Opportunities for the replacement of animals in the study of nausea and vomiting

Evaluating the Presence of Disgust in Animals

The emotion of disgust in humans is widely considered to represent a continuation of the disease-avoidance behavior ubiquitous in animals. The extent to which analogs of human disgust are evident in nonhuman animals, however, remains unclear. The scant research explicitly investigating disgust in animals has predominantly focused on great apes and suggests that disgust might be present in a highly muted form. In this review, we outline the main approaches to disgust. We then briefly discuss disease-avoidance behavior in nonhuman animals, proposing a set of criteria against which evidence for the presence or absence of disgust in animals can be evaluated. The resultant decision tree takes into account other plausible causes of avoidance and aversion when evaluating whether it is likely that the behavior represents disgust. We apply this decision tree to evaluate evidence of disgust-like behavior (e.g., avoidance of carrion and avoidance of feces-contaminated food) in several examples, including nonhuman great apes. Finally, we consider the large disparity between disgust in humans compared to muted disgust in other great apes, examining the possibility that heightened disgust in humans is a relatively recent cultural acquisition.

Assessment of Quercetin Antiemetic Properties: In Vivo and In Silico Investigations on Receptor Binding Affinity and Synergistic Effects

Quercetin (QUA), a flavonoid compound, is ubiquitously found in plants and has demonstrated a diverse range of biological activities. The primary objective of the current study is to assess the potential antiemetic properties of QUA using an in vivo and in silico approach. In this experiment, 4-day-old chicks were purchased to induce emesis by orally administering copper sulfate pentahydrate (CuSO4·5H2O) at a dose of 50 mg/kg (orally). Domperidone (DOM) (6 mg/kg), Hyoscine (HYS) (21 mg/kg), and Ondansetron (OND) (5 mg/kg) were treated as positive controls (PCs), and distilled water and a trace amount of Tween 80 mixture was employed as a negative control (NC). QUA was given orally at two distinct doses (25 and 50 mg/kg). Additionally, QUA (50 mg/kg) and PCs were administered separately or in combination to assess their antagonistic or synergistic effects on the chicks. The binding affinity of QUA and referral ligands towards the serotonin receptor (5HT3), dopamine receptors (D2 and D3), and muscarinic acetylcholine receptors (M1-M5) were estimated, and ligand-receptor interactions were visualized through various computational tools. In vivo findings indicate that QUA (25 and 50 mg/kg) has a significant effect on reducing the number of retches (16.50 ± 4.65 and 10.00 ± 4.19 times) and increasing the chick latency period (59.25 ± 4.75 and 94.25 ± 4.01 s), respectively. Additionally, QUA (50 mg/kg) in combination with Domperidone and Ondansetron exhibited superior antiemetic effects, reducing the number of retches and increasing the onset of emesis-inducing time. Furthermore, it is worth noting that QUA exhibited the strongest binding affinity against the D2 receptor with a value of -9.7 kcal/mol through the formation of hydrogen and hydrophobic bonds. In summary, the study found that QUA exhibited antiemetic activity in chicks, potentially by interacting with the D2 receptor pathway.

Placebo effects on nausea and motion sickness are resistant to experimentally-induced stress

Nausea often occurs in stressful situations, such as chemotherapy or surgery. Clinically relevant placebo effects in nausea have been demonstrated, but it remains unclear whether stress has an impact on these effects. The aim of this experimental study was to investigate the interplay between acute stress and placebo effects in nausea. 80 healthy female volunteers susceptible to motion sickness were randomly assigned to either the Maastricht Acute Stress Test or a non-stress control condition, and to either placebo treatment or no treatment. Nausea was induced by a virtual vection drum and behavioral, psychophysiological as well as humoral parameters were repeatedly assessed. Manipulation checks confirmed increased cortisol levels and negative emotions in the stressed groups. In the non-stressed groups, the placebo intervention improved nausea, symptoms of motion sickness, and gastric myoelectrical activity (normo-to-tachy (NTT) ratio). In the stressed groups, the beneficial effects of the placebo intervention on nausea and motion sickness remained unchanged, whereas no improvement of the gastric NTT ratio was observed. Results suggest that placebo effects on symptoms of nausea and motion sickness are resistant to experimentally-induced stress. Stress most likely interfered with the validity of the gastric NTT ratio to measure nausea and thus the gastric placebo effect.

Evidence for the efficacy of the emetic PP796 in paraquat SL20 formulations - a narrative review of published and unpublished evidence

BACKGROUND

The bipyridyl herbicide paraquat was first introduced into agriculture in the 1960s by Imperial Chemical Industries. Due to issues with unintentional poisoning, the centrally acting emetic PP796 was added in 1976 to the company's 20% paraquat ion soluble liquid (SL20) formulations (Gramoxone^®) at a concentration of 0.5 g/L or 0.05% (equivalent to 0.071 mg/kg in a 70 kg adult ingesting a minimum lethal dose of 10 mL) to induce early vomiting (within 30 min), reduce paraquat absorption from the gut, and prevent deaths. Its presence in paraquat products was subsequently mandated by the Food and Agriculture Organization Committee of Experts on Pesticides in Agriculture (predecessor to the current FAO/WHO Joint Meeting on Pesticide Specifications). However, no primary pre-clinical or clinical data have been published regarding the effectiveness of PP796. We reviewed the published literature and unpublished company reports for data on the effectiveness of PP796.

METHODS

PubMed and Google were searched for published studies on the emetic using the search terms "paraquat" and ["emetic" or "PP796"]. Company documents reporting pre-clinical and clinical studies were accessed at the website of U.S. Right to Know (https://usrtk.org/pesticides/paraquat-papers/). Primary study reports were sought as well as overviews written by company toxicologists.

RESULTS

Pre-clinical dog and monkey studies indicated that the PP796 EC50 dose for vomiting was around 0.5-2 mg/kg. Further increasing the PP796 concentration speeded up the time to first vomit and reduced the amount of paraquat absorbed (as assessed by the 0-24 h plasma area-under-the-curve) 100-fold compared to a control group receiving no PP796. However, the dose selected for paraquat SL20 formulations by the company (0.5 g/L or 0.05%) was based exclusively on a phase II study in the early 1970s involving five volunteers receiving 3 different doses, with only two individuals actually vomiting, supplemented by data from 37 patients taking 2 mg in clinical trials. A UK-mandated toxicovigilance study in the 1980s identified only 21 patients ingesting paraquat SL20 with PP796 for whom data on time to vomit was available; of these patients, 11 vomited within 30 min (52.4%, 95%CI 31-73.7%). No effect on mortality could be identified from any study of paraquat SL containing 0.05% PP796. A clinical study in Sri Lanka 30 years after the emetic was first introduced, of a revised formulation (Gramoxone^® Inteon) containing a three-fold higher amount of PP796, as well as MgSO4 and an alginate, showed increased rates of early vomiting and modestly reduced mortality for patients ingesting up to 100 mL.

CONCLUSION

Pre-clinical studies showed a clear dose response for PP796 to cause early vomiting, with effective doses in the 0.5-20 mg/kg range. A too low concentration of PP796 was selected for paraquat formulations based on an inadequate phase II study. Currently, evidence that PP796 at 0.05% in paraquat SL20 causes more rapid vomiting after ingestion is weak or unpublished; no evidence of clinical benefit or fewer deaths has been identified. There is no evidence to support the FAO/WHO Joint Meeting on Pesticide Specifications mandate to include PP796 or any other emetic in paraquat products. Products with higher emetic concentrations have been developed but are not widely used; it is possible they may prevent deaths.

Discovery of M3 Antagonist-PDE4 Inhibitor Dual Pharmacology Molecules for the Treatment of Chronic Obstructive Pulmonary Disease

In this paper, we report the discovery of dual M₃ antagonist-PDE4 inhibitor (MAPI) compounds for the inhaled treatment of pulmonary diseases. The identification of dual compounds was enabled by the intuition that the fusion of a PDE4 scaffold derived from our CHF-6001 series with a muscarinic scaffold through a common linking ring could generate compounds active versus both the transmembrane M₃ receptor and the intracellular PDE4 enzyme. Two chemical series characterized by two different muscarinic scaffolds were investigated. SAR optimization was aimed at obtaining M₃ nanomolar affinity coupled with nanomolar PDE4 inhibition, which translated into anti-bronchospastic efficacy ex vivo (inhibition of rat trachea contraction) and into anti-inflammatory efficacy in vitro (inhibition of TNFα release). Among the best compounds, compound 92a achieved the goal of demonstrating in vivo efficacy and duration of action in both the bronchoconstriction and inflammation assays in rat after intratracheal administration.

New Associations between Drug-Induced Adverse Events in Animal Models and Humans Reveal Novel Candidate Safety Targets

To improve our ability to extrapolate preclinical toxicity to humans, there is a need to understand and quantify the concordance of adverse events (AEs) between animal models and clinical studies. In the present work, we discovered 3011 statistically significant associations between preclinical and clinical AEs caused by drugs reported in the PharmaPendium database of which 2952 were new associations between toxicities encoded by different Medical Dictionary for Regulatory Activities terms across species. To find plausible and testable candidate off-target drug activities for the derived associations, we investigated the genetic overlap between the genes linked to both a preclinical and a clinical AE and the protein targets found to interact with one or more drugs causing both AEs. We discuss three associations from the analysis in more detail for which novel candidate off-target drug activities could be identified, namely, the association of preclinical mutagenicity readouts with clinical teratospermia and ovarian failure, the association of preclinical reflexes abnormal with clinical poor-quality sleep, and the association of preclinical psychomotor hyperactivity with clinical drug withdrawal syndrome. Our analysis successfully identified a total of 77% of known safety targets currently tested in in vitro screening panels plus an additional 431 genes which were proposed for investigation as future safety targets for different clinical toxicities. This work provides new translational toxicity relationships beyond AE term-matching, the results of which can be used for risk profiling of future new chemical entities for clinical studies and for the development of future in vitro safety panels.

Predictive in silico modeling of emetic potency of liquid cleaning products using an historical in vivo database

The induction of vomiting by activation of mechanisms protecting the body against ingested toxins is not confined to natural products but can occur in response to manmade medicinal and non-medicinal products such as liquid cleaning products where it is a commonly reported adverse effect of accidental ingestion. The present study examined the utility of an historic database (>30 years old) reporting emetic effects of 98 orally administered liquid cleaning formulations studied in vivo (canine model) to objectively identify the main pro-emetic constituents and to derive a predictive model. Data were analysed by categorizing the formulation constituents into 10 main groups followed by using multivariate correlation, partial least squares and recursive partitioning analysis. Using the ED₅₀ we objectively identified high ionic strength, non-ionic surfactants (alcohol ethoxylate) and alkaline pH as the main pro-emetic factors. Additionally, a mathematical model was developed which allows prediction of the ED₅₀ based on formulation. The limitations of the use of historic data and the model are discussed. The results have practical applications in new product formulation and safety but additionally the principles underpinning this in silico study have wider applicability in demonstrating the potential utility of such archival data in current research contributing to animal replacement.

Nanotechnology based blended chitosan-pectin hybrid for safe and efficient consolidative antiemetic and neuro-protective effect of meclizine hydrochloride in chemotherapy induced emesis

The aim of this study was to formulate an easily-administered, safe and effective dosage form loaded with meclizine for treatment of chemotherapy-induced nausea and vomiting (CINV) through the buccal route. CINV comprises bothersome side effects accompanying cytotoxic drugs administration in cancer patients. Meclizine was loaded in chitosan-pectin nanoparticles which were further incorporated within a buccal film. Different formulations were prepared based on a 2¹.3¹ full factorial study using Design Expert®8. The optimum formulation possessed favorable characters regarding its particle size (129 nm), entrapment efficiency (90%) and release profile. Moreover, its permeation efficiency through sheep buccal mucosa was assessed via Franz cell diffusion and confocal laser microscopy methods. Enhanced permeation was achieved compared with the free drug form. In-vivo performance was assessed using cyclophosphamide induced emesis. The proposed formulation exerted significant relief of the measured responses (reduced body weight and motor coordination, elevated emesis, anorexia, proinflammatory mediators and neurotransmitters that were also associated with scattered degenerated neurons and glial cells). The developed formulation ameliorated all behavioral, biochemical and histopathological changes induced by cyclophosphamide. The obtained data were promising suggesting that our bioadhesive formulation can offer an auspicious medication for treating distressing symptoms associated with chemotherapy for cancer patients.

Developing in vitro assays to transform gastrointestinal safety assessment: potential for microphysiological systems

Drug-induced gastrointestinal toxicities (DI-GITs) are among the most common adverse events in clinical trials. High prevalence of DI-GIT has persisted among new drugs due in part to the lack of robust experimental tools to allow early detection or to guide optimization of safer molecules. Developing in vitro assays for the leading GI toxicities (nausea, vomiting, diarrhoea, constipation, and abdominal pain) will likely involve recapitulating complex physiological properties that require contributions from diverse cell/tissue types including epithelial, immune, microbiome, nerve, and muscle. While this stipulation may be beyond traditional 2D monocultures of intestinal cell lines, emerging 3D GI microtissues capture interactions between diverse cell and tissue types. These interactions give rise to microphysiologies fundamental to gut biology. For GI microtissues, organoid technology was the breakthrough that introduced intestinal stem cells with the capability of differentiating into each of the epithelial cell types and that self-organize into a multi-cellular tissue proxy with villus- and crypt-like domains. Recently, GI microtissues generated using miniaturized devices with microfluidic flow and cyclic peristaltic strain were shown to induce Caco2 cells to spontaneously differentiate into each of the principle intestinal epithelial cell types. Second generation models comprised of epithelial organoids or microtissues co-cultured with non-epithelial cell types can successfully reproduce cross-'tissue' functional interactions broadening the potential of these models to accurately study drug-induced toxicities. A new paradigm in which in vitro assays become an early part of GI safety assessment could be realized if microphysiological systems (MPS) are developed in alignment with drug-discovery needs. Herein, approaches for assessing GI toxicity of pharmaceuticals are reviewed and gaps are compared with capabilities of emerging GI microtissues (e.g., organoids, organ-on-a-chip, transwell systems) in order to provide perspective on the assay features needed for MPS models to be adopted for DI-GIT assessment.

The current state of animal models in research: A review

Animal models have provided invaluable information in the pursuit of medical knowledge and alleviation of human suffering. The foundations of our basic understanding of disease pathophysiology and human anatomy can largely be attributed to preclinical investigations using various animal models. Recently, however, the scientific community, citing concerns about animal welfare as well as the validity and applicability of outcomes, has called the use of animals in research into question. In this review, we seek to summarize the current state of the use of animal models in research.

An assay of drug-induced emesis in the squirrel monkey (Saimiri sciureus)

BACKGROUND

Emesis has significant evolutionary value as a defense mechanism against ingested toxins; however, it is also one of the most common adverse symptoms associated with both disease and medical treatments of disease. The development of improved antiemetic pharmacotherapies has been impeded by a shortage of animal models.

METHODS

The present studies characterized the responses of the squirrel monkey to pharmacologically diverse emetic drugs. Subjects were administered nicotine (0.032-0.56 mg/kg), lithium chloride (150-250 mg/kg), arecoline (0.01-0.32 mg/kg), or apomorphine (0.032-0.32 mg/kg) and observed for emesis and prodromal hypersalivation.

RESULTS

Nicotine rapidly produced emesis and hypersalivation. Lithium chloride produced emesis with a longer time course without dose-dependent hypersalivation. Arecoline produced hypersalivation but not emesis. Apomorphine failed to produce emesis or hypersalivation.

CONCLUSIONS

The squirrel monkey is sensitive to drug-induced emesis by a variety of pharmacological mechanisms and is well-positioned to examine antiemetic efficacy and clinically important side effects of candidate antiemetic pharmacotherapies.

A History of Drug Discovery for Treatment of Nausea and Vomiting and the Implications for Future Research

The origins of the major classes of current anti-emetics are examined. Serendipity is a recurrent theme in discovery of their anti-emetic properties and repurposing from one indication to another is a continuing trend. Notably, the discoveries have occurred against a background of company mergers and changing anti-emetic requirements. Major drug classes include: (i) Muscarinic receptor antagonists-originated from historical accounts of plant extracts containing atropine and hyoscine with development stimulated by the need to prevent sea-sickness among soldiers during beach landings; (ii) Histamine receptor antagonists-searching for replacements for the anti-malaria drug quinine, in short supply because of wartime shipping blockade, facilitated the discovery of histamine (H1) antagonists (e.g., dimenhydrinate), followed by serendipitous discovery of anti-emetic activity against motion sickness in a patient undergoing treatment for urticaria; (iii) Phenothiazines and dopamine receptor antagonists-investigations of their pharmacology as "sedatives" (e.g., chlorpromazine) implicated dopamine receptors in emesis, leading to development of selective dopamine (D2) receptor antagonists (e.g., domperidone with poor ability to penetrate the blood-brain barrier) as anti-emetics in chemotherapy and surgery; (iv) Metoclopramide and selective 5-hydroxytryptamine3(5-HT3) receptor antagonists-metoclopramide was initially assumed to act only via D2 receptor antagonism but subsequently its gastric motility stimulant effect (proposed to contribute to the anti-emetic action) was shown to be due to 5-hydroxytryptamine4 receptor agonism. Pre-clinical studies showed that anti-emetic efficacy against the newly-introduced, highly emetic, chemotherapeutic agent cisplatin was due to antagonism at 5-HT3 receptors. The latter led to identification of selective 5-HT3 receptor antagonists (e.g., granisetron), a major breakthrough in treatment of chemotherapy-induced emesis; (v) Neurokinin1receptor antagonists-antagonists of the actions of substance P were developed as analgesics but pre-clinical studies identified broad-spectrum anti-emetic effects; clinical studies showed particular efficacy in the delayed phase of chemotherapy-induced emesis. Finally, the repurposing of different drugs for treatment of nausea and vomiting is examined, particularly during palliative care, and also the challenges in identifying novel anti-emetic drugs, particularly for treatment of nausea as compared to vomiting. We consider the lessons from the past for the future and ask why there has not been a major breakthrough in the last 20 years.

Safety of xylo-oligosaccharides (XOS) as a novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver a scientific opinion on a mixture of xylo-oligosaccharides (XOS) as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF is obtained from corncobs (Zea mays subsp. mays) via enzyme-catalysed hydrolysis and subsequent purification. The main components of the NF, the oligosaccharides, are resistant to human digestive enzymes and are fermented by colonic bacteria. The intention is to add the NF to a variety of foods such as bakery and dairy products, fruit jelly, chocolates and soy-drinks. The information provided on composition, specifications, production process and stability of the NF, does not raise safety concerns. There were effects observed in the animal studies with the NF or with other XOS which were considered by the Panel to be expected from the intake of non-digestible carbohydrates. The Panel notes that the acute and transient gastrointestinal observed in human intervention studies with the NF or with other XOS have also been associated with the consumption of other non-digestible carbohydrates. The Panel concludes that the NF, a mixture of XOS, is safe under the proposed uses and use levels. The target population is the general population.

Ghrelin projection from the lateral hypothalamus area to the dorsal vagal complex and its regulation of gastric motility in cisplatin-treated rats

OBJECTIVE

To investigate ghrelin projection from the lateral hypothalamus area (LHA) to the dorsal vagal complex (DVC) and its regulation of gastric motility in cisplatin-treated rats.

MATERIALS AND METHODS

In the present study, the protein and mRNA expression of ghrelin and its receptor GHSR-1a were measured by Western blot and PCR, respectively. The ghrelin fiber projections arising from the LHA and projecting to the DVC were investigated by retrograde tracing combined with fluoro-immunohistochemical staining. The effects of ghrelin in the DVC, electrical stimulation of the LHA, and electrical lesion of the DVC on gastric motility were measured in cisplatin-treated rats.

RESULTS

Ghrelin fibers originating in the LHA projected to the DVC. The protein and mRNA expression of GHSR-1a was greater in cisplatin-treated rats than in saline-treated rats. Conversely, the expression of ghrelin in the LHA and DVC was reduced in cisplatin-treated rats. Cisplatin treatment also reduced gastric contractions. Ghrelin administrated into the DVC significantly promoted gastric motility, an effect completely blocked by treatment with the ghrelin receptor antagonist [D-Lys-3]-GHRP-6. In addition, electrical stimulation of the LHA promoted gastric motility, though this effect was much weaker in cisplatin-treated rats than in control rats. The excitatory effect of electrical stimulation of the LHA on gastric motility was partially blocked by pretreatment of the DVC with [D-Lys-3]-GHRP-6. Electrical lesion of the DVC diminished the excitatory effect that was induced by electrical stimulation of the LHA.

CONCLUSIONS

DVC, especially AP, may have a role for gastric contraction induced by the stimulation of the LHA. This regulation on gastric motility was weaker in cisplatin-treated rats than in saline-treated rats, possibly due to reduced ghrelin expression in the LHA and ghrelin projection from the LHA to the DVC.

Gastric myoelectric activity during cisplatin-induced acute and delayed emesis reveals a temporal impairment of slow waves in ferrets: effects not reversed by the GLP-1 receptor antagonist, exendin (9-39)

Preclinical studies show that the glucagon-like peptide-1 (GLP-1) receptor antagonist, exendin (9-39), can reduce acute emesis induced by cisplatin. In the present study, we investigate the effect of exendin (9-39) (100 nmol/24 h, i.c.v), on cisplatin (5 mg/kg, i.p.)-induced acute and delayed emesis and changes indicative of ‘nausea’ in ferrets. Cisplatin induced 37.2 ± 2.3 and 59.0 ± 7.7 retches + vomits during the 0-24 (acute) and 24-72 h (delayed) periods, respectively. Cisplatin also increased (P<0.05) the dominant frequency of gastric myoelectric activity from 9.4 ± 0.1 to 10.4 ± 0.41 cpm and decreased the dominant power (DP) during acute emesis; there was a reduction in the % power of normogastria and an increase in the % power of tachygastria; food and water intake was reduced. DP decreased further during delayed emesis, where normogastria predominated. Advanced multifractal detrended fluctuation analysis revealed that the slow wave signal shape became more simplistic during delayed emesis. Cisplatin did not affect blood pressure (BP), but transiently increased heart rate, and decreased heart rate variability (HRV) during acute emesis; HRV spectral analysis indicated a shift to ‘sympathetic dominance’. A hyperthermic response was seen during acute emesis, but hypothermia occurred during delayed emesis and there was also a decrease in HR. Exendin (9-39) did not improve feeding and drinking but reduced cisplatin-induced acute emesis by ~59 % (P<0.05) and antagonised the hypothermic response (P<0.05); systolic, diastolic and mean arterial BP increased during the delayed phase. In conclusion, blocking GLP-1 receptors in the brain reduces cisplatin-induced acute but not delayed emesis. Restoring power and structure to slow waves may represent a novel approach to treat the side effects of chemotherapy.

Anti-nausea effects and pharmacokinetics of ondansetron, maropitant and metoclopramide in a low-dose cisplatin model of nausea and vomiting in the dog: a blinded crossover study

BACKGROUND

Nausea is a subjective sensation which is difficult to measure in non-verbal species. The aims of this study were to determine the efficacy of three classes of antiemetic drugs in a novel low dose cisplatin model of nausea and vomiting and measure change in potential nausea biomarkers arginine vasopressin (AVP) and cortisol. A four period cross-over blinded study was conducted in eight healthy beagle dogs of both genders. Dogs were administered 18 mg/m² cisplatin intravenously, followed 45 min later by a 15 min infusion of either placebo (saline) or antiemetic treatment with ondansetron (0.5 mg/kg; 5-HT₃ antagonist), maropitant (1 mg/kg; NK₁ antagonist) or metoclopramide (0.5 mg/kg; D₂ antagonist). The number of vomits and nausea associated behaviours, scored on a visual analogue scale, were recorded every 15 min for 8 h following cisplatin administration. Plasma samples were collected to measure AVP, cortisol and antiemetic drug concentrations.

RESULTS

The placebo treated group vomited an average number of 7 times (range 2-13). None of the dogs in either the ondansetron or maropitant treated groups vomited during the observation period. The onset of nausea-like behaviour in the placebo-treated group occurred at t_3.5h and peaked at t_4.75h with nausea behaviour score of 58.5 ± 4.6 mm. Ondansetron and maropitant reduced overall the area under the curve of nausea behaviour score by 90% and 25%, respectively. Metoclopramide had no effect on either vomiting or nausea. Cisplatin-induced nausea and vomiting caused concomitant increases in AVP and cortisol. In the placebo-treated group, AVP and cortisol increased from t_2.5h, peaked at t_5h (11.3 ± 2.9 pmol L^-1 and 334.0 ± 46.7 nmol/L, respectively) and returned to baseline by t_8h. AVP and cortisol increases were completely prevented by ondansetron and only partially by maropitant, while metoclopramide had no effect. The terminal half-lives (harmonic mean ± pseudo SD) for ondansetron, maropitant and metoclopramide were 1.21 ± 0.51, 5.62 ± 0.77 and 0.87 ± 0.17 h respectively.

CONCLUSIONS

5-HT₃ receptor antagonist ondansetron demonstrates the greatest anti-emetic and anti-nausea efficacy of the three drugs. AVP and cortisol appear to be selective biomarkers of nausea rather than emesis, providing a means of objectively measuring of nausea in the dog.

Alterations in the small intestinal wall and motor function after repeated cisplatin in rat

BACKGROUND

Gastrointestinal adverse effects occurring during cancer chemotherapy are well known and feared; those persisting once treatment has finished are relatively unknown. We characterized the alterations occurring in the rat small intestine, after repeated treatment with cisplatin.

METHODS

Male Wistar rats received saline or cisplatin (2 mg kg^-1  week^-1 , for 5 weeks, ip). Gastric motor function was studied non-invasively throughout treatment (W1-W5) and 1 week after treatment finalization (W6). During W6, upper gastrointestinal motility was also invasively studied and small intestinal samples were collected for histopathological and molecular studies. Structural alterations in the small intestinal wall, mucosa, submucosa, muscle layers, and lymphocytic nodules were histologically studied. Periodic acid-Schiff staining and immunohistochemistry for Ki-67, chromogranin A, and neuronal-specific enolase were used to detect secretory, proliferating, endocrine and neural cells, respectively. The expression of different markers in the tunica muscularis was analyzed by RT/qPCR.

KEY RESULTS

Repeated cisplatin induced motility alterations during and after treatment. After treatment (W6), the small intestinal wall showed histopathological alterations in most parameters measured, including a reduction in the thickness of circular and longitudinal muscle layers. Expression of c-KIT (for interstitial cells of Cajal), nNOS (for inhibitory motor neurons), pChAT, and cChAT (for excitatory motor neurons) increased significantly (although both ChATs to a lesser extent).

CONCLUSIONS & INFERENCES

Repeated cisplatin induces relatively long-lasting gut dysmotility in rat associated with important histopathological and molecular alterations in the small intestinal wall. In cancer survivors, the possible chemotherapy-induced histopathological, molecular, and functional intestinal sequelae should be evaluated.

Studies To Examine Potential Tolerability Differences between the 5-HT2C Receptor Selective Agonists Lorcaserin and CP-809101

Lorcaserin (LOR) is a selective 5-HT_2C receptor agonist that has been FDA approved as a treatment for obesity. The most frequently reported side-effects of LOR include nausea and headache, which can be dose limiting. We have previously reported that in the rat, while LOR produced unconditioned signs characteristic of nausea/malaise, the highly selective 5-HT_2C agonist CP-809101 (CP) produced fewer equivalent signs. Because this may indicate a subclass of 5-HT_2C agonists having better tolerability, the present studies were designed to further investigate this apparent difference. In a conditioned gaping model, a rodent test of nausea, LOR produced significantly higher gapes compared to CP consistent with it having higher emetogenic properties. Subsequent studies were designed to identify features of each drug that may account for such differences. In rats trained to discriminate CP-809101 from saline, both CP and LOR produced full generalization suggesting a similar interoceptive cue. In vitro tests of functional selectivity designed to examine signaling pathways activated by both drugs in CHO (Chinese hamster ovary) cells expressing h5-HT_2C receptors failed to identify evidence for biased signaling differences between LOR and CP. Thus, both drugs showed similar profiles across PLC, PLA₂, and ERK signaling pathways. In studies designed to examine pharmacokinetic differences between LOR and CP, while drug plasma levels correlated with increasing dose, CSF levels did not. CSF levels of LOR increased proportionally with dose; however CSF levels of CP plateaued from 6 to 12 mg/kg. Thus, the apparently improved tolerability of CP likely reflects a limit to CNS levels attained at relatively high doses.

Involvement of Cannabinoid Signaling in Vincristine-Induced Gastrointestinal Dysmotility in the Rat

Background: In different models of paralytic ileus, cannabinoid receptors are overexpressed and endogenous cannabinoids are massively released, contributing to gastrointestinal dysmotility. The antitumoral drug vincristine depresses gastrointestinal motility and a similar mechanism could participate in this effect. Therefore, our aim was to determine, using CB₁ and CB₂ antagonists, whether an increased endocannabinoid tone is involved in vincristine-induced gastrointestinal ileus.

Methods: First, we confirmed the effects of vincristine on the gut mucosa, by conventional histological techniques, and characterized its effects on motility, by radiographic means. Conscious male Wistar rats received an intraperitoneal injection of vincristine (0.1–0.5 mg/kg), and barium sulfate (2.5 ml; 2 g/ml) was intragastrically administered 0, 24, or 48 h later. Serial X-rays were obtained at different time-points (0–8 h) after contrast. X-rays were used to build motility curves for each gastrointestinal region and determine the size of stomach and caecum. Tissue samples were taken for histology 48 h after saline or vincristine (0.5 mg/kg). Second, AM251 (a CB₁ receptor antagonist) and AM630 (a CB₂ receptor antagonist) were used to determine if CB₁ and/or CB₂ receptors are involved in vincristine-induced gastrointestinal dysmotility.

Key results: Vincristine induced damage to the mucosa of ileum and colon and reduced gastrointestinal motor function at 0.5 mg/kg. The effect on motor function was particularly evident when the study started 24 h after administration. AM251, but not AM630, significantly prevented vincristine effect, particularly in the small intestine, when administered thrice. AM251 alone did not significantly alter gastrointestinal motility.

Conclusions: The fact that AM251, but not AM630, is capable of reducing the effect of vincristine suggests that, like in other experimental models of paralytic ileus, an increased cannabinoid tone develops and is at least partially responsible for the alterations induced by the antitumoral drug on gastrointestinal motor function. Thus, CB₁ antagonists might be useful to prevent/treat ileus induced by vincristine.

Ghrelin fibers from lateral hypothalamus project to nucleus tractus solitaries and are involved in gastric motility regulation in cisplatin-treated rats

Ghrelin can alleviate cancer chemotherapy-induced dyspepsia in rodents, though the neural mechanisms involved are not known. Therefore, ghrelin projections from the lateral hypothalamus (LH) and its involvement in the regulation of gastric motility in cisplatin-treated rats were investigated with a multi-disciplined approach. Retrograde tracing combined with fluoro-immunohistochemical staining were used to investigate ghrelin fiber projections arising from LH and projecting to nucleus tractus solitaries (NTS). Results revealed that ghrelin fibers originating in LH project to NTS. Expression of ghrelin and its receptor growth hormone secretagogue receptor (GHS-R1a) in LH and NTS were detected by Western Blot. 2days after cisplatin dosing, expression of ghrelin in LH decreased while GHS-R1a in both LH and NTS increased. In electrophysiological experiments, the effects of N-methyl-d-aspartate (NMDA) microinjection in LH on neuronal discharge of gastric distension-responsive neurons in NTS and gastric motility were assessed. NMDA in LH excited most of ghrelin-responsive gastric distension (GD)-sensitive neurons in NTS and promoted gastric motility. This effect was partially blocked by ghrelin antibody in NTS. Furthermore, the excitatory effects of NMDA in cisplatin-treated rats were weaker than those in saline-treated rats. Behaviorally, cisplatin induced a significant increase of kaolin consumption and decrease of food intake. These studies reveal a decreased expression of ghrelin in LH and up-regulation of GHS-R1a in LH and NTS, which are involved in the regulation of GD neuronal discharge in NTS and gastric motility.

He-Wei granules inhibit chemotherapy-induced vomiting (CINV) in rats by reducing oxidative stress and regulating 5-HT, substance P, ghrelin and obestatin

As a common side effect of a variety of chemotherapy drugs, CINV severely limits the clinical use of chemotherapy drugs.

Cannabinoids As Potential Treatment for Chemotherapy-Induced Nausea and Vomiting

Despite the advent of classic anti-emetics, chemotherapy-induced nausea is still problematic, with vomiting being somewhat better managed in the clinic. If post-treatment nausea and vomiting are not properly controlled, anticipatory nausea—a conditioned response to the contextual cues associated with illness-inducing chemotherapy—can develop. Once it develops, anticipatory nausea is refractive to current anti-emetics, highlighting the need for alternative treatment options. One of the first documented medicinal uses of Δ⁹-tetrahydrocannabinol (Δ⁹-THC) was for the treatment of chemotherapy-induced nausea and vomiting (CINV), and recent evidence is accumulating to suggest a role for the endocannabinoid system in modulating CINV. Here, we review studies assessing the therapeutic potential of cannabinoids and manipulations of the endocannabinoid system in human patients and pre-clinical animal models of nausea and vomiting.

What is nausea? A historical analysis of changing views

The connotation of "nausea" has changed across several millennia. The medical term 'nausea' is derived from the classical Greek terms ναυτια and ναυσια, which designated the signs and symptoms of seasickness. In classical texts, nausea referred to a wide range of perceptions and actions, including lethargy and disengagement, headache (migraine), and anorexia, with an awareness that vomiting was imminent only when the condition was severe. However, some recent articles have limited the definition to the sensations that immediately precede emesis. Defining nausea is complicated by the fact that it has many triggers, and can build-up slowly or rapidly, such that the prodromal signs and symptoms can vary. In particular, disengagement responses referred to as the "sopite syndrome" are typically present only when emetic stimuli are moderately provocative, and do not quickly culminate in vomiting or withdrawing from the triggering event. This review considers how the definition of "nausea" has evolved over time, and summarizes the physiological changes that occur prior to vomiting that may be indicative of nausea. Also described are differences in the perception of nausea, as well as the accompanying physiological responses, that occur with varying stimuli. This information is synthesized to provide an operational definition of nausea.

The importance of systematic approaches in the study of emesis

Nausea and vomiting are among the most basic of human experiences and unfortunately accompany a wide variety of clinical treatments as side effects. Despite decades of research, the neural mechanisms of nausea and vomiting (emesis) remain elusive. TRPV1 represents a possibly overlooked and understudied pharmacological target with anti-emetic potential.

Gastrointestinal Safety Pharmacology in Drug Discovery and Development

Although the basic structure of the gastrointestinal tract (GIT) is similar across species, there are significant differences in the anatomy, physiology, and biochemistry between humans and laboratory animals, which should be taken into account when conducting a gastrointestinal (GI) assessment. Historically, the percentage of cases of drug attrition associated with GI-related adverse effects is small; however, this incidence has increased over the last few years. Drug-related GI effects are very diverse, usually functional in nature, and not limited to a single pharmacological class. The most common GI signs are nausea and vomiting, diarrhea, constipation, and gastric ulceration. Despite being generally not life-threatening, they can greatly affect patient compliance and quality of life. There is therefore a real need for improved and/or more extensive GI screening of candidate drugs in preclinical development, which may help to better predict clinical effects. Models to identify drug effects on GI function cover GI motility, nausea and emesis liability, secretory function (mainly gastric secretion), and absorption aspects. Both in vitro and in vivo assessments are described in this chapter. Drug-induced effects on GI function can be assessed in stand-alone safety pharmacology studies or as endpoints integrated into toxicology studies. In silico approaches are also being developed, such as the gut-on-a-chip model, but await further optimization and validation before routine use in drug development. GI injuries are still in their infancy with regard to biomarkers, probably due to their greater diversity. Nevertheless, several potential blood, stool, and breath biomarkers have been investigated. However, additional validation studies are necessary to assess the relevance of these biomarkers and their predictive value for GI injuries.

The involvement of TRPV1 in emesis and anti-emesis

Diverse transmitter systems (e.g. acetylcholine, dopamine, endocannabinoids, endorphins, glutamate, histamine, 5-hydroxytryptamine, substance P) have been implicated in the pathways by which nausea and vomiting are induced and are targets for anti-emetic drugs (e.g. 5-hydroxytryptamine₃ and tachykinin NK₁ antagonists). The involvement of TRPV1 in emesis was discovered in the early 1990s and may have been overlooked previously as TRPV1 pharmacology was studied in rodents (mice, rats) lacking an emetic reflex. Acute subcutaneous administration of resiniferatoxin in the ferret, dog and Suncus murinus revealed that it had “broad–spectrum” anti-emetic effects against stimuli acting via both central (vestibular system, area postrema) and peripheral (abdominal vagal afferents) inputs. One of several hypotheses discussed here is that the anti-emetic effect is due to acute depletion of substance P (or another peptide) at a critical site (e.g. nucleus tractus solitarius) in the central emetic pathway. Studies in Suncus murinus revealed a potential for a long lasting (one month) effect against the chemotherapeutic agent cisplatin. Subsequent studies using telemetry in the conscious ferret compared the anti-emetic, hypothermic and hypertensive effects of resiniferatoxin (pungent) and olvanil (non-pungent) and showed that the anti-emetic effect was present (but reduced) with olvanil which although inducing hypothermia it did not have the marked hypertensive effects of resiniferatoxin. The review concludes by discussing general insights into emetic pathways and their pharmacology revealed by these relatively overlooked studies with TRPV1 activators (pungent an non-pungent; high and low lipophilicity) and antagonists and the potential clinical utility of agents targeted at the TRPV1 system.

The impact of vehicle motion during transport on animal welfare

Motion sickness is a common response in humans and some species of farm livestock during transport, but research on the impact of motion has been primarily focused on the use of animal models for humans. During livestock transportation, animals seek to minimise uncontrolled movements to reduce energy consumption and maintain posture. Road and sea transport of livestock can produce motion sickness and stress responses. Clinical signs are the result of autonomous nervous system activation. Studies conducted on road transportation effects in domestic animals showed several motion sickness behaviours including vomiting and, in ruminants, a reduction in rumination. However, there is a lack of knowledge on the impact of sea transport motion. Despite the paucity of data on livestock, there is sufficient evidence to believe that motion might affect animal welfare when animals are transported by road or sea.

Pioneering better science through the 3Rs: an introduction to the national centre for the replacement, refinement, and reduction of animals in research (NC3Rs)

The National Centre for the Replacement, Refinement, and Reduction of Animals in Research (NC3Rs) is an independent scientific organization that is based in the United Kingdom, which was set up by the government to lead the discovery and application of new technologies and approaches that minimize the use of animals in research and improve animal welfare. The NC3Rs uses a range of strategies to improve and advance science through application of the 3Rs. These include funding basic research, open innovation (CRACK IT), and programs run by inhouse scientists. We present several case studies from the NC3Rs portfolio, featuring asthma research, the use of nonhuman primates in monoclonal antibody development, and CRACK IT. Finally, we anticipate the future, as we use our experience to move into new research fields and expand toward international collaboration. Here we highlight how equipping scientists with relevant and emerging 3Rs tools can help overcome the challenges and limitations of the use of animals in research to the benefit of the whole bioscience community.

Visually induced nausea causes characteristic changes in cerebral, autonomic and endocrine function in humans

An integrated understanding of the physiological mechanisms involved in the genesis of nausea remains lacking. We aimed to describe the psychophysiological changes accompanying visually induced motion sickness, using a motion video, hypothesizing that differences would be evident between subjects who developed nausea in comparison to those who did not. A motion, or a control, stimulus was presented to 98 healthy subjects in a randomized crossover design. Validated questionnaires and a visual analogue scale (VAS) were used for the assessment of anxiety and nausea. Autonomic and electrogastrographic activity were measured at baseline and continuously thereafter. Plasma vasopressin and ghrelin were measured in response to the motion video. Subjects were stratified into quartiles based on VAS nausea scores, with the upper and lower quartiles considered to be nausea sensitive and resistant, respectively. Twenty-eight subjects were exposed to the motion video during functional neuroimaging. During the motion video, nausea-sensitive subjects had lower normogastria/tachygastria ratio and cardiac vagal tone but higher cardiac sympathetic index in comparison to the control video. Furthermore, nausea-sensitive subjects had decreased plasma ghrelin and demonstrated increased activity of the left anterior cingulate cortex. Nausea VAS scores correlated positively with plasma vasopressin and left inferior frontal and middle occipital gyri activity and correlated negatively with plasma ghrelin and brain activity in the right cerebellar tonsil, declive, culmen, lingual gyrus and cuneus. This study demonstrates that the subjective sensation of nausea is associated with objective changes in autonomic, endocrine and brain networks, and thus identifies potential objective biomarkers and targets for therapeutic interventions.

Differential hypoglycaemic, anorectic, autonomic and emetic effects of the glucagon-like peptide receptor agonist, exendin-4, in the conscious telemetered ferret

Background

Rodents are incapable of emesis and consequently the emetic potential of glucagon-like peptide-1 receptor (GLP-1R) agonists in studies designed to assess a potential blood glucose lowering action of the compound was missed. Therefore, we investigated if the ferret, a carnivore with demonstrated translation capability in emesis research, would identify the emetic potential of the GLP-1R agonist, exendin-4, and any associated effects on gastric motor function, appetite and cardiovascular homeostasis.

Methods

The biological activity of the GLP-1R ligands was investigated in vivo using a glucose tolerance test in pentobarbitone-anesthetised ferrets and in vitro using organ bath studies. Radiotelemetry was used to investigate the effect of exendin-4 on gastric myoelectric activity (GMA) and cardiovascular function in conscious ferrets; behaviour was also simultaneously assessed. Western blot was used to characterize GLP-1R distribution in the gastrointestinal and brain tissues.

Results

In anesthetised ferrets, exendin-4 (30 nmol/kg, s.c.) reduced experimentally elevated blood glucose levels by 36.3%, whereas the GLP-1R antagonist, exendin (9–39) (300 nmol/kg, s.c.) antagonised the effect and increased AUC_0–120 by 31.0% when injected alone (P < 0.05). In animals with radiotelemetry devices, exendin-4 (100 nmol/kg, s.c.) induced emesis in 1/9 ferrets, but inhibited food intake and decreased heart rate variability (HRV) in all animals (P < 0.05). In the animals not exhibiting emesis, there was no effect on GMA, mean arterial blood pressure, heart rate, or core body temperature. In the ferret exhibiting emesis, there was a shift in the GMA towards bradygastria with a decrease in power, and a concomitant decrease in HRV. Western blot revealed GLP-1R throughout the gastrointestinal tract but exendin-4 (up to 300 nM) and exendin (9–39), failed to contract or relax isolated ferret gut tissues. GLP-1R were found in all major brain regions and the levels were comparable those in the vagus nerve.

Conclusions

Peripherally administered exendin-4 reduced blood glucose and inhibited feeding with a low emetic potential similar to that in humans (11% vs 12.8%). A disrupted GMA only occurred in the animal exhibiting emesis raising the possibility that disruption of the GMA may influence the probability of emesis occurring in response to treatment with GLP-1R agonists.

Nausea: current knowledge of mechanisms, measurement and clinical impact

Nausea is a subjective sensation, which often acts as a signal that emesis is imminent. It is a widespread problem that occurs as a clinical sign of disease or as an adverse effect of a drug therapy or surgical procedure. The mechanisms of nausea are complex and the neural pathways are currently poorly understood. This review summarises the current knowledge of nausea mechanisms, the available animal models for nausea research and the anti-nausea properties of commercially available anti-emetic drugs. The review also presents subjective assessment and scoring of nausea. A better understanding of the underlying mechanisms of nausea might reveal potential clinically useful biomarkers for objective measurement of nausea in species of veterinary interest.

Measuring the nausea-to-emesis continuum in non-human animals: refocusing on gastrointestinal vagal signaling

Nausea and vomiting are ubiquitous as drug side effects and symptoms of disease; however, the systems that determine these responses are arguably designed for protection against food poisoning occurring at the level of the gastrointestinal (GI) tract. This basic biological pathway using GI vagal afferent communication to the brain is not well understood. Part of this lack of insight appears to be related to current experimental approaches, such as the use of experimental drugs, including systemic chemotherapy and brain penetrant agents, which activate parts of the nausea and vomiting system in potentially unnatural ways. Directly related to this issue is our ability to understand the link between nausea and vomiting, which are sometimes argued to be completely separate processes, with nausea as an unmeasurable response in animal models. An argument is made that nausea and emesis are the efferent limbs of a unified sensory input from the GI tract that is likely to be impossible to understand without more specific animal electrophysiological experimentation of vagal afferent signaling. The current paper provides a review on the use of animal models and approaches to defining the biological systems for nausea and emesis and presents a potentially testable theory on how these systems work in combination.

The role of the parasympathetic nervous system in visually induced motion sickness: systematic review and meta-analysis

The parasympathetic nervous system (PNS) has been implicated in the development of visually induced motion sickness. The objective of this study was to perform a systematic review and meta-analysis of the effect of visually induced motion sickness on validated parameters of PNS tone. Methods followed PRISMA recommendations. Controlled trials reporting validated measures of PNS tone in visually induced motion sickness in healthy adults were included. One reviewer performed the screening of articles and data extraction, and two reviewers independently performed methodological evaluation. Data were synthesised using standardised mean differences (SMDs) for all relevant outcomes using a random-effects model. Publication bias was assessed via funnel plots and Egger's test. The search strategy identified seven citations comprising 237 healthy individuals. The mean quality score was 4/10 (range 3-7). There was no difference between baseline PNS tone between individuals who developed visually induced motion sickness and those that did not. Visually induced motion sickness (VIMS)-sensitive individuals had a reduction in PNS tone, following exposure to the stimulus (mean weighted SMD = -0.45, 95% confidence interval -0.64 to -0.27, Z = -4.8, p < 0.0001). There was no evidence of heterogeneity or publication bias. These data suggest that baseline PNS parameters do not provide a useful measure of predicting the probability of developing visually induced motion sickness. However, a fall in PNS tone, as indicated by cardiac activity, is characteristic in sensitive individuals. Further work is needed to characterise these responses in clinical populations, in conjunction with improvements and standardisation in study design.

A novel human receptor involved in bitter tastant detection identified using Dictyostelium discoideum

Detection of substances tasting bitter to humans occurs in diverse organisms including the social amoeba Dictyostelium discoideum. To establish a molecular mechanism for bitter tastant detection in Dictyostelium, we screened a mutant library for resistance to a commonly used bitter standard, phenylthiourea. This approach identified a G-protein-coupled receptor mutant, grlJ(-), which showed a significantly increased tolerance to phenylthiourea in growth, survival and movement. This mutant was not resistant to a structurally dissimilar potent bitter tastant, denatonium benzoate, suggesting it is not a target for at least one other bitter tastant. Analysis of the cell-signalling pathway involved in the detection of phenylthiourea showed dependence upon heterotrimeric G protein and phosphatidylinositol 3-kinase activity, suggesting that this signalling pathway is responsible for the cellular effects of phenylthiourea. This is further supported by a phenylthiourea-dependent block in the transient cAMP-induced production of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) in wild-type but not grlJ(-) cells. Finally, we have identified an uncharacterized human protein γ-aminobutyric acid (GABA) type B receptor subunit 1 isoform with weak homology to GrlJ that restored grlJ(-) sensitivity to phenylthiourea in cell movement and PIP3 regulation. Our results thus identify a novel pathway for the detection of the standard bitter tastant phenylthiourea in Dictyostelium and implicate a poorly characterized human protein in phenylthiourea-dependent cell responses.

Duodenal application of Li+ in a submaximal therapeutic dose inhibits exocrine pancreatic secretion and modulates gastro-duodenal myoelectrical activity in a conscious pig model

This study tested whether duodenal application of lithium inhibits gastroduodenal motility, and whether it suppresses secretion from the exocrine pancreas. Five suckling pigs, 16–18 days old, were surgically fitted with 3 serosal electrodes on the wall of the gastric antrum and the duodenum for electromyography of smooth muscles, and with a pancreatic duct catheter and a duodenal T-cannula for collection and re-entrant flow of pancreatic juice. After the recovery period, on alternative days, each animal was tested once with an intraduodenal infusion of Li+ (100 mmol·L–1C3H5LiO3,10 mL·kg−1·h−1) for 1 h, and once with an intraduodenal infusion of NaCl (154 mM, 10 ml·kg−1·h−1), also for 1 h, with the first treatment, i.e., Li+ or NaCl, randomly assigned. Individual pigs served as their own controls, with data recorded prior to a treatment being used as the baseline. Li+ increased the duration of quiescence (P < 0.05) and activity phase (P < 0.05) in the antrum, thus increasing (P < 0.05) the duration of antral myoelectrical cycles. Li+ shortened (P < 0.05) phase I, but it did not affect phase II or phase III or the MMC in the duodenum. Li+ inhibited pancreatic juice outflow as well as pancreatic enzyme and bicarbonate output (P < 0.05 for all pancreatic parameters).

Pearls and pitfalls in experimental in vivo models of headache: Conscious behavioral research

Background

Physiological studies have been determinant for the understanding of migraine pathophysiology and the screening of novel therapeutics. At present, there is no animal model that translates fully the clinical symptoms of migraine, and generally these studies are conducted on anesthetized animals.

Methodology

Pain as well as non-painful symptoms such as photophobia, need to have a conscious individual to be experienced; therefore, the new development and adaptation of behavioral assays assessing pain and other non-painful symptomatology in conscious animals represents a great opportunity for headache research and it is exciting that more and more researchers are using behavioral paradigms.

Summary

This review will describe the different behavioral models for the study of headache that are performed in non-anesthetized conscious animals. The pearls and challenges for measuring hypersensitivity in rodents such as the common tests for measuring mechanical allodynia and thermal hyperalgesia have been the landmark for the development of assays that measure hypersensitivity in the craniofacial region. Here we describe the different behavioral assays that measure hypersensitivity in the craniofacial region as well as the established behavioral models of trigeminovascular nociception and non-nociceptive migrainous symptoms.

Cannabinoids may worsen gastric dysmotility induced by chronic cisplatin in the rat

BACKGROUND

Although cannabinoids have traditionally been used for the treatment and/or prevention of nausea and/or emesis, anorexia and weight loss induced by clinical use of antineoplastic drugs, their efficacy and safety in long-term treatments are still controversial. Our aim was to analyze the effects of the non-selective cannabinoid agonist WIN 55 212-2 (WIN) on gastrointestinal (GI) dysmotility and other adverse effects induced by repeated cisplatin administration in the rat.

METHODS

Male Wistar rats received two intraperitoneal injections once a week for 4 weeks: the first one was WIN, at non-psychoactive doses (0.5 or 1 mg kg(-1)), its vehicle or saline; the second one was cisplatin (2 mg kg(-1)) or saline. Radiographic techniques were used to determine the acute (after first dose), chronic (after last dose), and residual (1 week after treatment finalization) effects of cisplatin and/or WIN on GI motility. Bodyweight gain, food ingestion, and mechanical sensitivity were also tested.

KEY RESULTS

Weekly cisplatin induced mechanical allodynia, which WIN prevented, as well as weight gain reduction and anorexia, which WIN did not. Gastric emptying was dose-dependently delayed by cisplatin and this effect was enhanced upon chronic treatment. WIN aggravated cisplatin-induced gastric dysmotility. One week after treatment finalization, only minor alterations of GI motor function were found in rats treated with cisplatin, WIN or both.

CONCLUSIONS & INFERENCES

WIN weekly administered at low doses prevents neuropathy, but does not prevent anorexia or weight loss and aggravates gastric dysmotility induced by cisplatin. Cannabinoids should be handled with caution if chronically administered during chemotherapy.

Evaluation of chemically diverse 5-HT₂c receptor agonists on behaviours motivated by food and nicotine and on side effect profiles

RATIONALE

Selective 5-HT2C receptor agonists, such as lorcaserin, are being developed for the treatment of obesity. Studies suggest that they may also have therapeutic potential for addictive behaviours including nicotine dependence, although few drugs of this class have been evaluated.

OBJECTIVES

The primary aim was to evaluate the highly selective 5-HT2C agonist, CP-809101, against food-motivated (operant FR5 and progressive ratio schedules, palatability-induced feeding) and nicotine-motivated (intravenous self-administration, drug discrimination) behaviours in rats and to compare with equivalent findings for the structurally distinct 5-HT2C receptor agonists lorcaserin and Ro 60-0175. The secondary aims were to evaluate the side effect profiles of lorcaserin and CP-809101 and to determine the plasma levels of lorcaserin at a dose (1 mg/kg) that reduces both food and nicotine reinforcement for comparison to plasma concentrations reported in human trials.

RESULTS

CP-809101 (0.3-3 mg/kg SC) reduced responding for both nicotine and food and blocked the discriminative stimulus properties of nicotine in a similar manner to lorcaserin and Ro 60-0175. Behaviours such as hypolocomotion, chewing and ptosis became evident following both CP-809101 and lorcaserin administration at higher doses. Plasma levels of lorcaserin were of similar range to those reported in obesity trials.

CONCLUSIONS

These studies support the utility of 5-HT2C agonists as a therapeutic approach to treat nicotine dependence. Plasma exposure levels after acute lorcaserin treatment suggest that equivalent dosages could be used to evaluate these drugs in obesity and smoking cessation trials. Finally, there may be differences in the side effect profiles between lorcaserin and CP-809101, raising the possibility for tolerability differences amongst 5-HT2C agonists.

Separation of emetic and anorexic responses of exendin-4, a GLP-1 receptor agonist in Suncus murinus (house musk shrew)

The use of glucagon-like peptide-1 (7-36) amide (GLP-1) receptor agonists for the treatment of type 2 diabetes mellitus is commonly associated with nausea and vomiting. Therefore, the present studies investigated the potential of GLP-1 receptor ligands to modulate emesis and feeding in Suncus murinus. Exendin-4, a selective GLP-1 receptor agonist, was administered subcutaneously (1-30 nmol/kg) or intracerebroventricularly (0.03-3 nmol) after 12-h of fasting. In other studies, animals were pretreated with the GLP-1 receptor antagonist, exendin (9-39), or saline (5 μl) 15 min prior to exendin-4 (3 nmol, i.c.v.). Behaviour of animals and food and water intake were then recorded for 1-2 h; c-Fos expression was also assessed in the brains of animals in the i.c.v. studies. The subcutaneous administration of exendin-4 reduced food and water intake (p < 0.001) and induced emesis in 40% of animals (p > 0.05). The intracerebroventricular administration of exendin-4 also prevented feeding, and induced emesis (p < 0.01). In these studies, exendin (9-39) (30 nmol, i.c.v.) antagonised emesis induced by exendin-4 and the increased c-Fos expressions in the brainstem and hypothalamus (p < 0.05), but it was ineffective in reversing the exendin-4-induced inhibition of food and water intake (p > 0.05). These data suggest that exendin-4 exerts its emetic effects in the brainstem and/or hypothalamus via GLP-1 receptors. The action of exendin-4 to suppress feeding may involve non-classical GLP-1 receptors or other mechanisms.

Predicting the emetic liability of novel chemical entities: a comparative study

BACKGROUND AND PURPOSE

Emesis is a multi-system reflex, which is usually investigated using in vivo models. The aim of the study is to compare the response induced by emetic compounds across species and investigate whether dogs, ferrets and rats are all similarly predictive of humans.

EXPERIMENTAL APPROACH

A systematic review was carried out and relevant publications were identified from PubMed. The search was restricted to four species (human, dog, ferret, rat) and ten compounds representative of various mechanisms of emesis induction (apomorphine, cisplatin, cholecystokinin octapeptide, copper sulphate, cyclophosphamide, ipecacuanha, lithium chloride, morphine, nicotine, rolipram).

KEY RESULTS

1046 publications were reviewed, and 311 were included, the main reason for exclusion was the lack of quantitative data. Emetic or pica data were extracted as incidence, intensity or latency. All three animal species identified emetic liability but interspecies differences for dose sensitivity were detected.

CONCLUSIONS AND IMPLICATION

These results suggest that emetic liability can be reliably identified in a common laboratory species such as the rat. However, to evaluate the characteristics of the emetic response, no animal species is a universal predictor of emetic liability and the choice of species should be an informed decision based on the type of compound investigated. Limitations relating to the conduct and reporting of emesis studies were identified, the main ones being the lack of comparable outcome measures between human and animal data, and the limited availability of human data in the public domain.

Employment of a noninvasive magnetic method for evaluation of gastrointestinal transit in rats

AC Biosusceptometry (ACB) was previously employed towards recording gastrointestinal motility. Our data show a reliable and successful evaluation of gastrointestinal transit of liquid and solid meals in rats, considering the methods scarcity and number of experiments needed to endorsement of drugs and medicinal plants. ACB permits real time and simultaneous experiments using the same animal, preserving the physiological conditions employing both meals with simplicity and accuracy.

Refinement of the Charcoal Meal Study by Reduction of the Fasting Period

The aim of this investigation was to determine whether a shorter fasting period than the one historically employed for the charcoal meal test, could be used when measuring gastric emptying and intestinal transit within the same animal, and to ascertain whether the scientific outcome would be affected by this benefit to animal welfare. Rats and mice were fasted for 0, 3, 6 or 18 hours before the oral administration of vehicle or atropine. One hour later, the animals were orally administered a charcoal meal, then 20 minutes later, they were killed and the stomach and small intestine were removed. Intestinal transit time (the position of the charcoal front as a percentage of the total length of the small intestine) and relative gastric emptying (weight of stomach contents) were measured. Rats and mice fasted for six hours showed results for gastric emptying and intestinal transit which were similar to those obtained in animals fasted for 18 hours. Reducing the fasting period reduced the body weight loss in both species, and mice on shorter fasts could be group-housed, as hunger-induced fighting was lessened. Therefore, a fasting period of six hours was subsequently adopted for charcoal meal studies at our institution.