Randomized, double-blind, placebo-controlled study of aprepitant versus two dosages of olanzapine with ondansetron plus dexamethasone for prevention of chemotherapy-induced nausea and vomiting in patients receiving high-emetogenic chemotherapy.

PURPOSE: We assessed the efficacy of aprepitant (APR) or 10 or 5 mg OLN (OLN10 or OLN5) plus ondansetron and dexamethasone for chemotherapy-induced nausea/vomiting (CINV) prophylaxis in patients receiving high-emetogenic chemotherapy (HEC). METHODS: Patients who received doxorubicin + cyclophosphamide or cisplatin were given intravenous ondansetron and dexamethasone prior to chemotherapy and oral dexamethasone on days 2-4 and randomized 1:1:1 to receive APR125 on day 1 and APR80 on days 2-3 or OLN10 or OLN5 on days 1-4. Matched placebo controls were used. The primary endpoint was no nausea in ≤ 120 h. Secondary endpoints included CINV severity, complete response (CR) rate, adverse effects (AE), and quality of life. RESULTS: Of 141 patients, 104 received AC and 37 received cisplatin. The no-nausea rates were 33% (APR), 43.2% (OLN10; p = 0.24), and 37% (OLN5; p = 0.87). Grades 2-4 nausea were experienced by fewer patients for OLN10 than for APR (24-120 h, 8.7% vs. 27.7%, respectively; p = 0.02; overall period, 19.6% vs. 40.4%, respectively; p = 0.03). The median visual analog scale nausea score from 24 to 120 h was significantly lower for OLN10 (2.3) than for APR (1.2, p = 0.03). The degrees of vomiting, CR, and AE were similar between the APR and OLN10 groups. CINV was similar between the OLN5 and APR groups. CONCLUSIONS: Nausea was less severe for OLN10 than for APR in patients receiving HEC, but other measures were similar. CINV prevention efficacy was comparable between OLN5 and APR.

Ropinirole eye drops induce vomiting effectively in dogs: a randomised, double-blind, placebo-controlled clinical study.

There is a need for an effective and safe emetic agent that dog owners could easily administer to their dogs following veterinary advice in cases of potential poisoning. As a response to this need, a randomised, double-blind, multi-site, clinical field study was performed to assess the efficacy, safety and usability of ropinirole eye drops to induce vomiting in dogs. Ropinirole (target dose 3.75 mg/m2) was applied to eyes of 100 dogs, and 32 dogs received placebo. The drug was administered by the dog owner at a veterinary clinic under the supervision of a veterinarian and led to vomition in 95% of the ropinirole-treated dogs within 30 min. The median time to first vomit was 10 min (range: 3-37 min). None of the dogs receiving placebo vomited in this time period. All owners were able to administer the product and 96% of them assessed the administration to be very easy or easy, which was confirmed by the observing veterinarian. Some ocular signs were seen both with ropinirole and placebo, hyperaemia being the most common. All observed signs were transient and in most cases mild. Ropinirole eye drops provided an effective, safe and reliable means to induce emesis in dogs.

Reality of the emetogenic level of irinotecan.

PURPOSE: To assess the emetogenic potential of different chemotherapy (CT) regimens in daily clinical practice in an outpatient setting. To optimize antiemetic prophylaxis if necessary METHODS: Prospective and retrospective review of the emetogenic potential of CT regimens used in adult patients in an outpatient setting RESULTS: We assess the chemotherapy-induced nausea and vomiting (CINV) of 50 different CT regimens used on 157 different patients in an outpatient setting. We found that the CT usually classified as highly emetogenic, including cisplatin and anthracycline-cyclophosphamide combination, had the higher incidence of CINV (37.5 and 54.4% respectively). The antineoplastic drugs usually considered to be moderately emetogenic had, as expected, lower rates of emesis with the exception of irinotecan, which presented a pattern of nausea and/or vomiting (NV) similar to the highly emetogenic CT with a global incidence of 48.5%. The appearance of emetic symptoms had impact on quality of life in 70% of the patients, with nausea being the main emetic symptom. CONCLUSION: Antiemetic prophylaxis for highly emetogenic CT could be improve. Irinotecan CT regimens have a high emetogenic potential more than moderate and require more intensive antiemetic prophylaxis too.

Recovery of brodifacoum in vomitus following induction of emesis in dogs that had ingested rodenticide bait.

AIM: To assess the benefit of inducing emesis in dogs that have ingested rodenticide bait containing brodifacoum (BDF), by determining the amount of BDF in bait recovered from the vomitus relative to the estimated amount consumed. METHODS: Between 2014 and 2015 samples of vomitus from seven dogs that ingested rodenticide baits containing BDF were submitted by veterinarians in New Zealand. All seven dogs had been given apomorphine by the veterinarian and vomited within 1 hour of ingesting the bait. Some or all of the bait particles were retrieved from each sample and were analysed for concentrations of BDF using HPLC. Based on estimations of the mass of bait consumed, the concentration of BDF stated on the product label, and the estimated mass of bait in the vomitus of each dog, the amount of BDF in the vomited bait was calculated as a percentage of the amount ingested. RESULTS: For five dogs an estimation of the mass of bait ingested was provided by the submitting veterinarian. For these dogs the estimated percentage of BDF in the bait retrieved from the vomitus was between 10-77%. All dogs were well after discharge but only one dog returned for further testing. This dog had a normal prothrombin time 3 days after ingestion. CONCLUSIONS AND CLINICAL RELEVANCE: The induction of emesis within 1 hour of ingestion can be a useful tool in reducing the exposure of dogs to a toxic dose of BDF. The BDF was not fully absorbed within 1 hour of ingestion suggesting that the early induction of emesis can remove bait containing BDF before it can be fully absorbed.

Effects of naloxone on motion sickness in cats alone and with broad spectrum antiemetics.

Doses of naloxone far below those which elicit emesis increase the sensitivity to motion sickness. In order to evaluate the possible interaction with broad spectrum antiemetics, low doses of naloxone were tested alone and in combination with 8-hydroxy-2-(di-n-propylamine)tetralin (DPAT), fentanyl and the NK1 antagonist CP-99994. A modified autonomic symptom rating scale was unaffected by any drug and thus considered of little value. Fentanyl and NK1 antagonists decreased the duration of the retch/vomit sequence. Naloxone alone and in combination with each of the drugs increased the duration of retching/vomiting. Naloxone also increased the number of vomiting sequences. The results are interpreted in terms of possible site(s) of action of the antiemetic drugs.

2016 Updated MASCC/ESMO consensus recommendations: Emetic risk classification and evaluation of the emetogenicity of antineoplastic agents.

PURPOSE: Employing the same framework as in previous guideline updates, antineoplastic agents were classified into four emetic risk categories. The classification of the emetogenic level of new antineoplastic agents, especially for the oral drugs, represents an increasing challenge. Accurate reporting of emetogenicity of new antineoplastic agents in the absence of preventive antiemetic treatment is rarely available. METHODS: A systematic search was conducted for drugs approved after 2009 until June 2015 using EMBASE and PubMed. The search term was "drug name." The restrictions were language (English records only), date (2009 to 2015), and level of evidence ("clinical trial"). RESULTS: From January 2009 to June 2015, 42 new antineoplastic agents were identified and a systematic search was conducted to identify relevant studies to help define emetic risk levels. The reported incidence of vomiting varied across studies for many agents, but there was adequate evidence to allow 41 of the 42 new antineoplastic agents to be classified according to emetogenic risk. No highly emetogenic agents were identified. Seven moderately emetogenic agents, 26 low emetogenic, agents and eight minimal emetogenic agents were identified and classified accordingly. The MASCC/ESMO update committee also recommended reclassification of the combination of an anthracycline and cyclophosphamide (AC) as highly emetogenic. CONCLUSION: Despite several limitations, we have attempted to provide a reasonable approximation of the emetic risk associated with new antineoplastic agents through a comprehensive search of the available literature. Hopefully by the next update, more precise information on emetic risk will have been collected during new agent development process.

Comparison of the use of sodium carbonate (washing soda crystals) and apomorphine for inducing emesis in dogs.

OBJECTIVE: To describe the use of sodium carbonate and apomorphine in a historical cohort of dogs, compare the occurrence of emesis and report any adverse effects recorded. METHODS: This historical, observational study included information from medical records of dogs that received an emetic agent. The occurrence of emesis with apomorphine or sodium carbonate was calculated and the association between emesis and agent was explored, with the odds ratio and 95% confidence interval (CI) reported. A non-inferiority analysis of the occurrence of emesis for sodium carbonate was performed against an equivalence range of ±7% of the estimated occurrence of emesis with apomorphine. Owners were emailed a short survey about their dog's health after their visit to the hospital for induced emesis. RESULTS: Records for 787 dogs seen from January 2007 to December 2013 were included. For apomorphine, 382/392 dogs showed emesis (97%, 95% CI 95-100%). For sodium carbonate, 320/395 dogs showed emesis (81%, 95% CI 77-85%), which fell below the equivalence range for apomorphine (97 ± 7%, 90-100%) and was considered inferior. The odds ratio of emesis with apomorphine to sodium carbonate was 9.0 (95% CI 4.6-17.6). Of 18 responses to the survey, 5 reported abnormalities after emesis (3 with sodium carbonate, 2 with apomorphine). CONCLUSION: The occurrence of emesis with sodium carbonate was high but inferior to apomorphine. However, the advantages of sodium carbonate, including less expense and ease of accession compared with apomorphine, make it a viable choice in emergency medicine.

Modeling the emetic potencies of food-borne trichothecenes by benchmark dose methodology.

Trichothecene mycotoxins commonly co-contaminate cereal products. They cause immunosuppression, anorexia, and emesis in multiple species. Dietary exposure to such toxins often occurs in mixtures. Hence, if it were possible to determine their relative toxicities and assign toxic equivalency factors (TEFs) to each trichothecene, risk management and regulation of these mycotoxins could become more comprehensive and simple. We used a mink emesis model to compare the toxicities of deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, nivalenol, fusarenon-X, HT-2 toxin, and T-2 toxin. These toxins were administered to mink via gavage and intraperitoneal injection. The United States Environmental Protection Agency (EPA) benchmark dose software was used to determine benchmark doses for each trichothecene. The relative potencies of each of these toxins were calculated as the ratios of their benchmark doses to that of DON. Our results showed that mink were more sensitive to orally administered toxins than to toxins administered by IP. T-2 and HT-2 toxins caused the greatest emetic responses, followed by FX, and then by DON, its acetylated derivatives, and NIV. Although these results provide key information on comparative toxicities, there is still a need for more animal based studies focusing on various endpoints and combined effects of trichothecenes before TEFs can be established.

Emetic responses to T-2 toxin, HT-2 toxin and emetine correspond to plasma elevations of peptide YY3-36 and 5-hydroxytryptamine.

Trichothecene mycotoxins are a family of potent translational inhibitors that are associated with foodborne outbreaks of human and animal gastroenteritis in which vomiting is a clinical hallmark. Deoxynivalenol (DON, vomitoxin) and other Type B trichothecenes have been previously demonstrated to cause emesis in the mink (Neovison vison), and this response has been directly linked to secretion of both the satiety hormone peptide YY3-36 (PYY3-36) and neurotransmitter 5-hydroxytryptamine (5-HT). Here, we characterized the emetic responses in the mink to T-2 toxin (T-2) and HT-2 toxin (HT-2), two highly toxic Type A trichothecenes that contaminate cereals, and further compared these effects to those of emetine, a natural alkaloid that is used medicinally and also well known to block translation and cause vomiting. Following intraperitoneal (IP) and oral exposure, all three agents caused vomiting with evident dose-dependent increases in both duration and number of emetic events as well as decreases in latency to emesis. T-2 and HT-2 doses causing emesis in 50 % of treated animals (ED50s) were 0.05 and 0.02 mg/kg BW following IP and oral administration, respectively, whereas the ED50s for emetine were 2.0 and 1.0 mg/kg BW for IP and oral exposure, respectively. Importantly, oral administration of all three toxins elicited marked elevations in plasma concentrations of PYY3-36 and 5-HT that corresponded to emesis. Taken together, the results suggest that T-2 and HT-2 were much more potent than emetine and that emesis induction by all three translational inhibitors co-occurred with increases in circulating levels of PYY3-36 and 5-HT.

Weekly cisplatin (30-40 mg/m2) as radiosensitizer: Is it high or moderate emetic agent?

PURPOSE: The American Society of Clinical Oncology (ASCO) guideline recommends a high antiemetic prophylaxis for any dose of cisplatin. This hypothesis was tested by us in this analysis of solid tumor patients who received weekly cisplatin as a radiosensitizer in a dose range of 30-40 mg/m2. METHODS: This was a retrospective analysis of 181 solid tumor patients who received weekly cisplatin (in the dose range of 30-40 mg/m2) as a radiosensitizer between July 2015 and August 2015. The antiemetic prophylaxis schedule provided was classified as optimal (if a high antiemetic prophylaxis was provided) or suboptimal (if a nonhigh antiemetic prophylaxis was provided). The incidence of acute, delayed and breakthrough vomiting after chemotherapy was noted. SPSS version 20 was used for analysis. Fisher's exact test was used to determine the association between antiemetic schedule (suboptimal vs. optimal) and postchemotherapy emesis. RESULTS: In the present study, of 181 patients, only 25 patients (13.8%) received optimal antiemetic prophylaxis while the remaining 156 (86.2%) received suboptimal prophylaxis. In the cohort of patients with suboptimal prophylaxis, dexamethasone was omitted in all patients (100%) while NK receptor antagonist was omitted in 76 patients (48.7%). The rate of vomiting was lower in patients receiving optimal prophylaxis as compared to that in patients receiving suboptimal prophylaxis (12% vs. 39.75%; P - 0.005). CONCLUSION: Omission of dexamethasone followed by aprepitant was the main reason for suboptimal prophylaxis. High antiemetic prophylaxis in accordance with ASCO guidelines overall decreased the risk of emesis in patients receiving CTRT with weekly cisplatin in the dose range of 30-40 mg/m2.

A double-blind randomized Phase II study of olanzapine 10 mg versus 5 mg for emesis induced by highly emetogenic chemotherapy.

A randomized Phase II dose-finding trial comparing olanzapine 10 mg with olanzapine 5 mg for patients receiving highly emetogenic chemotherapy with cisplatin was started in June 2014. The purpose of the trial is to evaluate the efficacy and safety of the two olanzapine doses and to determine which is more promising as a test arm for comparison with the current standard antiemetic care (a combination of aprepitant, a 5-HT3 receptor antagonist and dexamethasone) in a subsequent Phase III trial. Patients receiving cisplatin-containing regimens will be randomized to the olanzapine 10 or 5 mg arm. A total of 150 patients will be accumulated from nine institutions over 2 years. The primary endpoint is complete response defined as no emetic episodes and no use of rescue medications in the delayed (24-120 h) phase. This trial has been registered at the UMIN Clinical Trials Registry as UMIN000014214.

Plasma pharmacokinetics and tissue and brain distribution of cisplatin in musk shrews.

PURPOSE: Cisplatin induces nausea and emesis, even with antiemetic supportive care. To assess platinum exposure, which could activate nausea and emesis, we quantitated platinum in the brain and various organs, and hindbrain and spinal cord substance P, a key neuropeptide for the neuronal signaling of nausea and emesis. METHODS: Musk shrews, a model species for nausea and emesis research, were dosed intraperitoneally with 20 mg/kg cisplatin and euthanized at up to 72 h after injection. Concentrations of platinum were quantitated in plasma ultrafiltrate, plasma, lung, kidney, combined forebrain and midbrain, hindbrain, and spinal cord by flameless atomic absorption spectrometry. Hindbrains and spinal cords were analyzed for substance P by immunohistochemistry after injection of 20 or 30 mg/kg. RESULTS: Plasma ultrafilterable platinum concentrations decreased rapidly till 60 min after dosing and then more slowly by 24 h. The concentrations of total platinum in both the fore- and midbrain and the hindbrain were similar at all time points and were at least 20-fold lower than plasma total platinum concentrations. There were no significant changes in substance P immunoreactivity after cisplatin dosing. Histology revealed damage to the renal cortex by 72 h after injection of cisplatin. CONCLUSIONS: This is the first study to examine platinum concentrations in musk shrews after administration of cisplatin and delineate substance P immunohistochemical staining in the hindbrain and spinal cord of this species. The platinum concentrations detected in the brain could potentially contribute to the neurological side effects of cisplatin, such as nausea and emesis.

Efficacy and safety of tranexamic acid as an emetic in dogs.

OBJECTIVE: To determine dose dependency of tranexamic acid-induced emesis and the time course of the antifibrinolytic potency of tranexamic acid in dogs. ANIMALS: 10 Beagles. PROCEDURES: In a dose-escalating experiment, ascending doses of tranexamic acid (10, 20, and 30 mg/kg, IV) were administered at 5-minute intervals until vomiting was observed. In a separate single-dose experiment, ascending doses of tranexamic acid (20, 30, 40, and 50 mg/kg, IV) were administered at 1-week intervals until vomiting was observed. Time to onset of vomiting and number of vomiting episodes were measured in both experiments. In a coagulation experiment, a single 50 mg/kg bolus of tranexamic acid was administered, and blood was obtained 1 hour before and 20 minutes, 3 hours, and 24 hours after administration. Antifibrinolytic potency of tranexamic acid was evaluated by use of a modified rotational thromboelastography method. RESULTS: Tranexamic acid induced vomiting in a dose-dependent manner. Vomiting frequency was ≤ 2 episodes, and vomiting concluded ≤ 250 seconds after administration. Antifibrinolytic potency of tranexamic acid was significantly higher at 20 minutes following administration, but not different by 24 hours, when compared with the potency measured before administration. No adverse effects were observed in any experiment. CONCLUSIONS AND CLINICAL RELEVANCE: IV administration of tranexamic acid induced emesis in a dose-dependent manner. The antifibrinolytic potency of tranexamic acid decreased in a time-dependent manner and was resolved ≤ 24 hours after administration. Further studies are warranted to investigate the emetic and other adverse effects of tranexamic acid in dogs of various breeds and ages.

Running-based pica in rats. Evidence for the gastrointestinal discomfort hypothesis of running-based taste aversion.

Voluntary running in an activity wheel establishes aversion to paired taste in rats. A proposed mechanism underlying this taste aversion learning is gastrointestinal discomfort caused by running. We tested this hypothesis by measuring the pica behavior (kaolin clay intake) of rats, because it is known that rats engage in pica behavior after various nausea-inducing treatments including irradiation, motion sickness, and injection of emetic drugs such as lithium chloride (LiCl). Following a demonstration of the already-known phenomenon of LiCl-based pica in Experiment 1, we successfully showed running-based pica behavior in Experiment 2 where the running treatment was compared with a non-running control treatment (i.e., confinement in a locked wheel). These results suggest that not only LiCl but also running induces nausea in rats, supporting the gastrointestinal discomfort hypothesis of running-based taste aversion learning.

Behavioral and neural substrates of habit formation in rats intravenously self-administering nicotine.

Tobacco addiction involves a transition from occasional, voluntary smoking towards habitual behavior that becomes increasingly resistant to quitting. The development of smoking habits may reflect a loss of behavioral control that can be modeled in rats. This study investigated the behavioral and neural substrates of habit formation in rats exposed to either brief (10 days) or extended (47 days) intravenous (IV) nicotine self-administration training. Following training, the first cohort of rats were exposed to a nicotine devaluation treatment, which involved repeated pairings of IV nicotine with lithium injection. They were then tested for sensitivity of responding to nicotine devaluation under extinction and reinstatement conditions. The second cohort of rats received equivalent self-administration training followed by processing of brain tissue for c-Fos immunohistochemistry. After brief training, devaluation suppressed nicotine-seeking during tests of extinction and reinstatement, confirming that responding is initially sensitive to current nicotine value, and therefore, goal directed. In contrast, after extended training, devaluation had no effect on extinction or reinstatement of responding, indicating that responding had become habitual. Complementary neuroanalysis revealed that extended nicotine self-administration was associated with increased c-Fos expression in brain regions implicated in habitual control of reward seeking, including activation of the dorsolateral striatum and substantia nigra pars compacta. These findings provide evidence of direct devaluation of an IV drug reward, that nicotine self-administration is initially goal-directed but becomes habitual with extended training, and that this behavioral transition involves activation of brain areas associated with the nigrostriatal system.

Broad-spectrum antiemetic efficacy of the L-type calcium channel blocker amlodipine in the least shrew (Cryptotis parva).

The dihydropyridine l-type calcium (Ca(2+)) channel blockers nifedipine and amlodipine reduce extracellular Ca(2+) entry into cells. They are widely used for the treatment of hypertensive disorders. We have recently demonstrated that extracellular Ca(2+) entry via l-type Ca(2+) channels is involved in emesis and that nifedipine has broad-spectrum antiemetic activity. The aim of this study was to evaluate the antiemetic efficacy of the longer-acting l-type Ca(2+) channel blocker, amlodipine. Fully effective emetic doses of diverse emetogens such as the l-type Ca(2+) channel agonist (FPL 64176) as well as selective and/or nonselective agonists of serotonergic 5-HT3 (e.g. 5-HT or 2-Me-5-HT)-, dopamine D2 (e.g. apomorphine or quinpirole)-, cholinergic M1 (e.g. pilocarpine or McN-A343)- and tachykininergic NK1 (e.g. GR73632)-receptors, were administered intraperitoneally (i.p.) in the least shrew to induce vomiting. The broad-spectrum antiemetic potential of amlodipine was evaluated against these emetogens. Subcutaneous (s.c.) administration of amlodipine (0.5-10mg/kg) attenuated in a dose-dependent and potent manner both the frequency and percentage of shrews vomiting in response to intraperitoneal (i.p.) administration of FPL 64176 (10mg/kg), 5-HT (5mg/kg), 2-Me-5-HT (5mg/kg), apomorphine (2mg/kg), quinpirole (2mg/kg), pilocarpine (2mg/kg), McN-A343 (2mg/kg), or GR73632 (5mg/kg). A combination of non-effective doses of amlodipine (0.5mg/kg, s.c.) and the 5-HT3 receptor antagonist palonosetron (0.05 mg/kg, s.c.) was more effective against FPL 64176-induced vomiting than their corresponding doses tested alone. Amlodipine by itself suppressed the frequency of acute cisplatin (10mg/kg, i.p)-induced vomiting in a dose-dependent manner. Moreover, a combination of a non-effective dose of amlodipine (1mg/kg) potentiated the antiemetic efficacy of a semi-effective dose of palonosetron (0.5mg/kg, s.c.) against acute vomiting caused by cisplatin. We confirm that influx of extracellular Ca(2±) ion underlies vomiting due to diverse causes and demonstrate that l-type Ca(2+) channel blockers are a new class of broad-spectrum antiemetics.

Emergency management and treatment of the poisoned small animal patient.

This article reviews management of the acutely poisoned veterinary patient, including initial telephone triage, appropriate communication and history gathering from the pet owner, decontamination methods (including the use of appropriate emetic agents and dosing of activated charcoal), and general treatment of the poisoned patient. Symptomatic and supportive care of the poisoned patient includes the use of fluid therapy, gastrointestinal support (eg, antacids), central nervous system support (eg, muscle relaxants, anticonvulsants), sedatives/reversal agents (eg, phenothiazines, naloxone, flumazenil), hepatoprotectants, and miscellaneous antidotal therapy.

Effectiveness of emetics to study plastic ingestion by Leach's Storm-petrels (Oceanodroma leucorhoa).

Most plastic ingestion studies rely on dissection of dead birds, which are found opportunistically, and may be biased. We used Leach's Storm-petrels (Oceanodroma leucorhoa) in Newfoundland to study the effect of dose volume, and the efficacy of emesis using syrup of ipecac as an emetic. Ipecac is a safe method of non-lethally sampling stomach contents, and recovered all ingested plastic. Almost half the storm-petrels sampled had ingested plastic, ranging from 0 to 17 pieces, and weighing 0.2-16.9 mg. Using the Ecological Quality Objective for Northern Fulmars, adjusted for storm-petrels smaller size, 43% exceeded the threshold of 0.0077 g of plastic. Many adult seabirds offload plastic to their offspring, so storm-petrel chicks likely experience a higher plastic burden than their parents. The ability to study plastic ingestion non-lethally allows researchers to move from opportunistic and haphazard sampling to hypothesis-driven studies on a wider range of taxa and age classes.

Chemotherapy-induced kaolin intake is increased by lesion of the lateral parabrachial nucleus of the rat.

Anticancer agents, such as cisplatin, stimulate nausea, vomiting, and behaviors indicative of malaise. Rats and mice do not possess a vomiting response, and, therefore, in these species, the ingestion of kaolin clay (a pica response) has been used as an index of malaise. In the rat, cisplatin-induced kaolin intake is inhibited by antiemetic treatments. In addition, cisplatin activates vagal afferent fibers in the gut, and kaolin intake induced by cisplatin is largely dependent on an intact vagus. Nevertheless, little is known about the brain pathways controlling pica. We investigated the role of the lateral parabrachial nucleus (lPBN), a major visceral afferent link between the hindbrain and forebrain, in cisplatin-induced c-Fos expression and pica. Injection of cisplatin (6 mg/kg ip) produced c-Fos expression in the ventrolateral (external) lPBN, a region receiving viscerosensory input. In rats with bilateral ibotenic acid lPBN lesions, cisplatin treatment substantially increased kaolin intake compared with controls ( approximately 30 g vs. approximately 5 g, respectively, over 24 h). Food intake was reduced by cisplatin treatment and by apomorphine, an emetic agent that acts centrally. Unlike cisplatin, however, apomorphine stimulated kaolin intake to a similar degree in both the lesioned and control rats, suggesting that lPBN damage neither produces nonspecific effects nor enhances malaise in general. These data suggest that lPBN-lesioned animals not only demonstrate pica after cisplatin treatment, but, in fact, show an exaggerated response that is greatly in excess of any treatment known to produce kaolin intake in rats.

Receptor-selective agonists induce emesis and Fos expression in the brain and enteric nervous system of the least shrew (Cryptotis parva).

Research on the mechanisms of emesis has implicated multiple neurotransmitters via both central (dorsal vagal complex) and peripheral (enteric neurons and enterochromaffin cells) anatomical substrates. Taking advantage of advances in receptor-specific agonists, and utilizing Fos expression as a functional activity marker, this study demonstrates a strong, but incomplete, overlap in anatomical substrates for a variety of emetogens. We used cisplatin and specific agonists to 5-HT(3) serotonergic, D(2)/D(3) dopaminergic, and NK(1) tachykininergic receptors to induce vomiting in the least shrew (Cryptotis parva), and quantified the resulting Fos expression. The least shrew is a small mammal whose responses to emetic challenges are very similar to its human counterparts. In all cases, the enteric nervous system, nucleus of the solitary tract, and dorsal motor nucleus of the vagus demonstrated significantly increased Fos immunoreactivity (Fos-IR). However, Fos-IR induction was notably absent from the area postrema following the dopaminergic and NK(1) receptor-specific agents. Two brain nuclei not usually discussed regarding emesis, the dorsal raphe nucleus and paraventricular thalamic nucleus, also demonstrated increased emesis-related Fos-IR. Taken together, these data suggest the dorsal vagal complex is part of a common pathway for a variety of distinct emetogens, but there are central emetic substrates, both medullary and diencephalic, that can be accessed without directly stimulating the area postrema.