Serotonin 3 receptor antagonists for obsessive-compulsive disorder: A systematic review and pairwise meta-analysis

The benefits of serotonin 3 receptor antagonists (5-HT3R-As) in obsessive-compulsive disorder (OCD) treatment remain unclear. Thus, this study aimed to perform a systematic review and a random-effects meta-analysis, including double-blind, randomized, placebo-controlled trials (DBRPCTs). The outcomes include the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) total score (primary), Y-BOCS obsession subscale score, Y-BOCS compulsive subscale score, treatment response, remission rate, all-cause discontinuation, and incidence of individual adverse events (nervousness/restlessness/anxiety, insomnia, headache, dizziness/lightheadedness, decreased appetite, constipation, nausea/vomiting, diarrhea, dry mouth, sweating/increased perspiration, itching/pruritus, tremor, and sexual dysfunction/decreased libido). The mean differences (MD) for continuous outcomes and risk ratios for dichotomous outcomes with 95% confidence intervals (CIs) were calculated. Our study included 10 DBRPCTs (n = 628). Pooled 5-HT3R-As outperformed placebo regarding Y-BOCS total score (MD = -5.08, 95% CI = -7.04, -3.12, N = 9, n = 560), Y-BOCS obsession subscale score, Y-BOCS compulsive subscale score, treatment response, and remission rate. Individually, all 5-HT3R-As outperformed placebo regarding Y-BOCS total score (granisetron: MD = -5.59, 95% CI = -8.79, -2.39, N = 3, n = 178, ondansetron: MD = -5.72, 95% CI = -8.06, -3.37, N = 6, n = 331, tropisetron: MD = -2.87, 95% CI = -5.19, -0.550, N = 1, n = 96). However, all-cause discontinuation and incidence of individual adverse events between pooled 5-HT3R-As and placebo were not significantly different. In conclusion, our meta-analysis suggested 5-HT3R-As as efficacious for symptom improvement in individuals with OCD. However, the number of individuals included in each study was small; thus, a replication randomized trial of 5-HT3R-As should be conducted using a larger sample size.

What is the ideal combination antiemetic regimen?

Postoperative nausea and vomiting (PONV) and post-discharge nausea and vomiting (PDNV) are frequent unpleasant complaints that patients and clinicians report after surgery. PONV and PDNV have been associated with postoperative complications and hospital discharge delays. Despite the extensive evidence describing the use of several regimens in different surgical populations, the ideal regimen has not been established. Several antiemetic drugs have been evaluated in more than 1000 clinical controlled trials for management of this complex emetogenic pathway, including the 5-hydroxytryptamine (5-HT₃) receptor antagonists, dopamine receptor antagonists, neurokinin-type receptor antagonists, antihistaminics, anticholinergics, and corticosteroids, with the 5-HT₃ receptor antagonists being the most commonly used for PONV prophylaxis. Because of the complex emetogenic pathway and multifactorial etiology of PONV, a multimodal approach using two or more drugs that act at different neuro-receptor sites is suggested in patients with one or more risk factors to successfully address PONV and reduce its incidence. Nevertheless, the most studied regimens in randomized clinical trials (RCTs) are the combination of serotonin 5-HT3 receptor antagonists with dexamethasone or dopamine receptor antagonists (droperidol). Therefore, the safest and more effective combination regimen appears to be the use of serotonin 5-HT3 receptor antagonist antiemetic drugs with dexamethasone.

5-HT3 blockade does not attenuate postspinal blood pressure change in cesarean section: A case-control study

Spinal anesthesia (SpA) for elective caesarean section (CS) is often accompanied by clinically relevant arterial hypotension. The Bezold-Jarisch reflex, causing postspinal hypotension, has been shown to be antagonized by serotonin type 3 (5-HT3) blockade. Our aim was to assess if routine prophylactic administration of the 5-HT3 antagonist ondansetron (ODS) attenuates postspinal change in maternal blood pressure.Elective CS under SpA were retrospectively analyzed. Eighty parturients having routinely received 8 mg ODS prior to SpA were compared with 80 patients having not (control group).Mean arterial blood pressure significantly decreased from baseline to the postspinal period (P < .0001) without differences in blood pressure decreases between the 2 groups. This also applied to the heart rate. Overall use of cafedrine/theodrenaline was higher in the ODS group (0.8 (0.4-1.6) mL vs 0.8 (0-1.0) mL in the control group, P = .01). APGAR values showed a presumably clinically irrelevant decrease in control group compared with the ODS group.Our results suggest that routine administration of ODS in a dosage of 8 mg does not effectively attenuate postspinal change in maternal blood pressure during CS in our setting. Given the wide variability of anesthetic techniques, only large prospective and randomized multicenter trials will ultimately serve to elucidate this issue.

Efficacy of Palonosetron as Antiemetic Prophylaxis for Post Operative Patients

Palonosetron is a new, potent and long-acting 5HT3-receptorsantagonist that had been approved by the FDA for use in postoperative nausea and vomiting (PONV) prophylaxis. The objective of this study was to investigate and compare the prophylactic effects of intravenously administered palonosetron, ondansetron and granisetron on prevention of postoperative nausea and vomiting after general anesthesia. This randomized double blind prospective clinical study was carried out in the Department of Anaesthesia, DMCH, Dhaka, Bangladesh from January 2014 to December 2015. A total of 102 patients who underwent laparoscopic cholecystectomy under general anesthesia, out of which patients who received Palonosetron were in Group A (n=34), patients who received Ondansetron were in group B (n=34) and patients who received Granisetron were in group C (n=34) and also the patients were selected randomly by lottery method. Statistical analyses of the results were obtained by using window based computer software devised with Statistical Packages for Social Sciences (SPSS-22). Nausea was found 3(8.8%) in group A, 8(23.5%) in group B and 6(17.6%) in group C. Vomiting was found 3(8.8%) in group A, 10(29.4%) in group B and 7(20.6%) in group C. Vomiting was significantly higher in group B compare with group A. For group B rescue anti-emetic injection motilon (metoclopramide hydrochloride) 5mg IV slowly was given. Palonosetron is effective prophylaxis against post operative nausea and vomiting.

Compatibility and stability of dezocine and tropisetron in 0.9% sodium chloride injection for patient-controlled analgesia administration

Tropisetron is an adjuvant for dezocine used in intravenous patient-controlled analgesia (PCA) and has been reported to provide superior pain control. It is efficacious in reducing the institutional incidence of postoperative nausea and vomiting (PONV), which decreases resource utilization and cost. However, no scientific evidence has been reported in the literature demonstrating analytical confirmation of the compatibility and stability of the combination of dezocine and tropisetron. Thus, the present study aimed to investigate the stability of dezocine with tropisetron in 0.9% sodium chloride injection form for PCA administration.Commercial solutions of dezocine and tropisetron were combined and examined for compatibility and stability when diluted with 0.9% sodium chloride injection in polyolefin bags and glass bottles stored at 4°C or 25°C for up to 14 days. The initial concentrations were 40 mg/100 mL dezocine and 5 mg/100 mL tropisetron. For all samples, the compatibility parameters (including precipitation, cloudiness, discoloration, and pH values) were evaluated. Chemical stability was also determined using high-performance liquid chromatographic (HPLC) analysis.After a 14-day period of storage at 4°C or 25°C, the initial concentrations of dezocine and tropisetron were maintained at at least 98%. All of the mixtures remained clear and colorless throughout the observation period, and no color change or precipitation was observed.These results indicated that admixtures of 40 mg/100 mL dezocine and 5 mg/100 mL tropisetron in 0.9% sodium chloride injection were stable for at least 14 days when stored in polyolefin bags or glass bottles at 4°C or 25°C and protected from light.

Compatibility and Stability of VARUBI (Rolapitant) Injectable Emulsion Admixed with Intravenous Granisetron Hydrochloride

Prophylaxis or therapy with a combination of a neurokinin 1 (NK-1) receptor antagonist (RA), a 5-hydroxytryptamine- 3 (5-HT3) RA, and dexamethasone is recommended by international antiemesis guidelines for the prevention of chemotherapy-induced nausea and vomiting for patients receiving highly emetogenic chemotherapy and for select patients receiving moderately emetogenic chemotherapy. VARUBI (rolapitant) is a substance P/NK-1 RA that was recently approved by the U.S. Food and Drug Administration as an injectable emulsion in combination with other antiemetic agents in adults for the prevention of delayed nausea and vomiting associated with initial and repeat courses of emetogenic cancer chemotherapy, including, but not limited to, highly emetogenic chemotherapy. Granisetron Hydrochloride Injection USP is one of the 5-HT3 RAs indicated for the prevention of nausea and/or vomiting associated with initial and repeat courses of emetogenic cancer therapy, including high-dose cisplatin. Herein, we describe the physical and chemical compatibility and stability of VARUBI (rolapitant) injectable emulsion (166.5 mg/92.5 mL [1.8 mg/mL], equivalent to 185 mg of rolapitant hydrochloride) admixed with Granisetron Hydrochloride Injection USP (1.0 mg/mL, equivalent to 1.12 mg/mL hydrochloride). Binary admixtures of VARUBI injectable emulsion and Granisetron Hydrochloride Injection USP were prepared and stored in VARUBI ready-to-use glass vials and in four types of commonly used intravenous administration (tubing) sets. Evaluation of the physical and chemical compatibility and stability of the admixtures in the VARUBI ready-to-use vials stored at room temperature (20°C to 25°C) under fluorescent light and under refrigeration (2°C to 8°C protected from light) was conducted at 0, 1, 6, 24, and 48 hours, and that of the admixtures in the intravenous tubing sets was evaluated at 0, 2, and 6 hours of storage at 20°C to 25°C. Physical stability was evaluated by visual examination of the container contents under normal room light, and measurement of turbidity, globule size, and particulate matter. Chemical stability was assessed by measuring the pH of the admixture and determining drug concentrations (potency) and impurity levels by high-performance liquid chromatographic analysis. The pH, turbidity, globule size, and particulate matter of all samples remained within narrow and acceptable ranges at all study time points, indicating that combining the two formulations into a binary admixture is physically and chemically compatible and stable. VARUBI injectable emulsion admixed with Granisetron Hydrochloride Injection USP demonstrated compatibility and stability in a ready-to-use glass vial for at least 24 hours at room temperature and 48 hours under refrigeration, as well as in the four intravenous tubing sets for at least 6 hours at 20°C to 25°C. No decrease of drug concentration (or potency) of any admixed components occurred in the samples stored at the two conditions and time periods studied based on high-performance liquid chromatographic analysis. The levels of impurities stayed below the safety limits set by International Conference on Harmonisation during the study period.

Compatibility and Stability of VARUBI (Rolapitant) Injectable Emulsion Admixed with Intravenous Palonosetron Hydrochloride Injection and Dexamethasone Sodium Phosphate Injection

Prophylaxis or therapy with a combination of a neurokinin 1 (NK-1) receptor antagonist (RA), a 5-hydroxytryptamine-3 (5-HT3) RA, and dexamethasone is recommended by international antiemesis guidelines for the prevention of chemotherapy-induced nausea and vomiting for patients receiving highly emetogenic chemotherapy and for selected patients receiving moderately emetogenic chemotherapy. VARUBI (rolapitant) is a substance P/NK-1 RA that was recently approved by the U.S. Food and Drug Administration as an injectable emulsion in combination with other antiemetic agents in adults for the prevention of delayed nausea and vomiting associated with initial and repeat courses of emetogenic cancer chemotherapy, including, but not limited to, highly emetogenic chemotherapy. Palonosetron is one of the 5-HT3 RAs indicated for the prevention of nausea and/or vomiting associated with initial and repeat courses of emetogenic cancer therapy, including high-dose cisplatin. Herein, we describe the physical and chemical compatibility and stability of VARUBI injectable emulsion (166.5 mg/92.5 mL [1.8 mg/mL, free base], equivalent to 185 mg of rolapitant hydrochloride) admixed with palonosetron injection 0.25 mg free base in 5 mL (equivalent to 0.28 mg hydrochloride salt) and with either 5 mL (20 mg) or 2.5 mL (10 mg) of dexamethasone sodium phosphate. Admixtures were prepared and stored in VARUBI injectable emulsion ready-to-use glass vials as supplied by the rolapitant manufacturer and in four types of commonly used intravenous administration (tubing) sets. Assessment of the physical and chemical compatibility and stability of the admixtures in the VARUBI ready-to-use vials stored at room temperature (20°C to 25°C) under fluorescent light and under refrigeration (2°C to 8°C protected from light) was conducted at 0, 1, 6, 24, and 48 hours, and that of the admixtures in the intravenous tubing sets was evaluated at 0, 2, and 6 hours of storage at 20°C to 25°C. Physical stability was evaluated by visual examination of the container contents under normal room light, and measurement of turbidity, globule size, and particulate matter. Chemical stability was assessed by measuring the pH of the admixture and determining drug concentrations (potency) and impurity levels by high-performance liquid chromatographic analysis. All samples were physically and chemically compatible throughout the study duration. The pH, turbidity, globule size, and particulate matter of the admixture stayed within narrow and acceptable ranges. VARUBI injectable emulsion admixed with intravenous palonosetron and dexamethasone was chemically and physically stable in the ready-to-use glass vials for at least 24 hours at room temperature and 48 hours under refrigeration, as well as in the four selected intravenous tubing sets for at least 6 hours at room temperature. No decrease of drug concentration (or potency) of any admixed components occurred in the samples stored at the two temperature ranges and time periods studied as measured by high-performance liquid chromatographic analysis.

Spinal 5-HT3 receptor mediates nociceptive effect on central neuropathic pain; possible therapeutic role for tropisetron

OBJECTIVES

To test the analgesic effect of 5-HT-3 receptor antagonist, tropisetron, in a clip compression injury model of spinal cord pain in rats.

METHODS

Four weeks post compression of the spinal cord at lumbar level, tropisetron was administered intrathecally at 100 μg and 150 μg dosages. Behavioral tests were assessed before administration. Fifteen minutes after injection, behavioral tests were repeated. Randall-Sellitto and plantar test was used for mechanical and thermal hyperalgesia, respectively. Mechanical and cold allodynia were evaluated by Von Frey filament and acetone droplets, respectively. The analgesic effect of tropisetron was compared with intrathecal administration of salicylate. Locomotor score was evaluated by Basso, Beattie and Bresnahan (BBB) test every week after spinal cord injury.

RESULTS

Intrathecal administration of tropisetron, decreased hyperalgesia and mechanical allodynia, but not cold allodynia were observed after compression of the spinal cord.

CONCLUSION

Blockade of 5-HT-3 receptors by tropisetron at the spinal level induces an antinociceptive effect on chronic central neuropathic pain and suggests that this compound may have potential clinical utility for the management of central neuropathic pain, particularly in patients with hyperalgesia and tactile allodynia.

Effect of (4a) a novel 5-HT3 receptor antagonist on chronic unpredictable mild stress induced depressive-like behavior in mice: an approach using behavioral tests battery

BACKGROUND

The inconsistent therapeutic outcome necessitates designing and identifying novel therapeutic interventions for depression. Hence, the present study deals with the investigation of antidepressant-like effects of a novel 5-HT3 receptor antagonist (4-phenylpiperazin-1-yl) (quinoxalin-2-yl) methanone (4a) on chronic unpredictable mild stress (CUMS) induced behavioral and biochemical alterations.

METHODS

Animals were subjected to different stressors for a period of 28 days. On day 15 after the subsequent stress procedure, mice were administered with (4a) (2 and 4 mg/kg p.o.), escitalopram (10 mg/kg p.o.), or vehicle (10 mL/kg p.o.) until day 28 along with the CUMS. Thereafter, behavioral battery tests like locomotor score, sucrose preference test, forced swim test (FST), tail suspension test (TST), and elevated plus maze (EPM) were performed. Biochemical assays like lipid peroxidation, nitrite levels, reduced glutathione (GSH), catalase, and superoxide dismutase (SOD) were estimated in the mice brain homogenate.

RESULTS

(4a) Dose dependently attenuated the behavioral alterations by increasing the sucrose consumption, reducing the immobility time in FST and TST, increasing the open arm number of entries and time in EPM. Furthermore, biochemical alterations were reversed by (4a) as examined by reduced lipid peroxidation and nitrite levels and elevated antioxidant enzyme levels like GSH, catalase and SOD.

CONCLUSIONS

(4a) exhibits antidepressant potential by reversing the CUMS induced behavioral and biochemical changes in mice.

Effects of ramosetron oral disintegrating tablets on gastric emptying: crossover study using the 13C-acetic acid breath test

BACKGROUND/AIMS

Ramosetron is a new selective 5-hydroxytryptamine type 3 (5-HT3) receptor antagonist that reportedly has more potent antiemetic effects than other 5-HT3 receptor antagonists. The aim of this study was to determine the effect of ramosetron pretreatment on gastric emptying using the 13C-acetic acid breath test.

METHODOLOGY

Ten healthy male and female volunteers participated in this randomized, twoway crossover study. After they had fasted overnight, the subjects were randomly assigned to receive 0.1 mg ramosetron 1 hour before ingestion of a test meal (200 kcal per 200 mL, containing 100 mg 13C acetate) or to receive the test meal alone. Under both conditions, breath samples were collected for 150 min following ingestion of the meal. Statistical comparison of the parameters between the two test conditions was performed.

RESULTS

No significant differences in the calculated parameters, including T 1/2, T lag, GEC or β and κ, were observed between the two test conditions.

CONCLUSIONS

The present study revealed that 0.1 mg ramosetron had no significant effect on the rate of gastric emptying. Thus, our results suggest that ramosetron can be administered safely, without gastrointestinal adverse effects, even to terminal cancer patients with delayed or accelerated gastric emptying abnormality.

Palonosetron versus first-generation 5-hydroxytryptamine type 3 receptor antagonists for emesis prophylaxis in patients undergoing allogeneic hematopoietic stem cell transplantation

First-generation 5-hydroxytryptamine type 3 (5-HT3) receptor antagonists (RAs) are currently the standard of care for prophylaxis against allo-HSCT-induced emesis. However, the efficacy of this combination in allo-HSCT recipients is not entirely satisfying. We sought to compare the efficacy of first-generation 5-HT3 RAs with that of second-generation 5-HT3 RAs in emesis prevention in allo-HSCT recipients. A total of 51 consecutive patients undergoing allo-HSCT for various hematological diseases in our institution were retrospectively reviewed. Patients who received daily first-generation 5-HT3 RAs, and 60-h palonosetron for emesis prophylaxis were stratified into the standard (n = 23) and palonosetron (n = 28) groups, respectively. Emesis severity and rescue therapy requirements in patients between these two groups were compared. Our results showed patients in standard and palonosetron groups had comparable severity of both acute and delayed emesis. However, 52.2 % of the patients in the standard group required rescue therapy, compared to only 21.4 % of the patients in the palonosetron group (p = 0.046). Subgroup analysis showed rescue therapy for acute emesis was required by 26.1 % of the patients in the standard group and by only 3.6 % of the patients in the palonosetron group (p = 0.037). In conclusion, palonosetron and first-generation 5-HT3 RAs were at least equally effective in emesis prophylaxis for allo-HSCT recipients. Patients receiving palonosetron, especially for acute emesis, required rescue therapy less frequently than those receiving first-generation 5-HT3 RAs.

Perioperative doses of ondansetron or dolasetron do not lengthen the QT interval

OBJECTIVE

To test the primary hypothesis that ondansetron or dolasetron extends the rate-corrected QT electrocardiographic interval (QTc) greater than 60 milliseconds or increases the fraction of patients with QTc greater than 500 milliseconds in patients having noncardiac surgery, and the secondary hypothesis that QTc prolongation is worse in diabetic patients.

PATIENTS AND METHODS

We extracted data from the Cleveland Clinic's Perioperative Health Documentation System between March 25, 2006, and September 30, 2010, and additional perioperative medications from Cleveland Clinic pharmacy's Epic Cost of Goods Sold (COGS) system. We searched for patients who had a preoperative electrocardiogram within 1 month of surgery and postoperatively within 2 hours. We excluded patients given an antiemetic drug other than ondansetron or dolasetron perioperatively, and those given amiodarone.

RESULTS

A total of 1429 patients given serotonin-3 receptor (5HT3R) antagonists and 1022 controls met the enrollment criteria. Seventeen percent of patients given 5HT3R antagonists (n=242) and 22% of controls (n=220) had postoperative QTc exceeding 500 milliseconds. Mean ± SD presurgical and postsurgical QTc, respectively, were 438±37 milliseconds and 464±41 milliseconds for 5HT3R antagonist patients and 443±40 milliseconds and 469±47 milliseconds for control patients. Univariable mean ± SD perioperative increases in QTc were 26±39 and 26±48 milliseconds in the 2 groups. After adjusting for confounding variables, there were no differences in the mean increase in QTc in patients who were and were not given 5HT3R antagonists: -0.1 milliseconds (97.5% CI, -5.2 to 5.0 milliseconds; multivariable P=.97). The QTc was prolonged, but not significantly, in diabetic patients given 5HT3R antagonists (P=.16).

CONCLUSIONS

The average QTc prolongation from baseline was only 6%. Perioperative use of ondansetron or dolasetron was not associated with extended QT prolongation, and these results did not vary by diabetic status. Perioperative use of 5HT3R antagonists does not produce potentially dangerous perioperative electrocardiographic changes and does not seem to warrant a drug safety warning from the Food and Drug Administration.

Netupitant PET imaging and ADME studies in humans

Netupitant is a new, selective NK1 receptor antagonist under development for the prevention of chemotherapy-induced nausea and vomiting. Two studies were conducted to evaluate the brain receptor occupancy (RO) and disposition (ADME) of netupitant in humans. Positron emission tomography (PET) imaging with the NK1 receptor-binding-selective tracer [(11) C]-GR205171 was used to evaluate the brain penetration of different doses of netupitant (100, 300, and 450 mg) and to determine the NK1 -RO duration. A NK1 -RO of 90% or higher was achieved with all doses in the majority of the tested brain regions at Cmax, with a long duration of RO. The netupitant minimal plasma concentration predicted to achieve a NK1 -RO of 90%, C90% , in the striatum was 225 ng/mL; after administration of netupitant 300 mg, concentrations exceeded the C90% . In the ADME study, a single nominal dose of [(14) C]-netupitant 300 mg was used to assess its disposition. Absorption was rapid and netupitant was extensively metabolized via Phase I and II hepatic metabolism. Elimination of >90% was predicted at day 29 and was principally via hepatic/biliary route (>85%) with a minor contribution of the renal route (<5%). In conclusion, these studies demonstrate that netupitant is a potent agent targeting NK1 receptors with long lasting RO. In addition, netupitant is extensively metabolized and is mainly eliminated through the hepatic/biliary route and to a lesser extent via the kidneys.

Selective serotonin 3 receptor antagonist treatment for schizophrenia: meta-analysis and systematic review

Double-blinded, randomized, placebo-control trials of selective serotonin 3 receptor antagonists (5-HT3R-ANTs) for schizophrenia have differed in outcome. This meta-analysis tests the hypothesis that 5-HT3R-ANTs are effective for the treatment for schizophrenia. We searched PubMed, the Cochrane Library database, and PsycINFO up to June 15, 2013. We conducted a systematic review and meta-analysis of individual patient data from randomized controlled trials comparing 5-HT3R-ANTs add-on therapy with placebo. The risk ratio (RR), 95 % confidence intervals (CI), and standardized mean difference (SMD) were calculated. A random-effects model was used. Six studies (total n = 311) were identified. These included one granisetron plus risperidone study, one ondansetron plus risperidone study, one ondansetron plus haloperidol, and three tropisetron plus risperidone studies. The statistically significant effects of 5-HT3R-ANTs add-on therapy on Positive and Negative Syndrome Scale (PANSS) total scores were SMD = -1.03, CI = -1.70 to -0.36, p = 0.003 (I (2) = 82 %, 5 studies, n = 261); on negative scores were SMD = -1.10, CI = -1.82 to -0.39, p = 0.002 (I (2) = 84 %, 5 studies, n = 261); and on PANSS general scores were SMD = -0.70, CI = -1.23 to -0.17, p = 0.01 (I (2) = 73 %, 5 studies, n = 261). However, 5-HT3R-ANTs add-on therapy was not superior to placebo in PANSS positive scores (SMD = -0.12, p = 0.33). Dropout due to all cause (RR = 0.80, p = 0.50), inefficacy (RR = 0.76, p = 0.65), or adverse events (RR = 0.84, p = 0.75) was similar in both groups. Constipation occurred significantly more often with 5-HT3R-ANTs than placebo (RR = 2.05, CI = 1.07-3.91, p = 0.03, NNH = 11, p = 0.02). 5-HT3R-ANTs add-on therapy is more beneficial on the psychopathology (especially negative symptoms) than controls in patients with schizophrenia, and 5-HT3R-ANTs seem to be well-tolerated treatments.

Spinal 5-HT3 receptors facilitate behavioural hypersensitivity induced by elevated calcium channel alpha-2-delta-1 protein

BACKGROUND

Peripheral nerve injury induces up-regulation of the calcium channel alpha-2-delta-1 proteins in the dorsal root ganglia and dorsal spinal cord that correlates with neuropathic pain development. Similar behavioural hypersensitivity was also observed in injury-free transgenic (TG) mice over-expressing the alpha-2-delta-1 proteins in neuronal tissues. To investigate pathways regulating alpha-2-delta-1 protein-mediated behavioural hypersensitivity, we examined whether spinal serotonergic 5-HT3 receptors are involved similarly in the modulation of behavioural hypersensitivity induced by either peripheral nerve injury in a nerve injury model or neuronal alpha-2-delta-1 over-expression in the TG model.

METHODS

The effects of blocking behavioural hypersensitivity in these two models by intrathecal or systemic injections of 5-HT3 receptor antagonist, ondansetron, were compared.

RESULTS

Our data indicated that the TG mice displayed similar behavioural hypersensitivities to non-painful mechanical stimulation (tactile allodynia) and painful thermal stimulation (thermal hyperalgesia) as that observed in the nerve injury model. Interestingly, tactile allodynia and thermal hyperalgesia in both models can be blocked similarly by intrathecal, but not systemic, injection of ondansetron.

CONCLUSIONS

Our data suggest that spinal 5-HT3 receptors are likely to play a role in alpha-2-delta-1-mediated behavioural hypersensitivities through a descending serotonergic facilitation.

[The effects of selective 5HT3 receptor blockade on physiological markers of abdominal pain in awake dogs]

In awake dogs, the visceromotor and cardioautonomic responses to the rectal balloon distension were studied before and after intravenous administration of a selective 5HT3 receptor antagonist granisetron. It was shown that balloon distension level up to 60 mmHg caused neither noticeable muscle responses nor substantial changes in heart rate. In turn, distending pressures of 80 mmHg and higher induced vigorous abdominal muscle contractions and tachycardia that were graded with increasing intensities of stimulation. Thus, the rectal stimulation with pressures 80 mmHg and more produced the changes in visceromotor and cardiovascular indices which could be considered as suitable indicators of visceral nociception in conscious animals. Based on monitoring of these physiological markers in a model of abdominal pain the dose-dependent antinociceptive effect of granisetron in awake dogs has been demonstrated for the first time. It was determined that granisetron in doses of 0.25, 0.5 or 1.0 mg/kg induced correspondingly 33.6 +/- 9.2, 58.0+/- 8.6 [see text] 76.7 +/- 5.5 % decrease in visceromotor response of dogs to nociceptive visceral stimulation. The effect occurred immediately after the drug administration and was lasting more than 90 min. In turn, the dose-dependent suppression of the rectal distension-induced tachycardia was less prominent and only observed during the initial period of granisetron action. The described model of abdominal pain in awake dogs might be useful for preclinical screening of new pharmacological substances, whereas the obtained data could contribute to the development of more efficient analgesics aimed in patients with irritable bowel syndrome.

Antidepressant and anxiolytic-like effects of 4n, a novel 5-HT3 receptor antagonist using behaviour based rodent models

The present study was designed to investigate the putative antidepressant and anxiolytic-like effects of N-n-Butylquinoxalin-2-carboxamide (4n), a novel 5-HT3 receptor antagonist, with an optimal log P (2.01) and pA2 value (7.3) greater than ondansetron (6.9) using rodent behavioural models of depression and anxiety. Acute treatment of 4n (1-4 mg/kg, ip) in mice produced antidepressant-like effect in forced swim test (FST) without affecting the baseline locomotion in actophotometer test in mice. 4n (2-4 mg/kg, ip) treatment also potentiated the 5-hydroxytryptophan (5-HTP) induced head twitch response in mice. Further, 4n (1-4 mg/kg, ip) treatment antagonized reserpine induced hypothermia in rats. Chronic treatment (14 days) with 4n (1-4 mg/kg) and paroxetine (10 mg/kg) significantly attenuated the behavioural anomalies induced by bilateral olfactory bulbectomy in rats in modified open field paradigm. An anxiogenic-like behaviour was induced by light alone as the stimulus using light-dark aversion test. 4n (2-4 mg/kg, ip) treatment significantly increased no. of transitions between dark and lit area and the time spent in the lit area. In conclusion, these preliminary investigations confirm that 4n exhibited antidepressant and anxiolytic-like effects in rodent models of depression and anxiety.

Ondansetron pretreatment reduces pain on injection of propofol

To assess the effectiveness of ondansetron pretreatment in alleviating propofol injection pain, 135 patients were randomly assigned to one of following three groups. Group 1 who received up to 2 mL pretreatment 50 mg tramadol in the saline, group 2 cases who received up to 2 mL pretreatment 4 mg ondansetron in saline, and group 3 who received up to 2 mL solution saline. A 20 gauge cannula was placed into the largest vein on the dorsum of the hand. Tourniquet was closed to the arm above the cannula and inflates to 70 mmHg, and then drug was injected. After 20 seconds, the tourniquet deflated, and propofol 2mg/kg injected over 10 seconds and pain assessment was made.

RESULTS

Tramadol and ondansetron significantly reduced the incidence and severity of propofol injection pain more than placebo (P=0.001). The efficacy of ondansetron in alleviating the pain on injection of propofol was no different from tramadol (P=0.330). Ondansetron pretreatment may be used to reduce the incidence of pain on injection of propofol, an advantage added to the useful prevention of postoperative nausea and vomiting.

Anti-depressant-like activity of a novel serotonin type-3 (5-HT3) receptor antagonist in rodent models of depression

N-Cyclohexyl-3-methoxyquinoxalin-2-carboxamide (QCM-13), a novel 5-HT3 antagonist identified from a series of compounds with higher pA2 (7.6) and good log P (2.91) value was screened in rodent models of depression such as forced swim test (FST), tail suspension test (TST), interaction studies with standard anti-depressants and confirmatory studies such as reversal of parthenolide induced depression and reserpine induced hypothermia. In FST (2 and 4 mg/kg) and TST (2 and 4 mg/kg), QCM-13 significantly reduced the duration of immobility in mice without affecting the base line locomotion. QCM-13 (2 and 4 mg/kg) was also found to have significant interaction with standard anti-depressants (fluoxetine and bupropion in FST and TST respectively). Further, reversal of parthenolide induced depression in mice and reserpine induced hypothermia in rat models indicate the serotonergic influence of QCM-13 for anti-depressant potential.

Serotonin-3 receptors in the posterior ventral tegmental area regulate ethanol self-administration of alcohol-preferring (P) rats

Several studies indicated the involvement of serotonin-3 ([5-hydroxy tryptamine] 5-HT(3)) receptors in regulating alcohol-drinking behavior. The objective of this study was to determine the involvement of 5-HT(3) receptors within the ventral tegmental area (VTA) in regulating ethanol self-administration by alcohol-preferring (P) rats. Standard two-lever operant chambers (Coulbourn Instruments, Allentown, PA) were used to examine the effects of seven consecutive bilateral microinfusions of ICS 205-930 (ICS), a 5-HT(3) receptor antagonist, directly into the posterior VTA on the acquisition and maintenance of 15% (vol/vol) ethanol self-administration. P rats readily acquired ethanol self-administration by the fourth session. The three highest doses (0.125, 0.25, and 1.25 microg) of ICS prevented acquisition of ethanol self-administration. During the acquisition postinjection period, all rats treated with ICS demonstrated higher responding on the ethanol lever, with the highest dose producing the greatest effect. In contrast, during the maintenance phase, the three highest doses (0.75, 1.0, and 1.25 microg) of ICS significantly increased responding on the ethanol lever; after the 7-day dosing regimen, responding on the ethanol lever returned to control levels. Microinfusion of ICS into the posterior VTA did not alter the low responding on the water lever and did not alter saccharin (0.0125% wt/v) self-administration. Microinfusion of ICS into the anterior VTA did not alter ethanol self-administration. Overall, the results of this study suggest that 5-HT(3) receptors in the posterior VTA of the P rat may be involved in regulating ethanol self-administration. In addition, chronic operant ethanol self-administration and/or repeated treatments with a 5-HT(3) receptor antagonist may alter neuronal circuitry within the posterior VTA.