Man P. Ngan

Anti-emetic activity of ghrelin in ferrets exposed to the cytotoxic anti-cancer agent cisplatin

Emesis may be modulated via multiple mechanisms. The actions of ghrelin suggest an ability to couple an induction of hunger with preparation of the stomach for ingestion of food. Such a process might reduce any tendency to vomit, so an anti-emetic activity of ghrelin was investigated in the ferret cisplatin-induced emesis model. In controls, intra-peritoneal cisplatin (10 mg/kg) induced 41.4+/-8.4 episodes of emesis comprising 310.4+/-55.3 retches and 28.8+/-6.9 vomits during the 6h observation; the latency to onset of the first emetic episode was 108.9+/-4.8 min. Intra-peritoneal ghrelin (1mg/kg, split as a 30 min pre- and 30 min-post dose) did not induce a change in behaviour or modify cisplatin-induced emesis (p>0.05). Intracerebroventricular (i.c.v.) administration (third ventricle) was achieved via a pre-implanted cannula. At the first emetic episode following cisplatin, ghrelin or vehicle (20 microl saline) was administered i.c.v. During the 30 min following the initial episode of emesis, control animals exhibited 18.0+/-2.6 emetic episodes comprising 160.3+/-24.1 retches and 13.8+/-2.7 vomits. Ghrelin 10 microg i.c.v. reduced the number of retches by 61.5% (p<0.05) and at a dose of 30 microg i.c.v. ghrelin reduced the number of episodes, individual retches and vomits by 74.4 (p<0.05), 80.4 (p<0.01), and 72.5% (p<0.05), respectively. At subsequent time periods there were no differences between ghrelin- or saline-treated animals (p>0.05). An ability of ghrelin to reduce emesis is consistent with a role in modulating gastro-intestinal functions and identifies a novel approach to the treatment of emesis.

Inhibition of emesis by tachykinin NK1 receptor antagonists in Suncus murinus (house musk shrew)

The anti-emetic potential of CP-122,721 ((+)-2S,3S)-3-(2-methoxy-5-trifluoromethoxybenzyl)amino-2-phenylpi peridine), CP-99,994 ((+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine), CP-100,263 ((-)-(2R,3R)-3-(2-methoxybenzylamino)-2-phenylpiperidine), RP 67580 ((3R, 7aR)-7,7-diphenyl-2-[1-imino-2-(2-methoxyphenyl)ethyl] po-hydroisoindol-4-one), FK 888 (N2-[(4R)-4-hydroxy-1-(1-methyl-1H-in-dole-3-yl)carbonyl-L-propyl] -N-methyl-N-phenylmethyl-1-3-(2-naphthyl)-alaninamide) and GR 82334 ([D-Pro9[spiro-g-lactam]Leu10]-physalaemin-(1-11)) was investigated to inhibit nicotine (5 mg/kg, s.c.)-, copper sulphate pentahydrate (120 mg/kg, intragastric)- and motion (4 cm horizontal displacement at 1 Hz for 5 min)-induced emesis in Suncus murinus. A 30 min intraperitoneal pre-treatment with CP-122,721, CP-99,994, RP 67580 and FK 888 significantly (P < 0.05) antagonized nicotine-induced emesis with ID50 values of 2.1, 2.3, 13.5 and 19.2 mg/kg, respectively CP-100,263, the less active enantiomer of CP-99,994, was inactive at doses up to 10 mg/kg. Infusion of GR 82334, CP-122,721, CP-99,994 and FK 888 into the dorsal vagal complex of the hindbrain also antagonized nicotine-induced emesis yielding ID50 values of 1.1, 3.0, 3.3 and 58.0 microg/dorsal vagal complex, respectively RP 67580 and CP-100,263 were inactive. RP 67580 and FK 888 failed to antagonize copper sulphate-induced emesis but CP-122,721 and CP-99,994 were active yielding ID50 values of 2.2 and 3.0 mg/kg, i.p., respectively. CP-99,994 also completely prevented motion-induced emesis at 10 mg/kg, i.p. (P < 0.05) and RP 67580 produced a significant reduction of motion-induced emesis at 10 mg/kg, i.p. (P < 0.05). These studies provide evidence of a central site of action of tachykinin NK1 receptor antagonists to inhibit nicotine-induced emesis in S. murinus and confirm the broad profile of inhibitory action. The rank order of potency of the antagonists following the intra-dorsal vagal complex administration suggests that the S. murinus tachykinin NK1 receptor has a unique pharmacological profile.

Differential activity of drugs to induce emesis and pica behavior in Suncus murinus (house musk shrew) and rats

We have previously reported that emetic stimuli induce kaolin ingestion behavior (pica behavior) in rats and mice (i.e., species that do not have the emetic reflex) and that the behavior may be analogous to gastrointestinal discomfort, such as nausea and emesis. We hypothesized that pica behavior may also occur in species capable of vomiting and that it may serve as an additional index of discomfort relevant to antiemetic drug development. The present experiments were conduced using Suncus murinus and rats and kaolin consumption was measured at 24 h after the administration of nicotine (1.25-5 mg/kg, s.c.), copper sulfate (10-120 mg/kg, p.o.), lithium chloride (50-200 mg/kg, i.p.) and cisplatin (1-30 mg/kg, i.p.). In S. murinus, all treatments, excepting lithium chloride, were emetic but none induce kaolin consumption. Conversely, all treatments induced kaolin consumption in rats without inducing emesis. The results indicate that pica behavior is not likely to be useful to assess gastrointestinal discomfort in S. murinus.

Action of 5-HT3 receptor antagonists and dexamethasone to modify cisplatin-induced emesis in Suncus murinus (house musk shrew)

Ondansetron (1-3 mg/kg), granisetron (0.3-1 mg/kg) and dexamethasone (0.3-1 mg/kg), administered at 12-h intervals, were investigated for their potential to prevent cisplatin (30 mg/kg, i.p.)-induced emesis during a 72-h observation period. Ondansetron appeared more active than granisetron to antagonise the emetic response occurring in the first 4-h (P<0.05) period, but none of the regimens significantly antagonised emesis during the 0-24- and 24-72-h periods (P>0.05). However, ondansetron was more active to antagonise emesis on day 1 using a more frequent drug administration, whereas bilateral vagotomy only reduced emesis for 2 h, and 5-HT, 2-methyl-5-HT and 1-m-chloro-phenylbiguanide (up to 20-30 mg/kg, i.p.) were not emetic. The combination of ondansetron 1 mg/kg and dexamethasone 1 mg/kg, both administered every 12 h, significantly delayed the onset of emesis (P<0.05) but failed to reduce the total numbers of retches+vomits over the 3-day period (P>0.05). Results are discussed in relation to the clinical situation.

5-HT3 receptors are not involved in conditioned taste aversions induced by 5-hydroxytryptamine, ipecacuanha or cisplatin

We have used the rat to examine the involvement of the 5-HT3 receptor in the mechanism(s) of conditioned taste aversion induced by 5-hydroxytryptamine (5-HT) and selected emetic drugs. 5-HT, ipecacuanha and cisplatin all induced conditioned taste aversion at doses known to induce emesis in other species but the responses were resistant to treatment with the 5-HT3 receptor antagonists ondansetron and granisetron. Further, m-chlorophenylbiguanide, a selective and potent 5-HT3 receptor agonist, failed to induce a conditioned taste aversion. The data provide strong evidence that the 5-HT3 receptor is not involved in conditioned taste aversion mechanisms in the rat. Results are discussed in terms of the usefulness of the rat conditioned taste aversion paradigm to anti-emetic research.

Action of metyrapone and tetracosactrin to modify cisplatin-induced acute and delayed emesis in the ferret

Cisplatin 5 mg/kg, i.p., induced an acute (day 1) and delayed (days 2 and 3) emetic response in the ferret that was used to investigate the potential anti-emetic activity of metyrapone and tetracosactrin and their potential interaction. The 11beta-hydroxylase enzymes inhibitor metyrapone 10-30 mg/kg, i.p., dose dependently potentiated the acute cisplatin-induce retching+vomiting response by up to 219% at the highest dose (P<0.001) but failed to affect significantly delayed emesis (P>0.05). The adrenocorticotropic hormone (ACTH) mimetic tetracosactrin 0.1 mg/kg, i.m., antagonised significantly the acute and delayed emetic response by 98% (P<0.01) and 75% (P<0.001), respectively. The anti-emetic action of tetracosactrin on acute but not delayed emesis was prevented by combination with metyrapone 10 mg/kg, i.p. Tetracosactrin 0.1 mg/kg, i.m., failed to modify apomorphine (0.25 mg/kg, s.c.)-induced emesis. The potential anti-emetic mechanism of action of metyrapone and tetracosactrin to modulate emesis is discussed.

Profile of Antiemetic Activity of Netupitant Alone or in Combination with Palonosetron and Dexamethasone in Ferrets and Suncus murinus (House Musk Shrew)

Background and Aims: Chemotherapy-induced acute and delayed emesis involves the activation of multiple pathways, with 5-hydroxytryptamine (5-HT; serotonin) playing a major role in the initial response. Substance P tachykinin NK1 receptor antagonists can reduce emesis induced by disparate emetic challenges and therefore have a clinical utility as broad inhibitory anti-emetic drugs. In the present studies, we investigate the broad inhibitory anti-emetic profile of a relatively new NK1 receptor antagonist, netupitant, alone or in combination with the long acting 5-HT3 receptor antagonist, palonosetron, for a potential to reduce emesis in ferrets and shrews. Materials and Methods: Ferrets were pretreated with netupitant and/or palonosetron, and then administered apomorphine (0.125 mg/kg, s.c.), morphine (0.5 mg/kg, s.c.), ipecacuanha (1.2 mg/kg, p.o.), copper sulfate (100 mg/kg, intragastric), or cisplatin (5–10 mg/kg, i.p.); in other studies netupitant was administered to Suncus murinus before motion (4 cm horizontal displacement, 2 Hz for 10 min). Results: Netupitant (3 mg/kg, p.o.) abolished apomorphine-, morphine-, ipecacuanha- and copper sulfate-induced emesis. Lower doses of netupitant (0.03–0.3 mg/kg, p.o.) dose-dependently reduced cisplatin (10 mg/kg, i.p.)-induced emesis in an acute (8 h) model, and motion-induced emesis in S. murinus. In a ferret cisplatin (5 mg/kg, i.p.)-induced acute and delayed emesis model, netupitant administered once at 3 mg/kg, p.o., abolished the first 24 h response and reduced the 24–72 h response by 94.6%; the reduction was markedly superior to the effect of a three times per day administration of ondansetron (1 mg/kg, i.p.). A single administration of netupitant (1 mg/kg, p.o.) plus palonosetron (0.1 mg/kg, p.o.) combined with dexamethasone (1 mg/kg, i.p., once per day), also significantly antagonized cisplatin-induced acute and delayed emesis and was comparable with a once-daily regimen of ondansetron (1 mg/kg, p.o.) plus aprepitant (1 mg/kg, p.o.) in combination with dexamethasone (1 mg/kg, i.p.). Conclusion: In conclusion, netupitant has potent and long lasting anti-emetic activity against a number of emetic challenges indicating broad inhibitory properties. The convenience of protection afforded by the single dosing of netupitant together with palonosetron was demonstrated and also is known to provide an advantage over other therapeutic strategies to control emesis in man.

Brain Activation by H1 Antihistamines Challenges Conventional View of Their Mechanism of Action in Motion Sickness: A Behavioral, c-Fos and Physiological Study in Suncus murinus (House Musk Shrew).

Motion sickness occurs under a variety of circumstances and is common in the general population. It is usually associated with changes in gastric motility, and hypothermia, which are argued to be surrogate markers for nausea; there are also reports that respiratory function is affected. As laboratory rodents are incapable of vomiting, Suncus murinus was used to model motion sickness and to investigate changes in gastric myoelectric activity (GMA) and temperature homeostasis using radiotelemetry, whilst also simultaneously investigating changes in respiratory function using whole body plethysmography. The anti-emetic potential of the highly selective histamine H1 receptor antagonists, mepyramine (brain penetrant), and cetirizine (non-brain penetrant), along with the muscarinic receptor antagonist, scopolamine, were investigated in the present study. On isolated ileal segments from Suncus murinus, both mepyramine and cetirizine non-competitively antagonized the contractile action of histamine with pKb values of 7.5 and 8.4, respectively; scopolamine competitively antagonized the contractile action of acetylcholine with pA2 of 9.5. In responding animals, motion (1 Hz, 4 cm horizontal displacement, 10 min) increased the percentage of the power of bradygastria, and decreased the percentage power of normogastria whilst also causing hypothermia. Animals also exhibited an increase in respiratory rate and a reduction in tidal volume. Mepyramine (50 mg/kg, i.p.) and scopolamine (10 mg/kg, i.p.), but not cetirizine (10 mg/kg, i.p.), significantly antagonized motion-induced emesis but did not reverse the motion-induced disruptions of GMA, or hypothermia, or effects on respiration. Burst analysis of plethysmographic-derived waveforms showed mepyramine also had increased the inter-retch+vomit frequency, and emetic episode duration. Immunohistochemistry demonstrated that motion alone did not induce c-fos expression in the brain. Paradoxically, mepyramine increased c-fos in brain areas regulating emesis control, and caused hypothermia; it also appeared to cause sedation and reduced the dominant frequency of slow waves. In conclusion, motion-induced emesis was associated with a disruption of GMA, respiration, and hypothermia. Mepyramine was a more efficacious anti-emetic than cetirizine, suggesting an important role of centrally-located H1 receptors. The ability of mepyramine to elevate c-fos provides a new perspective on how H1 receptors are involved in mechanisms of emesis control.

Corrigendum: Anti-emetic Action of the Brain-Penetrating New Ghrelin Agonist, HM01, Alone and in Combination With the 5-HT3 Antagonist, Palonosetron and With the NK1 Antagonist, Netupitant, Against Cisplatin- and Motion-Induced Emesis in Suncus murinus (House Musk Shrew)

[This corrects the article DOI: 10.3389/fphar.2018.00869.].

Establishment of a radiotelemetric recording technique in mice to investigate gastric slow waves: Modulatory role of putative neurotransmitter systems

What is the central question of this study? Gastric slow waves originating from the interstitial cells of Cajal–smooth muscle syncytium are usually studied in culture or in tissue segments, but nobody has described recordings of slow waves from awake, freely moving mice. Can radiotelemetry be used to record slow waves, and do they respond predictably to drug treatment? What is the main finding and its importance? Radiotelemetry can be used to record slow waves from awake, freely moving mice, permitting an examination of drug actions in vivo, which is crucial to drug discovery projects for characterizing the effects of drugs and metabolites on gastrointestinal function.