Lasmiditan ameliorates serotonergic itch in mice: Possible involvement of 5-HT1F receptors.

Previously, some allergic conditions involving pruritus have been linked to migraine, raising the possibility that migraine and itching may be governed by similar underlying mechanisms. We aimed to investigate the efficacy of Lasmiditan, a highly selective agonist of the 5-hydroxytryptamine 1F (5-HT1F) receptor and a recently approved medication for the treatment of migraine headaches, in ameliorating serotonergic itching. Forty animals were employed in the present study (n = 40). Eight animals were randomly assigned to each of the following study groups (n = 8, in each group): (1) "Normal Saline": This group was given intradermal injections of normal saline (2) "5-HT": The animals were injected with intradermal 5-HT, which was used to induce itching. (3) "Lasmiditan 0.3", "Lasmiditan 1", and "Lasmiditan 3" groups: injected with 5-HT as well as intraperitoneal Lasmiditan at different dose levels (0.3, 1, and 3 mg/kg, respectively). Scratching behavior was recorded for 60 min, and the skin tissue of three mice was sampled at the end of the behavioral experiment to assess the levels of TLR-4, IL-31, 5-HT1F receptor, CGRP & TRPV4. In the present study, we found that Lasmiditan when administered at 1 mg/kg effectively reduced serotonin-induced itching compared to the "5-HT" group (P < 0.0001). Following the administration of Lasmiditan (1 mg/kg), the expression levels of the 5-HT1F receptor significantly increased (P < 0.01). Further, the levels of TLR-4, IL-31, CGRP & TRPV4 were substantially reduced upon the administration of Lasmiditan (1 mg/kg). We found that Lasmiditan is effective in reducing serotonergic itch in mice through its interaction with the 5-HT1F receptor in the skin tissue of mice.

Morphometric analysis and functional insights into the serotonergic system of Girardia tigrina (Tricladida, Platyhelminthes).

Using immunocytochemistry, serotonergic nerve elements were documented in the nervous system of the planarian Girardia tigrina. Serotonin-immunopositive components were observed in the brain, ventral, dorsal and longitudinal nerve cords, transverse nerve commissures connecting the nerve cords, and in the nerve plexus. Whole-mount preparations of G. tigrina were analyzed by fluorescent and confocal laser scanning microscopy. An essential quantitative morphometric measurement of serotonin-immunopositive structures was conducted in three body regions (anterior, middle, and posterior) of the planarian. The number of serotonin neurons was maximal in the head region. The ventral nerve cords gradually decreased in thickness from anterior to posterior body ends. Physiological action of exogenously applied serotonin was studied in G. tigrina for the first time. It was found that serotonin (0.1 and 1 µmol L-1) accelerated eye regeneration. The transcriptome sequencing performed for the first time for the planarian G. tigrina revealed the transcripts of the tryptophan hydroxylase (trph), amino acid decarboxylase (aadc) and serotonin transporter (sert) genes. The data obtained indicate the presence of the components of serotonin pathway in G. tigrina. The identified transcripts can take part in serotonin turnover and participate in the realization of biological effects of serotonin in planarians, associated with eyes regeneration and differentiation.

Psilocybin in pharmacotherapy of obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) is a chronic mental disease that affects approximately 2% of the population. Obsessions and compulsions are troublesome for patients and may disturb their everyday activities. The pathogenesis of this disease is still not fully elucidated, but dysfunctions of serotonin-, dopamine- and glutamate-mediated neurotransmission together with early maladaptive schemas seem of importance. Pharmacological treatment includes drugs affecting the serotoninergic, dopaminergic, and glutamatergic systems, such as selective serotonin reuptake inhibitors (SSRIs). Providing that up to 40% of patients with OCD are resistant to the currently available medications, there is a need for novel and effective therapies. Recent discoveries suggest that psilocybin, a non-physically addictive psychoactive substance, may ameliorate disease symptoms. When used in appropriate doses and under strict clinical control, psilocybin appears as a valuable treatment for OCD. This narrative article provides a thorough overview of OCD's etiology, current treatment options, and the emerging evidence supporting psilocybin's efficacy in managing OCD symptoms.

Does vitamin D supplementation impact serotonin levels? A systematic review and meta-analysis.

Background and Aims: Vitamin D deficiency impacts a significant proportion of the world's population, and this deficiency has been linked to various conditions characterized by imbalanced serotonin regulation. The objective of this systematic review and meta-analysis was to evaluate the effect of vitamin D supplementation on serum serotonin levels. Methods: We conducted a comprehensive search of PubMed, Scopus, Cochrane Central for Randomized Clinical Trials, and Web of Science up to September 2022, without any language restrictions. The effect sizes were calculated using the standard mean difference (SMD) and 95% confidence interval (CI). Results: Six randomized clinical trials involving 356 participants were included in the analysis. Our findings indicated no significant changes in serotonin levels between the intervention and control groups (SMD: 0.24 ng/mL, 95% CI: -0.28, 0.75, p > 0.10). Subgroup analysis also did not reveal any significant changes in serotonin levels among children, participants with autism spectrum disorders, interventions lasting 10 weeks or longer, or those receiving vitamin D doses below 4000 IU/day. Conclusion: Although the results obtained in this systematic review are inconclusive, they support the need for further well-designed randomized trials to assess the potential role of vitamin D supplementation in regulating serotonin levels and potentially ameliorating depression and related disorders.

Prolonged Discontinuation Syndrome of Venlafaxine: A Case Study of Severe Gastrointestinal Manifestations.

This case report describes a 26-year-old female with a history of childhood depression who experienced severe gastrointestinal symptoms and significant weight loss following the discontinuation of venlafaxine, a serotonin-norepinephrine reuptake inhibitor (SNRI). After tapering off the medication, days after cessation, she developed early satiety, nausea, bloating, and vomiting, leading to severe malnutrition with a body mass index (BMI) of 14. Despite the onset of symptoms being within the typical duration for discontinuation syndrome, extensive medical evaluations revealed no physical cause for her symptoms. Psychological assessment showed no current depression or anxiety, and she denied any eating disorder behaviors, suggesting a prolonged discontinuation syndrome. Her symptoms improved with the initiation of mirtazapine. This case underscores the importance of careful management when discontinuing venlafaxine, highlighting the potential for prolonged and severe discontinuation symptoms.

Dysregulation of endometrial stromal serotonin homeostasis leading to abnormal phosphatidylcholine metabolism impairs decidualization in patients with recurrent implantation failure.

STUDY QUESTION: Does abnormal serotonin homeostasis contribute to impaired endometrial decidualization in patients with recurrent implantation failure (RIF)? SUMMARY ANSWER: Abnormal serotonin homeostasis in patients with RIF, which is accompanied by decreased monoamine oxidase (MAO) expression, affects the decidualization of endometrial stromal cells and leads to embryo implantation failure. WHAT IS KNOWN ALREADY: Previous studies have indicated that the expression of MAO, which metabolizes serotonin, is reduced in the endometrium of patients with RIF, and serotonin can induce disruption of implantation in rats. However, whether abnormal serotonin homeostasis leads to impaired decidualization in patients with RIF and, if so, the mechanism involved, remains unclear. STUDY DESIGN SIZE DURATION: Endometrial samples from 25 patients with RIF and 25 fertile patients were used to investigate the expression levels of monoamine oxidase A (MAOA), monoamine oxidase B (MAOB), and serotonin. We isolated human endometrial stromal cells to investigate the role of MAOA, MAOB, and serotonin in inducing decidualization in vitro and further explored the underlying mechanism using RNA-sequencing (RNA-seq) and liquid chromatography-mass spectrometry (LC/MS) analyses. PARTICIPANTS/MATERIALS SETTING METHODS: The levels of serotonin in the endometrium of patients with RIF were detected by ELISA and immunohistofluorescence, and the key genes involved in abnormal serotonin metabolism were analyzed via combination with single-cell sequencing data. The effects of MAOA or MAOB on the decidualization of stromal cells were investigated using an in vitro human endometrial stromal cell-induced decidualization model and a mouse artificially induced decidualization model. The potential mechanisms by which MAOA and MAOB regulate decidualization were explored by RNA-seq and LC/MS analysis. MAIN RESULTS AND THE ROLE OF CHANCE: We found that women with RIF have abnormal serotonin metabolism in the endometrium and attenuated MAO in endometrial stromal cells. Endometrial decidualization was accompanied by increased MAO in vivo and in vitro. However attenuated MAO caused an increased local serotonin content in the endometrium, impairing stromal cell decidualization. RNA-seq and LC/MS analyses showed that abnormal lipid metabolism, especially phosphatidylcholine metabolism, was involved in the defective decidualization caused by MAO deficiency. Furthermore, decidualization defects were rescued by phosphatidylcholine supplementation. LARGE SCALE DATA: RNA-seq information and raw data can be found at NCBI Bioproject number PRJNA892255. LIMITATIONS REASONS FOR CAUTION: This study revealed that impaired serotonin metabolic homeostasis and abnormally reduced MAO expression were among the reasons for RIF. However, the source and other potential functions of serotonin in the endometrium remain to be further explored. WIDER IMPLICATIONS OF THE FINDINGS: This study provides new insights into the mechanisms of serotonin homeostasis in human endometrial decidualization and new biomarkers or targets for the treatment of patients with RIF. STUDY FUNDING/COMPETING INTERESTS: X. Sheng is supported by grants from the National Natural Science Foundation of China (82001629), the Wenzhou Basic Public Welfare Research Project (Y20240030), the Youth Program of Natural Science Foundation of Jiangsu Province (BK20200116), and Jiangsu Province Postdoctoral Research Funding (2021K277B). H.S. is supported by grants from the National Natural Science Foundation of China (82030040). G.Y. is supported by grants from the National Natural Science Foundation of China (82171653). The authors declare no conflicts of interest.

Dexamethasone-sparing strategies in anthracycline and cyclophosphamide-based chemotherapy with a focus on 5-HT3 receptor antagonists: a network meta-analysis.

Background: The effectiveness of a dexamethasone-sparing strategy in the treatment of breast cancer with anthracycline-cyclophosphamide therapy when combined with first-generation 5-HT3 receptor antagonists (RAs) and neurokinin-1 RAs is unclear. This is attributable to a lack of evidence from direct comparison of multiple doses of DEX to a single dose of DEX in combination with first-generation 5-HT3 RAs in anthracycline-cyclophosphamide therapy. Our goal was to clarify the impact of dexamethasone-sparing strategies that involve both first-generation 5-HT3 RAs and palonosetron when combined with neurokinin-1 RAs, using a network meta-analysis. Materials and methods: A literature search was conducted on PubMed/Medline for articles published up to July 4, 2023. We included randomized controlled trials which assessed the efficacy of antiemetic regimens which combined 5-HT3 RAs and dexamethasone, with or without neurokinin-1 RAs, for the initial dose in anthracycline-cyclophosphamide therapy for patients with breast cancer. The primary outcome was the proportion of patients achieving a complete response during the delayed phase (CR-DP). Results: The difference in the proportion of patients achieving CR-DP between multiple and single doses of dexamethasone was 0.1% (95%CI: -12.4 to 12.5) with palonosetron and neurokinin-1 RAs, compared to 5.3% (95%CI: -13.4 to 23.0) with a single dose of a first-generation 5-HT3 receptor antagonist. Additionally, the difference was 12.7% (95% CI: -2.8 to 28.2) when comparing palonosetron against first-generation 5-HT3 RAs in combination with a single dose of dexamethasone and neurokinin-1 RAs. Conclusion: Palonosetron is recommended rather than a single dose of first-generation 5-HT3 RAs in dexamethasone-sparing strategies for anthracycline-cyclophosphamide therapy.

The activation of D2-like dopamine receptors increases NMDA currents in the dorsal raphe serotonergic neurons.

The dorsal raphe nucleus (DRN) receives dopaminergic inputs from the ventral tegmental area (VTA). Also, the DRN contains a small population of cells that express dopamine (DRNDA neurons). However, the physiological role of dopamine (DA) in the DRN and its interaction with serotonergic (5-HT) neurons is poorly understood. Several works have reported moderate levels of D1, D2, and D3 DA receptors in the DRN. Furthermore, it was found that the activation of D2 receptors increased the firing of putative 5-HT neurons. Other studies have reported that D1 and D2 dopamine receptors can interact with glutamate NMDA receptors, modulating the excitability of different cell types. In the present work, we used immunocytochemical techniques to determine the kind of DA receptors in the DRN. Additionally, we performed electrophysiological experiments in brainstem slices to study the effect of DA agonists on NMDA-elicited currents recorded from identified 5-HT DRN neurons. We found that D2 and D3 but not D1 receptors are present in this nucleus. Also, we demonstrated that the activation of D2-like receptors increases NMDA-elicited currents in 5-HT neurons through a mechanism involving phospholipase C (PLC) and protein kinase C (PKC) enzymes. Possible physiological implications related to the sleep-wake cycle are discussed.

Serotonin transporter knockout in rats reduces beta- and gamma-band functional connectivity between the orbitofrontal cortex and amygdala during auditory discrimination.

The orbitofrontal cortex and amygdala collaborate in outcome-guided decision-making through reciprocal projections. While serotonin transporter knockout (SERT-/-) rodents show changes in outcome-guided decision-making, and in orbitofrontal cortex and amygdala neuronal activity, it remains unclear whether SERT genotype modulates orbitofrontal cortex-amygdala synchronization. We trained SERT-/- and SERT+/+ male rats to execute a task requiring to discriminate between two auditory stimuli, one predictive of a reward (CS+) and the other not (CS-), by responding through nose pokes in opposite-side ports. Overall, task acquisition was not influenced by genotype. Next, we simultaneously recorded local field potentials in the orbitofrontal cortex and amygdala of both hemispheres while the rats performed the task. Behaviorally, SERT-/- rats showed a nonsignificant trend for more accurate responses to the CS-. Electrophysiologically, orbitofrontal cortex-amygdala synchronization in the beta and gamma frequency bands during response selection was significantly reduced and associated with decreased hubness and clustering coefficient in both regions in SERT-/- rats compared to SERT+/+ rats. Conversely, theta synchronization at the time of behavioral response in the port associated with reward was similar in both genotypes. Together, our findings reveal the modulation by SERT genotype of the orbitofrontal cortex-amygdala functional connectivity during an auditory discrimination task.

Evidence-based review and frontiers of migraine therapy.

BACKGROUND: Cyclic vomiting syndrome (CVS) is identified as one of the "episodic syndromes that may be associated with migraine," along with benign paroxysmal torticollis, benign paroxysmal vertigo, and abdominal migraine. It has been proposed that CVS and migraine may share pathophysiologic mechanisms of hypothalamic activation and altered dopaminergic signaling, and impaired sensorimotor intrinsic connectivity. The past decade has brought groundbreaking advances in the treatment of migraine and other headache disorders. While many of these therapies have yet to be studied in episodic syndromes associated with migraine including CVS and abdominal migraine, the potential shared pathophysiology among these conditions suggests that use of migraine-specific treatments may have a beneficial role even in those for whom headache is not the primary symptom. PURPOSE: This manuscript highlights newer therapies in migraine. Calcitonin gene-related peptide (CGRP) and its relation to migraine pathophysiology and the therapies that target the CGRP pathway, as well as a 5HT1F receptor agonist and neuromodulation devices used to treat migraine are briefly discussed as they may potentially prove to be useful in the future treatment of CVS.

Monoaminergic degeneration, cognition, and autonomic symptom trajectory in early Parkinson's disease.

INTRODUCTION: Parkinson's disease (PD) encompasses a range of non-motor symptoms attributed to deficits in various neurotransmitter systems. This study aimed to investigate the associations between cognitive and autonomic symptoms and the degeneration of brainstem monoaminergic nuclei, particularly the serotonergic and noradrenergic nuclei, in a prospective cohort of early PD patients. METHODS: Twenty-eight early PD patients (with an average disease duration of approximately three years) underwent baseline [18F]FP-CIT positron emission tomography (PET) scans, Montreal Cognitive Assessment (MoCA), and Composite Autonomic Symptom Scale-31 (COMPASS-31) evaluations, followed by repeat MoCA and COMPASS-31 assessments three years later. Regression models were utilized to analyze both cross-sectional and longitudinal changes in non-motor symptoms relative to baseline degeneration of the noradrenergic locus coeruleus (LC) and serotonergic raphe, normalized by striatal dopaminergic terminal loss. RESULTS: Baseline LC and raphe degeneration in early PD was cross-sectionally associated with poorer MoCA performances. Over the three-year follow-up, gastrointestinal symptoms exhibited progression, while cognitive scores remained stable. Profound baseline degeneration of the LC and raphe, relative to nigrostriatal terminal loss, were predictive of subsequent accelerated deterioration in gastrointestinal symptoms. CONCLUSION: Brainstem non-dopaminergic dysfunction in early PD is linked to cognitive dysfunction and predicts progression in gastrointestinal symptoms, offering potential indicators for worsening non-motor trajectories.

Flibanserin conquers murine depressive pseudodementia by amending HPA axis, maladaptive inflammation and AKT/GSK/STAT/BDNF trajectory: center-staging of the serotonergic/adrenergic circuitry.

Depressive pseudodementia (DPD) is a debilitating cognitive dysfunction that accompanies major and/or frequent depressive attacks. DPD has gained significant research attention owing to its negative effects on the patients' quality of life and productivity. This study tested the procognitive potential of Flibanserin (FBN), the serotonin (5HT) receptor modulator, against propranolol (PRP), as ß/5HT1A receptors blocker. Serving this purpose, female Wistar Albino rats were subjected to chronic unpredictable stress (CUS) and subsequently treated with FBN only (3mg/kg/day, p.o), PRP only (10mg/kg/day, p.o), or PRP followed by FBN, using the same doses. FBN ameliorated the behavioral/cognitive alterations and calmed the hypothalamic-pituitary-adrenal (HPA) axis storm by reducing the levels of stress-related hormones, viz, corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), corticosterone (CORT) parallel to epinephrine (EPI) hyperstimulation. The maladaptive inflammatory response, comprising of interleukin (IL)-1ß/6, and tumor necrosis factor (TNF)-α, was consequently blunted. This was contemporaneous to the partial restoration of the protein kinase-B (AKT)/glycogen synthase kinase (GSK)3ß/signal transducer and activator of transcription (STAT)-3 survival trajectory and the reinstatement of the levels of brain derived neurotrophic factor (BDNF). Microscopically, FBN repaired the hippocampal architecture and lessened CD68/GFAP immunoreactivity. Pre-administration of PRP partially abolished FBN effect along the estimated parameters, except for 5HT2A receptor expression and epinephrine level, to prove 5HT1A receptor as a fulcrum initiator of the investigated pathway, while its sole administration worsened the underlying condition. Ultimately, these findings highlight the immense procognitive potential of FBN, offering a new paradigm for halting DPD advancement via synchronizing adrenergic/serotonergic circuitry.

Effects of Probiotic Supplementation Added to a Weight Loss Program on Anthropometric Measures, Body Composition, Eating Behavior, and Related Hormone Levels in Patients with Food Addiction and Weight Regain After Bariatric Surgery: A Randomized Clinical Trial.

PURPOSE: Weight regain after metabolic bariatric surgery is a common problem. Food addiction is an eating disorder that can be one of the reasons for weight regain in these patients. This study aimed to evaluate the effects of probiotic supplementation with a weight loss program and cognitive behavioral therapy (CBT) on anthropometric measures, eating behavior, food addiction, and related hormone levels, in patients with food addiction and weight regain after metabolic bariatric surgery. MATERIALS AND METHODS: This randomized, triple-blind, placebo-controlled clinical trial was conducted on patients with food addiction and weight regain after metabolic bariatric surgery. Participants (n = 50) received a weight loss program and CBT plus probiotic, or placebo for 12 weeks. Then, anthropometric measurements, biochemical markers, eating behavior, and food addiction were assessed. RESULTS: Weight and body mass index (BMI) decreased significantly in the probiotic group compared to placebo (p = 0.008, p = 0.001, respectively). Fat mass was significantly decreased in the probiotic group (p < 0.001). Moreover, a significant improvement was observed in the probiotic group's eating behavior and food addiction compared to the placebo group (p < 0.001). Serum levels of leptin decreased significantly (p = 0.02), and oxytocin serum levels increased significantly (p = 0.008) in the probiotic group compared to the placebo group. CONCLUSION: Adding probiotic supplements to the weight loss program and CBT is superior to the weight loss program and CBT alone in improving weight loss, eating behavior, and food addiction in patients with food addiction and weight regain after metabolic bariatric surgery.

Serotonylation in tumor-associated fibroblasts contributes to the tumor-promoting roles of serotonin in colorectal cancer.

Accumulated studies have highlighted the diverse roles of 5-hydroxytryptamine (5-HT), or serotonin, in cancer biology, particularly in colorectal cancer (CRC). While 5-HT primarily exerts its effects through binding to various 5-HT receptors, receptor-independent mechanisms such as serotonylation remain unclear. This study revealed that depleting 5-HT, either through genetic silencing of Tph1 or using a selective TPH1 inhibitor, effectively reduced the growth of CRC tumors. Interestingly, although intrinsic 5-HT synthesis exists in CRC, it is circulating 5-HT that mediates the cancer-promoting function of 5-HT. Blocking the function of 5-HT receptors showed that the oncogenic roles of 5-HT in CRC operate through a mechanism that is separate from its receptor. Instead, serotonylation of histone H3Q5 (H3Q5ser) was found in CRC cells and cancer-associated fibroblasts (CAFs). H3Q5ser triggers a phenotypic switch of CAFs towards an inflammatory-like CAF (iCAF) subtype, which further enhances CRC cell proliferation, invasive characteristics, and macrophage polarization. Knockdown of the 5-HT transporter SLC22A3 or inhibition of TGM2 reduces H3Q5ser levels and reverses the tumor-promoting phenotypes of CAFs in CRC. Collectively, this study sheds light on the serotonylation-dependent mechanisms of 5-HT in CRC progression, offering insights into potential therapeutic strategies targeting the serotonin pathway for CRC treatment.

Mind over matter: the microbial mindscapes of psychedelics and the gut-brain axis.

Psychedelics have emerged as promising therapeutics for several psychiatric disorders. Hypotheses around their mechanisms have revolved around their partial agonism at the serotonin 2 A receptor, leading to enhanced neuroplasticity and brain connectivity changes that underlie positive mindset shifts. However, these accounts fail to recognise that the gut microbiota, acting via the gut-brain axis, may also have a role in mediating the positive effects of psychedelics on behaviour. In this review, we present existing evidence that the composition of the gut microbiota may be responsive to psychedelic drugs, and in turn, that the effect of psychedelics could be modulated by microbial metabolism. We discuss various alternative mechanistic models and emphasize the importance of incorporating hypotheses that address the contributions of the microbiome in future research. Awareness of the microbial contribution to psychedelic action has the potential to significantly shape clinical practice, for example, by allowing personalised psychedelic therapies based on the heterogeneity of the gut microbiota.

Curcumin Reduces Depression in Obese Patients with Type 2 Diabetes: A Randomized Controlled Trial.

Type 2 diabetes and depression co-occur in a bidirectional manner. Curcumin supplements exhibit antidepressant effects that may mitigate depression by modulating neurotransmitters and reducing inflammatory and oxidative stress pathways. This study aimed to evaluate the efficacy of curcumin in improving depression severity in obese type 2 diabetes patients. The study employed a randomized, double-blind, placebo-controlled trial design with 227 participants. The primary end-point was depression severity assessed using the Patient Health Questionnaire-9. Biomarkers were measured at baseline and at 3-, 6-, 9-, and 12-month intervals. The biomarkers assessed were serotonin levels, pro-inflammatory cytokines (interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha), antioxidant activities (total antioxidant status, glutathione peroxidase, and superoxide dismutase), and malondialdehyde. After 12 months, the curcumin group exhibited significantly improved depression severity (p = 0.000001). The curcumin group had higher levels of serotonin (p < 0.0001) but lower levels of interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha (p < 0.001 for all) than the placebo group. Total antioxidant status, glutathione peroxidase activity, and superoxide dismutase activity were elevated in the curcumin group, whereas malondialdehyde levels were greater in the placebo group (p < 0.001 for all). These findings suggest curcumin may have antidepressant effects on obese type 2 diabetes patients.

Differential Impact of Serotonin Signaling Methylphenidate on Young versus Adult: Insights from Behavioral and Dorsal Raphe Nucleus Neuronal Recordings from Freely Behaving Rats.

Methylphenidate (MPD) remains a cornerstone pharmacological intervention for managing ADHD, yet its increasing usage among ordinary youth and adults outside clinical contexts necessitates a thorough investigation into its developmental effects. This study seeks to simultaneously investigate the behavioral and neuronal changes within the dorsal raphe (DR) nucleus, a center of serotonergic neurons in the mammalian brain, before and after the administration of varying doses of acute and chronic MPD in freely behaving young and adult rats implanted with DR recording electrodes. Wireless neuronal and behavioral recording systems were used over 10 consecutive experimental days. Eight groups were examined: saline, 0.6, 2.5, and 10.0 mg/kg MPD for both young and adult rats. Six daily MPD injections were administered on experimental days 1 to 6, followed by a three-day washout period and MPD re-administration on experimental day 10 (ED10). The analysis of neuronal activity recorded from 504 DR neurons (DRNs) in young rats and 356 DRNs in adult rats reveals significant age-dependent differences in acute and chronic MPD responses. This study emphasizes the importance of aligning electrophysiological evaluations with behavioral outcomes following extended MPD exposure, elucidating the critical role of DRNs and serotonin signaling in modulating MPD responses and delineating age-specific variations in young versus adult rat models.

DNA Sequence Variations Affecting Serotonin Transporter Transcriptional Regulation and Activity: Do They Impact Alcohol Addiction?

Genetic features of alcohol dependence have been extensively investigated in recent years. A large body of studies has underlined the important role of genetic variants not only in metabolic pathways but also in the neurobiology of alcohol dependence, mediated by the neuronal circuits regulating reward and craving. Serotonin transporter (5-HTT), encoded by the SLC6A4 gene (Solute carrier family 6-neurotransmitter transporter-member 4), is targeted by antidepressant drugs such as selective serotonin reuptake inhibitors (SSRIs) and plays a pivotal role in serotoninergic transmission; it has been associated with psychiatric diseases and alcohol dependence. Transcriptional regulation and expression of 5-HTT depend not only on epigenetic modifications, among which DNA methylation (CpG and non-CpG) is primarily involved, but also on sequence variations occurring in intron/exon regions and in untranslated regions in 5' and 3', being the first sequences important for the splicing machinery and the last for the binding of transcription factors and micro RNAs. This work intends to shed light on the role of sequence variations known to affect the expression or function of 5-HTT in alcohol-dependent individuals. We found a statistically significant difference in the allelic (p = 0.0083) and genotypic (p = 0.0151) frequencies of the tri-allelic polymorphism, with higher function alleles and genotypes more represented in the control population. Furthermore, we identified three haplotypes more frequent in subjects with AUD (p < 0.0001) and one more frequent in the control population (p < 0.0001). The results obtained for the tri-allelic polymorphism in alcohol dependence confirm what is already present in part of the literature. The role of haplotypes requires further studies to be clarified.

The Invisible Fraction within Melanin Capable of Absorbing UV Light and with Fluorescent Properties: Is It Lacking Consideration?

Expanding on earlier observations, we show that many melanin materials, in vitro synthesized from a wide range of precursors, can be fractionated into a dark-colored precipitate and a near-colorless, dispersible fraction. The dispersible fractions exhibited absorbance in the UVA and UVB range of the electromagnetic spectrum, but none in the visible range. In addition, fluorescent properties were associated with all dispersible fractions obtained. FT-IR spectroscopic analyses were performed to compare both types of fractions. Overall, it appears that some of the properties associated with melanin (UV absorbance, fluorescence) may not necessarily reside in the dark-colored portion of melanin, but in a colorless fraction of the material. It remains to be seen whether any of these in vitro observations have any relevance in vivo. However, we raise the possibility that the presence of a colorless fraction within melanin materials and their associated properties may have received inadequate attention. Given the important association between melanin, UV protection, and skin cancer, it is worthwhile to consider this additional aspect of melanin chemistry.

Subsets of Nanometer Vesicles in the Fly Release Differential Fractions of Vesicular Serotonin Content during Exocytosis.

Serotonin, a monoamine neurotransmitter, is important in both the central nervous system (CNS) and the peripheral nervous system. Malfunction of serotonin signaling leads to various disorders. We studied serotonin signaling from serotonergic neurons inside the ventral nerve cord of Drosophila melanogaster. Serotonergic neurons and stimulated release were visualized and achieved with mCherry and channelrhodopsin-2, an optogenetically transfected ion channel, respectively, and two electrochemical techniques quantified serotonin release and vesicular content. Mean vesicular serotonin content released during exocytosis from these neurons was 84%, considerably higher than previous studies regarding octopamine (4.5%) and glutamate release (31%). Serotonin content within all vesicles is uniformly changed when serotonin concentration is inhibited or enhanced. However, serotonin release exhibits two Gaussian distributions: higher frequency of small release events, and similar or slightly higher frequency of large events, resulting in differential release fractions ranging from partial (30 to 35%) to full (100%) release after treatment with agents to either enhance or diminish release. This is the first example of consistent full exocytotic release events we have observed in any system. We suggest one pool of vesicles can release significantly diverse fractions of transmitter load during exocytosis, a potentially novel pathway to regulate exocytosis and neuronal signaling.