OBJECTIVE: To investigate the effect of 5-hydroxytryptamine (5-HT) on the proliferation, apoptosis and colony-forming unit-megakaryocyte (CFU-MK) of Meg-01 cells and its possible mechanisms. METHODS: The uptake and metabolism of 5-HT in Meg-01 cells were analysed by reverse-phase high-performance liquid chromatography (RP-HPLC) with electrochemical detection. The expression of 5-HT2B receptor (5-HT2BR) in megakaryocytes was detected by immunofluorescence staining. The cell proliferation and viability were measured by MTT and Trypan blue staining after Meg-01 cells were single-cultured or co-cultured with different concentrations of 5-HT/5-HT2BR inhibitor Ketanserin for 48 h. Meg-01 cells were incubated with 5-HT/ Ketanserin for 72 h, then the flow cytometry was used to detect early apoptosis of the cells and the activity of caspase-3. Using CFU-MK assay to investigate the effect of 5-HT on the differentiation of megakaryocytes. RESULTS: 5-HT could be uptaken by Meg-01 cells, and metabolized into 5-hydroxyindoleacetic acid (5-HIAA). The expression of 5-HT2BR on megakaryocytes could be detected after immunofluorescence staining. 5-HT could promote the proliferation of Meg-01 cells at a dose-dependent manner (r =0.82), with the most significant effect observed at a concentration of 200 nmol/L (P < 0.001). Trypan blue staining also indicated that 200 nmol/L 5-HT had the most significant effect on the viability of Meg-01 cells (P < 0.05). The proliferation of Meg-01 cells treated with 5-HT was increased compared with the untreated control (P < 0.001), while the combination of 5-HT with ketanserin downregulated this effect. 5-HT significantly reduced the early apoptosis rate (P < 0.001) and caspase-3 activity (P < 0.05) of Meg-01 cells, while addition of ketanserin significantly increased the early apoptosis rate of Meg-01 cells (P < 0.001) and caspase-3 activity also increased to some extent. 5-HT promoted the formation of CFU-MK in bone marrow cells in a dose-dependent manner (r =0.89). The addition of ketanserin reduced the promoting effect of 5-HT on CFU-MK formation (P < 0.01). CONCLUSION There may be monoamine oxidase present in megakaryocytes, which can metabolize and decompose 5-HT into 5-HIAA. 5-HT may promote the proliferation and differentiation of megakaryocytes through 5-HT2BR. Besides, 5-HT can also reduce the apoptosis of megakaryocytes, and its anti-apoptotic effect may be mediated by 5-HT2BR and caspase-3 pathways.
Apoptosis/drug effects* ; Cell Proliferation/drug effects* ; Megakaryocytes/metabolism* ; Serotonin/pharmacology* ; Humans ; Receptor, Serotonin, 5-HT2B/metabolism* ; Caspase 3/metabolism* ; Cell Differentiation

Neuropathic pain, often featuring allodynia, imposes significant physical and psychological burdens on patients, with limited treatments due to unclear central mechanisms. Addressing this challenge remains a crucial unsolved issue in pain medicine. Our previous study, using protein kinase C gamma (PKCγ)-tdTomato mice, highlights the spinal feedforward inhibitory circuit involving PKCγ neurons in gating neuropathic allodynia. However, the regulatory mechanisms governing this circuit necessitate further elucidation. We used diverse transgenic mice and advanced techniques to uncover the regulatory role of the descending serotonin (5-HT) facilitation system on spinal PKCγ neurons. Our findings revealed that 5-HT neurons from the rostral ventromedial medulla hyperpolarize spinal inhibitory interneurons via 5-HT_2C receptors, disinhibiting the feedforward inhibitory circuit involving PKCγ neurons and exacerbating allodynia. Inhibiting spinal 5-HT_2C receptors restored the feedforward inhibitory circuit, effectively preventing neuropathic allodynia. These insights offer promising therapeutic targets for neuropathic allodynia management, emphasizing the potential of spinal 5-HT_2C receptors as a novel avenue for intervention.
Animals ; Neuralgia/physiopathology* ; Protein Kinase C/metabolism* ; Receptor, Serotonin, 5-HT2C/metabolism* ; Hyperalgesia/physiopathology* ; Mice, Transgenic ; Mice ; Spinal Cord/metabolism* ; Serotonin/metabolism* ; Male ; Neurons/metabolism* ; Mice, Inbred C57BL

The 5-hydroxytryptamine 2A receptor (5-HT_2AR) is one of the key targets in the development of novel antidepressants. To develop new antidepressants targeting the 5-HT_2A receptor, this study established a high-throughput screening method for drugs targeting the 5-HT_2A receptor based on the principle of detecting calcium flux signals. The immunofluorescence assay and western blotting were employed to evaluate receptor expression levels in the 5-HT_2AR-CHO cell line. The reaction system parameters, including cell seeding density, DMSO concentration, and dye incubation time, were optimized with Z'-factor and signal window values as evaluation indicators. The specificity, precision, stability, and applicability of the method were assessed. Results indicated that the 5-HT_2AR-CHO cell line stably expressed high levels of the 5-HT_2A receptor. The optimized screening method involved a reaction system with 10 000 cells/well, 0.2% DMSO, and 2 h incubation with Calcium 6 dye. The method demonstrated excellent specificity, with inter-batch precision below 10% for the detection of 5-hydroxytryptamine (5-HT) at low, medium, and high concentrations. Testing four compounds that target the 5-HT_2A receptor- agonists 2,5-dimethoxy-4-iodoamphetamine (DOI), 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), and lysergic acid diethylamide (LSD), along with the antagonist MDL100907-yielded Z'-factors (at EC₈₀) greater than 0.85 and signal window values over 0.91. The EC₅₀ values of these compounds were in the nanomolar range, and their potency rank order aligned with previously reported data, confirming the reliability of the established method. When being applied to the detection of 38 known active compounds, the method efficiently identified 5-HT_2A receptor agonists and antagonists while showing no response to non-target compounds. In conclusion, this study successfully constructs a high-throughput screening approach for 5-HT_2A receptor-targeting drugs based on calcium flux signals. The method possesses strong specificity, high sensitivity, and robust stability, being suitable for screening antidepressants targeting the 5-HT_2A receptor.
High-Throughput Screening Assays/methods* ; Receptor, Serotonin, 5-HT2A/metabolism* ; Animals ; CHO Cells ; Cricetulus ; Calcium Signaling/drug effects* ; Antidepressive Agents/pharmacology* ; Humans ; Serotonin 5-HT2 Receptor Antagonists/pharmacology* ; Calcium/metabolism*

Going back to basics prior to mentioning the use of antipsychotics in patients with pain, the International Association for the Study of Pain (IASP) definition of pain can be summarized as an unpleasant experience, composed of sensory experience caused by actual tissue damage and/or emotional experience caused by potential tissue damage. Less used than antidepressants, antipsychotics have also been used for treating this unpleasant experience as adjuvant analgesics without sufficient evidence from research. Because recently developed atypical antipsychotics reduce the adverse reactions of extrapyramidal symptoms, such as acute dystonia, pseudo-parkinsonism, akathisia, and tardive dyskinesia caused by typical antipsychotics, they are expected to be used more frequently in various painful conditions, while increasing the risk of metabolic syndromes (weight gain, diabetes, and dyslipidemia). Various antipsychotics have different neurotransmitter receptor affinities for dopamine (D), 5-hydroxytryptamine (5-HT), adrenergic (α), histamine (H), and muscarinic (M) receptors. Atypical antipsychotics antagonize transient, weak D₂ receptor bindings with strong binding to the 5-HT(2A) receptor, while typical antipsychotics block long-lasting, tight D₂ receptor binding. On the contrary, antidepressants in the field of pain management also block the reuptake of similar receptors, mainly on the 5-HT and, next, on the norepinephrine, but rarely on the D receptors. Antipsychotics have been used for treating positive symptoms, such as delusion, hallucination, disorganized thought and behavior, perception disturbance, and inappropriate emotion, rather than the negative, cognitive, and affective symptoms of psychosis. Therefore, an antipsychotic may be prescribed in pain patients with positive symptoms of psychosis during or after controlling all sensory components.
Affective Symptoms ; Analgesics ; Antidepressive Agents ; Antipsychotic Agents ; Delusions ; Dopamine ; Drug-Related Side Effects and Adverse Reactions ; Dystonia ; Hallucinations ; Histamine ; Humans ; Movement Disorders ; Norepinephrine ; Pain Management ; Prolactin ; Psychomotor Agitation ; Psychotic Disorders ; Receptor, Serotonin, 5-HT2A ; Receptors, Neurotransmitter ; Serotonin ; Weight Gain

Genes related to serotonin are associated with responses to treatment for depression. We examined associations between the serotonin transporter (5-HTT) and serotonin 2a receptor (5-HTR2a) genes and responses to treatment for depressive disorders in acute coronary syndrome (ACS). A total of 255 patients who met the DSM-IV major or minor depressive disorder and recently developed ACS were randomly assigned to the escitalopram (n=127) or placebo (n=128) group in this 24-week double-blind trial (ClinicalTrial.gov identifier: NCT00419471). Remission was defined as a Hamilton Rating Scale for Depression (HAMD) score < or =7. Assays were performed for the 5-HTTLPR, STin2 VNTR, 5-HTR2a 102T/C, and 5-HTR2a 1438A/G genotypes. Escitalopram was superior to placebo for treating depressive disorder with ACS but there were no significant associations between serotonergic genes and treatment responses even when considering ACS severity. The effect of escitalopram was independent of 5-HTT and 5-HTR2a polymorphisms.
Acute Coronary Syndrome* ; Citalopram* ; Depression ; Depressive Disorder* ; Diagnostic and Statistical Manual of Mental Disorders ; Genotype ; Humans ; Receptor, Serotonin, 5-HT2A ; Serotonin ; Serotonin Plasma Membrane Transport Proteins

OBJECTIVE: Migraine, a highly prevelant headache disorder, is regarded as a polygenic multifactorial disease. Serotonin (5-HT) and their respective receptors have been implicated in the patogenesis. METHODS: We investigated the 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT2C receptor gene polymorphisms and their association with migraine in Turkish patients. The rs6295, rs1300060, rs1228814, rs6311, rs6313, rs6314, rs6318, rs3813929 (−759C/T) and rs518147 polymorphisms were analyzed in 135 patients with migraine and 139 healthy subjects, using a BioMark 96.96 dynamic array system. RESULTS: We found no difference in the frequency of the analyzed eight out of nine polymorpisms between migraine and control groups. However, a significant association was found between the rs3813929 polymorphism in the promoter region of 5-HTR2C gene and migraine. Also, the allele of rs3813929 was more common in the migraine group. CONCLUSION: This result suggests that the 5-HTR2C rs3813929 polymorphism can be a genetic risk factor for migraine in a Turkish population.
Alleles ; Genetic Association Studies ; Headache ; Headache Disorders ; Healthy Volunteers ; Humans ; Migraine Disorders* ; Polymorphism, Single Nucleotide ; Promoter Regions, Genetic ; Receptor, Serotonin, 5-HT2C ; Risk Factors ; Serotonin*

BACKGROUNDOur previous studies have demonstrated that the levels of 5-hydroxytryptamine (5-HT) and 5-HT 2A receptor (5-HT2AR) in serum and platelet were associated with depression and myocardial infarction (MI), and pretreatment with ginseng fruit saponins (GFS) before MI and depression had an effect on the 5-HT system. In this study, the effects of GFS on the 5-HT system in the Sprague-Dawley (SD) rats with MI, depression, and MI + depression were evaluated.

METHODSA total of eighty SD rats were allocated to four groups: MI, depression, MI + depression, and control groups (n = 20 in each group). Each group included two subgroups (n = 10 in each subgroup): Saline treatment subgroup and GFS treatment subgroup. The levels of 5-HT, 5-HT2AR, and serotonin transporter (SERT) were quantified in serum, platelet lysate, and brain tissue through the enzyme-linked immunosorbent assay method, respectively.

RESULTSCompared with those in the saline treatment subgroups, the levels of 5-HT in serum and platelet lysate statistically significantly increased in the GFS treatment subgroups of MI, depression, and MI + depression groups (serum: all P = 0.000; platelet lysate: P = 0.002, 0.000, 0.000, respectively). However, the 5-HT levels in brain homogenate significantly decreased in the GFS treatment subgroups compared with those in the saline treatment subgroups in MI and depression groups (P = 0.025 and 0.044 respectively), and no significant difference was observed between saline and GFS treatment subgroups in MI + depression group (P = 0.663). Compared with that in GFS treatment subgroup of control group, the 5-HT2AR levels in the platelet lysate significantly decreased in GFS treatment subgroups of MI, depression, and MI + depression groups (all P = 0.000). Compared to those in the saline treatment subgroups, the serum SERT levels significantly decreased in the GFS treatment subgroups in MI, depression, and MI + depression groups (P = 0.009, 0.038, and P = 0.001, respectively), while the SERT levels of platelet lysate significantly decreased in GFS treatment subgroup of MI group (P = 0.000), significantly increased in GFS treatment subgroup of depression group (P = 0.019), and slightly changed in GFS treatment subgroup of MI + depression group (P = 0.219). No significant changes for SERT levels in brain homogenate could be found between the saline and GFS treatment subgroups in MI, depression, and MI + depression groups (P = 0.421, 0.076 and P = 0.642).

CONCLUSIONSThis study indicated that GFS might inhibit the reuptake of 5-HT from serum to platelet according to decreased 5-HT2AR in platelet and SERT in serum and platelet. The change of 5-HT in serum after GFS treatment was inconsistent with that in the brain. It seemed that GFS could not pass through the blood-brain barrier to affect the central serotonergic system.

Animals ; Blood-Brain Barrier ; drug effects ; metabolism ; Depression ; drug therapy ; Disease Models, Animal ; Enzyme-Linked Immunosorbent Assay ; Myocardial Infarction ; drug therapy ; Panax ; chemistry ; Rats ; Rats, Sprague-Dawley ; Receptor, Serotonin, 5-HT2B ; metabolism ; Saponins ; chemistry ; therapeutic use ; Serotonin ; metabolism ; Serotonin Plasma Membrane Transport Proteins ; metabolism

Ketamine is an anesthetic with hypertensive effects, which make it useful for patients at risk of shock. However, previous ex vivo studies reported vasodilatory actions of ketamine in isolated arteries. In this study, we reexamined the effects of ketamine on arterial tones in the presence and absence of physiological concentrations of 5-hydroxytryptamine (5-HT) and norepinephrine (NE) by measuring the isometric tension of endothelium-denuded rat mesenteric arterial rings. Ketamine little affected the resting tone of control mesenteric arterial rings, but, in the presence of 5-HT (100~200 nM), ketamine (10~100 µM) markedly contracted the arterial rings. Ketamine did not contract arterial rings in the presence of NE (10 nM), indicating that the vasoconstrictive action of ketamine is 5-HT-dependent. The concentration-response curves (CRCs) of 5-HT were clearly shifted to the left in the presence of ketamine (30 µM), whereas the CRCs of NE were little affected by ketamine. The left shift of the 5-HT CRCs caused by ketamine was reversed with ketanserin, a competitive 5-HT(2A) receptor inhibitor, indicating that ketamine facilitated the activation of 5-HT(2A) receptors. Anpirtoline and BW723C86, selective agonists of 5-HT(1B) and 5-HT(2B) receptors, respectively, did not contract arterial rings in the absence or presence of ketamine. These results indicate that ketamine specifically enhances 5-HT(2A) receptor-mediated vasoconstriction and that it is vasoconstrictive in a clinical setting. The facilitative action of ketamine on 5-HT(2A) receptors should be considered in ketamine-induced hypertension as well as in the pathogenesis of diseases such as schizophrenia, wherein experimental animal models are frequently generated using ketamine.
Animals ; Arteries ; Blood Pressure ; Humans ; Hypertension ; Ketamine* ; Ketanserin ; Mesenteric Arteries* ; Models, Animal ; Norepinephrine ; Rats* ; Receptor, Serotonin, 5-HT2A ; Schizophrenia ; Serotonin ; Shock ; Vasoconstriction

This study was performed to investigate the sedative-hypnotic activity of gamma-aminobutyric acid (GABA)-enriched fermented marine organisms (FMO), including sea tangle (FST) and oyster (FO) by Lactobacillus brevis BJ20 (L. brevis BJ20). FST and FO were tested for their binding activity of the GABA(A)-benzodiazepine and 5-HT(2C) receptors, which are well-known molecular targets for sleep aids. We also measured the sleep latency and sleep duration during pentobarbital-induced sleep in mice after oral administration of FST and FO. In GABA(A) and 5-HT(2C) receptor binding assays, FST displayed an effective concentration-dependent binding affinity to GABA(A) receptor, similar to the binding affinity to 5-HT(2C) receptor. FO exhibited higher affinity to 5-HT(2C) receptor, compared with the GABA(A) receptor. The oral administration of FST and FO produced a dose-dependent decrease in sleep latency and increase in sleep duration in pentobarbital-induced hypnosis. The data demonstrate that FST and FO possess sedative-hypnotic activity possibly by modulating GABA(A) and 5-HT(2C) receptors. We propose that FST and FO might be effective agents for treatment of insomnia.
Administration, Oral ; Animals ; Aquatic Organisms* ; gamma-Aminobutyric Acid ; Hypnosis ; Lactobacillus brevis ; Mice ; Ostreidae ; Receptor, Serotonin, 5-HT2C ; Receptors, GABA-A ; Sleep Initiation and Maintenance Disorders

5-hydroxytryptamine (5-HT) released in inflammatory tissues plays a pivotal role in pain hypersensitivity. However, it is not clear whether 5-HT2A receptors in the inflamed tissues mediate this effect. The present study investigated the contribution of 5-HT2A receptors in the periphery to chronic inflammatory pain. Complete Freund's adjuvant (CFA) was injected subcutaneously in the hindpaw of rats. The selective 5-HT2A receptor antagonist ketanserin was given in the inflamed site. Paw withdrawal latency responding to heat or mechanical stimuli was measured. Expression of neuropeptide Y (NPY) in the spinal dorsal horn and dorsal root ganglia (DRG) was assayed using immunohistochemistry technique. The results showed that ketanserin administered in the inflamed site inhibited thermal hyperalgesia in a dose-dependent manner (20, 40 and 80 µg) induced by the intraplantar injection of CFA. Ketanserin given once per day at a dose of 80 µg abolished heat hyperalgesia and also attenuated mechanical allodynia on the third day. CFA injection increased the expression of NPY in superficial laminae of the spinal cord, but not in the DRG. The local treatment of ketanserin completely inhibited CFA-induced increase in NPY expression in superficial laminae of the spinal cord. These results indicated that activation of 5-HT2A receptors in the inflamed tissues was involved in the pathogenesis of inflammatory pain and the blockade of 5-HT2A receptors in the periphery could relieve pain hypersensitivity and normalize the cellular disorder in the spinal dorsal horn associated with pathological pain. The present study suggests that the peripheral 5-HT2A receptors can be a promising target for pharmaceutical therapy to treat chronic inflammatory pain without central nervous system side effects.
Animals ; Freund's Adjuvant ; adverse effects ; Ganglia, Spinal ; metabolism ; Hot Temperature ; Hyperalgesia ; chemically induced ; drug therapy ; Inflammation ; drug therapy ; Ketanserin ; pharmacology ; Neuropeptide Y ; metabolism ; Pain ; drug therapy ; Pain Measurement ; Rats ; Receptor, Serotonin, 5-HT2A ; metabolism ; Serotonin ; Serotonin 5-HT2 Receptor Antagonists ; pharmacology ; Spinal Cord Dorsal Horn ; metabolism