No description available.

Kai Hong Kwok. / Thesis submitted in: December 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 90-98). / Abstract also in Chinese. / Chapter Chapter 1 --- Introduction / Chapter 1.1. --- Classification of β-adrenoceptor in cardiovascular system --- p.1 / Chapter 1.2. --- Vasodilator effects of β-adrenoceptor-agonists and their mechanisms --- p.4 / Chapter 1.3. --- Role of endothelium in β-adrenoceptor-mediated vasodilation --- p.7 / Chapter 1.4. --- Role of K+ channels in β-adrenoceptor-mediated relaxation --- p.11 / Chapter 1.5. --- Other aspect regarding the vascular response to stimulation of B-adrenoceptor --- p.15 / Chapter 1.6. --- Clinical aspect of B-adrenoceptor agents --- p.15 / Chapter Chapter 2 --- Methods and Materials / Chapter 2.1. --- Tissue Preparation --- p.19 / Chapter 2.1.1. --- Preparation of the isolated rat mesenteric artery --- p.19 / Chapter 2.1.2. --- Removal of the functional endothelium --- p.19 / Chapter 2.1.3. --- Organ bath set-up --- p.20 / Chapter 2.1.4. --- Length-tension relationship and an optimal resting tension --- p.22 / Chapter 2.2. --- Experimental Procedure --- p.22 / Chapter 2.2.1. --- Relaxant effects of the B-adrenoceptor agonists --- p.24 / Chapter 2.2.2. --- Effects of putative K+ channel blockers --- p.24 / Chapter 2.2.3. --- Effects of inhibitors of nitric oxide activity --- p.25 / Chapter 2.2.4. --- Effect of indomethacin --- p.25 / Chapter 2.2.5. --- "Effects of K+ channel opener, nitric oxide donor and forskolin" --- p.26 / Chapter 2.3. --- Chemicals and Solutions --- p.26 / Chapter 2.3.1. --- Chemicals and drugs --- p.26 / Chapter 2.3.2. --- Preparation of drug stock solutions --- p.26 / Chapter 2.3.3. --- Solutions --- p.28 / Chapter 2.4. --- Statistical Analysis --- p.28 / Chapter Chapter 3 --- Results / Chapter 3.1. --- Relaxant Effect of Isoprenaline --- p.29 / Chapter 3.1.1. --- Relaxant effect of isoprenaline --- p.29 / Chapter 3.1.2. --- Effects of inhibitors of nitric oxide activity --- p.29 / Chapter 3.1.3. --- Effect of charybdotoxin on the vasorelaxant response to isoprenaline --- p.32 / Chapter 3.1.4. --- Effect of glibenclamide on the vasorelaxant response to isoprenaline --- p.32 / Chapter 3.1.5. --- Effect of TPA+ on isoprenaline-induced relaxation --- p.36 / Chapter 3.1.6. --- Effect of TPA+ in the presence of iberiotoxin or glibenclamide --- p.36 / Chapter 3.1.7. --- Effect of Ba2+ on the vasorelaxant effect of isoprenaline --- p.41 / Chapter 3.1.8. --- Effect of raising extracellular K+ on isoprenaline-mediated relaxation --- p.41 / Chapter 3.2. --- Relaxant Effect of Dobutamine --- p.44 / Chapter 3.2.1. --- Effects of inhibitors of endothelium-derived factors on the relaxant effect of dobutamine --- p.44 / Chapter 3.2.2. --- Antagonism of the effect of dobutamine by β1-adrenoceptor antagonist --- p.44 / Chapter 3.2.3. --- Effects of putative Kca channel blockers on the relaxant effect of dobutamine --- p.51 / Chapter 3.2.4. --- Effect of TPA+ on the relaxant effect of dobutamine --- p.55 / Chapter 3.2.5. --- Effect of raising extracellular K+ on the relaxant effect of dobutamine --- p.55 / Chapter 3.3. --- Relaxant Effect of Fenoterol --- p.57 / Chapter 3.3.1. --- Effect of inhibitors of nitric oxide activity on the relaxant effect of fenoterol --- p.57 / Chapter 3.3.2. --- Effect of charybdotoxin on the relaxant effect of fenoterol --- p.57 / Chapter 3.3.3. --- Effect of TPA+ on the relaxant effect of fenoterol --- p.64 / Chapter 3.3.4. --- Effect of glibenclamide on the relaxant effect of fenoterol --- p.64 / Chapter 3.3.5. --- Effect of raising extracellular K+ on fenoterol-mediated relaxation --- p.64 / Chapter 3.4. --- Effects of cAMP- and cGMP-elevating agents --- p.69 / Chapter 3.4.1. --- Effects of inhibitors of endothelium-derived factors on the relaxation induced by nitroprusside and forskolin --- p.69 / Chapter 3.4.2 --- Effect of charybdotoxin on relaxant effect of forskolin --- p.69 / Chapter 3.4.3 --- Effect of Ba2+ on the vasorelaxant effect of forskolin --- p.76 / Chapter 3.4.4 --- Effect of TPA+ on the relaxant effect of forskolin --- p.76 / Chapter 3.4.5 --- Effect of glibenclamide on the relaxant effects of forskolin and cromakalim --- p.76 / Chapter Chapter 4 --- Discussion / Chapter 4.1. --- Effect of Isoprenaline and Fenoterol --- p.77 / Chapter 4.2. --- Effect of Dobutamine --- p.83 / Chapter 4.3. --- Conclusion --- p.88 / References --- p.90 / Publications --- p.98

Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / "August 2002." Typescript. Vita. Includes bibliographical references (leaves 132-150).

Thesis (Ph. D.)--Michigan State University. Neuroscience, 2008. / Title from PDF t.p. (Proquest, viewed on Aug. 17, 2009) Includes bibliographical references (p. 202-230). Also issued in print.

A fluoxetina, fármaco inibidor seletivo da recaptação de serotonina (ISRS), tem sido amplamente utilizada no tratamento da depressão. Este antidepressivo possui diversos efeitos sobre o sistema cardiovascular podendo alterar a função cardíaca e a inibição da função de diversos receptores e canais iônicos diretamente envolvidos na regulação do tônus vasomotor. Crestani et al. (2011) demonstraram que ratos tratados cronicamente com fluoxetina exibem aumento da pressão arterial e redução do componente simpático do baroreflexo. Estes resultados sugerem aumento do tônus vasomotor e desequilíbrio de fatores responsáveis por sua regulação. A hipótese do trabalho é que o tratamento crônico com fluoxetina aumentará a reatividade vascular a estímulos contráteis e diminuirá para estímulos relaxantes. Portanto o objetivo do presente trabalho foi investigar se o tratamento crônico com fluoxetina promove alterações de reatividade no leito mesentérico arterial isolado de ratos e em artérias mesentéricas isoladas. Foram utilizados ratos Wistar (230-270 gr) divididos em 2 grupos: (I) veículo (água por 21 dias) e (II) fluoxetina crônico (fluoxetina 10 mg/kg/dia por 21 dias na água de beber). Protocolos de reatividade vascular da artéria mesentérica de resistência e do leito arterial mesentérico (LAM), de expressão gênica e proteica de componentes das vias de sinalização envolvidos nestas respostas foram realizados. O tratamento crônico com fluoxetina promoveu redução da resposta contrátil a fenilefrina. Este resultado foi associado a uma menor expressão de tirosina hidroxilase e recaptação de noradrenalina nas terminações simpáticas do LAM. A sinalização da ERK1/2 também foi diminuída. Em contraste, houve aumento da resposta contrátil ao cloreto de potássio, sem alteração da contração a estimulação elétrica periarterial. O tratamento com fluoxetina promoveu ainda aumento de óxido nítrico (NO), maior fosforilação do resíduo serina1177 da eNOS e sensibilidade dos canais para K+ ativados por ATP (KATP). Em conclusão, a fluoxetina promove redução da resposta contrátil no LAM devido ao aumento de NO e participação de canais para K+. Além disso, a regulação negativa da liberação de noradrenalina e da sinalização da ERK1/2 pode contribuir para a menor resposta contrátil no músculo liso vascular. O aumento da resposta relaxante na artéria mesentérica de resistência pode ser mediado pelo aumento de NO, maior fosforilação da eNOS e ativação de canais para KATP . / Fluoxetine, a selective serotonin reuptake inhibitor (SSRI) drug, has been widely used in the treatment of depression. This antidepressant has several effects on the cardiovascular system and may alter cardiac function and also inhibits the function of several receptors and ion channels directly involved in the regulation of vasomotor tone. Crestani et al. (2011) reported that rats chronically treated with fluoxetine exhibit increased blood pressure and reduced sympathetic component of the baroreflex. These results suggest increased vasomotor tone and imbalance of factors responsible for its regulation. We hypothesize that the chronic treatment with fluoxetine will increase vascular reactivity to contractile stimulus and will reduce to relaxant stimulus. Therefore the objective of this study was to investigate whether chronic treatment with fluoxetine promotes changes on the reactivity of isolated mesenteric arterial bed and resistance mesenteric arteries from rats. Wistar rats (230-270 g) were used and divided in two groups: (I) vehicle (water for 21 days) and (II) chronic fluoxetine (fluoxetine 10 mg/ kg/ day for 21 days in drinking water). Protocols of vascular reactivity were performed on resistance mesenteric arteries and mesenteric arterial bed (MAB). In addition, gene and protein expression of the signaling pathways involved in these responses was evaluated. Chronic treatment with fluoxetine decreased contractile response to phenylephrine. This result was associated with reduced tyrosine hydroxylase expression as well as noradrenaline (NA) reuptake in MAB sympathetic nerve endings. Similarly, ERK 1/2 signaling was decreased. In contrast, fluoxetine treatment increased contractile response to potassium chloride (KCl) without changing the electric field stimulation-(EFS)-induced contraction. Fluoxetine treatment also increased nitric oxide (NO), the phosphorylation levels of eNOS at serine1177 residue and KATP channels sensitivity. In conclusion, fluoxetine promotes reduction of the contractile response in MAB due to increase in NO and K+ channels contribution. In addition, negative regulation of NA release and ERK 1/2 signaling may contribute to decrease smooth muscle contractile response. Increased resistance mesenteric artery relaxant response may be mediated by increased NO, eNOS phosphorylation and KATP channels activation.

A fluoxetina, fármaco inibidor seletivo da recaptação de serotonina (ISRS), tem sido amplamente utilizada no tratamento da depressão. Este antidepressivo possui diversos efeitos sobre o sistema cardiovascular podendo alterar a função cardíaca e a inibição da função de diversos receptores e canais iônicos diretamente envolvidos na regulação do tônus vasomotor. Crestani et al. (2011) demonstraram que ratos tratados cronicamente com fluoxetina exibem aumento da pressão arterial e redução do componente simpático do baroreflexo. Estes resultados sugerem aumento do tônus vasomotor e desequilíbrio de fatores responsáveis por sua regulação. A hipótese do trabalho é que o tratamento crônico com fluoxetina aumentará a reatividade vascular a estímulos contráteis e diminuirá para estímulos relaxantes. Portanto o objetivo do presente trabalho foi investigar se o tratamento crônico com fluoxetina promove alterações de reatividade no leito mesentérico arterial isolado de ratos e em artérias mesentéricas isoladas. Foram utilizados ratos Wistar (230-270 gr) divididos em 2 grupos: (I) veículo (água por 21 dias) e (II) fluoxetina crônico (fluoxetina 10 mg/kg/dia por 21 dias na água de beber). Protocolos de reatividade vascular da artéria mesentérica de resistência e do leito arterial mesentérico (LAM), de expressão gênica e proteica de componentes das vias de sinalização envolvidos nestas respostas foram realizados. O tratamento crônico com fluoxetina promoveu redução da resposta contrátil a fenilefrina. Este resultado foi associado a uma menor expressão de tirosina hidroxilase e recaptação de noradrenalina nas terminações simpáticas do LAM. A sinalização da ERK1/2 também foi diminuída. Em contraste, houve aumento da resposta contrátil ao cloreto de potássio, sem alteração da contração a estimulação elétrica periarterial. O tratamento com fluoxetina promoveu ainda aumento de óxido nítrico (NO), maior fosforilação do resíduo serina1177 da eNOS e sensibilidade dos canais para K+ ativados por ATP (KATP). Em conclusão, a fluoxetina promove redução da resposta contrátil no LAM devido ao aumento de NO e participação de canais para K+. Além disso, a regulação negativa da liberação de noradrenalina e da sinalização da ERK1/2 pode contribuir para a menor resposta contrátil no músculo liso vascular. O aumento da resposta relaxante na artéria mesentérica de resistência pode ser mediado pelo aumento de NO, maior fosforilação da eNOS e ativação de canais para KATP . / Fluoxetine, a selective serotonin reuptake inhibitor (SSRI) drug, has been widely used in the treatment of depression. This antidepressant has several effects on the cardiovascular system and may alter cardiac function and also inhibits the function of several receptors and ion channels directly involved in the regulation of vasomotor tone. Crestani et al. (2011) reported that rats chronically treated with fluoxetine exhibit increased blood pressure and reduced sympathetic component of the baroreflex. These results suggest increased vasomotor tone and imbalance of factors responsible for its regulation. We hypothesize that the chronic treatment with fluoxetine will increase vascular reactivity to contractile stimulus and will reduce to relaxant stimulus. Therefore the objective of this study was to investigate whether chronic treatment with fluoxetine promotes changes on the reactivity of isolated mesenteric arterial bed and resistance mesenteric arteries from rats. Wistar rats (230-270 g) were used and divided in two groups: (I) vehicle (water for 21 days) and (II) chronic fluoxetine (fluoxetine 10 mg/ kg/ day for 21 days in drinking water). Protocols of vascular reactivity were performed on resistance mesenteric arteries and mesenteric arterial bed (MAB). In addition, gene and protein expression of the signaling pathways involved in these responses was evaluated. Chronic treatment with fluoxetine decreased contractile response to phenylephrine. This result was associated with reduced tyrosine hydroxylase expression as well as noradrenaline (NA) reuptake in MAB sympathetic nerve endings. Similarly, ERK 1/2 signaling was decreased. In contrast, fluoxetine treatment increased contractile response to potassium chloride (KCl) without changing the electric field stimulation-(EFS)-induced contraction. Fluoxetine treatment also increased nitric oxide (NO), the phosphorylation levels of eNOS at serine1177 residue and KATP channels sensitivity. In conclusion, fluoxetine promotes reduction of the contractile response in MAB due to increase in NO and K+ channels contribution. In addition, negative regulation of NA release and ERK 1/2 signaling may contribute to decrease smooth muscle contractile response. Increased resistance mesenteric artery relaxant response may be mediated by increased NO, eNOS phosphorylation and KATP channels activation.

Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 132-150). Also available on the Internet.

Vasoconstrictor tone in the splanchnic circulation redistributes blood flow during hemorrhage and resuscitation. A metabolic sensor, 5’adenosine monophosphate-activated protein kinase (AMPK), has been proposed to relax arteries by inhibiting myosin light chain (MLC) kinase (MLCK) and rho kinase (ROCK) activities. Because AMPK activation might be beneficial in re-establishing splanchnic blood flow during resuscitation, we sought to explore the relative ability of AMPK activators (AICAR, A769662, berberine (BBR) and simvastatin (SIMV)) to relax mesenteric artery (MA) contraction. Our data revealed that these drugs caused vasorelaxation when tissues were stimulated either with KCl (producing primarily a Ca2+ dependent contraction) or phenylephrine (PE; producing a primarily Ca2+ independent contraction). We further investigated the potential mechanisms by which BBR induced mesenteric artery relaxation. We found that BBR did not inhibit MLC phosphorylation, nor did it phosphorylate AMPK, and therefore is likely working through another mechanism to cause vasorelaxation. Notably, PE induced an increase in AMPK phosphorylation and, of all the AMPK activators examined, only AICAR phosphorylated AMPK in rabbit mesenteric artery, which provides a guide for future studies.

Introduction: La lésion d'ischémie - reperfusion (I/R) intestinale est associée à une mortalité élevée.Le rôle de la transmigration des neutrophiles est probablement essentiel dans le dysfonctionnement de la barrière induit par la lésion I/R et la nécrose subséquente. Le but de notre étude était d'évaluer, au niveau pré-clinique, la valeur thérapeutique potentielle du peptide P8RI (un agoniste de CD31) dans la lésion I/R de l'intestine grêle.Méthodes: I/R intestinale a été induite chez des rats Wistar par clampage de l'artère mésentérique supérieure (AMS) pendant 30 min suivi par 4 h de reperfusion. Trois groupes de rats ont été comparés:P8RI (n = 20, I/R et P8RI 2,5 mg/kg/h de reperfusion), I/R témoins positifs (n = 21, I/R et infusion de sérum physiologique) et témoins (n = 14, dissection de l'AMS sans clampage et infusion de sérum physiologique). La matrix métallopeptidase 9 (MMP-9) dans la plasma, le liquide péritonéal et l'intestin; la MPO intestinale, l'ADN libre plasmatique, les taux d'hémoglobine intraluminale e tl'épaisseur épithéliale ont été évalués comme marqueurs intermédiaires de la lésion intestinale. La détection du matériel génétique d'E.coli par PCR quantitative dans le sang a été également réalisée chez les témoins positifs et chez les rats traités par P8RI pendant la période de reperfusion. Le CD31clivé dans le plasma a été mesuré par une méthode d'ELISA maison. Résultats: La grade histologique de l'intestin grêle chez les animaux traités par P8RI est supérieur àcelui des témoins positifs d'I/R (p < 0,05). P8RI protège l'intestin grêle contre la destruction épithéliale induite par lésion I/R (p < 0,01). Il y a une corrélation négative significative entre l'abrasion épithéliale et le score de Chiu de classement histologique de la lésion I/R mésentérique (r = -0,7245, p < 0.001).P8RI protège l'intestin grêle de la MPO in situ, de la libération de la MMP-9 (p < 0,05) et des complications hémorragiques digestives causées par lésion I/R (p < 0,01). Les taux plasmatiques et péritonéaux accrus de MMP-9, induits par I/R, sont significativement réduits par P8RI (p < 0,05 et p <0,01, respectivement). L'ADN d'E.coli circulant est significativement plus élevé chez les rats de témoins positifs que dans le groupe P8RI (p < 0,05). L'ADN libre plasmatique pendant la reperfusion chez les rats de témoins positifs augmente significativement plus que celle des rats du groupe P8RI (p< 0,05). P8RI n'a aucun effet sur le compte neutrophilaire sanguin, mais induit une diminution significative de CD31 clivé dans le plasma pendant l'I/R mésentérique (p < 0,01). Les corrélations entre l'abrasion épithéliale et l'ADN libre, MMP-9, CD31 clivé plasmatiques, les taux de MMP-9 et MPO intestinale suggèrent que le mécanisme protecteur de P8RI implique l'inhibition de l'activation neutrophilaire, y compris le clivage de CD31. Conclusions: Cette étude suggère que le traitement par le peptide P8RI, un agoniste de CD31, réduit de la façon préventive, la lésion I/R de l'intestin grêle chez les rats. / Background: Intestinal ischemia/reperfusion (I/R) injury is associated with a high mortality. The roleof transmigration of PMNs is probably essential in I/R-induced intestinal barrier dysfunction andsubsequent necrosis. The aim of this study was to evaluate, at a preclinical level, the potentialtherapeutic value of P8RI peptide (a CD31 agonist), in small bowel I/R injury.Methods: Intestinal I/R was induced in Wistar rats by superior mesenteric artery (SMA) clamping for30 min followed by 4 h of reperfusion. Three groups of rats were compared: P8RI (n=20, I/R and P8RI2.5mg/kg/h infusion), I/R positive controls (n=21, I/R and normal saline infusion), and sham operatednegative controls (n=14, SMA dissection with no clamping and normal saline infusion). Plasma,peritoneal fluid and intestinal matrix metallopeptidase 9 (MMP-9), intestinal MPO, plasma cf-DNA,intraluminal hemoglobin levels and epithelial thickness were all evaluated as intermediate markers ofintestinal injury. Detection of E.coli genetic material by quantitative PCR in blood was also performedin I/R controls and P8RI-treated rats during the reperfusion period. Plasma cleaved CD31 wasmeasured by homemade ELISA.Results: The small bowel histologic grade in P8RI-treated animals was higher than in I/R controls (p <0.05). P8RI protected against epithelial destruction induced by I/R injury (p < 0.01). There was asignificant negative correlation between epithelial abrasion and Chiu's score of histologic grading ofmesenteric I/R injury (r = -0.7245, p < 0.001). P8RI protected the small bowel from in situ MPO andMMP-9 release (p < 0.05) and digestive bleeding complications due to I/R injury (p < 0.01). Theincreased plasma and peritoneal MMP-9 levels induced by I/R were significantly reduced by P8RI (p <0.05 and p < 0.01, respectively). Plasma cf-DNA during reperfusion in I/R controls increasedsignificantly more than in the P8RI group (p < 0.05). E.coli DNA was significantly higher in I/Rcontrols than in the P8RI group (p < 0.05). P8RI had no effect on blood neutrophil counts but induceda significant diminution of cleaved CD31 in plasma during mesenteric I/R (p < 0.01). Correlationsbetween epithelial abrasion and plasma cf-DNA, MMP-9, cleaved CD31, intestinal MMP-9 and MPOlevels suggest that the protective mechanism of P8RI might involve the inhibition of neutrophilactivation, including CD31 cleavage.Conclusions: This study suggests that a treatment by P8RI peptide, a CD31 agonist, reduces smallbowel I/R injury in rats

Previous studies have shown that L-tryptophan treatment has been known to reduce blood pressure (BP) in hypertensive rats. L-tryptophan is converted to serotonin (5-HT), a potent vasoconstrictor agonist. The direct vascular effects of L-tryptophan, an essential amino acid, and the mechanism that contributes to the fall in BP have not been fully explored. The present study aims to examine the direct vascular responses to both D- and L- tryptophan using perfused mesenteric vascular bed, an ex-vivo preparation that represents the resistance function of circulation. Perfusion was maintained at a constant flow rate (5 mL/min) with Krebs buffer (pH 7.4, 37˚C) after isolation from 12 to 14 week old male Sprague-Dawley rats. The basal perfusion pressure (PP) (mean ± SEM) was 27 ± 3 mmHg. Inclusion of D- and L-isomers in the perfusion medium led to concentration-dependent increase in PP. While the maximal response (Emax) was similar, D-tryptophan (EC50: 0.25 ± 0.12* µmol; Emax: 128 ± 8 mmHg) was more potent (lower EC50 value; *p < 0.01) than L-tryptophan (EC50: 0.79 ± 0.30 µmol; Emax: 141 ± 7 mmHg). Inclusion of increasing concentrations (2, 5 and 10 nM) of the 5-HT2A selective antagonist, ketanserin, led to parallel right-ward shifts in the concentration-response curves to D- and L-tryptophan with restoration of their Emax. In contrast, the α1 selective agonist, methoxamine (30 µM), constricted preparations, both D- (IC50: 0.94 ± 0.30* µmol; Imax: 96 ± 2%) and L-tryptophan (IC50: 2.8 ± 1.0 µmol Imax: 88± 1%) evoked concentration-dependent vasodilatation, an effect that was resistant to blockade by either ketanserin or other 5-HT antagonists. Again, D-tryptophan was more potent than L-tryptophan in the presence of 5-HT antagonist (*p < 0.05). Neither the removal of endothelium nor incubation with selective inhibitors of dilatory mediators released from the endothelium, failed to alter the vasodilator responses to D- and L-tryptophan. In potassium chloride depolarized preparations, L-tryptophan evoked an additive vasoconstrictor response. The vasodilator responses to L-tryptophan persisted in the presence of glibenclamide, a KATP channel inhibitor, or tetraethyl ammonium, a BKCa channel inhibitor, or BaCl2, a Kir channel inhibitor, or ouabain, a Na+-K+-ATPase pump inhibitor. These data confirm that the essential amino acid, L-tryptophan, as well as its D-isomer, evoke a biphasic vasoconstrictor and vasodilator responses in the resistance type mesenteric vascular bed. While the vasoconstrictor responses are mediated by activation of vascular 5-HT receptors, the endothelium-independent vasodilator responses are not linked to activation of vascular 5-HT receptors, vascular potassium channels, Na+-K+-ATPase pump or via inhibition of voltage-operated Ca2+-channels. Plasma concentration of L-tryptophan is about 90 - 120 µM. The endothelium/5-HT independent direct vasodilator responses characterized here for the first time could account for the antihypertensive/ BP lowering effect of L-tryptophan reported earlier by other laboratories.