Involvement of substance P in the development of cisplatin-induced acute and delayed pica in rats

Evaluating proxies for motion sickness in rodent

Motions sickness (MS) occurs when the brain receives conflicting sensory signals from vestibular, visual and proprioceptive systems about a person's ongoing position and/or motion in relation to space. MS is typified by symptoms such as nausea and emesis and implicates complex physiological aspects of sensations and sensorimotor reflexes. Use of animal models has been integral to unraveling the physiological causality of MS. The commonly used rodents (rat and mouse), albeit lacking vomiting reflex, reliably display phenotypic behaviors of pica (eating of non-nutritive substance) and conditioned taste aversion (CTAver) or avoidance (CTAvoi) which utilize neural substrates with pathways that cause gastrointestinal malaise akin to nausea/emesis. As such, rodent pica and CTAver/CTAvoi have been widely used as proxies for nausea/emesis in studies dealing with neural mechanisms of nausea/emesis and MS, as well as for evaluating therapeutics. This review presents the rationale and experimental evidence that support the use of pica and CTAver/CTAvoi as indices for nausea and emesis. Key experimental steps and cautions required when using rodent MS models are also discussed. Finally, future directions are suggested for studying MS with rodent pica and CTAver/CTAvoi models.

[Consideration of the Characteristics of Oral Iron Preparations from the Viewpoint of the Mechanism of Nausea and Vomiting]

The nausea and vomiting that occur as a result of oral iron administration for the treatment of iron-deficiency anemia (IDA) can cause significant physical and emotional stress in patients. Because iron is absorbed from the intestine as ferrous iron, the most widely used treatment for IDA is oral ferrous agents. However, ferrous forms are more toxic than ferric forms because ferrous forms readily generate free radicals. A randomized, double-blind, active-controlled, multicenter non-inferiority study conducted in Japan showed that ferric citrate hydrate (FC) was just as effective as sodium ferrous citrate (SF) in the treatment of IDA, with a lower incidence of adverse reactions such as nausea and vomiting compared with SF. Animal studies have shown that chemotherapy-induced nausea and vomiting (CINV) involves the release of 5-hydroxytryptamine from enterochromaffin cells by free radicals, and that some chemotherapeutic agents cause hyperplasia of these cells. Enterochromaffin cells also contain substance P, which is known to be also closely related to CINV. We found that administration of SF to rats causes hyperplasia of enterochromaffin cells in the small intestine, whereas FC has no effect on enterochromaffin cells. Oral iron agents may induce nausea and vomiting via the effect of ferrous iron on reactive oxygen species production in the intestine and subsequent enterochromaffin cell hyperplasia. Further research to elucidate the detailed mechanism of enterochromaffin cell hyperplasia induced by ferrous iron preparations is needed to develop a treatment for iron deficiency anemia that causes less gastrointestinal damage.

Glucose-Dependent Insulinotropic Polypeptide and Substance P Mediate Emetic Response Induction by Masked Trichothecene Deoxynivalenol-3-Glucoside through Ca2+ Signaling

Deoxynivalenol (DON), the most naturally-occurring trichothecenes, may affect animal and human health by causing vomiting as a hallmark of food poisoning. Deoxynivalenol-3-glucoside (D3G) usually co-occurs with DON as its glucosylated form and is another emerging food safety issue in recent years. However, the toxicity of D3G is not fully understood compared to DON, especially in emetic potency. The goals of this research were to (1) compare emetic effects to D3G by oral and intraperitoneal (IP) routes and relate emetic effects to brain-gut peptides glucose-dependent insulinotropic polypeptide (GIP) and substance P (SP) in mink; (2) determine the roles of calcium-sensing receptor (CaSR) and transient receptor potential (TRP) channel in D3G’s emetic effect. Both oral and IP exposure to D3G elicited marked emetic events. This emetic response corresponded to an elevation of GIP and SP. Blocking the GIP receptor (GIPR) diminished emetic response induction by GIP and D3G. The neurokinin 1 receptor (NK-1R) inhibitor Emend^® restrained the induction of emesis by SP and D3G. Importantly, CaSR antagonist NPS-2143 or TRP channel antagonist ruthenium red dose-dependently inhibited both D3G-induced emesis and brain-gut peptides GIP and SP release; cotreatment with both antagonists additively suppressed both emetic and brain-gut peptide responses to D3G. To summarize, our findings demonstrate that activation of CaSR and TRP channels contributes to D3G-induced emesis by mediating brain-gut peptide exocytosis in mink.

Current Approaches to Monitor Macromolecules Directly from the Cerebral Interstitial Fluid

Gaining insights into the pharmacokinetic and pharmacodynamic properties of lead compounds is crucial during drug development processes. When it comes to the treatment of brain diseases, collecting information at the site of action is challenging. There are only a few techniques available that allow for the direct sampling from the cerebral interstitial space. This review concerns the applicability of microdialysis and other approaches, such as cerebral open flow microperfusion and electrochemical biosensors, to monitor macromolecules (neuropeptides, proteins, …) in the brain. Microdialysis and cerebral open flow microperfusion can also be used to locally apply molecules at the same time at the site of sampling. Innovations in the field are discussed, together with the pitfalls. Moreover, the ‘nuts and bolts’ of the techniques and the current research gaps are addressed. The implementation of these techniques could help to improve drug development of brain-targeted drugs.

Substance P Increases the Excitability of Dorsal Motor Nucleus of the Vagus Nerve via Inhibition of Potassium Channels

Increases in the substance P (SP) concentration in the medial portion of the dorsal motor nucleus of the vagus nerve (mDMV) in the brainstem are closely associated with chemotherapy induced nausea and vomiting (CINV). However, the underlying cellular and molecular mechanisms of action are not well understood. In this study, we investigated the effects of SP on mDMV neurons using whole-cell patch-clamp recordings from rat brainstem slices. Application of different concentrations of SP induced tonic and phasic responses. Submicromolar concentrations of induced an inward shift of the holding current by increasing membrane input resistance. The response was mimicked by acidification of the extracellular solution and inhibited by a neurokinin type 1 receptor antagonist. These responses have equilibrium potentials close to the K⁺ equilibrium potential. In addition, a TWIK-related acid-sensitive K⁺ channel 3 (TASK-3) inhibitor, PK-THPP, induced responses similar to those produced by submicromolar SP concentrations. Micromolar concentrations of SP facilitated γ-aminobutyric acid (GABA) release but diminished glutamate release; these changes were blocked by a GABA_B receptor antagonist and a neurokinin type 3 receptor antagonist, respectively. In current-clamp recordings, submicromolar SP concentrations increased neuronal excitability by depolarizing membrane potentials. However, neither the increase in SP concentration to the micromolar range nor the addition of GABA_A and ionotropic glutamate receptor antagonists affected neuronal excitability. Thus, SP increases the excitability of mDMV neurons by inhibiting K⁺ conductance.

Effect and Mechanism of Herbal Medicines on Cisplatin-Induced Anorexia

Cisplatin is a well-known chemotherapeutic agent used to treat various types of cancers; however, it can also induce anorexia, which results in reduced food intake, loss of body weight, and lower quality of life. Although drugs such as megestrol acetate and cyproheptadine are used to decrease this severe feeding disorder, they can also induce side effects, such as diarrhea and somnolence, which limit their widespread use. Various types of herbal medicines have long been used to prevent and treat numerous gastrointestinal tract diseases; however, to date, no study has been conducted to analyze and summarize their effects on cisplatin-induced anorexia. In this paper, we analyze 12 animal studies that used either a single herbal medicine extract or mixtures thereof to decrease cisplatin-induced anorexia. Among the herbal medicines, Ginseng Radix was the most used, as it was included in seven studies, whereas both Glycyrrhizae Radix et Rhizoma and Angelicae Gigantis Radix were used in four studies. As for the mechanisms of action, the roles of serotonin and its receptors, cytokines, white blood cells, ghrelin, and leptin were investigated. Based on these results, we suggest that herbal medicines could be considered a useful treatment method for cisplatin-induced anorexia.

Mechanisms of Nausea and Vomiting: Current Knowledge and Recent Advances in Intracellular Emetic Signaling Systems

Nausea and vomiting are common gastrointestinal complaints that can be triggered by diverse emetic stimuli through central and/or peripheral nervous systems. Both nausea and vomiting are considered as defense mechanisms when threatening toxins/drugs/bacteria/viruses/fungi enter the body either via the enteral (e.g., the gastrointestinal tract) or parenteral routes, including the blood, skin, and respiratory systems. While vomiting is the act of forceful removal of gastrointestinal contents, nausea is believed to be a subjective sensation that is more difficult to study in nonhuman species. In this review, the authors discuss the anatomical structures, neurotransmitters/mediators, and corresponding receptors, as well as intracellular emetic signaling pathways involved in the processes of nausea and vomiting in diverse animal models as well as humans. While blockade of emetic receptors in the prevention of vomiting is fairly well understood, the potential of new classes of antiemetics altering postreceptor signal transduction mechanisms is currently evolving, which is also reviewed. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide potential answers.

Involvement of 5-Serotonin and Substance p Pathways in Dichroa Alkali Salt-Induced Acute Pica in Rats

Dichroa alkali salt (DAS) is the active ingredient of Changshan, a traditional Chinese antimalarial medicine. However, owing to its vomiting side effects, its clinical use is limited. Recently, DAS-induced vomiting has attracted broad attention; however, the mechanisms involved have not yet been elucidated. The present study aimed to explore DAS induced vomiting and decipher the potential role of the 5-serotonin (5-HT) and substance p (SP) signaling pathways. We used a combination of approaches in the context of a rat pica model, such as immunoblot analysis, HPLC-ECD, ELISA, quantitative real-time PCR, pharmacological inhibition, and immunohistochemistry assays. We demonstrated that DAS contributed to Changshan-induced vomiting via the activation of the 5-HT and SP signaling pathways. DAS could induce a dose-dependent kaolin intake in the rat pica model. Moreover, DAS caused a similar profile as Cisplatin (DDP): “low-dose double-peak, high-dose single-peak pica phenomenon”. Interestingly, treatment with DAS stimulated the peripheral ileum and central medulla oblongata and augmented the release of 5-HT, SP, and preprotachykinin-A and the expression of 5-HT₃ and NK₁ receptors in the two issues in acute phase. Additionally, the 5-HT₃ and NK₁ receptor antagonists effectively alleviated DAS-induced kaolin intake and significantly reduced DAS-induced 5-HT and SP levels in the two issues in acute phase. Similar responses were not observed in the context of dopamine receptor inhibition. This study innovatively revealed that the 5-HT and SP-mediated vomiting network plays an important role in DAS-induced acute vomiting; of note, ondansetron, and aprepitant can effectively antagonize DAS-induced vomiting. Our results suggest a potential therapeutic strategy (based on drugs approved for human use) to prevent the DAS-associated adverse reactions.

Prevention of cisplatin-induced nausea and vomiting by seabuckthorn (Hippophae rhamnoides L.) seed oil: Insights at the level of orexin-A in rats

OBJECTIVES

Nausea and vomiting are perennial problems in cancer patients undergoing chemotherapy. Orexin-A (OXA) has been shown to regulate feeding and gastric motility. Seabuckthorn (Hippophae rhamnoides L.) seed oil (SSO) has been proved to promote digestion and bowel movements. We investigated whether SSO alleviated cisplatin-induced vomiting and its possible mechanism involved in OXA.

MATERIALS AND METHODS

Rats were randomly divided into normal control group (NCG), cisplatin group (CG), SSO low-dose group (SLG), SSO middle-dose group (SMG) SSO high-dose group (SHG), and ondansetron group (OG). Rats were pretreated respectively with SSO (0.850, 1.675, and 3.350 g/kg·BW) and ondansetron (2 mg/kg·BW) in SLG, SMG, SHG, and OG for 6 days, and the same volume of saline in NCG and CG groups. On the 6th day, cisplatin (6 mg/kg, IP) was administered in all groups except NCG. The cumulative food and kaolin intake, gastric emptying, plasma OXA level, OX1R mRNA and protein expression in the hypothalamus and brainstem, and OXA expression in the lateral hypothalamic area (LHA) were observed, and the HPLC method was used to analyze the composition of SSO.

RESULTS

Kaolin intake in cisplatin-induced vomiting rats was significantly reduced (P<0.05) and gastric emptying delayed by cisplatin was improved (P<0.05-0.01) by pretreatment with SSO. Plasma OXA concentration, OX1R expression in the hypothalamus and brainstem increased significantly (P<0.05-0.01). Furthermore, OXA expression in LHA also increased significantly (P<0.05).

CONCLUSION

SSO prevents cisplatin-induced vomiting in rats, which is possibly involved in increasing peripheral and central OXA and the expression of OX1R in the hypothalamus and brainstem.

RNA-Seq reveals inflammatory mechanisms of Xiao-Ban-Xia-Tang decoction to ameliorate cisplatin-induced emesis in a rat pica model

OBJECTIVES

Xiao-Ban-Xia-Tang decoction (XBXT), an antiemetic formula in traditional Chinese medicine, has been proved to be a potential treatment for chemotherapy-induced nausea and vomiting (CINV), but the underlying mechanisms are not adequately understood. This study aimed to investigate changes in the ileum transcriptome after cisplatin and XBXT treatment and to reveal whether the antiemetic mechanisms of XBXT are related to its anti-inflammatory effect.

METHODS

The pica model was established by a single intraperitoneal injection of 6 mg/kg cisplatin in Wistar rats. Tissues from the gastric antrum and ileum were stained with hematoxylin-eosin to observe gastrointestinal tract pathological changes. Based on the differentially expressed genes (DEGs) which were altered by cisplatin and reversed by XBXT, the transcriptome data of rat ileum were analyzed by GO, KEGG, and PPI analyses. Several inflammatory DEGs were validated by RT-PCR.

RESULTS

XBXT could reduce kaolin intake up to 72 h after modeling and alleviate the inflammatory damage of gastric antrum and ileum induced by cisplatin. According to the transcriptome profile, there were 75 DEGs down-regulated by cisplatin and up-regulated by XBXT and 343 DEGs up-regulated by cisplatin and down-regulated by XBXT. XBXT could blunt the overexpression of tryptophan hydroxylase 1 (the rate-limiting enzyme of serotonin synthesis) in ileum. Enrichment analysis showed that inhibiting overexpression of several conventional inflammation pathways and pro-inflammation cytokines were related to the antiemetic effectiveness of XBXT.

CONCLUSIONS

This study implies that inhibiting inflammatory signaling pathways and synthesis of serotonin might be potential mechanisms of XBXT's antiemetic effect against CINV.

The Antiemetic Effect of Xiao-Ban-Xia-Tang Formula against Cisplatin-Induced Emesis is Mediated through Inhibition of NLRP3 Inflammasome Activation in a Rat Pica Model

Xiao-Ban-Xia-Tang (XBXT), a traditional Chinese medicine formula, has been used for the treatment of emesis for nearly 2000 years, but its underlying mechanism is not yet fully clarified. The purpose of this study is to reveal the antiemetic mechanisms of XBXT by focusing on the NLRP3 inflammasome pathway in a chemotherapy-induced rat pica model. The pica model was generated by a single intraperitoneal injection of cisplatin in this study. Consumption of kaolin (a type of clay) and food and body weight were recorded every 24 hours. Cisplatin-induced increase in kaolin consumption (pica) was used to quantify chemotherapy-induced nausea and vomiting (CINV). Tissue from the ileum and antrum was stained with hematoxylin eosin (HE) to observe pathological changes. The levels of reactive oxygen species (ROS) and inflammatory cytokines, including IL-1β and IL-18 in serum, were detected by ELISA. In addition, changes in the NLRP3 inflammasome activation in the ileum and antrum were investigated using western blot and immunofluorescence microscopy. The results showed that oral administration of XBXT and ondansetron inhibited acute and delayed pica and significantly protected against the gastrointestinal pathological injury induced by cisplatin. The levels of ROS, IL-1β, and IL-18 in the serum of cisplatin-treated rats were also remarkably decreased by XBXT and ondansetron. Moreover, we found that XBXT can inhibit cisplatin-induced NLRP3 inflammasome activation. The present study indicates that the inhibition of the NLRP3 inflammasome activation might be one of the potential mechanisms for the therapeutic effects of XBXT against CINV.

GDF15 Induces Anorexia through Nausea and Emesis

Growth differentiation factor 15 (GDF15) is a cytokine that reduces food intake through activation of hindbrain GFRAL-RET receptors and has become a keen target of interest for anti-obesity therapies. Elevated endogenous GDF15 is associated with energy balance disturbances, cancer progression, chemotherapy-induced anorexia, and morning sickness. We hypothesized that GDF15 causes emesis and that its anorectic effects are related to this function. Here, we examined feeding and emesis and/or emetic-like behaviors in three different mammalian laboratory species to help elucidate the role of GDF15 in these behaviors. Data show that GDF15 causes emesis in Suncus murinus (musk shrews) and induces behaviors indicative of nausea/malaise (e.g., anorexia and pica) in non-emetic species, including mice and lean or obese rats. We also present data in mice suggesting that GDF15 contributes to chemotherapy-induced malaise. Together, these results indicate that GDF15 triggers anorexia through the induction of nausea and/or by engaging emetic neurocircuitry.

Revisiting the physiology of nausea and vomiting-challenging the paradigm

PURPOSE

The predominant neurotransmitters and receptors for acute and delayed chemotherapy-induced nausea and vomiting (CINV) are represented in the current paradigm, which reflects successful control of emesis. However, control of nausea (N) lags behind management of vomiting (V). This review aims to re-examine and incorporate new information about the mechanisms of V and N.

METHODS

The initial literature search focused on CINV. Keywords in articles led to subsequent discovery of publications focused on N&V in other medical and scientific fields (e.g., gastroenterology, neurology, cannabinoid science, neuropharmacology, and motion sickness). Using keywords to identify other sources continued until no further recent, meaningful publications were found.

RESULTS

More than 86% of references were from recent non-oncology journals and books, suggesting there are many areas for cross-fertilization research into mechanisms and management of N&V-particularly of N, which involves overlapping and dissimilar CNS areas from V. Information from cited articles was incorporated into visual representation of N&V, which is certainly not exhaustive but supports highly complex processes in the stomach and gut, the vagus nerve and spinal cord neurons, the nucleus tractus solitarii, and the anterior insular cortex and anterior cingulate cortex with input from the amygdala.

CONCLUSIONS

These data support the idea that mechanisms for N, whatever the cause, must be highly similar. Continued research into nausea, including patient-reported evaluation and outcomes, is important; interventions for nausea could be considered adjuvants to current standard of care antiemetics and be individualized, depending on patient-reported efficacy and adverse effects and preferences.

Effects of ondansetron and [6]-gingerol on pica and gut microbiota in rats treated with cisplatin

Purpose

[6]-gingerol is one of the main components of ginger with many biological activities. In this study, the effects of ondansetron and [6]-gingerol on pica and gut microbiota in rats injected with cisplatin were evaluated.

Materials and methods

Rat model of cisplatin-induced pica was established, and the effects of ondansetron and [6]-gingerol on the gut microbiota were further studied by 16S rDNA gene analysis.

Results

The results showed that the total intake of kaolin of the rats injected with cisplatin was significantly increased, and treatment of ondansetron and [6]-gingerol in advance could significantly ameliorate the pica induced by cisplatin. The body weight of the rats injected with cisplatin was decreased compared with the control group. The 16S rDNA gene analysis has shown that ondansetron, [6]-gingerol and cisplatin could increase the relative abundance of Bacteroidetes and decrease Firmicutes on phylum level.

Conclusion

[6]-gingerol was as effective as ondansetron in the treatment of pica induced by cisplatin in rats, and it seemed that [6]-gingerol had the potential to ameliorate the alteration of gut microbiome, but it needs further study.

Isoflurane induces c-Fos expression in the area postrema of the rat

INTRODUCTION

Volatile anesthetics are speculated to cause postoperative nausea and vomiting via stimulation of the chemoreceptor trigger zone (CTZ). However, the precise mechanism underlying the emetic action of these drugs is not well understood. In this study, we assessed whether isoflurane induced the expression of c-Fos, a neuronal activation marker, in the area postrema (AP), the locus of the CTZ, in rats, which do not have vomiting action.

MATERIALS AND METHODS

Male rats were exposed to 1.3% isoflurane for 0-240 min, or to various concentrations of isoflurane (0, 1.3%, or 2.6%) for 120 min. Finally, the rats were exposed to 1.3% isoflurane for 120 min after ondansetron administration. After the treatments, immunohistochemistry of the rat AP was performed using c-Fos antibody staining.

RESULTS

One-way analysis of variance showed that isoflurane exposure significantly increased c-Fos expression in the AP; however, the rats pretreated with 4 mg/kg ondansetron showed significantly decreased c-Fos expression. Moreover, we evaluated the effect of the anesthetic on inducing pica in the rats, and found that kaolin intake was not influenced by isoflurane exposure.

CONCLUSION

Overall, these results suggest that isoflurane activates AP neurons and may be involved in the emetic mechanism of isoflurane. This study further suggests the feasibility of using rats as a model for studying emetic mechanisms of drugs, despite their lack of vomit action.

Alterations of colonic sensitivity and gastric dysmotility after acute cisplatin and granisetron

BACKGROUND

Cisplatin is a highly emetogenic antineoplastic drug and induces peripheral neuropathy when given in cycles. Granisetron, a 5-HT₃ antagonist, is clinically used to prevent chemotherapy-induced nausea/emesis and abdominal pain in irritable bowel syndrome. The effects of cisplatin on visceral sensitivity and those of granisetron in the context of cancer chemotherapy are not well known.

METHODS

Adult male Wistar rats received two intraperitoneal injections 30 minutes apart: granisetron (1 mg kg^-1 )/vehicle and cisplatin (6 mg kg^-1 )/vehicle. Thereafter, nausea-like behavior was measured as bedding intake for 4 hours, and gastric dysmotility was measured radiographically for 8 hours. Gastric weight and size were determined ex vivo and samples of the forestomach, corpus, ileum, and colon were obtained for histological analysis at 4 and 30 hours after cisplatin/vehicle. Visceral sensitivity was measured as abdominal contractions in response to mechanical intracolonic stimulation 2 hours after cisplatin/vehicle.

KEY RESULTS

Cisplatin-induced bedding intake and gastric dysmotility, and granisetron blocked these effects, which occurred in the absence of frank mucositis. Visceral sensitivity was reduced to a similar extent by both drugs alone or in combination.

CONCLUSIONS AND INFERENCES

Cisplatin-induced bedding intake and gastric dysmotility were blocked by granisetron, confirming the involvement of serotonin acting on 5-HT₃ receptors. Unexpectedly, visceral sensitivity to colonic distension was reduced, to the same extent, by cisplatin, granisetron, and their combination, suggesting important mechanistic differences with nausea and gastric dysmotility that warrant further investigation.

Arcuate Nucleus Orexin-A Signaling Alleviates Cisplatin-Induced Nausea and Vomiting Through the Paraventricular Nucleus of the Hypothalamus in Rats

The most common side effects of cisplatin chemotherapy are nausea and vomiting, and the overwhelming majority of research studies on the mechanism of cisplatin-induced nausea have been focused on the “vomiting center.” As a modulatory center of gastric motility, the roles of the hypothalamus in nausea and vomiting remain unclear. In the present study, we investigated the effects of exogenous orexin-A injected into the arcuate nucleus (ARC) on cisplatin-induced nausea and vomiting, and the possible underlying mechanism. Kaolin intake was calculated daily in cisplatin-treated and saline-treated rats. Gastric motility recording, injections into the ARC, and lesions of the paraventricular nucleus (PVN) were used to study the effects of orexin-A and the hypothalamic nucleus on disorders of gastrointestinal function in cisplatin-treated rats. The pathway from the ARC to the PVN was observed through Fluoro-Gold retrograde tracing. Furthermore, an NPY Y1 receptor antagonist was administered to explore the possible mechanisms involved in the effects of orexin-A in the ARC. We illustrated that exogenous orexin-A injected into the ARC reduced kaolin intake and promoted gastric motility in cisplatin-treated rats, and these effects could have been blocked by an ipsilateral PVN lesion or co-injected antagonist of orexin-A-SB334867. Additional results showed that orexin-A-activated neurons in the ARC communicated directly with other neurons in the PVN that express neuropeptide Y (NPY). Furthermore, activation of the downstream NPY pathway was required for the observed effects of orexin in the ARC on cisplatin-induced nausea and vomiting. These findings reveal a novel neurobiological circuit from the ARC to the PVN that might provide a potential target for the prevention and treatment of cisplatin-induced nausea and vomiting.

Anorectic responses to T-2 toxin, HT-2 toxin, diacetoxyscirpenol and neosolaniol correspond to plasma elevations of neurotransmitters 5-hydroxytryptamine and substance P

Trichothecene mycotoxins commonly contaminate cereal grains and are often linked to human and animal food poisoning. The rapid onset of anorexia is a common hallmark of trichothecenes-induced toxicity. Although the neurotransmitters 5-hydroxytryptamine (5-HT) and substance P (SP) are known to regulate appetite, it remains unknown whether these two neurotransmitters are involved in type A trichothecenes-induced anorectic response. The goal of this study is to relate plasma 5-HT and SP to anorectic responses induced by type A trichothecenes T-2 toxin (T-2), HT-2 toxin (HT-2), diacetoxyscirpenol (DAS) and neosolaniol (NEO). These four toxins evoked robust anorectic response and secretion of plasma 5-HT and SP at 1 mg/kg bw. Following oral exposure, plasma 5-HT and SP were elevated and all peaked at 2 h for T-2, HT-2, DAS and NEO. Following intraperitoneal (IP) administration, plasma 5-HT and SP were peaked at 6 h, 6 h, 2 h, 2 h and 2 h, 6 h, 2 h, 2 h for T-2, HT-2, DAS and NEO, respectively. Elevations of plasma 5-HT and SP markedly corresponded to anorexia induction by T-2, HT-2, DAS and NEO. Altogether, the results presented herein indicated that 5-HT and SP play contributory roles in anorectic responses induced by T-2, HT-2, DAS and NEO.

Synthesis, Characterization and Biocompatibility of N-palmitoyl L-alanine-based Organogels as Sustained Implants of Granisetron and Evaluation of thier Antiemetic Effect

PURPOSE

To assess the gelation power of N-palmitoyl L-alanine derivatives in injectable oils and to use the best chosen organogel as parenteral implant of granisetron for the treatment of emesis.

METHODS

Twelve N-palmitoyl L-alanine derived organogels were developed and evaluated in terms of morphology, thermal properties and in vivo performance. The ability of the selected formula to form in situ gel upon subcutaneous injection in rats and its biocompatibility were monitored over 2 weeks by histopathological examination of the injection site.

RESULTS

The acid derivative (N-palmitoyl L-alanine; PA) was superior to ester derivatives. The chosen formula (PA/safflower oil 10% w/v) was successful in forming an in situ gel of granisetron when subcutaneously injected in rats, lasting for 2 weeks and proved to be biocompatible by histopathological examination. Moreover, it exerted an extended antiemetic activity by decreasing the cisplatin-induced pica for a duration of 96 h and reduced preprotachykinin A mRNA expression and Substance P level for up to 4 days (gastric tissue) or 5 days (medulla oblongata) in rats.

CONCLUSION

Granisetron organogel could be considered as a safe, sustained-release and supportive anticancer treatment in both acute and chronic emesis as well as an accompanying treatment with chemotherapeutics in cancer cases.

Cisplatin increases the number of enterochromaffin cells containing substance P in rat intestine

We previously reported that cisplatin potentiated ileal 5-hydroxytryptamine (5-HT) metabolism and caused pathological changes with an inflammatory response in the delayed phase (72 h) after administration to rats. In the present study, we further investigated the time-dependent effect of cisplatin on ileal 5-HT metabolism and the effects of combining cisplatin and anti-inflammatory drugs on ileal tryptophan hydroxylase expression and pica (the consumption of non-nutritive materials such as kaolin). Cyclooxygenase-2 (COX-2) expression was significantly increased at 24 h after cisplatin (5 mg/kg, intraperitoneal) administration. Cisplatin significantly increased ileal 5-HT content at 48 h after administration and the number of L-tryptophan hydroxylase-expressing cells (i.e., enterochromaffin cells) in the ileal mucosa within 24 h after administration. It also caused a significant increase in the number of substance P-expressing cells. Immunohistochemical double staining revealed that most of the enterochromaffin cells contained substance P. Neither daily treatment with dexamethasone (1 mg/kg, subcutaneous) nor meloxicam (3 mg/kg, subcutaneous), a selective COX-2 inhibitor, affected the cisplatin-induced increase in the number of enterochromaffin cells. Meloxicam had no effect on cisplatin-induced pica, although dexamethasone almost completely inhibited it. This study demonstrated that cisplatin administration induced COX-2 expression and increased the number of enterochromaffin cells in the acute phase (i.e., within 24 h). However, COX-2 expression in the ileum seems to have little direct effect on the mechanism of the induction of enterochromaffin cells and pica.

Strain differences in the development of cisplatin-induced pica behavior in mice

INTRODUCTION

Pica behavior, kaolin ingestion, in rats and mice can be used as an assessment of nausea and vomiting; however, we observed that the incidence of pica behavior in ICR strain mice varied markedly. We investigated the susceptibility of four strains of mice (ICR, BALB/c, C57BL/6, and DBA/2) to the development of pica behavior.

METHODS

Mice received cisplatin (7.5 mg/kg, i.p.) with or without a serotonin 5-HT₃ receptor antagonist (granisetron: 0.1 mg/kg, i.p.) or tachykinin NK₁ receptor antagonist (fosaprepitant: 30 mg/kg, i.p.), and then their daily kaolin intake was measured for 2 days. We examined the expression of preprotachykinin (PPT)-A mRNA in the medulla of cisplatin-treated mice 8 and 32 h after drug administration.

RESULTS

All mice except for ICR strain significantly increased kaolin intake after cisplatin administration. Among the tested strains, DBA/2 mice compared to BALB/c and C57BL/6 mice notably showed pica behavior on both days (P < 0.0001). The expression of PPT-A mRNA was significantly increased 8 h after cisplatin administration in all strains, but the increase remained on the second day only in DBA/2 mice (P < 0.05). Granisetron significantly inhibited pica behavior in DBA/2 mice on the first day (P < 0.0001), but not the second day; however, fosaprepitant completely inhibited the pica behavior on both days (P < 0.001).

DISCUSSION

These results indicate that cisplatin-induced pica behavior in mice is likely to be influenced by the genotype, and that DBA/2 mice are useful to analyze the emetogenic or anti-emetic potential of drugs in preclinical studies.

Neurokinin-1 receptor blocker CP-99 994 improved emesis induced by cisplatin via regulating the activity of gastric distention responsive neurons in the dorsal motor nucleus of vagus and enhancing gastric motility in rats

BACKGROUND

Nowadays, chemotherapy induced nausea and vomiting (CINV) is still common in patients with cancer. It was reported that substance P mediated CINV via neurokinin-1 (NK₁ ) receptor and antagonists of NK₁ receptor has been proved useful for treating CINV but the mechanism are not fully understood. This study aimed to examine the role of NK₁ receptor blocker, CP-99 994, when administrated into dorsal motor nucleus of vagus (DMNV), on the cisplatin-induced emesis in rats and the possible mechanism.

METHODS

Rats' kaolin intake, food intake, and bodyweight were recorded every day; gastric contraction activity was recorded in conscious rats through a force transducer implanted into the stomach; gastric emptying was monitored using the phenol red method; single unit extracellular firing in the DMNV were recorded.

KEY RESULTS

DMNV microinjection of CP-99 994 reduced the changes of increased kaolin consumption and suppressed food intake in cisplatin-treated rats; enhanced the gastric contraction activity dose-dependently in control and cisplatin-treated rats but enhanced gastric emptying only in cisplatin-treated rats; reduced the firing rate of gastric distention inhibited (GD-I) neurons but increased the firing rate of GD excited (GD-E) neurons in the DMNV. The effects of CP-99 994 on gastric motility and neuronal activity were stronger in cisplatin-treated rats than those of control rats.

CONCLUSIONS AND INFERENCES

Our results suggested that CP-99 994 could improve emesis induced by cisplatin by regulating gastric motility and gastric related neuronal activity in the DMNV.

Differential effects of aprepitant, a clinically used neurokinin-1 receptor antagonist on the expression of conditioned psychostimulant versus opioid reward

RATIONALE

Neurokinin-1 receptor (NK1R) signaling modulates behaviors associated with psychostimulants and opioids. Psychostimulants, such as amphetamine (AMPH) and cocaine, bind to monoamine transporters and alter their functions. Both dopamine and norepinephrine transporters are regulated by NK1R activation suggesting a role for NK1R mediated catecholamine transporter regulation in psychostimulant-mediated behaviors.

OBJECTIVES

The effect of in vivo administration of aprepitant (10 mg/kg) on the expression of AMPH (0.5 and 2 mg/kg) and cocaine (5 and 20 mg/kg)-induced conditioned place preference (CPP) as well as locomotor activation was examined in C57BL/6J mice. The effect of aprepitant on morphine (1 and 5 mg/kg)-induced CPP was also examined to identify the specific actions of aprepitant on psychostimulant versus opioid-induced behaviors.

RESULTS

Aprepitant administration significantly attenuated the CPP expression and locomotor activation produced by AMPH and cocaine. In contrast, aprepitant significantly enhanced the expression of CPP produced by morphine while significantly suppressing the locomotor activity of the mice conditioned with morphine. Aprepitant by itself did not induce significant CPP or conditioned place aversion or locomotor activation or suppression.

CONCLUSIONS

Attenuation of AMPH or cocaine-induced CPP and locomotor activation by aprepitant suggests a role for NK1R signaling in psychostimulant-mediated behaviors. Stimulation of morphine-induced CPP expression and suppression of locomotor activity of morphine-conditioned mice suggest differential effects of NK1R antagonism on conditioned psychostimulant versus opioid reward. Collectively, these findings indicate that clinically used NK1R antagonist, aprepitant may serve as a potential therapeutic agent in the treatment of psychostimulant abuse.

Detection of Nausea-Like Response in Rats by Monitoring Facial Expression

Patients receiving cancer chemotherapy experience nausea and vomiting. They are not life-threatening symptoms, but their insufficient control reduces the patients’ quality of life. To identify methods for the management of nausea and vomiting in preclinical studies, the objective evaluation of these symptoms in laboratory animals is required. Unlike vomiting, nausea is defined as a subjective feeling described as recognition of the need to vomit; thus, determination of the severity of nausea in laboratory animals is considered to be difficult. However, since we observed that rats grimace after the administration of cisplatin, we hypothesized that changes in facial expression can be used as a method to detect nausea. In this study, we monitored the changes in the facial expression of rats after the administration of cisplatin and investigated the effect of anti-emetic drugs on the prevention of cisplatin-induced changes in facial expression. Rats were housed in individual cages with free access to food and tap water, and their facial expressions were continuously recorded by infrared video camera. On the day of the experiment, rats received cisplatin (0, 3, and 6 mg/kg, i.p.) with or without a daily injection of a 5-HT₃ receptor antagonist (granisetron: 0.1 mg/kg, i.p.) or a neurokinin NK₁ receptor antagonist (fosaprepitant: 2 mg/kg, i.p.), and their eye-opening index (the ratio between longitudinal and axial lengths of the eye) in the recorded video image was calculated. Cisplatin significantly and dose-dependently induced a decrease of the eye-opening index 6 h after the cisplatin injection, and the decrease continued for 2 days. The acute phase (day 1), but not the delayed phase (day 2), of the decreased eye-opening index was inhibited by treatment with granisetron; however, fosaprepitant abolished both phases of changes. The time-course of changes in facial expression are similar to clinical evidence of cisplatin-induced nausea in humans. These findings indicate that the monitoring of facial expression has the potential to be useful for the detection of a nausea-like response in laboratory animals.

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.

Challenges for the in vivo quantification of brain neuropeptides using microdialysis sampling and LC-MS

In recent years, neuropeptides and their receptors have received an increased interest in neuropharmacological research. Although these molecules are considered relatively small compared with proteins, their in vivo quantification using microdialysis is more challenging than for small molecules. Low microdialysis recoveries, aspecific adsorption and the presence of various multiply charged precursor ions during ESI-MS/MS detection hampers the in vivo quantification of these low abundant biomolecules. Every step in the workflow, from sampling until analysis, has to be optimized to enable the sensitive analysis of these compounds in microdialysates.

Administration of olanzapine as an antiemetic agent changes glucose homeostasis in cisplatin-treated rats

We investigated the effects of olanzapine on cisplatin-induced pica (the consumption of non-nutrient materials such as kaolin) and glucose homeostasis in rats to clarify the effects of olanzapine when used as an anti-emetic drug. Rats were injected intraperitoneally (i.p.) with either 5 mg/kg cisplatin or saline. Additionally, 2 or 10 mg/kg olanzapine were administered i.p. to the rats 10 min before the administration of cisplatin and subsequently administered every 24 h for 3 d. Kaolin and food intake was measured using an automatic monitoring apparatus. Plasma glucose levels were measured by an enzyme electrode method. The plasma levels of insulin and intact proinsulin were measured by enzyme-linked immunosorbent assay (ELISA). The proinsulin-to-insulin (P/I) ratio was calculated. Cisplatin significantly increased kaolin intake, but decreased food intake and body weight up to 72 h. Olanzapine had no effect on these parameters. Neither olanzapine nor cisplatin alone had a significant effect on the plasma levels of glucose, insulin, or proinsulin. However, a combination of olanzapine and cisplatin significantly decreased plasma insulin levels, but increased plasma intact proinsulin levels and the P/I ratio. Our results suggest that an additive deterioration of insulin-secreting beta-cell function and disturbance of glucose homeostasis should be considered during treatment of patients with olanzapine for cisplatin-induced nausea and vomiting.