. In vivo Fe3O4@CS treatment results in the recovery of 5-hydroxytryptophan and serotonin levels and improvement of neuronal signal transduction ability in a depression mouse model, thus ameliorating depressive-like behaviors. The presented strategy of restoring serotonin synthesis in situ based on a tryptophan hydroxylase-like nanozyme provides a more accurate and efficient approach for the treatment of depression.

Vibrational spectra of serotonin by terahertz time domain spectroscopy and DFT simulations

Serotonin is an important biogenic monoamine neurotransmitter that has major influences on mental health disorders; its structural and conformational changes have important roles in the biological functions of the human body. The decreased serotonin levels in the human body are majorly attributed to the causes of anxiety, depressive disorders, mood disorders, etc. Therefore, the quantification of serotonin in our bodies is of utmost importance in unearthing the origin of such physiological disorders. In this study, Terahertz-Time Domain Spectroscopy (THz-TDS) is employed to characterize the unique THz fingerprint of serotonin in the frequency range 0-3 THz. The characteristic THz absorption peaks of serotonin are observed at 0.54, 0.84, and 1.10 THz. In addition, Density Functional Theory (DFT) calculations are performed to investigate the vibrational properties of serotonin. For the vibrational assignment of modes, we have used Potential Energy Distribution (PED) analysis. Furthermore, studies have been conducted on the variation of serotonin concentration in a polyethylene (PE) host medium. The effect of the serotonin concentration in the PE host is studied using the complex refractive index (CRI) model. The sensitivity of detection of serotonin concentration is 0.015 for an increment of 2% concentration in PE medium. This work maps the spectral features of serotonin in the THz range, suggesting that THz-TDS can be used to understand and treat the physiological disorders related to serotonergic systems.

Molecules in the Serotonin-Melatonin Synthesis Pathway Have Distinct Interactions with Lipid Membranes

The neurotransmitter serotonin is involved in physiological processes such as appetite, sleep, and mood and diseases such as anxiety and depression. Traditionally, the effects of serotonin were thought to be initiated by binding to its target transmembrane receptors. It is also known that serotonin can bind directly to the membrane with high affinity and modulate lipid dynamics, lateral segregation of lipids, vesicular association, and membrane protein activity. We investigated if other small molecules in the serotonin metabolic pathway, some of which are known to be signaling molecules while some others are not, have similar membrane modulating effects. Therefore, we examined serotonin and several of its metabolites: 5-hydroxytryptophan (5-HTP), serotonin, N-acetylserotonin (NAS), and melatonin in model membranes mimicking synaptic membranes. Using 2H NMR spectroscopy of deuterated 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC), we observed that all metabolites disorder the synaptic membrane-mimicking model membranes. The largest disordering effect was observed for NAS and the smallest for tryptophan. Using fluorescence correlation spectroscopy, it was found that only NAS promotes vesicular association similar to that of serotonin, while the others did not. Furthermore, we found that the serotonin metabolites differed in their membrane distribution by employing solid state 1H magic angle spinning nuclear Overhauser enhancement spectroscopy (NOESY) experiments in simple POPC membranes. Similar results were obtained in synaptic membrane mimics using molecular dynamics simulations. In conclusion, while the causal correlation between membrane modulation effects and membrane distribution for the serotonin metabolites remains elusive, this study suggests that small-molecule metabolites and drugs can have drastic biological effects mediated through the membrane. The finding that small changes in structure lead to very different membrane modulation and distributions suggests the possibility of developing membrane modulating drugs in the future.

Parental Serotonin Modulation Alters Monoamine Balance in Identified Neurons and Affects Locomotor Activity in Progeny of Lymnaea stagnalis (Mollusca: Gastropoda)

Monoamine neurotransmitters play a critical role in the development and function of the nervous system. In this study, we investigated the impact of parental serotonin (5-HT) modulation on the monoamine balance in the identified apical neurons of Lymnaea stagnalis embryos and its influence on embryonic locomotor activity. Using immunocytochemical and pharmacological approaches, we detected serotonin in the apical neurons of veliger-stage embryos, observing that the relative 5-HT level within these neurons varied with seasonal conditions. Pharmacological elevation of parental 5-HT levels significantly increased the relative 5-HT level in the oocytes and subsequently in the apical neurons of their offspring. Notably, while the relative dopamine (DA) levels in these neurons remained stable, the increase in the relative 5-HT level significantly enhanced the embryos' rotational locomotion. The expression of tryptophan hydroxylase (TPH), a key enzyme in serotonin synthesis, is a prerequisite for the elevation of the relative 5-HT level in apical neurons and is detected as early as the gastrula stage. Importantly, neither a reduction of 5-HT in the maternal organism by chlorpromazine application nor its pharmacological elevation via serotonin precursor (5-HTP) application at the cleavage stage affected the monoamine balance in apical neurons. These findings provide novel insights into how the parental 5-HT level selectively alters the monoamine phenotype of the identified neurons, offering a model for studying environmentally induced neural plasticity in early development.

Mechanisms underlying stress effects on the brain: Basic concepts and clinical implications

Chronic stress impacts the brain through complex physiological, neurological, and immunological responses. The stress response involves the activation of the sympathetic-adrenal-medullary (SAM) system and the hypothalamic-pituitary-adrenal (HPA) axis, releasing stress hormones like norepinephrine and cortisol. While these responses are adaptive short-term, chronic stress disrupts homeostasis, increasing the risk of cardiovascular diseases, neurodegenerative disorders, and psychiatric conditions such as depression. This dysregulation is linked to persistent neuroinflammation, oxidative stress, and neurotransmitter imbalances involving dopamine and serotonin, impairing neuroplasticity and leading to structural changes in critical brain areas, such as the hippocampus and prefrontal cortex. Moreover, stress affects gene expression, particularly neuroinflammatory pathways, contributing to long-term cognitive function and emotional regulation alterations. Advancements in neuroimaging and molecular techniques, including MRI, PET, and SPECT, hold promise for identifying biomarkers and better understanding stress-induced brain changes. These insights are critical for developing targeted interventions to mitigate the adverse effects of chronic stress on brain health.

The Continued Mismeasurement of Plasma Serotonin: A Systematic Review

Studies reporting on the analysis of free plasma (platelet-poor plasma, PPP) serotonin (5-hydroxytryptamine, 5-HT) in plasma obtained from healthy humans have been systematically reviewed. The review covered the period from 2010 to July 2024 and is a follow-up of a similar review published in 2011 which found that nearly all published reported of PPP 5-HT were clearly and markedly erroneously high. This problem has persisted unabated with nearly all retrieved 47 reports from the past 14 years also apparently being erroneously high. Possible causes and consequences of the problem are discussed along with potential approaches to improving the analysis and reporting of plasma 5-HT. Most of the errors appear to arise from pre-analytical problems that occur during the preparation of PPP due to residual platelets and/or due to the release of platelet 5-HT. The large number of fields interested in plasma 5-HT and the disparate publication venues appear to have contributed to a general lack of awareness of the difficulties with analyzing plasma 5-HT. The reporting of erroneous plasma 5-HT values has led to unsupported conclusions about possible alterations in plasma 5-HT and about the role of plasma 5-HT across a wide range of biomedical research areas.

Reduced expression of the serotonin transporter impacts mitochondria in a sexually dimorphic manner

Neuropsychiatric and neurodevelopmental disorders are complex conditions that arise from a variety of interacting genetic and environmental factors. Among these factors, altered serotonergic signalling and mitochondrial dysfunction are strongly implicated, with a growing body of evidence to suggesting that serotonergic signalling is an important regulator of mitochondrial biogenesis. The serotonin transporter (SERT) functions to regulate synaptic 5-HT, and human allelic variants of the serotonin reuptake transporter-linked polymorphic region (5-HTTLPR) are associated with reduced SERT expression and increased susceptibility for developing neuropsychiatric disorders. Using the heterozygous (HET) variant of the SERT knockout rat to model reduced SERT expression, Western blotting was used to measure the abundance of TOMM20 and the complex I protein MT-CO1 as metrics for mitochondrial mass and abundance of respiratory complex IV. Mitochondrial activity was determined by dye reduction. We found sex-based and region-specific differences in mitochondrial mass and activity and that male and females show differing responses to reduced SERT expression. Our findings suggest that the sexually dimorphic differences in serotonergic signalling impact mitochondrial function and that these differences may be important for understanding sex differences in neuropsychiatric and neurodevelopmental disorders.

Comparing the efficacy of serotonin and ethylene glycol tetraacetate on postpartum hypocalcemia

Inducing a transient state of hypocalcemia prepartum mobilizes stored Ca before the abrupt demand for Ca at parturition thus more tightly regulating postpartum hypocalcemia. Prepartum transient hypocalcemia can be achieved through intravenous infusions of either the precursor to serotonin, 5-hydroxy-tryptophan (5HTP) or a Ca chelating agent, ethylene glycol tetraacetic acid (EGTA). This study aimed to compare the ability of 5HTP and EGTA treatments to prevent postpartum hypocalcemia. We hypothesized that the 2 methods would be similarly effective compared with the control. Cows received either 5HTP, EGTA, 5HTP+EGTA, or control saline (n = 6/treatment) beginning 7 d before expected calving date through parturition (range 4-13 d). The 5HTP treatment was administered daily as a single 1-L dose at 1 mg/kg of BW. Saline and EGTA were infused for 6 h/d. Infusion rates of EGTA were adjusted to maintain blood ionized Ca (iCa) between 0.7 and 0.8 mM, inducing subclinical hypocalcemia, which occurs when iCa is 0.61-0.9 mM. Mammary biopsies were collected from rear quarters at 6, 30, 54, and 78 h postpartum. Cows in the 5HTP+EGTA group required less EGTA to maintain low iCa during infusions and had the lowest total Ca concentrations during infusions. Therefore, 5HTP and EGTA likely use different mechanisms to reduce blood Ca, which can occur simultaneously, resulting in an additive effect in blood Ca reduction. Control cows were subclinically hypocalcemic through 48 h postpartum, and 2 became clinically hypocalcemic. All other treatments were normocalcemic through 96 h postpartum and had significantly greater iCa than the control from 12 to 24 h postpartum. Administering 5HTP increased blood serotonin concentrations from the start of infusions through 72 h postpartum. Cows receiving EGTA or 5HTP+EGTA had decreased mammary Ca compared with the control at 54 and 78 h after calving. Mammary tissue quantitative PCR and Western blot analysis revealed increased gene and protein expression of Ca release-activated Ca modulator 1 on the day of parturition compared with 30 and 78 h postpartum. Mammary gland gene expression of the calcium-sensing receptor was decreased 78 h postpartum compared with 6 and 30 h postpartum. Although 5HTP and EGTA both prevented postpartum hypocalcemia, EGTA significantly increased iCa through 48 h post-calving rather than the 24 h in the 5HTP group. The 5HTP+EGTA and EGTA treatments were equally effective at regulating periparturient calcemic status, indicating that the additive effect of 5HTP and EGTA did not persist beyond parturition.

Sensory processing sensitivity in adult dental patients and its relation to perceived stress, cortisol, and serotonin secretion

Sensory processing sensitivity (SPS) is a biologically determined trait that influences how individuals respond to external and internal stimuli. A high level of SPS is characterized by three factors: increased emotional reactivity, heightened sensitivity to subtle stimuli, and greater susceptibility to overstimulation, all of which may impact well-being and health. This study examined the relationships between SPS, perceived stress, affect, and biochemical responses in adult dental patients (N = 157) on the day of a routine dental visit. Biochemical measures included morning cortisol and serotonin secretion (saliva samples), and cortisol concentration accumulated in recent months (hair sample). Perceived stress and negative and positive affect were assessed while patients waited for a dental procedure. The correlation analysis revealed that higher SPS level was associated with elevated hair cortisol and more negative affect. Cluster analyses tested SPS and its factors independently, revealing that individuals with higher SPS had higher cortisol levels in saliva and hair samples, as well as greater perceived stress and negative affect. Salivary serotonin levels showed varied relationships with different SPS factors, indicating the need to analyze SPS as a multidimensional construct. The results indicate that increased hair and salivary cortisol may be considered as biomarkers of SPS. In the context of patient-centered care, considering SPS levels may contribute to enhanced motivation for regular dental visits and improved treatment adherence.

Management of serotonin syndrome (toxicity)

Serotonin syndrome (toxicity), resulting from an excessive accumulation of serotonin in the central nervous system, it can occur due to various factors such as the initiation of medication, overdose or drug interactions. Diagnosing serotonin toxicity presents challenges as there are no definitive criteria. This review delves into the pathophysiology, incidence, clinical assessment and management of serotonin toxicity, stressing the significance of promptly recognizing and managing severe cases. Diagnosis relies primarily relies on clinical assessment due to the absence of specific laboratory tests. The Hunter Serotonin Toxicity criteria are commonly utilized but have only been validated in the overdose setting. Assessing the severity of toxicity is crucial for guiding management decisions. Supportive care, discontinuation of causative agents and symptomatic treatment are prioritized in management. Mild toxicity often requires withdrawal or reduction of the serotonergic agent, while more severe toxicity requires more aggressive resuscitative and supportive care. Severe serotonin toxicity characterized by hyperthermia and rigidity requires aggressive supportive measures, including benzodiazepines, intubation, paralysis and active cooling. Animal studies suggest potential benefits of 5-HT2A receptor antagonists in preventing hyperthermia and fatalities, but only at high doses. Their clinical effectiveness remains uncertain, and evidence is predominately from case series and case reports. Although commonly used, serotonin antagonists like cyproheptadine lack conclusive evidence of efficacy. Other serotonin antagonists such as chlorpromazine and olanzapine have been explored but evidence is limited to case reports. Hence, the cornerstone of treating severe cases does not lie in 'antidote' administration or even diagnosis but in effective early resuscitative and supportive care.

Molecular and cellular mechanisms of itch sensation and the anti-itch drug targets

Itch is an uncomfortable feeling that evokes a desire to scratch. This protective reflex can effectively eliminate parasites that invade the skin. When itchy skin becomes severe or lasts for more than six weeks, it has deleterious effects on both quality of life and productivity. Despite decades of research, the complete molecular and cellular coding of chronic itch remains elusive. This persistent condition often defies treatment, including with antihistamines, and poses a significant societal challenge. Obtaining pathophysiological insights into the generation of chronic itch is essential for understanding its mechanisms and the development of innovative anti-itch medications. In this review we provide a systematic overview of the recent advancement in itch research, alongside the progress made in drug discovery within this field. We have examined the diversity and complexity of the classification and mechanisms underlying the complex sensation of itch. We have also delved into recent advancements in the field of itch mechanism research and how these findings hold potential for the development of new itch treatment medications. But the treatment of clinical itch symptoms still faces significant challenges. Future research needs to continue to delve deeper, not only to discover more itch-related pathways but also to explore how to improve treatment efficacy through multitarget or combination therapy.