5-HT3 Receptor Research Articles

Alterations in descending brain-spinal pathways regulating colorectal motility in a rat model of Parkinson's disease.

Patients with Parkinson's disease (PD) often have constipation. It is assumed that a disorder of the regulatory mechanism of colorectal motility by the central nervous system is involved in the constipation, but this remains unclear. The aim of this study was to investigate whether central neural pathways can modulate colorectal motility in a rat model of PD. PD model rats were generated by injection of 6-hydroxydopamine into a unilateral medial forebrain bundle and destruction of dopaminergic neurons in the substantia nigra. Colorectal motility was measured in vivo in anesthetized rats. Intraluminal administration of capsaicin, as a noxious stimulus, induced colorectal motility in sham-operated rats but not in PD rats. Intrathecally administered dopamine (DA) and serotonin (5-HT), which mediate the prokinetic effect of capsaicin, at the L6-S1 levels enhanced colorectal motility in PD rats similarly to that in sham-operated rats. In PD rats, capsaicin enhanced colorectal motility only when a GABAA receptor antagonist was preadministered into the lumbosacral spinal cord. Capsaicin-induced colorectal motility was abolished by intrathecal administration of a D2-like receptor antagonist but not by administration of 5-HT2 and 5-HT3 receptor antagonists. These findings demonstrate that the inhibitory GABAergic component becomes operative and the stimulatory serotonergic component is suppressed in PD rats. The alteration of the central regulatory mechanism of colorectal motility is thought to be related to the occurrence of constipation in PD patients. Our findings provide a new insight into the pathogenesis of defecation disorders observed in PD.NEW & NOTEWORTHY In a rat model of Parkinson's disease, the component of descending brain-spinal pathways that regulate colorectal motility through a mediation of the lumbosacral defecation center was altered from stimulatory serotonergic neurons to inhibitory GABAergic neurons. Our findings suggest that chronic constipation in Parkinson's disease patients may be associated with alterations in central regulatory mechanisms of colorectal motility. The plasticity in the descending pathway regulating colorectal motility may contribute to other disease-related defecation abnormalities.

2023 updated MASCC/ESMO consensus recommendations: prevention of nausea and vomiting following multiple-day chemotherapy, high-dose chemotherapy, and breakthrough nausea and vomiting

PurposeThis review is an update of the MASCC/ESMO 2015 recommendations for the prophylaxis of acute and delayed nausea and vomiting induced by multiple-day chemotherapy, high-dose chemotherapy, and breakthrough nausea and vomiting.MethodsA systematic literature search was conducted using PubMed from June 1, 2015, through February 1, 2023.ResultsWe identified 56 references (16 were duplications or invalid), leaving 40 manuscripts for this search. The panel classified level I evidence (three manuscripts) and level II evidence (14 manuscripts). High-dose chemotherapy and stem cell transplant were discussed in four of these manuscripts, and multiple-day chemotherapy treatment in 15. Some manuscripts covered both topics. Additionally, a search for breakthrough nausea and vomiting resulted in 12 “hits.” No new relevant studies were identified.ConclusionsThe recommendations for patients receiving high-dose chemotherapy with stem cell transplants and patients undergoing multiple-day cisplatin were updated. For patients receiving high-dose chemotherapy for stem cell transplant, a combination of a 5-HT3 receptor antagonist with dexamethasone and aprepitant is recommended. Olanzapine could be considered part of the antiemetic regimen. Patients receiving multiple-day cisplatin should receive a 5-HT3 receptor antagonist plus dexamethasone plus aprepitant plus olanzapine. For patients experiencing breakthrough nausea and vomiting, the available evidence suggests using a single dose of olanzapine daily for 3 days.

Characterization of a novel RNAi yeast insecticide that silences mosquito 5-HT1 receptor genes

G protein-coupled receptors (GPCRs), which regulate numerous intracellular signaling cascades that mediate many essential physiological processes, are attractive yet underexploited insecticide targets. RNA interference (RNAi) technology could facilitate the custom design of environmentally safe pesticides that target GPCRs in select target pests yet are not toxic to non-target species. This study investigates the hypothesis that an RNAi yeast insecticide designed to silence mosquito serotonin receptor 1 (5-HTR1) genes can kill mosquitoes without harming non-target arthropods. 5-HTR.426, a Saccharomyces cerevisiae strain that expresses an shRNA targeting a site specifically conserved in mosquito 5-HTR1 genes, was generated. The yeast can be heat-inactivated and delivered to mosquito larvae as ready-to-use tablets or to adult mosquitoes using attractive targeted sugar baits (ATSBs). The results of laboratory and outdoor semi-field trials demonstrated that consumption of 5-HTR.426 yeast results in highly significant mortality rates in Aedes, Anopheles, and Culex mosquito larvae and adults. Yeast consumption resulted in significant 5-HTR1 silencing and severe neural defects in the mosquito brain but was not found to be toxic to non-target arthropods. These results indicate that RNAi insecticide technology can facilitate selective targeting of GPCRs in intended pests without impacting GPCR activity in non-targeted organisms. In future studies, scaled production of yeast expressing the 5-HTR.426 RNAi insecticide could facilitate field trials to further evaluate this promising new mosquito control intervention.

Pharmacological and computational analysis of the involvement of the 5-HT4 receptor in the antidepressant-like effect of N-(3-(phenylselanyl)prop-2-yn-1-yl)benzamide in mice

The serotonin type 4 receptor (5-HT4R)shows promise as a target for treating major depressive disorder (MDD). Studies have demonstrated that 5-HT4R agonists have a faster antidepressant-like effect compared to conventional medications. Developing drugs that modulate this receptor could lead to faster and more effective MDD treatments. The compound N-(3-(phenylselanyl)prop-2-yn-1-yl)benzamide (SePB) induces an antidepressant-like effect in mice. The present study explored if the 5-HT4R mediates SePB's antidepressant effect. For this, male Swiss mice were treated with GR113808 (0.1 mg/kg, intraperitoneally – i.p.), a 5-HT4R antagonist, and SePB (10 mg/kg, intragastrically – i.g), and then subjected to the tail-suspension test (TST) and open-field test (OFT). In silico tests were conducted to analyze SePB's binding affinity to the 5-HT4R and identify participating amino acid residues. The administration of GR113808 blocked the antidepressant-like effect of SePB in the TST without changing locomotor activity in the OFT. Moreover, SePB exhibited a high binding affinity between the 5-HT4R (−7.9 kcal/mol) and the amino acid residues Leu298, Asp100, Thr97, Arg96, Glu80, Leu81, Cys184, Val185, and Phe186 seem to be important for this interaction. The involvement of the 5-HT4R in the antidepressant-like effect of SePB suggests potential for novel therapies in MDD.

Design and in silico evaluation of oxadiazole linked chromone derivatives as anti-depressant agents

Depression is a common CNS disorder due to disturbances in the serotonin and dopamine level within the brain. In this study, different derivatives (C1-C32) of oxadiazole-linked chromone were designed and in silico studies were performed to investigate its anti-depressant activities. Compounds were docked with 5HT1 receptors to do so and MMGBSA and ADMET properties were evaluated. Further, compounds pharmacophore modeling and antidepressant activity were calculated using the phase and PASS tools. Among 32 designed compounds, C15, C29 and C31 showed the highest docking scores of -7.617, -7.269 and -7.325 kcal/mol and exhibited significant interaction with 5HT1 receptors compared to the standard drug imipramine. Compound C15 showed the highest binding efficiency with a binding energy of -77.79; the expected common is having a binding energy of -47.20. ADME properties show that all the designed compounds followed the rule of five. Further ligand-receptor complex potential interactions were evaluated using pharmacophore modeling, indicating that the compound has steric and electronic features to ensure the interaction with the selected receptor. Further, the antidepressant activity was predicted. Compounds C15 and C21 have the highest possibility of being antidepressant molecules with 0.827 and 0.833 pa values.

Effect of ondansetron in maternal hypotension during cesarean delivery: an observational study

Background: Spinal anesthesia is the most common anesthetic technique for cesarean delivery. Thus, hypotension is associated with a reduction in uteroplacental flow which may induce fetal morbidity. Activation of the Bezold Jarisch reflex (mediated by 5HT3 receptors) can worsen hypotension and decrease cardiac output. We studied the effect of ondansetron administration before spinal anesthesia on the trajectory of blood pressure during cesarean delivery. Methods: We conducted a retrospective chart review of all cesarean deliveries that occurred between April 1st 2020 and April 1st 2021 and included 85 pregnant women (43 with ondansetron and 42 in the control group). Data were obtained from the electronic medical record database of the British Hospital of Buenos Aires. Socio- demographic, obstetric, anesthetic and perioperative characteristics of patients were assessed. Results: There were no significant differences in the trajectories of the change from baseline of mean arterial blood pressure between ondansetron and control group (0.14% (95% CI: 0.06 to 0.21) per minute). This also applied to heart rate (-0.10% per minute (95% CI: -0.19 to 0.01). The need of any infusion (phenylephrine or atropine) comparing ondansetron to the reference group was 1.12 (95% CI: 0.68, 1.85). There were eight events of shivering (16.3%) in the ondansetron exposed group and four events of shivering (8.5%) in the reference group. APGAR values showed no clinical difference between groups. Conclusions: In this single-center cohort study, we did not observe an effect of routine administration of ondansetron before spinal anesthesia in cesarean section on improving arterial blood pressure or heart rate throughout the procedure.

99mTc(CO)3-labeled 1-(2-Pyridyl)piperazine derivatives as radioligands for 5-HT7 receptors.

The 5-hydroxytryptamine receptor (5-HTR) family includes seven classes of receptors. The 5-HT7R is the newest member of this family and contributes to different physiological and pathological processes. As a pathology, glioblastoma multiform (GBM) overexpresses 5-HT7R; hence, this study aims to develop radiolabeled aryl piperazine derivatives as 5-HT7R imaging agents. METHODS: Compounds 6 and 7 as 1-(3-nitropyridin-2-yl)piperazine derivatives were radiolabeled with fac-[99mTc(CO)3(H2O)3]+ and 99mTc(CO)3-[6] and 99mTc(CO)3-[7] were obtained with high radiochemical purity (RCP > 94%).The stability of the radiotracers was evaluated in both saline and mouse serum. Specific binding on different cell lines including U-87 MG, MCF-7, SKBR3, and HT-29 was performed. The biodistribution of these radiotracers was evaluated in normal and U-87 MG Xenografted models. Finally, 99mTc(CO)3-[6] and 99mTc(CO)3-[7] were applied for in vivo imaging in U-87 MG Xenografted models. Specific binding study indicates that 99mTc(CO)3-[6] and 99mTc(CO)3-[7] can recognize 5-HT7R of U87-MG cell line. The biodistribution study in normal mice indicates that the brain uptake of 99mTc(CO)3-[6] and 99mTc(CO)3-[7] is the highest at 30min post-injection (0.8 ± 0.25 and 0.64 ± 0.18%ID/g, respectively). The data of the biodistribution study in the U87-MG xenograft model revealed that these radiotracers could accumulate in the tumor site, and the highest tumor uptake was observed at 60min post-injection (3.38 ± 0.65 and 3.27 ± 0.5%ID/g, respectively). The injection of pimozide can block the tumor's radiotracer uptake, indicating the binding of these radiotracers to the 5-HT7R. The imaging study in the xenograft model also confirms the biodistribution data. The acquired images clearly show the tumor site, and the tumor-to-muscle ratio for 99mTc(CO)3-[6] and 99mTc(CO)3-[7] at 60min was 3.33 and 3.88, respectively. CONCLUSIONS: 99mTc(CO)3-[6] and 99mTc(CO)3-[7] can visualize tumorin theU87-MG xenograft modeldueto their affinitytoward5-HT7R.

5-HT<sub>3</sub> receptors in GtoPdb v.2023.3

The 5-HT3 receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on 5-Hydroxytryptamine (serotonin) receptors [69]) is a ligand-gated ion channel of the Cys-loop family that includes the zinc-activated channels, nicotinic acetylcholine, GABAA and strychnine-sensitive glycine receptors. The receptor exists as a pentamer of 4 transmembrane (TM) subunits that form an intrinsic cation selective channel [7]. Five human 5-HT3 receptor subunits have been cloned and homo-oligomeric assemblies of 5-HT3A and hetero-oligomeric assemblies of 5-HT3A and 5-HT3B subunits have been characterised in detail. The 5-HT3C (HTR3C, Q8WXA8), 5-HT3D (HTR3D, Q70Z44) and 5-HT3E (HTR3E, A5X5Y0) subunits [86, 125], like the 5-HT3B subunit, do not form functional homomers, but are reported to assemble with the 5-HT3A subunit to influence its functional expression rather than pharmacological profile [127, 66, 161]. 5-HT3A, -C, -D, and -E subunits also interact with the chaperone RIC-3 which predominantly enhances the surface expression of homomeric 5-HT3A receptor [161]. The co-expression of 5-HT3A and 5-HT3C-E subunits has been demonstrated in human colon [85]. A recombinant hetero-oligomeric 5-HT3AB receptor has been reported to contain two copies of the 5-HT3A subunit and three copies of the 5-HT3B subunit in the order B-B-A-B-A [9], but this is inconsistent with recent reports which show at least one A-A interface [99, 154]. The 5-HT3B subunit imparts distinctive biophysical properties upon hetero-oligomeric 5-HT3AB versus homo-oligomeric 5-HT3A recombinant receptors [35, 44, 59, 88, 143, 132, 82], influences the potency of channel blockers, but generally has only a modest effect upon the apparent affinity of agonists, or the affinity of antagonists ([19], but see [44, 33, 38]) which may be explained by the orthosteric binding site residing at an interface formed between 5-HT3A subunits [99, 154]. However, 5-HT3A and 5-HT3AB receptors differ in their allosteric regulation by some general anaesthetic agents, small alcohols and indoles [142, 139, 73]. The potential diversity of 5-HT3 receptors is increased by alternative splicing of the genes HTR3A and HTR3E [67, 21, 127, 126, 123]. In addition, the use of tissue-specific promoters driving expression from different transcriptional start sites has been reported for the HTR3A, HTR3B, HTR3D and HTR3E genes, which could result in 5-HT3 subunits harbouring different N-termini [156, 82, 123]. To date, inclusion of the 5-HT3A subunit appears imperative for 5-HT3 receptor function.

Nicotinic acetylcholine receptors (nACh) in GtoPdb v.2023.3

Nicotinic acetylcholine (ACh) receptors are members of the Cys-loop family of transmitter-gated ion channels that includes the GABAA, strychnine-sensitive glycine and 5-HT3 receptors [215, 3, 159, 225, 259]. All nicotinic receptors are pentamers in which each of the five subunits contains 4 TM domains. Genes encoding a total of 17 subunits (α1-10, β1-4, γ, δ and ε) have been identified [120]. All subunits with the exception of α8 (present in avian species) have been identified in mammals. All α subunits possess two tandem cysteine residues near to the site involved in acetylcholine binding, and subunits not named α lack these residues [159]. The orthosteric ligand binding site is formed by residues within at least three peptide domains on the α subunit (principal component), and three on the adjacent subunit (complementary component). Nicotinic ACh receptors contain several allosteric modulatory sites. One such site, for positive allosteric modulators (PAMs) and allosteric agonists, has been proposed to reside within an intrasubunit cavity between the 4 TM domains [264, 87]; see also [106]). The high resolution crystal structure of the molluscan ACh binding protein, a structural homologue of the extracellular binding domain of a nicotinic receptor pentamer, in complex with several nicotinic receptor ligands (e.g.[35]) and the crystal structure of the extracellular domain of the α1 subunit bound to α-bungarotoxin at 1.94Â resolution [55], has revealed the orthosteric binding site in detail (reviewed in [215, 120, 39, 198]). Nicotinic receptors at the somatic neuromuscular junction of adult animals have the stoichiometry (α1)2β1δε, whereas an extrajunctional (α1)2β1γδ receptor predominates in embryonic and denervated skeletal muscle and other pathological states. Other nicotinic receptors are assembled as combinations of α(2-6) and β(2-4) subunits. For α2, α3, α4 and β2 and β4 subunits, pairwise combinations of α and β (e.g. α3β4 and α4β2) are sufficient to form a functional receptor in vitro, but far more complex isoforms may exist in vivo (reviewed in [96, 93, 159]). There is strong evidence that the pairwise assembly of some α and β subunits can occur with variable stoichiometry [e.g. (α4)2(β2)2 or (α4)3(β2)2] which influences the biophysical and pharmacological properties of the receptor [159]. α5 and β3 subunits lack function when expressed alone, or pairwise, but participate in the formation of functional hetero-oligomeric receptors when expressed as a third subunit with another α and β pair [e.g. α4α5αβ2, α4αβ2β3, α5α6β2, see [159] for further examples]. The α6 subunit can form a functional receptor when co-expressed with β4 in vitro, but more efficient expression ensues from incorporation of a third partner, such as β3 [263]. The α7, α8, and α9 subunits form functional homo-oligomers, but can also combine with a second subunit to constitute a hetero-oligomeric assembly (e.g. α7β2 and α9α10). For functional expression of the α10 subunit, co-assembly with α9 is necessary. The latter, along with the α10 subunit, appears to be largely confined to cochlear and vestibular hair cells. Comprehensive listings of nicotinic receptor subunit combinations identified from recombinant expression systems, or in vivo, are given in [159]. In addition, numerous proteins interact with nicotinic ACh receptors modifying their assembly, trafficking to and from the cell surface, and activation by ACh (reviewed by [158, 9, 118]).The nicotinic receptor Subcommittee of NC-IUPHAR has recommended a nomenclature and classification scheme for nicotinic acetylcholine (nACh) receptors based on the subunit composition of known, naturally- and/or heterologously-expressed nACh receptor subtypes [143]. Headings for this table reflect abbreviations designating nACh receptor subtypes based on the predominant α subunit contained in that receptor subtype. An asterisk following the indicated α subunit denotes that other subunits are known to, or may, assemble with the indicated α subunit to form the designated nACh receptor subtype(s). Where subunit stoichiometries within a specific nACh receptor subtype are known, numbers of a particular subunit larger than 1 are indicated by a subscript following the subunit (enclosed in parentheses- see also [46]).

Possible Role of 5-Hydroxytryptamine (5-HT) Receptor on Human Sperm Motility Regulation.

The purpose of this study is to examine whether 5-hydroxytryptamine (5-HT, also known as serotonin) regulates human sperm motility, focusing on 5-HT receptors. Immunofluorescent staining revealed the existence of seven types of 5-HT receptors with a heterogeneous pattern of reactive sites. In detail, 5-HT1B, 5-HT6, and 5-HT7 were detected in the post-acrosomal and mid-piece regions. The 5-HT2A and 5-HT5A receptors were mainly localized in the equatorial segment. 5-HT3A and 5-HT4 receptors were present in the neck and post-acrosomal regions. When examining the effects of 5-HT receptor antagonists on sperm motility, only the 5-HT2A receptor antagonist significantly reduced sperm motility. This suggests that the 5-HT2A receptor may have a regulatory function in sperm motility. Eventually, progressive motility should be attenuated to penetrate the oocyte for fertilization. The current study indicated heterogenous expression patterns and plausible functions of 5-HT receptors in human sperm.

Efficacy and safety of 5-hydroxytryptamine-3 (5-HT3) receptor antagonists in augmentation with selective serotonin reuptake inhibitors (SSRIs) in the treatment of moderate to severe obsessive–compulsive disorder: a systematic review and meta-analysis of randomized clinical trials

Obsessive–compulsive disorder (OCD) is the fourth most common mental disorder, and selective serotonin reuptake inhibitors (SSRIs) are the cornerstone of its pharmacological treatment. About 40–60% of the cases are treatment-refractory, and this makes searching for second-line treatment necessary. 5-Hydroxytryptamine-3 (5-HT3) antagonists are among the many medications that have been used in augmentation with SSRIs. In this systematic review and meta-analysis, we assessed the efficacy and safety of 5-HT3 receptor antagonists in augmentation with SSRIs in treating moderate to severe OCD. We searched PubMed, Web of Science, Scopus, Cochrane library, and Google Scholar for relevant trials published up to December 2022. The effect size was the mean difference in Yale-Brown obsessive compulsive scale (Y-BOCS) scores before and after receiving 5-HT3 receptor antagonist drugs in augmentation with SSRIs in moderate to severe OCD patients. We included 6 randomized-controlled trails (RCTs) with 334 patients assessing the effect of the augmentation of SSRIs with ondansetron, granisetron, and tropisetron on treating moderate to severe OCD. Our results were in favor of the experimental group in total (Z = 8.37, P < 0.00001), in the compulsion subgroup (Z = 5.22, P < 0.00001), and in the obsession subgroup (Z = 8.33, P < 0.00001). They are well-tolerated, and have mild side effects and do not result in withdrawal. Augmentation of 5-HT3 antagonists with SSRIs can be beneficial in treating moderate to severe OCD. Further multi-center trials under adequate conditions in longer periods are needed to help come up with a comprehensive action plan.

Efficacy and safety of Aprepitant-containing triple therapy for the prevention and treatment of chemotherapy-induced nausea and vomiting: A meta-analysis.

Most cancer patients suffer from the pain of chemotherapy-induced nausea and vomiting (CINV). This meta-analysis was performed to evaluate the efficacy and safety of a regimen consisting of aprepitant, dexamethasone, and 5-HT3 receptor antagonists in the prevention and treatment of CINV. A systematic literature search was conducted across multiple databases, including PubMed, EMbase, Cochrane Library, MEDLINE, CENTRAL, HEED, CNKI, Wanfang, and VIP, to identify randomized controlled trials (RCTs) investigating the use of triple therapy (aprepitant, 5-HT3 receptor antagonist, and dexamethasone) to prevent and treat CINV. Meta-analysis was performed using RevMan 5.4 and Stata17 software, employing either a fixed-effect or random-effect model based on statistical heterogeneity. A meta-analysis of 23 randomized controlled trials (RCTs) involving 7956 patients was conducted. Efficacy: Results showed significantly improved complete responses (CRs) for CINV in the test group versus the control group in the overall, acute, and delayed phases. Furthermore, in the test group, substantial alleviation of nausea symptoms was observed in the delayed and overall phases but not in the acute phase. Safety: There was no statistically significant difference in the incidence of febrile neutropenia, diarrhea, anorexia, and headache between the 2 groups. The incidence of fatigue and hiccups in the test group was higher than that in the control group; however, the incidence of constipation was significantly lower. Aprepitant-containing triple therapy is highly effective in the prevention and treatment of CINV, with reliable medication safety.

Captive ERVWE1 triggers impairment of 5-HT neuronal plasticity in the first-episode schizophrenia by post-transcriptional activation of HTR1B in ALKBH5-m6A dependent epigenetic mechanisms

BackgroundAbnormalities in the 5-HT system and synaptic plasticity are hallmark features of schizophrenia. Previous studies suggest that the human endogenous retrovirus W family envelope (ERVWE1) is an influential risk factor for schizophrenia and inversely correlates with 5-HT4 receptor in schizophrenia. To our knowledge, no data describes the effect of ERVWE1 on 5-HT neuronal plasticity. N6-methyladenosine (m6A) regulates gene expression and impacts synaptic plasticity. Our research aims to systematically investigate the effects of ERVWE1 on 5-HT neuronal plasticity through m6A modification in schizophrenia.ResultsHTR1B, ALKBH5, and Arc exhibited higher levels in individuals with first-episode schizophrenia compared to the controls and showed a strong positive correlation with ERVWE1. Interestingly, HTR1B was also correlated with ALKBH5 and Arc. Further analyses confirmed that ALKBH5 may be an independent risk factor for schizophrenia. In vitro studies, we discovered that ERVWE1 enhanced HTR1B expression, thereby activating the ERK-ELK1-Arc pathway and reducing the complexity and spine density of 5-HT neurons. Furthermore, ERVWE1 reduced m6A levels through ALKBH5 demethylation. ERVWE1 induced HTR1B upregulation by improving its mRNA stability in ALKBH5-m6A-dependent epigenetic mechanisms. Importantly, ALKBH5 mediated the observed alterations in 5-HT neuronal plasticity induced by ERVWE1.ConclusionsOverall, HTR1B, Arc, and ALKBH5 levels were increased in schizophrenia and positively associated with ERVWE1. Moreover, ALKBH5 was a novel risk gene for schizophrenia. ERVWE1 impaired 5-HT neuronal plasticity in ALKBH5-m6A dependent mechanism by the HTR1B-ERK-ELK1-Arc pathway, which may be an important contributor to aberrant synaptic plasticity in schizophrenia.

New characterization of dihydroergotamine receptor pharmacology in the context of migraine: utilization of a β-arrestin recruitment assay

IntroductionDihydroergotamine mesylate (DHE) is an established effective acute therapy for migraine and is often characterized by its broad receptor pharmacology. Knowledge of DHE pharmacology largely comes from studies employing older methodologies.ObjectiveTo assess DHE receptor activity using high-throughput methods to screen for functional ß-arrestin activity at G protein–coupled receptors (GPCRs).MethodsFunctional receptor activities of DHE and sumatriptan succinate (both 10 μM) were screened against 168 GPCRs using the gpcrMAX assay. Agonist and antagonist effects were considered significant if receptor activity was &amp;gt;30% or inhibited by &amp;gt;50%, respectively. Radiolabeled ligand binding assays were performed for DHE (0.01–300 nM for 5-HT3 and 4E; 0.3–10,000 nM for 5-HT1B, α-adrenergic2B [i.e., α2B-adrenoceptor], D2, and D5) to assess specific binding to select receptors.ResultsDHE (10 μM) exhibited agonist activity at α-adrenergic2B, CXC chemokine receptor 7 (CXCR7), dopamine (D)2/5, and 5-hydroxytryptamine (5-HT)1A/1B/2A/2C/5A receptors and antagonist activity at α-adrenergic1B/2A/2C (i.e., α1B/2A/2C-adrenoceptors), calcitonin receptor–receptor activity modifying protein 2 (CTR-RAMP2) or amylin 2 (AMY2), D1/3/4/5, and 5-HT1F receptors. Sumatriptan succinate (10 μM) exhibited agonist activity at the 5-HT1B/1E/1F/5A receptors. DHE demonstrated a half-maximal inhibitory concentration (IC50) of 149 nM at the 5-HT1F receptor and a half-maximal effective concentration (EC50) of 6 μM at the CXCR7 receptor. DHE did not bind to the 5-HT3 receptor at concentrations up to 300 nM and bound poorly to 5-HT4E and D5 receptors (IC50 of 230 and 370 nM, respectively). DHE bound strongly to the D2, 5-HT1B, and α-adrenergic2B receptors (IC50 of 0.47, 0.58, and 2.8 nM, respectively).ConclusionBy using a high-throughput β-arrestin recruitment assay, this study confirmed the broad receptor profile of DHE and provided an update on DHE receptor pharmacology as it relates to migraine.

Investigating the Mechanisms Involved in Scopolamine-Induced Memory Degradation

In the present study, the mechanisms involved in scopolamine-induced memory impairment have been investigated. The molecular events that take place during memory mostly include mechanisms that are seen in the acquisition phase. Results show that one of the mechanisms of memory destruction caused by scopolamine, in addition to weakening the cholinergic system, is the indirect effect of scopolamine on other neurotransmitter systems, including the glutamatergic system. Scopolamine injection increases dopamine by inhibiting M2/4 muscarinic auto receptors. These auto receptors are located on dopaminergic presynaptic neurons, and their activation reduces the release of dopamine. Therefore, blocking these auto receptors by scopolamine can increase the release of dopamine. Both D1 and D2 receptors are involved in the process of learning and memory. In general, stimulation of dopamine D1 receptors follows an inverted U-shaped dose-response curve, meaning that both insufficient and excessive amounts of dopamine cause memory impairment. Therefore, one of the mechanisms of scopolamine-induced memory impairment can be an indirect effect on the dopaminergic system. Effect on cell membrane potential, effect on neuron plasticity and interaction with acetylcholine. Serotonin plays a complex role in memory and learning. Serotonin receptors (5-HT2A) also play a role in memory function through their effect on calcium transport. This action is similar to dopamine receptors and other G-protein-coupled receptors, which activate phospholipase C, enter calcium into the cell, and activate calcineurin. Activation of 5-HT2A receptors as well as 5-HT4 receptors by specific agonists of these receptors enhances LTP, which plays a very important role in memory. On the other hand, specific 5-HT3 receptor antagonist improves LTP. 5-HT6 receptor antagonist can improve memory function. Therefore, different serotonin receptors have different roles on memory function, and the interaction between scopolamine and these receptors needs further study. It has been shown that histamine increases the secretion of acetylcholine in the hippocampus and postsynaptic H1 and presynaptic H3 receptors play an important role in memory and learning, but whether scopolamine can cause memory impairment through interaction with histamine receptors, not reviewed.

412 Awardee Talk: New Insights into Mechanisms of Serotonin Receptor-Mediated Vasoactivity and Complex Interactions with Ergot Alkaloids in Bovine Vasculature

Abstract Ergovaline (ERV), produced in toxic endophyte-infected tall fescue, causes potent vasoconstriction of bovine vasculature by interacting with serotonin (5-HT) receptors. Ergovaline acts as a partial agonist of 5-HT2A-mediated vasoconstriction. The duration of ERV exposure affects 5-HT-mediated vasoactivity of mesenteric blood vessels. If ERV and 5-HT exposure occur simultaneously, ERV can increase 5-HT-mediated vasoconstriction. If 5-HT exposure occurs after blood vessels have had prior ERV exposure, increasing levels of 5-HT can induce vasorelaxation of blood vessels. To better understand mechanisms of 5-HT-mediated vasorelaxation, lateral saphenous veins from steers (n = 5) were assessed for vasoactivity in response to increasing concentrations of selective 5-HT receptor agonists 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. 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. Increasing concentrations of 5-HT resulted in divergent vasoconstriction and vasorelaxation responses that were dose-dependent. Serotonin caused an 86.3% increase (P &amp;lt; 0.01) in relaxation activity at 1×10-7 M and 5-HT caused a 166% increase (P &amp;lt; 0.01) in contraction activity at 1x10-4 M. Increasing concentrations of the selective 5-HT1B agonist did not result in any vasoactive response. Increasing concentrations of agonists selective for 5-HT2B, 5-HT4, or 5-HT7 resulted in a 27.3%, 91.6%, or 43.9% (P &amp;lt; 0.01) increase in maximal vasorelaxation activity. Of these 5-HT receptor agonists, the selective 5-HT4 receptor agonist resulted in the lowest -log IC50 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 (control), a selective 5-HT2A antagonist (1×10-5M), or selective antagonists of 5-HT2A and 5-HT4 simultaneously for 5-min before the pre-contraction with phenylephrine and additions of 5-HT. Antagonism of the 5-HT2A receptor did not result in increased vasorelaxation activity compared with control. Antagonism of the 5-HT2A receptor and 5-HT4 receptor simultaneously inhibited vasorelaxation activity and increased (P &amp;lt; 0.01) the maximal contractile response occurring at 1×10-4 M by 47% compared with control. Approximately 84% of the maximal vasorelaxation activity occurring in response to 5-HT could be accounted for through 5-HT4. These data provide strong evidence that 5-HT4 is the primary receptor involved with 5-HT-mediated vasorelaxation in bovine lateral saphenous vein. More research is needed to determine if 5-HT4-mediated vasorelaxation is responsible for relaxation responses observed in blood vessels with prior ERV exposure. This will aid in the development of strategies for alleviating symptoms of sustained vasoconstriction that occur during fescue toxicosis in ruminants.

Prevention of CINV in Patients with Multiple Myeloma or Lymphoma Undergoing Hematopoietic Stem Cell Transplantation: NEPA Versus Ondansetron. a Monocentric Real-Life Experience

INTRODUCTION: Chemotherapy-induced nausea and vomiting (CINV) are adverse events that compromise quality of life and treatment compliance in patients undergoing autologous hematopoietic stem cell transplantation (ASCT). Polychemotherapy regimens, used as conditioning regimens for ASCT in lymphomas, and high-dose melphalan (≥140 mg/mq), used in multiple myeloma (MM), have high emetogenic risk. Control of CINV is difficult and there is no uniformity for its prophylaxis. Antiemetic guidelines recommend, for prophylaxis, co-administration of a triplet regimen of a serotonine (5-HT3) receptor antagonist (RA), as Ondansetron, a neurokinin-1 RA, and dexamethasone. Netupitant-Palonosetron (NEPA), an oral formulation derived from the combination of Netupitant (NK1-RA) and Palonsetron, has been approved as prophylaxis of CINV but its experience in the stem cell transplant setting is still limited. AIMS: The primary aim of this study was to compare the efficacy of Ondansetron versus NEPA in terms of reduction of CINV in patients affected by lymphoma or MM who undergone ASCT. The secondary aims included comparing the duration of CINV, based on the use of Ondansetron or NEPA, and their safety profile in terms of reduction of extrahaematological toxicity (as mucositis or diarrhea). METHODS: In this retrospective monocentric study, we enrolled 76 patients (48 with MM and 28 with lymphoma), who underwent ASCT between March 2021 and March 2022. All patients with MM received high dose of melphalan, those with lymphoma received FEAM. Regarding antiemetics patients were divided according to whether they received NEPA or Ondansetron . Patients' characteristics are in Table 1. RESULTS: Among all, fifty patients (65%) reported CINV of any grade. In particular, the group experiencing CINV included about half of patients treated with NEPA (56%) and almost all those treated with Ondansetron (91%). Among the 26 patients who didn't report CINV (35%), the majority received NEPA (92%) (P = 0.0032) (Fig. 1a). Focusing on patients with MM, 33 experienced CINV (68%), and they were 59% of MM patients treated with NEPA and 93% of those treated with Ondansetron. Fifteen patients did not experience CINV (32%) and almost all of them (93%) had been treated with NEPA (P = 0.037) (Fig. 1b). Sixty-one percent of the 28 patients with lymphoma reported CINV (P= 0.1914) (Fig. 1c). Mean duration of CINV was significantly shorter for patients treated with NEPA than for those treated with Ondansetron (4.8 days vs 9.2 days) (P= 0.002) (Fig. 1d). Regarding extraematological toxicity of chemotherapy, as mucositis and diarrhea, we didn't find any significant difference between the two groups of patients. Regarding the outcome to NEPA, complete response rate (no emesis, no rescue medication) was 37% during overall phases of CINV, 28% of patients had complete control (complete response with no more than mild nausea) and 31% had uncontrolled nausea. Conversely, in the Ondansetron group, only 5% of patients had complete response and 95% had uncontrolled nausea (Fig. 1e). All patients with uncontrolled nausea required a rescue therapy. According to CTCAE, 69% of patients receiving NEPA had grade 1 nausea and 6% had none, while all patients receiving Ondansetron had CINV and 85% of them had grade 2 nausea. CONCLUSIONS: In our experience, NEPA has shown superiority in the prevention of CINV, in highly emetogenic regimens in both patients with myeloma or lymphoma, with advantages on the severity and the duration of CINV. Given the high burden of CINV in the whole population analyzed in the study, regardless of the antiemetic used, it would be useful to identify patients at greatest risk and standardize CINV prophylaxis and treatment protocols depending on the different chemotherapy regimens and their emetogenic risk.

Differential contribution of 5-HT4, 5-HT5, and 5-HT6 receptors to acute pruriceptive processing induced by chloroquine and histamine in mice.

The involvement of serotonin (5-HT) and/or noradrenaline in acute pruriceptive processing in the central nervous system (CNS) has been reported using antidepressants, such as milnacipran, a serotonin and noradrenaline reuptake inhibitor, and mirtazapine, a noradrenergic and specific serotonergic antidepressant; however, the roles of 5-HT receptor family in acute pruriceptive processing have not been fully elucidated in the CNS. In the present study, scratching behavior induced by chloroquine (CQ) was ameliorated by milnacipran or mirtazapine, and these effects were reversed by SB207266, a 5-HT4 antagonist, or SB258585, a 5-HT6 antagonist, but not by SB258585, a 5-HT5 antagonist. Moreover, CQ-induced scratches were mitigated by intrathecal injection of 5-HT4 agonists, such as BIMU8 and ML10302, and the 5-HT6 agonist, WAY208466. Conversely, histamine-induced scratches were not affected by the 5-HT4 agonists or a 5-HT6 agonist. Similarly, the amelioration of histamine-induced scratches by these antidepressants was not reversed by the 5-HT4, 5-HT5, or 5-HT6 receptor antagonist. Therefore, 5-HT is involved in the amelioration of CQ-induced scratches by milnacipran and mirtazapine, and 5-HT4, 5-HT5, and 5-HT6 receptors play differential roles in acute pruriceptive processing after administration of CQ or histamine.

5-HT6 Receptors Control GABAergic Transmission and CA1 Pyramidal Cell Output of Dorsal Hippocampus.

The blockade of 5-HT6 receptors represents an experimental approach that might ameliorate the memory deficits associated with brain disorders, including Alzheimer's disease and schizophrenia. However, the synaptic mechanism by which 5-HT6 receptors control the GABAergic and glutamatergic synaptic transmission is barely understood. In this study, we demonstrate that pharmacological manipulation of 5-HT6 receptors with the specific agonist EMD 386088 (7.4nM) or the antagonist SB-399885 (300nM) modulates the field inhibitory postsynaptic potentials of the dorsal hippocampus and controls the strength of the population spike of pyramidal cells. Likewise, pharmacological modulation of 5-HT6 controls the magnitude of paired-pulse inhibition, a phenomenon mediated by GABAergic interneurons acting via GABAA receptors of pyramidal cells. The effects of pharmacological manipulation of the 5-HT6 receptor were limited to GABAergic transmission and did not affect the strength of field excitatory postsynaptic potentials mediated by the Schaffer collaterals axons. Lastly, in a modified version of the Pavlovian autoshaping task that requires the activation of the hippocampal formation, we demonstrated that the anti-amnesic effect induced by the blockade of the 5-HT6 receptor is prevented when the GAT1 transporter is blocked, suggesting that modulation of GABAergic transmission is required for the anti-amnesic properties of 5-HT6 receptor antagonists.

Dual action of serotonin on local excitatory and inhibitory neural circuits regulating the corticotropin-releasing factor neurons in the paraventricular nucleus of the hypothalamus.

Serotonergic neurons originating from the raphe nuclei have been proposed to regulate corticotropin-releasing factor (CRF) neurons in the paraventricular nucleus of the hypothalamus (PVH). Since glutamate- and γ-aminobutyric acid (GABA)-containing neurons, constituting the hypothalamic local circuits, innervate PVH CRF neurons, we examined whether they mediate the actions of serotonin (5-hydroxytryptamine [5-HT]) on CRF neurons. Spontaneous excitatory postsynaptic currents (sEPSCs) or spontaneous inhibitory postsynaptic currents (sIPSCs) were recorded in PVH CRF neurons, under whole cell patch-clamp, using the CRF-modified yellow fluorescent protein (Venus) ΔNeo mouse. Serotonin elicited an increase in the frequency of sEPSCs in 77% of the cells and a decrease in the frequency of sIPSCs in 71% of the cells, tested in normal medium. Neither the amplitude nor decay time of sEPSC and sIPSC was affected, thus the site(s) of action of serotonin may be presynaptic. In the presence of tetrodotoxin (TTX), serotonin had no significant effects on either parameter of sEPSC or sIPSC, indicating that the effects of serotonin are action potential-dependent, and that the presynaptic interneurons are largely intact within the slice; distant neurons may exist, though, since some 20%-30% of neurons did not respond to serotonin without TTX. We next examined through what receptor subtype(s) serotonin exerts its effects on presynaptic interneurons. DOI (5-HT2A/2C agonist) mimicked the action of serotonin on the sIPSCs, and the serotonin-induced decrease in sIPSC frequency was inhibited by a selective 5-HT2C antagonist RS102221. 8-OH-DPAT (5-HT1A/7 agonist) mimicked the action of serotonin on the sEPSCs, and the serotonin-induced increase in sEPSC frequency was inhibited by a selective 5-HT7 antagonist SB269970. Thus, serotonin showed a dual action on PVH CRF neurons, by upregulating glutamatergic- and downregulating GABAergic interneurons; the former may partly be mediated by 5-HT7 receptors, whereas the latter by 5-HT2C receptors. The CRF-Venus ΔNeo mouse was useful for the electrophysiological examination.