5-HT4 Receptor Agonist Research Articles

Experience of using Russian rizatriptan 10 mg tablets in routine clinical practice: results of a multicenter post-registration observational study “OPYT”

One of the key mediator systems involved in the pathogenesis of migraine is the serotonergic system, which led to the development and introduction of serotonin 5-HT1 receptor agonists (triptans) into clinical practice as the most important means of preventing migraine attacks. Serotonin 5-HT1 receptor agonists have a high selectivity for the 5-HT1B and 5-HT1D receptor subtypes, which ensures their effect on the pathogenesis of migraine attack development.Objective: to evaluate the efficacy of a standard dose of Relonova in the relief of four moderate to severe migraine attacks in outpatients in reallife clinical practice, including assessment of the rate of attack relief, the effect of the drug on headache intensity, concomitant symptoms and the general condition of the patient.Material and methods. The study involved 415 patients with migraine (319 women and 96 men; mean age 35.7±7.8 years). A total of 1660 migraine attacks were analyzed. The average number of migraine days per month was 6.72±3.99. Migraine attacks with aura were observed in 125 patients (30.1%). Patients stopped four migraine attacks and filled out self-monitoring diaries. Treatment efficacy was assessed according to the European Headache Federation (EHF) Consensus Algorithm for Determining Effective Treatment of a Migraine Attack.Results. After taking Relonova, pain became mild or disappeared completely in 30 minutes in 52% of patients, in 76% in 1 hour, in 93% in 2 hours, in 99% in 4 hours and in 99% of patients in 24 hours. A recurrence of the headache occurred in 8.8% of the attacks. Additional analgesic treatment after 30 minutes was required in 14% of cases, after which period the frequency did not exceed 2%. Adverse events were observed in 4% of patients and were mild. The overwhelming majority (90%) of study participants were able to successfully terminate three attacks and were responders.Conclusion. Relonova is an effective and safe agent to stop migraine attack and can be recommended for use in daily clinical practice.

Advances in clinical research on pharmacological management of chemotherapy-induced constipation in gastrointestinal tumor: A perspective.

Gastrointestinal tumors, including those of the stomach, colon, rectum, and esophagus, present significant global health challenges. Chemotherapy, essential for treating these cancers, often causes constipation, adversely affecting patients' quality of life. This study examines the mechanisms behind chemotherapy-induced constipation, such as the direct impact of chemotherapeutic drugs on intestinal function, reduced fluid intake, decreased physical activity, opioid use, and psychological stress. While traditional treatments like stimulant and osmotic laxatives are commonly used, emerging therapies such as 5-HT4 receptor agonists and probiotics show promise. Traditional Chinese medicine offers additional strategies with herbal remedies and dietary adjustments. Future research should prioritize precision medicine, combining pharmacological and non-pharmacological approaches, and developing innovative therapeutics utilizing biologics and nanotechnology. Ongoing research is crucial for improving chemotherapy-induced constipation management, aiming to enhance treatment outcomes and the quality of life for chemotherapy patients with gastrointestinal tumors.

Effects of morroniside isolated from Cornus officinalis fruits on functional gastrointestinal disorders and gastric ulcer in mice

The dried fruits of Cornus officinalis (Cornaceae) are used in Kampo medicine (e.g. Hachimigan and Goshajinkigan) to treat senile osteoporosis, diabetes, gastric atony, frequent urination, and diarrhea/constipation associated with aging. The present study investigated the effects of a C. officinalis fruit extract and morroniside, an iridoid compound from isolated these fruits, on the reduction in gastric emptying small intestinal motility caused by 5-hydroxytryptamine (5-HT) and 1-(3-chlorophenyl) biguanide (5-HT3 receptor agonist), and gastric ulcers induced by 150 or 75 mM HCl/90 % EtOH (HCl-EtOH) and/or 5-HT in mice. C. officinalis extract (500 mg/kg) and morroniside (20 and 50 mg/kg) suppressed the reduction in gastric emptying induced by 5-HT- and 5-HT3 agonist. C. officinalis extract, morroniside and 5-HT3 receptor antagonist (ramosetron) attenuated 5-HT-induced diarrhea. Furthermore, morroniside (20 and 50 mg/kg) prevented EtOH/HCl-induced gastric ulcers and those caused by 5-HT. Morroniside (20 and 50 mg/kg) attenuated elevations in the plasma levels of corticosterone, corticotropin-releasing factor (CRF), and adrenocorticotropic hormone (ACTH) in 75 mM HCl/90 % EtOH- and 5-HT-treated mice. The results obtained herein suggest the potential of morroniside as an effective treatment for irritable bowel syndrome, such as diarrhea and functional dyspepsia (reductions in gastric emptying and small intestinal motility), caused by 5-HT. The present study suggests a role for morroniside in the regulation of elevations in CRF, ACTH, and corticosterone levels through hypothalamic-pituitary-adrenal axis activity induced by stress loading, such as a 5-HT treatment and/or HCl/EtOH stimulation.

101 5-HT4 receptor-mediated vasorelaxation occurs through a cyclic mononucleotide-dependent mechanism in the isolated bovine lateral saphenous vein

Abstract Serotonin (5-HT)-mediated vasorelaxation of the isolated bovine lateral saphenous vein occurs primarily through 5-HT4 receptor activation. Vasorelaxation responses mediated through 5-HT4 have only been documented to occur in cattle and sheep and thus, may represent a novel vasorelaxation mechanism that is specific to ruminants. In tissues from other species, the 5-HT4 receptor and its associated G protein couple with adenylate cyclase. However, the mechanisms contributing to 5-HT4-mediated vasorelaxation in vascular tissue remain undefined. To better understand the mechanisms of 5-HT4-mediated vasorelaxation, lateral saphenous veins from cattle (n = 4) were collected and assessed for vasoactivity in response to increasing concentrations of a selective 5-HT4 receptor agonist (BIMU-8) in the absence and presence of selective inhibitors of downstream proteins involved with cyclic mononucleotide-mediated signaling. Isolated vessel segments were suspended in chambers of a multi-myograph containing 5 mL of continuously oxygenated Krebs-Henseleit buffer and equilibrated to 1 g tension for 90 min. After the equilibration period, vessels were exposed to dimethyl sulfoxide (DMSO; vehicle control) or selective inhibitors of downstream protein targets dissolved in DMSO (1×10-5 M) for 5 min. Vessels were pre-contracted with 1×10-4 M phenylephrine for 10 min to achieve a sustained increase in tension. After the 10-min pre-contraction period, vessels were exposed to increasing concentrations (1×10-9 to 1×10-4) of BIMU-8 non-cumulatively. Vasoactive response data were normalized as a percentage of the maximum contractile response induced by the phenylephrine pre-contraction. In the absence of selective inhibitors (control), BIMU-8 induced (P < 0.01) dose-dependent relaxations (mean -log EC50 = 6.30 M) with a 112% increase in maximal vasorelaxation activity occurring at 1×10-4 M. In the presence of the selective inhibitors for adenylate cyclase (NKY80) or guanylate cyclase (NS2028), 66% and 86% of the vasorelaxation responses to BIMU-8 were attenuated (P < 0.01), respectively. In the presence of the selective inhibitors for protein kinase A [protein kinase A inhibitor fragment (6-22) amide] or protein kinase G (Rp-8-bromo-PET-Cyclic GMPS), 66% and 97% of the maximal vasorelaxation responses to BIMU-8 were attenuated (P < 0.01), respectively. In the presence of non-selective inhibitors for Ca2+ channels and K+ channels, vasorelaxation responses to BIMU-8 were attenuated (P < 0.01). In the presence of selective inhibitors for the protein phosphatase 1 and 2A subunits of myosin light chain (calyculin A) and heat shock protein synthesis (quercetin), vasorelaxation responses to BIMU-8 were attenuated (P < 0.01). The findings of the current study demonstrate that 5-HT4-receptor mediated vasorelaxation occurs through a cyclic mononucleotide-dependent mechanism involving cross-activation of protein kinase A and G signaling. Downstream proteins involved in the signaling cascade leading to vasorelaxation include Ca2+ channels, K+ channels, myosin light chain phosphatase, and heat shock proteins. More research is needed to fully describe the cellular and molecular mechanisms responsible for 5-HT4 receptor-mediated vasorelaxation.

Peripheral Serotonin Controls Dietary Fat Absorption and Chylomicron Secretion via 5-HT4 Receptor in Males.

Postprandial dyslipidemia is commonly present in people with type 2 diabetes and obesity and is characterized by overproduction of apolipoprotein B48-containing chylomicron particles from the intestine. Peripheral serotonin is emerging as a regulator of energy homeostasis with profound implications for obesity; however, its role in dietary fat absorption and chylomicron production is unknown. Chylomicron production was assessed in Syrian golden hamsters by administering an olive oil gavage and IP poloxamer to inhibit lipoprotein clearance. Administration of serotonin or selective serotonin reuptake inhibitor, fluoxetine, increased postprandial plasma triglyceride (TG) and TG-rich lipoproteins. Conversely, inhibiting serotonin synthesis pharmacologically by p-chlorophenylalanine (PCPA) led to a reduction in both the size and number of TG-rich lipoprotein particles, resulting in lower plasma TG and apolipoprotein B48 levels. The effects of PCPA occurred independently of gastric emptying and vagal afferent signaling. Inhibiting serotonin synthesis by PCPA led to increased TG within the intestinal lumen and elevated levels of TG and cholesterol in the stool when exposed to a high-fat/high-cholesterol diet. These findings imply compromised fat absorption, as evidenced by reduced lipase activity in the duodenum and lower levels of serum bile acids, which are indicative of intestinal bile acids. During the postprandial state, mRNA levels for serotonin receptors (5-HTRs) were upregulated in the proximal intestine. Administration of cisapride, a 5-HT4 receptor agonist, alleviated reductions in postprandial lipemia caused by serotonin synthesis inhibition, indicating that serotonin controls dietary fat absorption and chylomicron secretion via 5-HT4 receptor.

Association between a selective 5-HT4 receptor agonist and incidence of major depressive disorder: emulated target trial.

The serotonin 4 receptor (5-HT4R) is a promising target for the treatment of depression. Highly selective 5-HT4R agonists, such as prucalopride, have antidepressant-like and procognitive effects in preclinical models, but their clinical effects are not yet established. To determine whether prucalopride (a 5-HT4R agonist and licensed treatment for constipation) is associated with reduced incidence of depression in individuals with no past history of mental illness, compared with anti-constipation agents with no effect on the central nervous system. Using anonymised routinely collected data from a large-scale USA electronic health records network, we conducted an emulated target trial comparing depression incidence over 1 year in individuals without prior diagnoses of major mental illness, who initiated treatment with prucalopride versus two alternative anti-constipation agents that act by different mechanisms (linaclotide and lubiprostone). Cohorts were matched for 121 covariates capturing sociodemographic factors, and historical and/or concurrent comorbidities and medications. The primary outcome was a first diagnosis of major depressive disorder (ICD-10 code F32) within 1 year of the index date. Robustness of the results to changes in model and population specification was tested. Secondary outcomes included a first diagnosis of six other neuropsychiatric disorders. Treatment with prucalopride was associated with significantly lower incidence of depression in the following year compared with linaclotide (hazard ratio 0.87, 95% CI 0.76-0.99; P = 0.038; n = 8572 in each matched cohort) and lubiprostone (hazard ratio 0.79, 95% CI 0.69-0.91; P < 0.001; n = 8281). Significantly lower risks of all mood disorders and psychosis were also observed. Results were similar across robustness analyses. These findings support preclinical data and suggest a role for 5-HT4R agonists as novel agents in the prevention of major depression. These findings should stimulate randomised controlled trials to confirm if these agents can serve as a novel class of antidepressant within a clinical setting.

WAY-208466, a 5-HT6 receptor agonist, increases food motivation in primates: A behavioural and PET imaging study opening perspectives in eating disorders

The 5-HT6 receptor (5-HT6R) is highly expressed in the anterior striatum, a region involved in food-intake and anxiety-related behaviours that shows abnormal activity in anorexia nervosa (AN) patients. Indeed, 5-HT6R antagonists decrease food motivation across species. Rodent studies have shown the acute anxiolytic properties of WAY-208466, a selective 5-HT6R agonist. Thus, we hypothesized that this agent could increase food motivation and decrease anxiety-related behaviours by impacting cortico-striatal circuits. We administered acute (0.1 mg/kg) and subchronic (0.03 and 0.1 mg/kg) intramuscular injections to four macaques performing a food-choice task and expressing spontaneous behaviours. We used PET imaging with the [18F]2FNQ1P specific tracer to determine 5-HT6R occupancy in several regions that could be linked with the induced behavioural changes. Acute and subchronic activation of 5-HT6R transmission led to a reversible increase in food motivation. WAY-208466 also decreased anxiety-like behaviours when given acutely but not subchronically. However, in the subchronic protocol, the higher dose led to increased activity characterized by movements and object-related behaviour expression. PET imaging revealed that these behavioural changes could be sustained by cortico-striatal circuits involved in food intake. These findings demonstrate that this 5-HT6R agonist subchronic treatment successfully increases food motivation but does not fully achieve the expected anxiolytic effect in monkeys. It suggests that targeting 5-HT6Rs may be a promising approach for treating the restrictive subtype of AN, which, unlike anxiety, has not been shown to benefit from treatment with selective serotonin reuptake inhibitors.

Induction of long-term hyperexcitability by memory-related cAMP signaling in isolated nociceptor cell bodies.

Persistent hyperactivity of nociceptors is known to contribute significantly to long-lasting sensitization and ongoing pain in many clinical conditions. It is often assumed that nociceptor hyperactivity is mainly driven by continuing stimulation from inflammatory mediators. We have tested an additional possibility: that persistent increases in excitability promoting hyperactivity can be induced by a prototypical cellular signaling pathway long known to induce late-phase long-term potentiation (LTP) of synapses in brain regions involved in memory formation. This cAMP-PKA-CREB-gene transcription-protein synthesis pathway was tested using whole-cell current clamp methods on small dissociated sensory neurons (primarily nociceptors) from dorsal root ganglia (DRGs) excised from previously uninjured ("naïve") rats. Six-hour treatment with the specific Gαs-coupled 5-HT4 receptor agonist, prucalopride, or with the adenylyl cyclase activator, forskolin, induced long-term hyperexcitability (LTH) in DRG neurons that manifested 12-24 hours later as action potential (AP) discharge (ongoing activity, OA) during artificial depolarization to -45 mV, a membrane potential that is normally subthreshold for AP generation. Prucalopride treatment also induced significant long-lasting depolarization of resting membrane potential (from -69 to -66 mV), enhanced depolarizing spontaneous fluctuations (DSFs) of membrane potential, and indications of reduced AP threshold and rheobase. LTH was prevented by co-treatment of prucalopride with inhibitors of PKA, CREB, gene transcription, and protein synthesis. As in the induction of synaptic memory, many other cellular signals are likely to be involved. However, the discovery that this prototypical memory induction pathway can induce nociceptor LTH, along with reports that cAMP signaling and CREB activity in DRGs can induce hyperalgesic priming, suggest that early, temporary, cAMP-induced transcriptional and translational mechanisms can induce nociceptor LTH that might last for long periods. An interesting possibility is that these mechanisms can also be reactivated by re-exposure to inflammatory mediators such as serotonin during subsequent challenges to bodily integrity, "reconsolidating" the cellular memory and thereby extending the duration of persistent nociceptor hyperexcitability.

Role of calcitonin gene-related peptide (CGRP) receptor antagonist in acute and preventive treatment of migraine.

Migraine is the most common neurological disease in the world. It is characterized by recurrent attacks of severe headaches of a one-sided, throbbing nature, often accompanied by sensory and motor disturbances and generally associated with nausea and increased sensitivity to light and sound. Migraine treatment can be divided into emergency treatment and preventive treatment, which aims to reduce the overall frequency and severity of attacks. In the first case, nonsteroidal anti-inflammatory drugs (NSAIDs) can be used, but in some patients they do not have the desired effect. The gold standard in the fight against migraine pain are triptans (selective serotonin 5-HT1 receptor agonists), although they too are not effective in all patients. Current understanding suggests that CGRP plays a significant role in the pathophysiology of migraines. Evidence supporting this includes increased CGRP levels during migraine attacks, causing inflammation and activation of other pathophysiological processes responsible for pain. The hope for patients are CGRP receptor antagonists, which greatly expand therapeutic options.

Activation of 5-HT6 Receptors in the Ventrolateral Orbital Cortex Produces Anti-Anxiodepressive Effects in a Rat Model of Neuropathic Pain.

The comorbidity of anxiety and depression frequently occurs in patients with neuropathic pain. The ventrolateral orbital cortex (VLO) plays a critical role in mediating neuropathic pain and anxiodepression in rodents. Previous studies suggested that 5-HT6 receptors in the VLO are involved in neuropathic pain. Strong evidence supports a close link between 5-HT6 receptors and affective disorders such as depression and anxiety disorders. However, it remains unclear whether the 5-HT6 receptors in the VLO are involved in neuropathic pain-induced anxiodepression. Using a rat neuropathic pain model of spared nerve injury (SNI), we demonstrated that rats exhibited significant anxiodepression-like behaviors and the expression of VLO 5-HT6 receptors obviously decreased four weeks after SNI surgery. Microinjection of the 5-HT6 receptor agonist EMD-386088 into the VLO or overexpression of VLO 5-HT6 receptors alleviated anxiodepression-like behaviors. These effects were blocked by pre-microinjection of a selective 5-HT6 receptor antagonist (SB-258585) or inhibitors of AC (SQ-22536), PKA (H89), and MEK1/2 (U0126) respectively. Meanwhile, the expression of p-ERK, p-CREB, and BDNF in the VLO decreased four weeks after SNI surgery. Furthermore, administration of EMD-386088 upregulated the expression of BDNF, p-ERK, and p-CREB in the VLO of SNI rats, which were reversed by pre-injection of SB-258585. These findings suggest that activating 5-HT6 receptors in the VLO has anti-anxiodepressive effects in rats with neuropathic pain via activating AC-cAMP-PKA-MERK-CREB-BDNF signaling pathway. Accordingly, 5-HT6 receptor in the VLO could be a potential target for the treatment of the comorbidity of neuropathic pain and anxiodepression.

Induction of long-term hyperexcitability by memory-related cAMP signaling in isolated nociceptor cell bodies

Persistent hyperactivity of nociceptors is known to contribute significantly to long-lasting sensitization and ongoing pain in many clinical conditions. It is often assumed that nociceptor hyperactivity is mainly driven by continuing stimulation from inflammatory mediators. We have tested an additional possibility: that persistent increases in excitability promoting hyperactivity can be induced by a prototypical cellular signaling pathway long known to induce late-phase long-term potentiation (LTP) of synapses in brain regions involved in memory formation. This cAMP-PKA-CREB-gene transcription-protein synthesis pathway was tested using whole-cell current clamp methods on small dissociated sensory neurons (primarily nociceptors) from dorsal root ganglia (DRGs) excised from previously uninjured (“naïve”) male rats. Six-hour treatment with the specific Gαs-coupled 5-HT4 receptor agonist, prucalopride, or with the adenylyl cyclase activator forskolin induced long-term hyperexcitability (LTH) in DRG neurons that manifested 12–24 h later as action potential (AP) discharge (ongoing activity, OA) during artificial depolarization to −45 mV, a membrane potential that is normally subthreshold for AP generation. Prucalopride treatment also induced significant long-lasting depolarization of resting membrane potential (from −69 to −66 mV), enhanced depolarizing spontaneous fluctuations (DSFs) of membrane potential, and produced trends for reduced AP threshold and rheobase. LTH was prevented by co-treatment of prucalopride with inhibitors of PKA, CREB, gene transcription, or protein synthesis. As in the induction of synaptic memory, many other cellular signals are likely to be involved. However, the discovery that this prototypical memory induction pathway can induce nociceptor LTH, along with reports that cAMP signaling and CREB activity in DRGs can induce hyperalgesic priming, suggest that early, temporary, cAMP-induced transcriptional and translational mechanisms can induce nociceptor LTH that might last for long periods. The present results also raise the question of whether reactivation of primed signaling mechanisms by re-exposure to inflammatory mediators linked to cAMP synthesis during subsequent challenges to bodily integrity can “reconsolidate” nociceptor memory, extending the duration of persistent hyperexcitability.

Serotonin receptor-mediated vasorelaxation occurs primarily through 5-HT4 activation in bovine lateral saphenous vein.

To better understand mechanisms of serotonin- (5-HT) mediated vasorelaxation, isolated lateral saphenous veins from cattle were assessed for vasoactivity using myography in response to increasing concentrations of 5-HT or selective 5-HT receptor agonists. Vessels were pre-contracted with 1 × 10-4 M phenylephrine and exposed to increasing concentrations of 5-HT or 5-HT receptor agonists that were selective for 5-HT1B, 5-HT2B, 5-HT4, and 5-HT7. Vasoactive response data were normalized as a percentage of the maximum contractile response induced by the phenylephrine pre-contraction. At 1 × 10-7 M 5-HT, a relaxation was observed with an 88.7% decrease (p < 0.01) from the phenylephrine maximum. At 1 × 10-4 M 5-HT, a contraction was observed with a 165% increase (p < 0.01) from the phenylephrine maximum. Increasing concentrations of agonists selective for 5-HT2B, 5-HT4, or 5-HT7 resulted in a 27%, 92%, or 44% (p < 0.01) decrease from the phenylephrine maximum, respectively. Of these 5-HT receptor agonists, the selective 5-HT4 receptor agonist resulted in the greatest potency (-log EC50) value (6.30) compared with 5-HT2B and 5-HT7 receptor agonists (4.21 and 4.66, respectively). To confirm the involvement of 5-HT4 in 5-HT-mediated vasorelaxation, blood vessels were exposed to either DMSO (solvent control) or a selective 5-HT4 antagonist (1 × 10-5 M) for 5-min prior to the phenylephrine pre-contraction and 5-HT additions. Antagonism of the 5-HT4 receptor attenuated the vasorelaxation caused by 5-HT. Approximately 94% of the vasorelaxation occurring in response to 5-HT could be accounted for through 5-HT4, providing strong evidence that 5-HT-mediated vasorelaxation occurs through 5-HT4 activation in bovine peripheral vasculature.

Neuroprotective and Neurite Outgrowth Stimulating Effects of New Low-Basicity 5-HT7 Receptor Agonists: In Vitro Study in Human Neuroblastoma SH-SY5Y Cells

There is some evidence that the serotonin receptor subtype 7 (5-HT7) could be new therapeutic target for neuroprotection. The aim of this study was to compare the neuroprotective and neurite outgrowth potential of new 5-HT7 receptor agonists (AH-494, AGH-238, AGH-194) with 5-CT (5-carboxyamidotryptamine) in human neuroblastoma SH-SY5Y cells. The results revealed that 5-HT7 mRNA expression was significantly higher in retinoic acid (RA)-differentiated cells when compared to undifferentiated ones and it was higher in cell cultured in neuroblastoma experimental medium (DMEM) compared to those placed in neuronal (NB) medium. Furthermore, the safety profile of compounds was favorable for all tested compounds at concentration used for neuroprotection evaluation (up to 1 μM), whereas at higher concentrations (above 10 μM) the one of the tested compounds, AGH-194 appeared to be cytotoxic. While we observed relatively modest protective effects of 5-CT and AH-494 in UN-SH-SY5Y cells cultured in DMEM, in UN-SH-SY5Y cells cultured in NB medium we found a significant reduction of H2O2-evoked cell damage by all tested 5-HT7 agonists. However, 5-HT7-mediated neuroprotection was not associated with inhibition of caspase-3 activity and was not observed in RA-SH-SY5Y cells exposed to H2O2. Furthermore, none of the tested 5-HT7 agonists altered the damage induced by 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenylpyridinium ion (MPP +) and doxorubicin (Dox) in UN- and RA-SH-SY5Y cells cultured in NB. Finally we showed a stimulating effect of AH-494 and AGH-194 on neurite outgrowth. The obtained results provide insight into neuroprotective and neurite outgrowth potential of new 5-HT7 agonists.

The Serotonin 4 Receptor Subtype: A Target of Particular Interest, Especially for Brain Disorders.

In recent years, particular attention has been paid to the serotonin 4 receptor, which is well expressed in the brain, but also peripherally in various organs. The cerebral distribution of this receptor is well conserved across species, with high densities in the basal ganglia, where they are expressed by GABAergic neurons. The 5-HT4 receptor is also present in the cerebral cortex, hippocampus, and amygdala, where they are carried by glutamatergic or cholinergic neurons. Outside the central nervous system, the 5-HT4 receptor is notably expressed in the gastrointestinal tract. The wide distribution of the 5-HT4 receptor undoubtedly contributes to its involvement in a plethora of functions. In addition, the modulation of this receptor influences the release of serotonin, but also the release of other neurotransmitters such as acetylcholine and dopamine. This is a considerable asset, as the modulation of the 5-HT4 receptor can therefore play a direct or indirect beneficial role in various disorders. One of the main advantages of this receptor is that it mediates a much faster antidepressant and anxiolytic action than classical selective serotonin reuptake inhibitors. Another major benefit of the 5-HT4 receptor is that its activation enhances cognitive performance, probably via the release of acetylcholine. The expression of the 5-HT4 receptor is also altered in various eating disorders, and its activation by the 5-HT4 agonist negatively regulates food intake. Additionally, although the cerebral expression of this receptor is modified in certain movement-related disorders, it is still yet to be determined whether this receptor plays a key role in their pathophysiology. Finally, there is no longer any need to demonstrate the value of 5-HT4 receptor agonists in the pharmacological management of gastrointestinal disorders.

PHARMACOLOGIC TREATMENT OF THE IRRITABLE BOWEL SYNDROME: A COMPREHENSIVE SYSTEMATIC REVIEW

Background: Abdominal pain and changes in stool frequency are two of the symptoms of Irritable Bowel Syndrome (IBS), a chronic gastrointestinal illness. As there is no known cure, treatment focuses on symptom management. Patients struggle with psychological and emotional issues that lower their quality of life. Clinical trials have demonstrated the therapeutic effects of several therapeutic drugs, which may improve GI symptoms and general quality of life. Effective treatment of IBS requires an understanding of the connection between pharmaceutical medicines and the illness. Methods: Following PRISMA 2020 guidelines, this systematic review concentrated on full-text English literature published between 2014 and 2024. Editorials and review articles that appeared in the same journal as the submission were not accepted without a DOI. The literature was assembled using a variety of online databases, including ScienceDirect, PubMed, and SagePub. Result: The study screened about 20.000 publications using reputable sources including Science Direct, SagePub, and PubMed. Seven papers were found to be pertinent for systematic investigation, after which the entire material was examined in more detail. Conclusion: IBS treatment has shown significant improvement in patients with Minesapride, a novel 5-HT4 receptor agonist, and tenapanor. Tenapanor showed significant improvement in symptoms, treatment metrics, and satisfaction, while geraniol improved the inflammatory profile. Melatonin showed improvement in IBS score and GI symptoms, but no significant improvement in frequency of defecations per week. Amitriptyline showed effectiveness over placebo, while co-micronized PEA/PD improved IBS symptoms in children.

A randomized phase 2 study of the 5-HT4 receptor agonist felcisetrag for postoperative gastrointestinal dysfunction after bowel surgery

BackgroundFelcisetrag (5-hydroxytryptamine-4 receptor [5-HT4] agonist) is under investigation as prophylaxis or active treatment for accelerating resolution of gastrointestinal function post-surgery. MethodsPhase 2, randomized, placebo-controlled, parallel five-arm, double-blind, multicenter study (NCT03827655) in 209 adults undergoing open or laparoscopic-assisted bowel surgery. Patients received intravenous placebo, felcisetrag 0.1 mg/100 ​mL or 0.5 mg/100 ​mL pre-surgery only, or pre-surgery and daily post-surgery until return of gastrointestinal function or for up to 10 days. Primary endpoint: time to recovery of gastrointestinal function. ResultsMedian time to recovery of gastrointestinal function was 2.6 days for both felcisetrag 0.5 ​mg daily and 0.5 ​mg pre-surgery versus 1.9 days for placebo (p ​> ​0.05). There were no notable differences in adverse events between treatment arms. ConclusionsFelcisetrag was well tolerated with no new safety concerns. However, no clinically meaningful difference in time to recovery of gastrointestinal function versus placebo was observed. Further investigation of the utility of 5-HT4 agonists in complicated, open abdominal surgeries may be warranted.

Synthesis and Structure-Activity Relationships of 2,5-Dimethoxy-4-Substituted Phenethylamines and the Discovery of CYB210010: A Potent, Orally Bioavailable and Long-Acting Serotonin 5-HT2 Receptor Agonist.

Structure-activity studies of 4-substituted-2,5-dimethoxyphenethylamines led to the discovery of 2,5-dimethoxy-4-thiotrifluoromethylphenethylamines, including CYB210010, a potent and long-acting serotonin 5-HT2 receptor agonist. CYB210010 exhibited high agonist potency at 5-HT2A and 5-HT2C receptors, modest selectivity over 5-HT2B, 5-HT1A, 5-HT6, and adrenergic α2A receptors, and lacked activity at monoamine transporters and over 70 other proteins. CYB210010 (0.1-3 mg/kg) elicited a head-twitch response (HTR) and could be administered subchronically at threshold doses without behavioral tolerance. CYB210010 was orally bioavailable in three species, readily and preferentially crossed into the CNS, engaged frontal cortex 5-HT2A receptors, and increased the expression of genes involved in neuroplasticity in the frontal cortex. CYB210010 represents a new tool molecule for investigating the therapeutic potential of 5-HT2 receptor activation. In addition, several other compounds with high 5-HT2A receptor potency, yet with little or no HTR activity, were discovered, providing the groundwork for the development of nonpsychedelic 5-HT2A receptor ligands.

Enhancing the action of serotonin by three different mechanisms prevents spontaneous seizure-induced mortality in Dravet mice.

Sudden unexpected death in epilepsy (SUDEP) is an underestimated complication of epilepsy. Previous studies have demonstrated that enhancement of serotonergic neurotransmission suppresses seizure-induced sudden death in evoked seizure models. However, it is unclear whether elevated serotonin (5-HT) function will prevent spontaneous seizure-induced mortality (SSIM), which is characteristic of human SUDEP. We examined the effects of 5-HT-enhancing agents that act by three different pharmacological mechanisms on SSIM in Dravet mice, which exhibit a high incidence of SUDEP, modeling human Dravet syndrome. Dravet mice of both sexes were evaluated for spontaneous seizure characterization and changes in SSIM incidence induced by agents that enhance 5-HT-mediated neurotransmission. Fluoxetine (a selective 5-HT reuptake inhibitor), fenfluramine (a 5-HT releaser and agonist), SR 57227 (a specific 5-HT3 receptor agonist), or saline (vehicle) was intraperitoneally administered over an 8-day period in Dravet mice, and the effect of these treatments on SSIM was examined. Spontaneous seizures in Dravet mice generally progressed from wild running to tonic seizures with or without SSIM. Fluoxetine at 30 mg/kg, but not at 20 or 5 mg/kg, significantly reduced SSIM compared with the vehicle control. Fenfluramine at 1-10 mg/kg, but not .2 mg/kg, fully protected Dravet mice from SSIM, with all mice surviving. Compared with the vehicle control, SR 57227 at 20 mg/kg, but not at 10 or 5 mg/kg, significantly lowered SSIM. The effect of these drugs on SSIM was independent of sex. Our data demonstrate that elevating serotonergic function by fluoxetine, fenfluramine, or SR 57227 significantly reduces or eliminates SSIM in Dravet mice in a sex-independent manner. These findings suggest that deficits in serotonergic neurotransmission likely play an important role in the pathogenesis of SSIM, and fluoxetine and fenfluramine, which are US Food and Drug Administration-approved medications, may potentially prevent SUDEP in at-risk patients.

5-HT4 receptor agonists treatment reduces tau pathology and behavioral deficit in the PS19 mouse model of tauopathy.

Accumulation of tau in synapses in the early stages of Alzheimer's disease (AD) has been shown to cause synaptic damage, synaptic loss, and the spread of tau pathology through trans-synaptically connected neurons. Moreover, synaptic loss correlates with a decline in cognitive function, providing an opportunity to investigate therapeutic strategies to target synapses and synaptic tau to rescue or prevent cognitive decline in AD. One of the promising synaptic targets is the 5-HT4 serotonergic receptor present postsynaptically in the brain structures involved in the memory processes. 5-HT4R stimulation exerts synaptogenic and pro-cognitive effects involving synapse-to-nucleus signaling essential for synaptic plasticity. However, it is not known whether 5-HT4R activation has a therapeutic effect on tau pathology. The goal of this study was to investigate the impact of chronic stimulation of 5-HT4R by two agonists, prucalopride and RS-67333, in PS19 mice, a model of tauopathy. We utilized gradient assays to isolate pre- and post-synaptic compartments, followed by biochemical analyses for tau species and ubiquitinated proteins in the synaptic compartments and total brain tissue. Next, we performed kinetic assays to test the proteasome's hydrolysis capacity in treatment conditions. Moreover, behavioral tests such as the open field and non-maternal nest-building tests were used to evaluate anxiety-like behaviors and hippocampal-related cognitive functioning in the treatment paradigm. Our results show that 5-HT4R agonism reduced tauopathy, reduced synaptic tau, increased proteasome activity, and improved cognitive functioning in PS19 mice. Our data suggest that enhanced proteasome activity by synaptic mediated signaling leads to the enhanced turnover of tau initially within synapses where the receptors are localized, and over time, the treatment attenuated the accumulation of tau aggregation and improved cognitive functioning of the PS19 mice. Therefore, stimulation of 5-HT4R offers a promising therapy to rescue synapses from the accumulation of toxic synaptic tau, evident in the early stages of AD.

Cholecystokinin-Induced Duodenogastric Bile Reflux Increases the Severity of Indomethacin-Induced Gastric Antral Ulcers in Re-fed Mice.

We examined the involvement of cholecystokinin (CCK) in the exacerbation of indomethacin (IND)-induced gastric antral ulcers by gastroparesis caused by atropine or dopamine in mice. Male mice were fed for 2h (re-feeding) following a 22-h fast. Indomethacin (IND; 10mg/kg, s.c.) was administered after re-feeding; gastric lesions were examined 24h after IND treatment. In another experiment, mice were fed for 2h after a 22-h fast, after which the stomachs were removed 1.5h after the end of the feeding period. Antral lesions, the amount of gastric contents, and the gastric luminal bile acids concentration were measured with or without the administration of the pro- and antimotility drugs CCK-octapeptide (CCK-8), atropine, dopamine, SR57227 (5-HT3 receptor agonist), apomorphine, lorglumide (CCK1 receptor antagonist), ondansetron, and haloperidol alone and in combination. IND produced severe lesions only in the gastric antrum in re-fed mice. CCK-8, atropine, dopamine, SR57227 and apomorphine administered just after re-feeding increased bile reflux and worsened IND-induced antral lesions. These effects were significantly prevented by pretreatment with lorglumide. Although atropine and dopamine also increased the amount of gastric content, lorglumide had no effect on the delayed gastric emptying provoked by atropine and dopamine. Both ondansetron and haloperidol significantly inhibited the increase of bile reflux and the exacerbation of antral lesions induced by atropine and dopamine, respectively, but did not affect the effects of CCK-8. These results suggest that CCK-CCK1 receptor signal increases bile reflux during gastroparesis induced by atropine and dopamine, exacerbating IND-induced antral ulcers.