5-hydroxytryptamine (5-HT) cellular sequestration during chronic exposure delays 5-HT₃ receptor resensitization due to Its subsequent release

The serotonergic synapse is dynamically regulated by serotonin (5-hydroxytryptamine (5-HT)) with elevated levels leading to the down-regulation of the serotonin transporter and a variety of 5-HT receptors, including the 5-HT type-3 (5-HT(3)) receptors. We report that recombinantly expressed 5-HT(3) receptor binding sites are reduced by chronic exposure to 5-HT (IC(50) of 154.0 ± 45.7 μm, t(½) = 28.6 min). This is confirmed for 5-HT(3) receptor-induced contractions in the guinea pig ileum, which are down-regulated after chronic, but not acute, exposure to 5-HT. The loss of receptor function does not involve endocytosis, and surface receptor levels are unaltered. The rate and extent of down-regulation is potentiated by serotonin transporter function (IC(50) of 2.3 ± 1.0 μm, t(½) = 3.4 min). Interestingly, the level of 5-HT uptake correlates with the extent of down-regulation. Using TX-114 extraction, we find that accumulated 5-HT remains soluble and not membrane-bound. This cytoplasmically sequestered 5-HT is readily releasable from both COS-7 cells and the guinea pig ileum. Moreover, the 5-HT level released is sufficient to prevent recovery from receptor desensitization in the guinea pig ileum. Together, these findings suggest the existence of a novel mechanism of down-regulation where the chronic release of sequestered 5-HT prolongs receptor desensitization

Cisplatin-induced emesis: systematic review and meta-analysis of the ferret model and the effects of 5-HT3 receptor antagonists

PURPOSE: The ferret cisplatin emesis model has been used for ~30 years and enabled identification of clinically used anti-emetics. We provide an objective assessment of this model including efficacy of 5-HT(3) receptor antagonists to assess its translational validity. METHODS: A systematic review identified available evidence and was used to perform meta-analyses. RESULTS: Of 182 potentially relevant publications, 115 reported cisplatin-induced emesis in ferrets and 68 were included in the analysis. The majority (n = 53) used a 10 mg kg(−1) dose to induce acute emesis, which peaked after 2 h. More recent studies (n = 11) also used 5 mg kg(−1), which induced a biphasic response peaking at 12 h and 48 h. Overall, 5-HT(3) receptor antagonists reduced cisplatin (5 mg kg(−1)) emesis by 68% (45–91%) during the acute phase (day 1) and by 67% (48–86%) and 53% (38–68%, all P < 0.001), during the delayed phase (days 2, 3). In an analysis focused on the acute phase, the efficacy of ondansetron was dependent on the dosage and observation period but not on the dose of cisplatin. CONCLUSION: Our analysis enabled novel findings to be extracted from the literature including factors which may impact on the applicability of preclinical results to humans. It reveals that the efficacy of ondansetron is similar against low and high doses of cisplatin. Additionally, we showed that 5-HT(3) receptor antagonists have a similar efficacy during acute and delayed emesis, which provides a novel insight into the pharmacology of delayed emesis in the ferret

Identification of critical residues in loop E in the 5-HT(3AS)R binding site

BACKGROUND: The serotonin type 3 receptor (5-HT(3)R) is a member of a superfamily of ligand gated ion channels. All members of this family share a large degree of sequence homology and presumably significant structural similarity. A large number of studies have explored the structure-function relationships of members of this family, particularly the nicotinic and GABA receptors. This information can be utilized to gain additional insights into specific structural and functional features of other receptors in this family. RESULTS: Thirteen amino acids in the mouse 5-HT(3AS)R that correspond to the putative E binding loop of the nicotinic α7 receptor were chosen for mutagenesis. Due to the presence of a highly conserved glycine in this region, it has been suggested that this binding loop is comprised of a hairpin turn and may form a portion of the ligand-binding site in this ion channel family. Mutation of the conserved glycine (G147) to alanine eliminated binding of the 5-HT(3)R antagonist [(3)H]granisetron. Three tyrosine residues (Y140, Y142 and Y152) also significantly altered the binding of 5-HT(3)R ligands. Mutations in neighboring residues had little or no effect on binding of these ligands to the 5-HT(3AS)R. CONCLUSION: Our data supports a role for the putative E-loop region of the 5-HT(3)R in the binding of 5-HT, mCPBG, d-tc and lerisetron. 5-HT and mCPBG interact with Y142, d-tc with Y140 and lerisetron with both Y142 and Y152. Our data also provides support for the hypothesis that this region of the receptor is present in a loop structure

Quality of Postoperative Pain Management after Midfacial Fracture Repair—An Outcome-oriented Study

Objectives There is a lack of literature regarding the procedure-specific quality of acute postoperative pain management after midfacial fracture repair. The purpose of the presented prospective clinical study was to evaluate postoperative pain management after surgical repair of midfacial fractures. Materials and methods Eighty-five adults were evaluated on the first postoperative day following midfacial repair using the questionnaire of the Quality Improvement in Postoperative Pain Management (QUIPS) project. The main outcome measures were patients’ characteristics and clinical- and patient-reported outcome parameters. Results Overall, pain on the first postoperative day was moderate. A significant correlation between process and outcome parameters could be shown. Duration of surgery above the calculated median was significantly associated with higher maximum pain intensity (p = 0.017). Patients requiring opioids in the recovery room presented significantly higher pain on activity (p = 0.029) and maximum pain (p = 0.035). Sleeping impairment (p = 0.001) and mood disturbance (p = 0.008) were significantly more prevalent in patients undergoing repair of a centrolateral midfacial fracture. Conclusions QUIPS is a simple and qualified tool to evaluate the procedure specific quality of acute postoperative pain management. Pain on the first postoperative day following midfacial fracture repair seems overall to be moderate. Nearly a third of the patients showed inadequate postoperative pain management. To prevent inadequate postoperative pain management, it is necessary to establish a continued procedure-specific outcome measurement

Applicability of the National Comprehensive Cancer Network/Multinational Association of Supportive Care in Cancer Guidelines for Prevention and Management of Chemotherapy-Induced Nausea and Vomiting in Southeast Asia: A Consensus Statement.

A meeting of regional experts was convened in Manila, Philippines, to develop a resource-stratified chemotherapy-induced nausea and vomiting (CINV) management guideline. In patients treated with highly emetogenic chemotherapy in general clinical settings, triple therapy with a serotonin (5-hydroxytryptamine-3 [5-HT3]) antagonist (preferably palonosetron), dexamethasone, and aprepitant is recommended for acute CINV prevention. In resource-restricted settings, triple therapy is still recommended, although a 5-HT3 antagonist other than palonosetron may be used. In both general and resource-restricted settings, dual therapy with dexamethasone (days 2 to 4) and aprepitant (days 2 to 3) is recommended to prevent delayed CINV. In patients treated with moderately emetogenic chemotherapy, dual therapy with a 5-HT3 antagonist, preferably palonosetron, and dexamethasone is recommended for acute CINV prevention in general settings; any 5-HT3 antagonist can be combined with dexamethasone in resource-restricted environments. In general settings, for the prevention of delayed CINV associated with moderately emetogenic chemotherapy, corticosteroid monotherapy on days 2 and 3 is recommended. If aprepitant is used on day 1, it should be continued on days 2 and 3. Prevention of delayed CINV with corticosteroids is preferred in resource-restricted settings. The expert panel also developed CINV management guidelines for anthracycline plus cyclophosphamide combination schedules, multiday cisplatin, and chemotherapy with low or minimal emetogenic potential, and its recommendations are detailed in this review. Overall, these regional guidelines provide definitive guidance for CINV management in general and resource-restricted settings. These consensus recommendations are anticipated to contribute to collaborative efforts to improve CINV management in Southeast Asia

The Effects of Serotonin Receptor Antagonists on Contraction and Relaxation Responses Induced by Electrical Stimulation in the Rat Small Intestine

Background: The main source of 5-HT in body is in enterchromafin cells of intestine, different studies mentioned different roles for endogenous 5-HT and receptors involved and it is not clearified the mechanism of action of endogenous 5-HT. Objectives: To study the role of endogenous 5-HT on modulation of contraction and relaxation responses induced by electrical field stimulation (EFS) in different regions of the rat intestine. Materials and Methods: Segments taken from the rat duodenum, jejunum, mid and terminal ileum were vertically mounted, connected to a transducer and exposed to EFS with different frequencies in the absence and presence of various inhibitors of enteric mediators i. e. specific 5-HT receptor antagonists. Results: EFS-induced responses were sensitive to TTX and partly to atropine, indicating a major neuronal involvement and a cholinergic system. Pre-treatment with WAY100635 (a 5-HT1A receptor antagonist) and granisetron up to 10.0 µM, GR113808 (a 5-HT4 receptor antagonist), methysergide and ritanserin up to 1.0 µM, failed to modify responses to EFS inall examined tissues. In the presence of SB258585 1.0 µM (a 5-HT6 receptor antagonist) there was a trend to enhance contraction in the proximal part of the intestine and reduce contraction in the distal part. Pre-treatment with SB269970A 1.0 µM (5-HT7 receptor antagonist) induced a greater contractile response to EFS at 0.4 Hz only in the duodenum. Conclusions: The application of 5-HT1A, 5-HT2, 5-HT3, 5-HT4, 5-HT6 and 5-HT7 receptor antagonists, applied at concentrations lower than 1.0 µM did not modify the EFS-induced contraction and relaxation responses, whichsuggests the unlikely involvement of endogenous 5-HT in mediating responses to EFS in the described test conditions. Keywords: Electric Stimulation Therapy; Serotonin 5-HT1 Receptor Antagonists; Intestine, Smal

The Comparison Effect of Preoperative Ondansetron and Metoclopramide in Reducing Nausea and Vomitting after Loparoscopic Cholecystectomy

Background & Objectives: Postoperative nausea and vomiting (PONV) is one of the most common complications of anesthesia and without prophylactic intervention occurs in about one-third of patients under general anesthesia. The aim of this study was to compare the efficacy of ondansetron and metoclopramide in reducing PONV after laparoscopic cholecystectomy. Methods: In this study, 90 patients undergoing laparoscopic cholecystectomy were randomly allocated into three equal groups (n =30) and in the first group 10 mg metoclopramide, in the second group 4 mg ondansetron and for placebo group 2 cc normal saline preoperatively were injected. Anesthesia complications in recovery and nausea and vomiting in recovery and 6 hours and 24 hours after surgery were evaluated. Data were analyzed by SPSS software with chi-square test and analysis of variance (ANOVA). P <0.05 was considered significant. Results: The incidence of nausea in placebo group was 66.7 %, in metoclopramide group was 43.3 % and in ondansetron group was 33.3 %. The difference only between placebo and ondansetron groups was significant (p =0.019). The incidence of vomiting in placebo group was 56.7%, in metoclopramide group was 20% and in ondansetron group was 26.7% and there was significant difference between placebo and ondansetron groups (p =0.035) and between placebo and metoclopramide groups (p =0.007), whereas there was not any significant difference between intervention groups (p =0.12). Also anti-emetic drug administration in ondansetron group (40%) in comparison with metoclopramide (63.3%) and placebo (66.7%) was lower, but this difference was not statistically significant (p = 0.07). Conclusion: For prevention of vomiting after laparoscopic cholecystectomy, both metoclopramide and ondansetron are effective. In comparing these two drugs, in preventing of nausea ondansetron is more effective than metoclopramide, whereas there was not any significant difference between two drugs in preventing of vomiting

N-acetyl-cysteine treatment inhibits depletion of brain glutathione levels in rats : implications for schizophrenia

C1 - Journal Articles RefereedA pilot study was conducted to evaluate the usefulness of granisetron for the treatment of antidepressant induced sexual dysfunction in women. Twelve women with antidepressant induced sexual dysfunction (AISD) were assigned granisetron (n=5) or placebo (n=7) in a 14-day randomized, double-blind, placebo-controlled study. One participant in the granisetron group did not complete the study. Participants were assessed at baseline, day 7 and day 14 using the Feiger Sexual Function and Satisfaction Questionnaire and the Arizona Sexual Experience Scale. No statistical differences were measured at baseline or at endpoint between the granisetron or placebo group. This study did not produce evidence supporting the usefulness of granisetron in AISD

A randomized double-blind trial to compare the clinical efficacy of granisetron with metoclopramide, both combined with dexamethasone in the prophylaxis of chemotherapy-induced delayed emesis

Background: The prophylactic use of 5-HT3 receptor antagonists (setrons), after the first 24 h (acute phase) of exposure to emetic chemotherapy, to decrease the incidence of ‘delayed phase' emesis increases costs. We designed a study to evaluate the efficacy of a setron (granisetron) in the delayed phase, compared with metoclopramide, each combined with a corticosteroid. Patients and methods: Patients on their first course of single-day emetic chemotherapy (cisplatin, carboplatin, doxorubicin, cyclophosphamide and others) received granisetron 2 mg p.o. and dexamethasone 8 mg p.o. on day 1, followed for 5 days by dexamethasone 4 mg p.o. od combined with either metoclopramide 20 mg p.o. tds or granisetron 1 mg bd in a double-blinded double-dummy protocol. Patients evaluated the results using a diary card. Randomization was stratified by institution, sex, emetic chemotherapy naïve versus previous, alcohol consumption and platinum versus non-platinum regimen. Results: 131 evaluable patients received granisetron in the delayed phase, and 127 received metoclopramide. Control of acute emesis in both arms was similar (86% granisetron; 85% metoclopramide). The 35 patients experiencing acute emesis had poor control in the delayed phase, with only four granisetron and three metoclopramide patients having no or mild nausea and no vomiting. Conclusions: In daily practice, a combination of oral dexamethasone and oral granisetron achieves an extremely high control of acute emesis (86% protection). Our data suggest that routine prescription of setrons for delayed phase control is not advisable as it increases costs without any benefit for the majority of patients. Delayed emesis in the rare patients with acute phase emesis remains an unsolved proble