BR-bombesin: a novel bombesin-related peptide from the skin secretion of the Chaco tree frog (Boana raniceps) with physiological gastric effects.

Bombesin mediates several biological activities in the gastrointestinal (GI) tract and central nervous system in mammals, including smooth muscle contraction, secretion of GI hormones and regulation of homeostatic mechanisms. Here, we report a novel bombesin-like peptide isolated from Boana raniceps. Its amino acid sequence, GGNQWAIGHFM-NH2, was identified and structurally confirmed by HPLC, MS/MS and 454-pyrosequencing; the peptide was named BR-bombesin. The effect of BR-bombesin on smooth muscle contraction was assessed in ileum and esophagus, and its anti-secretory activity was investigated in the stomach. BR-bombesin exerted significant contractile activity with a concentration-response curve similar to that of commercially available bombesin in ileum strips of Wistar rats. In esophageal strips, BR-bombesin acted as an agonist, as many other bombesin-related peptides act, although with different behavior compared to the muscarinic agonist carbachol. Moreover, BR-bombesin inhibited stomach secretion by approximately 50% compared to the untreated control group. This novel peptide has 80% and 70% similarity with the 10-residue C-terminal domain of human neuromedin B (NMB) and human gastrin releasing peptide (GRP10), respectively. Molecular docking analysis revealed that the GRP receptor had a binding energy equal to - 7.3 kcal.mol-1 and - 8.5 kcal.mol-1 when interacting with bombesin and BR-bombesin, respectively. Taken together, our data open an avenue to investigate BR-bombesin in disorders that involve gastrointestinal tract motility and acid gastric secretion.

Vasodilatory action of trans-4-methoxy-ß-nitrostyrene in rat isolated pulmonary artery.

Trans-4-methoxy-ß-nitrostyrene (T4MN) induced more potent vasorelaxant effects in resistance arteries from hypertensive rats than its parent drug, ß-nitrostyrene 1-nitro-2-phenylethene (NPe). To better understand the influence of insertion of the electron-releasing methoxy group in the aromatic ring of NPe, we investigated vasorelaxant effects of T4MN in isolated pulmonary artery and compared them with those of NPe in view of the potential interest of T4MN in pulmonary arterial hypertension. T4MN and NPe both caused concentration-dependent vasorelaxation in pulmonary artery rings pre-contracted with either phenylephrine (1 µmol/L) or KCl (60 mmol/L), an effect unaffected by endothelium removal. In endothelium-intact preparations pre-contracted with phenylephrine, the vasorelaxant effect of T4MN was more potent than that of NPe. However, unlike NPe, this effect was significantly reduced following pretreatment with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (10 µmol/L, a guanylate cyclase inhibitor) or tetraethylammonium (5 mmol/L, a potassium channel blocker). T4MN abolished the CaCl2 -induced contractions in pulmonary artery preparations stimulated with phenylephrine (PHE) under Ca2+ -free conditions in the presence of verapamil, to preferentially activate receptor-operated calcium channels. From these findings, we propose that T4MN evokes endothelium-independent vasorelaxant effects in isolated rat pulmonary artery, partially by inhibiting Ca2+ influx through L-type Ca2+ channels, as well as by activating soluble guanylate cyclase and potassium channels. The present results suggest the therapeutic potential of T4MN in treating pulmonary arterial hypertension.

Impairment of rat oesophageal muscle contractility associated with experimental non-erosive oesophageal mucosal damage.

NEW FINDINGS: What is the central question of this study? Is the responsiveness of isolated segments of the rat oesophagus to contractile or relaxant stimuli susceptible to acute luminal exposure of the oesophagus to an acid solution that contains pepsin and bile salt? What is the main finding and its importance? The study reveals that luminal acidity is an important factor that disrupts barrier function in the oesophagus to allow the diffusion of noxious agents, such as bile acid, that alter the contractile status of the oesophageal body, even in the absence of inflammation. ABSTRACT: We investigated whether the experimental simulation of duodenogastro-oesophageal reflux alters the contractile responsiveness of rat oesophageal strips. After 30 min of luminal exposure to a solution at acid pH that contained pepsin and taurodeoxycholic acid, isolated strips of the rat oesophagus and gastro-oesophageal junction were subjected to contractile or relaxing stimuli. Acid challenge decreased the responsiveness of oesophageal strips to contractile stimulation, especially in oesophageal preparations that were mounted following the circular orientation of the muscularis externa layer. The contractility of longitudinal preparations of the rat oesophagus appeared less susceptible to the deleterious effects of acid challenge. In contrast, the responsiveness of ring-like preparations from the gastro-oesophageal junction to contractile stimulation was unaltered by acid challenge. Taurodeoxycholic acid decreased the responsiveness of circular oesophageal preparations to KCl, an effect that was exacerbated by luminal acidity. On the contrary, although the relaxant ability of the rat oesophagus did not change, acid challenge increased the relaxant efficacy of sodium nitroprusside and isoprenaline in strips of the gastro-oesophageal junction. A significant decrease in transepithelial electrical resistance was seen when the oesophageal mucosa was challenged at pH 1 but not at pH 4. Treatment with alginate blunted the deleterious effects of acid challenge on transepithelial electrical resistance and the responsiveness of oesophageal preparations to KCl. The present findings support the notion that luminal acidity is an important factor that disrupts barrier function in the oesophagus to allow the diffusion of noxious agents, such as bile acid, that alter the contractile status of the oesophagus.

Dual excitatory and smooth muscle-relaxant effect of ß-phenylethylamine on gastric fundus strips in rats.

ß-Phenylethylamine (ß-PEA) is a trace amine with chemical proximity to biogenic amines and amphetamines. It is an endogenous agonist of trace amine-associated receptors (TAARs) that acts as a neuromodulator of classic neurotransmitters in the central nervous system. At high concentrations, ß-PEA contracts smooth muscle, and a role for TAARs in these responses has been postulated. The high dietary intake of trace amines has been associated with such symptoms as hypertension and migraine, especially after the intake of foods containing such compounds. In gastrointestinal tissues, TAAR expression was reported, although the effect of ß-PEA on gastric contractile behaviour is unknown. Here, isolated strips that were obtained from the rat gastric fundus were stimulated with high micromolar concentrations of ß-PEA. Under resting tonus, ß-PEA induced contractions. In contrast, when the strips were previously contracted with KCl, a relaxant response to ß-PEA was observed. The contractile effect of ß-PEA was inhibited by 5-hydroxytryptamine (5-HT) receptor antagonists (i.e., cyproheptadine and ketanserin) but not by the TAAR1 antagonist EPPTB. In gastric fundus strips that were previously contracted with 80 mmol/L KCl, the relaxant effect of ß-PEA intensified in the presence of 5-HT receptor antagonists, which was inhibited by EPPTB and the adenylyl cyclase inhibitor MDL-12,330A. The guanylyl cyclase inhibitor ODQ did not alter the relaxant effects of ß-PEA. In conclusion, ß-PEA exerted dual contractile and relaxant effects on rat gastric fundus. The contractile effect appeared to involve the recruitment of 5-HT receptors, and the relaxant effect of ß-PEA on KCl-elicited contractions likely involved TAAR1 .

Gastrointestinal effects of standardized Brazilian phytomedicine (Arthur de Carvalho Drops®) containing Matricaria recutita, Gentiana lutea and Foeniculum vulgare.

Arthur de Carvalho Drops® (ACD) is a traditional Brazilian herbal medicine used to treat functional gastrointestinal disorders (FGIDs). ACD is a formulation of herbal extracts from Matricaria recutita (chamomile), Foeniculum vulgare (fennel) and Gentiana lutea L. (gentian). Considering the popular use for FGIDs, the aim of this work was to investigate the ACD effect on gastric and intestinal parameters with emphasis in a mechanistic approach using isolated duodenal preparations of rodents. Analytical method was developed and validated for quantify three actives principles/markers (Apigenin-7-glucoside, gentiopicroside and anethole) in ACD. The treatment with ACD significantly reduced the emetogenic stimuli induced by cisplatin in rats, showed a laxative effect, reduced the bethanechol-enhanced gastrointestinal transit and completely reversed the contraction induced by carbachol in rat duodenum. However, ACD did not alter the secretory gastric volume or total gastric acidity. The ACD affect the contractions of duodenal smooth muscle mediated by Ca2+ channels and it is also able to inhibit the contractile response mediated by the release from its intracellular store. Furthermore, the relaxant effects of ACD appear independent of the nitric oxide pathway in rat duodenum. These results suggest that ACD could be beneficial for the treatment of disorders of the gastrointestinal tract.

Extracellular acidosis selectively inhibits pharmacomechanical coupling induced by carbachol in strips of rat gastric fundus.

NEW FINDINGS: What is the central question of this study? Acute acidosis that results from short-term exercise is involved in delayed gastric emptying in rats and the lower responsiveness of gastric fundus strips to carbachol. Does extracellular acidosis decrease responsiveness to carbachol in tissues of sedentary rats? How? What is the main finding and its importance? Extracellular acidosis inhibits cholinergic signalling in the rat gastric fundus by selectively influencing the Gq/11 protein signalling pathway. Acute acidosis that results from short-term exercise delays gastric emptying in rats and decreases the responsiveness to carbachol in gastric fundus strips. The regulation of cytosolic Ca2+ concentrations appears to be a mechanism of action of acidosis. The present study investigated the way in which acidosis interferes with gastric smooth muscle contractions. Rat gastric fundus isolated strips at pH 6.0 presented a lower magnitude of carbachol-induced contractions compared with preparations at pH 7.4. This lower magnitude was absent in carbachol-stimulated duodenum and KCl-stimulated gastric fundus strips. In Ca2+ -free conditions, repeated contractions that were induced by carbachol progressively decreased, with no influence of extracellular pH. In fundus strips, CaCl2 -induced contractions were lower at pH 6.0 than at pH 7.4 but only when stimulated in the combined presence of carbachol and verapamil. In contrast, verapamil-sensitive contractions that were induced by CaCl2 in the presence of KCl did not change with pH acidification. In Ca2+ store-depleted preparations that were treated with thapsigargin, the contractions that were induced by extracellular Ca2+ restoration were smaller at pH 6.0 than at pH 7.4, but relaxation that was induced by SKF-96365 (an inhibitor of store-operated Ca2+ entry) was unaltered by extracellular acidification. At pH 6.0, the phospholipase C inhibitor U-73122 relaxed carbachol-induced contractions less than at pH 7.4, and this phenomenon was absent in tissue that was treated with the RhoA kinase blocker Y-27632. Thus, extracellular acidosis inhibited pharmacomechanical coupling in gastric fundus by selectively inhibiting the Gq/11 protein signalling pathway, whereas electromechanical coupling remained functionally preserved.

Nitric Oxide and Hydrogen Sulfide Interact When Modulating Gastric Physiological Functions in Rodents.

AIM: The objective was to evaluate the effects of nitric oxide (NO) and hydrogen sulfide (H2S) donors and possible interactions between these two systems in modulating gastric function. METHODS: Mice received saline, sodium nitroprusside (SNP), or sodium hydrosulfite (NaHS), and after 1 h, the animals were killed for immunofluorescence analysis of CSE or eNOS expressions, respectively. Other groups received saline, SNP, NaHS, Lawesson's reagent (H2S donor), PAG + SNP, L-NAME, L-NAME + NaHS, or L-NAME + Lawesson's reagent. Then, the gastric secretions (mucous and acid), gastric blood flow, gastric defense against ethanol, and gastric motility (gastric emptying and gastric contractility) were evaluated. RESULTS: SNP and NaHS increased the expression of CSE or eNOS, respectively. SNP or Lawesson's reagent did not alter gastric acid secretion but increased mucus production, and these effects reverted with PAG and L-NAME treatment, respectively. SNP or NaHS increased gastric blood flow and protected the gastric mucosa against ethanol injury, and these effects reverted with PAG and L-NAME treatments, respectively. SNP delayed gastric emptying when compared with saline, and PAG partially reversed this effect. NaHS accelerate gastric emptying, and L-NAME partially reversed this effect. SNP and NaHS alone induced gastric fundus and pylorus relaxation. However, pretreatment with PAG or L-NAME reversed these relaxant effects only in the pylorus but not in the gastric fundus. CONCLUSION: NO and H2S interact in gastric physiological functions, and this "cross-talk" is important in the control of mucus secretion, gastric blood flow, gastric mucosal defense, and gastric motility, but not in the control of basal gastric acid secretion.

Mechanism of the vasorelaxant effect induced by trans-4-methyl-ß-nitrostyrene, a synthetic nitroderivative, in rat thoracic aorta.

Mechanisms underlying the vasorelaxant effects of trans-4-methyl-ß-nitrostyrene (T4MeN) were studied in rat aortic rings. In endothelium-intact preparations, T4MeN fully and similarly relaxed contractions induced by phenylephrine (PHE) (IC50  = 61.41 [35.40-87.42] µmol/L) and KCl (IC50  = 83.50 [56.63-110.50] µmol/L). The vasorelaxant effect of T4MeN was unchanged by endothelium removal, pretreatment with L-NAME, indomethacin, tetraethylammonium, ODQ or MDL-12,330A. Under Ca2+ -free conditions, T4MeN significantly reduced with a similar potency: (i) phasic contractions induced by PHE, but not by caffeine; (ii) contractions due to CaCl2 in aortic preparations stimulated with PHE (in the presence of verapamil) or high KCl; (iii) contractions evoked by the restoration of external Ca2+ levels after depletion of intracellular Ca2+ stores in the presence of thapsigargin. In contrast, T4MeN was more potent at inhibiting contractions evoked by the tyrosine phosphatase inhibitor, sodium orthovanadate, than those induced by the activator of PKC, phorbol-12,13-dibutyrate. These results suggest that T4MeN induces an endothelium- independent vasorelaxation that appears to occur intracellularly through the inhibition of contractions that are independent of Ca2+ influx from the extracellular milieu but involve phosphorylation of tyrosine residues.

Side-Effects of Irinotecan (CPT-11), the Clinically Used Drug for Colon Cancer Therapy, Are Eliminated in Experimental Animals Treated with Latex Proteins from Calotropis procera (Apocynaceae).

Intestinal mucositis (IM) is the critical side effect of irinotecan (CPT-11), which is the front-line drug used for the treatment of colorectal cancer. This study aimed to evaluate the effectiveness of latex proteins (LP) from Calotropis procera to prevent IM and diarrhea in animals. Swiss mice were treated daily with saline or LP (1, 5, or 50 mg/kg, i.v.) 24 h prior to CTP-11 (75 mg/kg/4 days, i.p) and for additional 6 days. Animal survival, body weight variation, and diarrhea were registered. After animal sacrifice (day 7 post first injection of CPT-11), intestinal samples were collected to study morphology and inflammatory parameters. Animals given LP exhibited improved parameters (survival, body weight, and absence of diarrhea) as compared with the CPT-11 control. The severity of IM observed in animals given CPT-11 was reduced in animals treated with LP. Treatment with LP also prevented the reduction in the villus/crypt ratio promoted by CPT-11. The rise in MPO activity and pro-inflammatory cytokines, over-contractility of the smooth muscle, and diarrhea were all abrogated in LP-treated mice. Markedly reduced immunostaining intensity for COX-2, TNF-α, IL-1ß, iNOS, and NF-κB was observed in the intestinal tissue of animals treated with LP. The side-effects of CPT-11 were eliminated by LP treatment in experimental animals and improved clinical parameters characteristic of IM All known biochemical pathogenesis. Copyright © 2016 John Wiley & Sons, Ltd.

A simple laboratory exercise with rat isolated esophagus and stomach fundus to reveal functional differences between striated and smooth muscle cells.

This study describes an undergraduate student laboratory activity using isolated preparations from rat gastrointestinal tissues that possess contractile profiles typically exhibited by striated and smooth muscle cells. While students are introduced to an ex vivo methodology, they can compare differences in trace experiments, twitch aspects, phasic and tonic properties, force-frequency relationships, and pharmacological responsiveness of esophageal (striated) and fundic (smooth muscle) segments. Muscle strips were subjected to electrical field stimulation (EFS) applied by platinum electrodes immersed in the physiological solution. The contractile profile of EFS responses varied between these two types of gut preparations. Atropine and tubocurarine revealed differential inhibitory influences in esophagus or fundus tissues; caffeine and procaine produced similar effects, i.e., potentiation and blockade of the EFS-induced contractile response in these tissues, respectively. Experimental results obtained during the activity helped the improvement of student learning about basic concepts previously discussed in theoretical lectures. To measure student learning with this laboratory exercise, a questionnaire was applied before and after the activity, and the number of expected correct answers, concerning the mechanisms of contraction in striated and smooth muscle, could be clearly evidenced.

Vasorelaxant effects of 2-nitro-1-phenyl-1-propanol in rat aorta.

2-Nitro-1-phenyl-1-propanol (NPP) is a nitro alcohol that is known as an intermediate in the synthesis of sympathomimetic agents, such as norephedrine. The present study investigated the vasoactive effects of NPP on rat aorta. In endothelium-intact aortic rings, NPP fully relaxed contractions that were induced by phenylephrine, KCl, and U-46619. The relaxant effects of NPP on phenylephrine-elicited contractions remained unaffected by NG-nitro-l-arginine methyl ester (l-NAME), indomethacin, propranolol, tetraethylammonium, 4-aminopyridine, and glibenclamide. Conversely, pretreatment with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), cis-N-(2-phenylcyclopentyl)-azacyclotridec-1-en-2-amine hydrochloride (MDL-12,330A), and N-[2-(P-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H-89) reduced the ability of NPP to relax contractions that were elicited by phenylephrine. NPP inhibited the vasoconstrictor response that was induced by Ca2+ in aortic rings that were stimulated by pharmacomechanical or electromechanical coupling with phenylephrine and 60 mmol/L KCl, respectively, and after the depletion of intracellular Ca2+ stores. Such effects of NPP were significantly reversed by pretreatment with the guanylyl cyclase inhibitor ODQ and weakly influenced by the adenylyl cyclase inhibitor MDL-12,330A. In Ca2+ -free medium, NPP inhibited transient contractions that were induced by phenylephrine but not caffeine. In homogenates of aortic rings, NPP increased cyclic guanosine 3',5'-monophosphate (cGMP) and cyclic adenosine 3'-5'-monophosphate levels, but this effect was statistically significant only for cGMP. In conclusion, in contrast to the vasoconstrictor amine norephedrine, NPP is a vasodilator in rat aorta, and its relaxant effects are likely attributable to cGMP production.

α-Terpineol Induces Gastric Retention of Liquids by Inhibiting Vagal Parasympathetic Pathways in Rats.

α-Terpineol is a monoterpene with smooth muscle relaxant properties. In this study, its effects on the gastric emptying rate of awake rats were evaluated with emphasis on the mode by which it induces gastrointestinal actions. Administered by gavage, α-terpineol (50 mg/kg) delayed gastric emptying of a liquid test meal at 10 min postprandial. Hexamethonium or guanethidine did not interfere with the retarding effect induced by α-terpineol, but atropine and L-NG-nitroarginine methyl ester abolished it. In vagotomized rats, α-terpineol did not delay gastric emptying. In isolated strips of gastric fundus, concentration-effect curves in response to carbamylcholine were higher in magnitude after treatment with the monoterpene. α-Terpineol (1 to 2000 µM) relaxed sustained contractions induced by carbamylcholine or a high K+ concentration in a concentration-dependent manner. This relaxing effect was not affected by the presence of L-NG-nitroarginine methyl ester, 1 H-[1, 2, 4]oxadiazolo[4,3-a]quinoxalin-1-one, tetraethylammonium, or atropine. Smooth muscle contractions induced by electrical field stimulation were inhibited by α-terpineol. In conclusion, α-terpineol induced gastric retention in awake rats through mechanisms that depended on intact vagal innervation to the stomach, which involved cholinergic/nitrergic signalling. Such a retarding effect induced by α-terpineol appears not to result from a direct action of the monoterpene on gastric smooth muscle cells.

Cardiovascular effects of a labdenic diterpene isolated from Moldenhawera nutans in conscious, spontaneously hypertensive rats.

CONTEXT: The labdenic diterpene labd-8(17)-en-15-oic acid (labd-8) isolated from a methanolic extract of Moldenhawera nutans Queiroz & Alkin (Leguminosae) has hypotensive and tachycardiac properties in normotensive rats. A part of the hypotensive effect was due to a reduction in the sympathetic nerve drive to vessels, an event admittedly enhanced in spontaneously hypertensive rats (SHRs). OBJECTIVES: We assessed whether the cardiovascular effects induced by labd-8 could be enhanced in SHRs. MATERIALS AND METHODS: For in vivo experiments, arterial and venous catheters were implanted under anesthesia for blood pressure recording and drug administration, respectively. For in vitro experiments, thoracic aorta rings were suspended in organ baths containing warm (37 °C) perfusion medium that was continuously bubbled with carbogen. RESULTS: Intravenous injection of labd-8 (1, 3, 5, and 10 mg/kg) induced similar dose-dependent hypotension and tachycardia in both SHRs and Wistar-Kyoto rats (WKY). In SHRs, only the tachycardia response to labd-8 was significantly reduced by pretreatment with methylatropine or propranolol. However, both cardiovascular effects of labd-8 were reduced by hexamethonium while remained unchanged by l-NAME. In isolated aortic preparations from SHRs, labd-8 (1-1000 µg/mL) relaxed potassium-induced contractions with an IC50 (geometric mean [95% confidence interval]) value (536.5 [441.0-631.9] µg/mL) significantly greater than that (157.6 [99.1-250.5] µg/mL) obtained in preparations from WKY rats. CONCLUSION: In SHRs, the hypotension induced by labd-8 is associated with a reflex tachycardia and seems mediated partly through withdrawal of sympathetic vasomotor tone and partly through an active vasorelaxation. Its magnitude was not enhanced when compared with WKY rats likely because of impaired vasorelaxant effects of labd-8 in preparations from SHRs.

Vasorelaxation induced by methyl cinnamate, the major constituent of the essential oil of Ocimum micranthum, in rat isolated aorta.

The aim of the present study was to investigate the vascular effects of the E-isomer of methyl cinnamate (E-MC) in rat isolated aortic rings and the putative mechanisms underlying these effects. At 1-3000 µmol/L, E-MC concentration-dependently relaxed endothelium-intact aortic preparations that had been precontracted with phenylephrine (PHE; 1 µmol/L), with an IC50 value (geometric mean) of 877.6 µmol/L (95% confidence interval (CI) 784.1-982.2 µmol/L). These vasorelaxant effects of E-MC remained unchanged after removal of the vascular endothelium (IC50 725.5 µmol/L; 95% CI 546.4-963.6 µmol/L) and pretreatment with 100 µmol/L N(G) -nitro-l-arginine methyl ester (IC50 749.0 µmol/L; 95% CI 557.8-1005.7 µmol/L) or 10 µmol/L 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (IC50 837.2 µmol/L; 95% CI 511.4-1370.5 µmol/L). Over the concentration range 1-3000 µmol/L, E-MC relaxed K(+) -induced contractions in mesenteric artery preparations (IC50 314.5 µmol/L; 95% CI 141.9-697.0 µmol/L) with greater potency than in aortic preparations (IC50 1144.7 µmol/L; 95% CI 823.2-1591.9 µmol/L). In the presence of a saturating contractile concentration of K(+) (150 mmol/L) in Ca(2+) -containing medium combined with 3 µmol/L PHE, 1000 µmol/L E-MC only partially reversed the contractile response. In contrast, under similar conditions, E-MC nearly fully relaxed PHE-induced contractions in aortic rings in a Ba(2+) -containing medium. In preparations that were maintained under Ca(2+) -free conditions, 600 and 1000 µmol/L E-MC significantly reduced the contractions induced by exogenous Ca(2+) or Ba(2+) in KCl-precontracted preparations, but not in PHE-precontracted preparations (in the presence of 1 µmol/L verapamil). In addition, E-MC (1-3000 µmol/L) concentration-dependently relaxed the contractions induced by 2 mmol/L sodium orthovanadate. Based on these observations, E-MC-induced endothelium-independent vasorelaxant effects appear to be preferentially mediated by inhibition of plasmalemmal Ca(2+) influx through voltage-dependent Ca(2+) channels. However, the involvement of a myogenic mechanism in the effects of E-MC is also possible.

Linalool-rich rosewood oil induces vago-vagal bradycardic and depressor reflex in rats.

Cardiovascular effects of the linalool-rich essential oil of Aniba rosaeodora (here named as EOAR) in normotensive rats were investigated. In anesthetized rats, intravenous (i.v.) injection of EOAR induced dose-dependent biphasic hypotension and bradycardia. Emphasis was given to the first phase (phase 1) of the cardiovascular effects, which is rapid (onset time of 1-3 s) and not observed in animals submitted to bilateral vagotomy or selective blockade of neural conduction of vagal C-fibre afferents by perineural treatment with capsaicin. Phase 1 was also absent when EOAR was directly injected into the left ventricle injection, but it was unaltered by i.v. pretreatment with capsazepine, ondansetron or HC030031. In conscious rats, EOAR induced rapid and monophasic hypotensive and bradycardiac (phase 1) effects that were abolished by i.v. methylatropine. In endothelium-intact aortic rings, EOAR fully relaxed phenylephrine-induced contractions in a concentration-dependent manner. The present findings reveal that phase 1 of the bradycardiac and depressor responses induced by EOAR has a vago-vagal reflex origin resulting from the vagal pulmonary afferents stimulation. Such phenomenon appears not to involve the recruitment of C-fibre afferents expressing 5HT3 receptors or the two chemosensory ion channels TRPV1 and TRPA1 . Phase 2 hypotensive response appears resulting from a direct vasodilatory action.

Therapeutic effects of a lipid transfer protein isolated from Morinda citrifolia L. (noni) seeds on irinotecan-induced intestinal mucositis in mice.

This work aimed to evaluate the activity of a lipid transfer protein isolated from Morinda citrifolia L. seeds, McLTP1, on the development of intestinal mucositis following irinotecan administration. McLTP1 (0.5, 2, and 8 mg/kg, i.v.) was injected into mice 1h before irinotecan administration (75 mg/kg, i.p.; 4 days), and then for additional 6 days. Seven days after the first dose of irinotecan, diarrhea was assessed, and the intestine was removed for histological evaluation, assessment of intestinal over-contractility, measurement of myeloperoxidase (MPO), proinflammatory cytokines and chemokine (IL-1, IL-6, and KC levels - a murine homolog of human IL-8 chemokine), analysis of cyclooxygenase 2 (COX-2), nuclear factor kappa B (NF-κB), and nitric oxide synthase (iNOS) expression. At the two highest doses, McLTP1 administration decreased mortality and diarrhea. McLTP1 (8 mg/kg, i.v.) significantly prevented irinotecan-induced intestinal damage and led to a reduction in over-contractility of the intestinal muscle (p < 0.05). Moreover, McLTP1 decreased the MPO, IL-1ß, IL-6, and KC levels by 74.7%, 42%, 92.9%, and 95.9%, respectively. Also, the expression of COX-2, NF-κB, and iNOS was reduced. Our study provides a potential new therapeutic for preventing irinotecan-induced mucositis, improved clinical parameters, and reduced inflammation.

The essential oil of Eucalyptus tereticornis and its constituents, α- and ß-pinene, show accelerative properties on rat gastrointestinal transit.

The essential oil of Eucalyptus tereticornis (EOET) has pharmacological activities but their effects on the gastrointestinal tract are yet unknown. It possesses α- and ß-pinene as minor constituents, isomers largely used as food or drink additives. In this work, we studied their actions on gut motility. After feeding with a liquid test meal, conscious rats received perorally EOET, α-, or ß-pinene, and the fractional dye retention was determined. EOET and its constituents decreased the gastric retention. In anesthetized rats, pinenes increased gastric tonus, while enhancing the meal progression in the small intestine of conscious rats. Both α- and ß-pinene contracted gastric strips IN VITRO but relaxed the duodenum. Conversely, EOET relaxed both the gastric and duodenal strips. In conclusion, EOET accelerates the gastric emptying of liquid, and part of its action is attributed to the contrasting effects induced by α- and ß-pinene on the gut.

Soluble guanylate cyclase stimulator, trans-4-methoxy-ß-nitrostyrene, has a beneficial effect in monocrotaline-induced pulmonary arterial hypertension in rats.

The soluble guanylate cyclase (sGC)/GMPc pathway plays an important role in controlling pulmonary arterial hypertension (PAH). We investigated whether the novel sGC stimulator trans-4-methoxy-ß-nitrostyrene (T4MN), ameliorates monocrotaline (MCT)-induced PAH. At Day 0, rats were injected with MCT (60 mg/kg, s. c.). Control (CNT) rats received an equal volume of monocrotaline vehicle only (s.c.). Four weeks later, MCT-treated rats were orally treated for 14 days with T4MN (75 mg/kg/day) (MCT-T4MN group) or its vehicle (MCT-V group), and with sildenafil (SIL; 50 mg/kg) (MCT-SIL group). Compared to the CNT group, MCT treatment induced a significant increase in both the Fulton index and RV systolic pressure but significantly reduced the maximum relaxation induced by acetylcholine. Indeed, MCT treatment increased the wall thickness of small and larger pulmonary arterioles. Oral treatment with T4MN and SIL reduced the Fulton index and RV systolic pressure compared to the MCT-V group. Maximum relaxation induced by acetylcholine was significantly enhanced in MCT-SIL group. Both T4MN and SIL significantly reduced the enhanced wall thickness of small and larger pulmonary arterioles. Treatment with T4MN has a beneficial effect on PAH by reducing RV systolic pressure and consequently right ventricular hypertrophy, and by reducing pulmonary artery remodeling. T4MN may represent a new therapeutic or complementary approach for the treatment of PAH.

Vasorelaxant effect of trans-4-chloro-ß-nitrostyrene, a synthetic nitroderivative, in rat thoracic aorta.

Previously, we showed that 1-nitro-2-phenylethene, a nitrostyrene derivative of 1-nitro-2-phenylethane, induced vasorelaxant effects in rat aorta preparations. Here, we studied mechanisms underlying the vasorelaxant effects of its structural analog, trans-4-chloro-ß-nitrostyrene (T4CN), in rat aortic rings. Increasing concentrations of T4CN (0.54-544.69 µm) fully and similarly relaxed contractions induced by phenylephrine (PHE, 1 µm) or KCl (60 mm) in endothelium-intact aortic rings with IC50 values of 66.74 [59.66-89.04] and 79.41 [39.92-158.01] µm, respectively. In both electromechanical and pharmacomechanical couplings, the vasorelaxant effects of T4CN remained unaltered by endothelium removal, as evidenced by the IC50 values (108.35 [56.49-207.78] and 65.92 [39.72-109.40] µm, respectively). Pretreatment of endothelium-intact preparations with L-NAME, ODQ, glibenclamide, or TEA did not change the vasorelaxant effect of T4CN. Under Ca2+ -free conditions, T4CN significantly reduced the phasic contractions induced by caffeine or PHE, as well as the contractions due to exogenous CaCl2 in aortic preparations stimulated with PHE (in the presence of verapamil). These results suggest that in rat aortic rings, T4CN induced vasorelaxation independently from the activation of soluble guanylate cyclase/cGMP pathway, an effect that may be related to the electrophilicity of the substituted chloro-nitrostyrene. This vasorelaxation seems to involve inhibition of both calcium influx from the extracellular milieu and calcium mobilization from intracellular stores mediated by IP3 receptors and by ryanodine-sensitive Ca2+ channels.

Differential effects of ß-methylphenylethylamine and octopamine on contractile parameters of the rat gastrointestinal tract.

This study tested the effects of ß-methylphenylethylamine (ß-MPEA) and octopamine on contractile parameters of the gastrointestinal tract in rats. We hypothesized that some of their effects result from interactions with trace amine (TA)-associated receptors or serotoninergic 5-hydroxytryptamine (5-HT) receptors. ß-MPEA-induced contractions in rat gastric fundus strips under resting tonus conditions, but induced relaxation in preparations that were previously contracted with carbachol. Octopamine relaxed gastric fundus strips maintained at resting tonus or contracted with carbachol. The contractile effect of ß-MPEA was reduced by cyproheptadine and methiothepin, antagonists of excitatory 5-HT receptors. The relaxing effect of ß-MPEA on gastric fundus was insensitive to pretreatment with N-(3-ethoxyphenyl)-4-(1-pyrrolidinyl)-3-(trifluoromethyl)benzamide (EPPTB) and tropisetron, antagonists of TA1 and 5-HT4 receptors, respectively. Both EPPTB and tropisetron inhibited the relaxant effects of octopamine on carbachol-contracted preparations. Contrarily, EPPTB did not reduce the relaxant effects of RO5263397 (TA1 agonist) or zacopride (5-HT4 agonist). Octopamine, but not ß-MPEA, delayed the gastrointestinal transit of a liquid test meal in awaken rats. In isolated preparations of the small intestine under resting conditions, ß-MPEA did not alter the basal tonus, but octopamine relaxed it. Intestinal preparations previously contracted with carbachol relaxed after the addition of octopamine and decreased the magnitude of their spontaneous rhythmic contractions in a tropisetron-dependent manner. Thus, ß-MPEA and octopamine exerted pharmacological actions on the rat gastrointestinal tract. The excitatory effects of ß-MPEA involved 5-HT receptors. Octopamine inhibited the rat gut contractility through the likely involvement of 5-HT4 and TA receptors. Overall, octopamine effectively inhibited rat gastrointestinal transit.