CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A distensÃo mecÃnica do Ãtrio direito (DA) aumenta a motilidade gÃstrica em ratos anestesiados (Palheta et al., 2010). Resolvemos avaliar o efeito da DA sobre o esvaziamento gÃstrico (EG) de lÃquido em ratos acordados e as eventuais vias neuro-humorais relacionadas ao fenÃmeno. Utilizamos ratos albinos machos (n=361, 250-280g) que receberam um balÃo de silicone posicionado no Ãtrio direito. Decorridos 24h, monitoramos a pressÃo venosa central (PVC), freqÃÃncia cardÃaca (FC) e a pressÃo arterial mÃdia (PAM) e apÃs os 20-min iniciais os animais foram aleatoriamente prÃ-tratados com: Salina (S, 0,1 ml/100g, i.v.), Atropina (A, 0,5 mg/kg, i.v.), Guanetidina (GT, 10 mg/kg, i.p.), HexametÃnio (H, 10mg/kg, i.v.), L-NAME (3mg/kg, i.v.), L-Arg (100mg/kg, i.v.) + L-NAME (3 mg/kg, i.v.), Azul de metileno (MB, 3 mg/kg, i.v.), Glibenclamida (GB, 1 mg/kg, i.p.) ou Glibenclamida + DiazÃxido (3mg/kg, i.v.) [GB + D], Dexametasona (DEX, 1mg/kg, i.p.), Anantin (ANT, 5 &#61549;g, i.v.) ou Atosibana (AT, 40 &#61549; g/kg/h, i.v.). AlÃm disto, em grupos separados realizamos 72h antes da DA Ã vagotomia (V), ou esplancnotomia+ gangliectomia celÃaca (SC) ou denervaÃÃo cardÃaca aferente com capsaicina (ACD). Em outro conjunto de animais realizamos aurilectomia direita uma semana antes da DA (AX). Em seguida ao tratamento farmacolÃgico realizamos protocolo de falsa DA (controle) ou DA com 50&#61549;L do balÃo intra-atrial durante 5min. Decorridos 20 min. da DA, os ratos foram alimentados por via oral com soluÃÃo teste e, apÃs 10-min sacrificados para estudo do EG. AlÃm disto, determinamos os nÃveis plasmÃticos de ocitocina (OT), PeptÃdeo NatriurÃtico Atrial (ANP) e corticosterona (CORT). Para verificaÃÃo da atividade neuronal avaliamos a expressÃo da proteÃna Fos e OT nas regiÃes hipotalÃmicas do nÃcleo paraventricular (PVN) ou supra-Ãptico (SON). Comparado ao controle, a DA diminuiu o EG (p <0,05). AlÃm disso, a DA aumentou a PVC e a FC. A DA diminuiu o EG (p<0,05) nos grupos S, A, GT, L-arginina + L-NAME, MB e GB+D. JÃ o prÃ-tratamento com H, L-NAME, GB, DEX, ANT ou AT, bem como a SV, SC, ACD ou AX preveniu o efeito do DA sobre o EG. AlÃm disso, a DA aumentou os nÃveis plasmÃticos de OT e CORT, mas nÃo alterou o de ANP. Apesar da DA aumentar o nÃmero de neurÃnios imunorreativos para c-fos nas regiÃes parvocellular medial e posterior do PVN, nÃo observamos tal achado nas regiÃes magnocellular do PVN ou do SON, tambÃm nÃo houve diferenÃa significativa para o nÃmero de neurÃnios imunorreativos para Fos-OT apÃs DA. Portanto a diminuiÃÃo do EG de lÃquidos apÃs a DA em ratos acordados depende de uma via aferente cardÃaca mediada por receptores de baixa pressÃo, sendo que tanto neurÃnios simpÃticos como parassimpÃticos participam da cascata mediada pela OT, ANP e NO atravÃs de canais para K+-ATP dependentes. / Right atrium mechanical stretch (AS) increases gastric motility in anesthetized rats. We aimed to study the effect of AS on gastric emptying (GE) in awake rats and the related neuro-humoral pathways ivolved. Male albino rats (N=361, 250-280g) had a silicone balloon inserted in the right atrium. After 24-h, the central venous pressure (CVP), heart rate (HR) and the mean arterial pressure (MAP) were monitored and after the initial 20-min, animals were randomly pre-treated with: saline (S, 0.1 ml/100g, i.v.), Atropine (A, 0.5mg/kg, i.v.), Guanethidine (GT, 10mg/kg, i.p.), hexamethonium (H, 10mg/kg, i.v.), L-NAME (3mg/kg, i.v.), L-Arginine (100mg/kg, i.v.)+L-NAME (3mg/kg, i.v.), Methylene Blue (MB, 3mg/kg, i.v.), Glibenclamide (GB, 1mg/kg, i.p) or Glibenclamide+Diazoxide (3mg/kg, i.v.) [GB+D], Dexamethazone (DEX, 1mg/kg, i.p.), Anantin (ANT, 5&#61549;g, i.v.) or Atosiban (AT, 40&#61549;g/kg/h, i.v.). Besides, in a separate group, we realized vagotomy (V), or splanchnotomy + celiac gangliectomy (SC) or afferent cardiac denervation with capsaicin (ACD) 72h before AS. In another set of animals, we realized right appendectomy (AX) one week before AS. Next, AS with saline zero (sham) or 50&#61549;L was performed during 5min. In this group, rats were gavage fed with a test meal 20-min after AS and euthanized 10-min afterwards to study GE. Moreover we determined plasmatic levels of Ocytocin (OT), Atrial Natriuretic Peptide (ANP) and Corticosterone (CORT), and determined the neuronal activity in the paraventricular (PVN) or supraoptic (SON) hypothalamic regions by measuring expressed double-labeled c-fos-OT. Comparing to Sham, AS decreased GE (p<0.05). Besides, AS increased CVP and HR. AS decreased GE (p <0.05) in S, A, GT, L-Arginine+L-NAME, MB and GB+D groups. However pre-treatment with, H, L-NAME, GB, DEX, ANT or AT, as well as SV, SC, ACD or AX prevented the effect of AS on GE. AS increased OT and CORT plasmatic levels, but did not alter ANP. In spite of AS increasing the number of c-fos expressing neurons in the parvocellular region, we did not observe this finding in the magnocellular regions of PVN or SON. Besides, AS did not alter the number of fos-OT double-labeled neurons. Therefore the decrease of GE of fluids after AS in awake rats depends on an afferent pathway mediated by cardiac low pressure receptors, and both sympathetic and parasympathetic neurons participate in the cascade mediated by OT, ANP and NO through K +-ATP dependent channels.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / INTRODUÃÃO: Recentemente, foi demonstrado que o H2S està envolvido em inÃmeras funÃÃes fisiolÃgicas e patolÃgicas, sendo produzido em muitos tecidos de mamÃferos. OBJETIVOS: Avaliar o papel do H2S na defesa da mucosa e no controle da motilidade gÃstrica em camundongos, bem como estudar a participaÃÃo dos canais de KATP, dos neurÃnios sensoriais sensÃveis à capsaicina e dos receptores TRPV1 neste efeito. MÃTODOS: Camundongos Swiss foram prÃ-tratados com L-cisteÃna (25, 50 ou 100 mg/kg, v.o), NaHS (75, 150 ou 300 Âmol/kg, v.o) ou LawessonÂs (3, 9, 27 ou 81 Âmol/kg, v.o). Trinta minutos depois, o etanol 50% (0,5ml/25g, v.o) foi administrado. Depois de 1 h, os animais foram sacrificados e os estÃmagos abertos para determinaÃÃo da Ãrea da lesÃo usando planimetria computadorizada. AlÃm disso, fragmentos de tecidos foram removidos para anÃlise microscÃpica e dosagem de glutationa e malondialdeÃdo. Para o estudo do esvaziamento gÃstrico, outro grupo experimental foi tratado, por gavagem, com as mesmas doses de L-cisteÃna, NaHS ou LawessonÂs, decorridos 30 min os animais receberam uma soluÃÃo glicosada (5%) contendo vermelho de fenol (0,75 mg/ml) em cada animal. ApÃs 10, 20 ou 30 min os animais foram sacrificados e o esvaziamento gÃstrico foi avaliado por tÃcnica de espectrofotometria. Em outro grupo experimental os animais foram prÃ-tratados com glibenclamida (3 e 10 mg/Kg, v.o.) ou capsazepina (10 mg/kg, i.p). ApÃs 1h, foram administrados a L-cisteÃna (50 mg/kg) ou os doadores de H2S (NaHS 150 Âmol/kg ou o reagente de LawessonÂs 27Âmol/kg, v.o). Trinta minutos depois, o etanol 50% foi administrado para avaliaÃÃo da lesÃo gÃstrica e soluÃÃo de vermelho de fenol foi administrada para avaliar o esvaziamento gÃstrico conforme descrito anteriormente. Para o estudo dos neurÃnios aferentes, foi realizado protocolo de ablaÃÃo dos com doses neurotÃxicas de capsaicina. ApÃs 8 dias, os animais receberam NaHS ou o LawessonÂs e o protocolo de lesÃo gÃstrica por etanol 50% foi determinado como descrito acima. TambÃm foi determinado a contratilidade espontÃnea do fundo gÃstrico incubado com doses crescentes de NaHS ou KCl (controle) utilizando um transdutor de forÃa isomÃtrico acoplado a um sistema de aquisiÃÃo de dados. RESULTADOS: A administraÃÃo de L-cisteÃna, NaHS ou Reagente de LawessonÂs preveniu, de forma dose dependente, a lesÃo por etanol no estÃmago. Essa proteÃÃo foi acompanhada do aumento de GSH e diminuiÃÃo dos nÃveis gÃstricos de MDA quando comparado com o grupo tratado apenas com etanol. Glibenclamida (10 mg/kg) e a capsazepina reverteram completamente esse efeito protetor dos doadores de H2S. Nos animais depletados de neurÃnios aferentes, tambÃm houve uma reversÃo do efeito protetor dos doadores de H2S e da L-cisteÃna. O NaHS, o LawessonÂs e a L-cisteÃna promoveram aceleraÃÃo do esvaziamento gÃstrico quando comparado com o controle, de maneira dose dependente. Este efeito procÃnÃtico foi abolido pela prÃ-administraÃÃo de glibenclamida e capsazepina O NaHS tambÃm foi capaz de induzir um aumento no tÃnus basal que iniciou-se com mÃximo efeito na concentraÃÃo de 300 ÂM em relaÃÃo à contraÃÃo controle de KCl. CONCLUSÃES: o H2S preveniu a lesÃo gÃstrica, o consumo de GSH e aumento da peroxidaÃÃo lipÃdica na mucosa gÃstrica, induzidos pela administraÃÃo de etanol em camundongos. O H2S tambÃm apresentou efeito procinÃtico, acelerando o esvaziamento gÃstrico de lÃquidos em camundongos. Podemos inferir que esses efeitos devem-se a ativaÃÃo dos canais de KATP, dos neurÃnios sensoriais sensÃveis à capsaicina e dos receptores TRPV1. / INTRODUCTION: Recently, the involvement of H2S has been demonstrated in several physiological and pathological conditions, being constitutively produced in mammalian tissues. AIM: To study the role of H2S on both the gastric mucosa defense and the control of gastric motility in mice, and additionally to evaluate the participation of KATP channels, capsaicin-sensitive afferent neurons and TRPV1 receptors in these effects. METHODS: Swiss mice were pre-treated with either L-cysteine (25, 50 or 100 mg/kg, p.o), NaHS (75, 150 or 300 Âmol/kg, p.o) or LawessonÂs reagent (3, 9, 27 or 81 Âmol/kg, p.o). The animals were then given ethanol 50% (0.5ml/25g, p.o.) 30 min later. After 1h of ethanol instillation, the mice were sacrificed and had the stomach collected to measure the injured area through planimetry software. Moreover some samples were obtained to histopathological analysis, glutathione (GSH), and malonyldialdehyde (MDA) dosages. In the study of gastric empty, the animals were administered L-cysteine, NaHS or LawessonÂs reagent, and 30 min later a phenol red solution (0.75 mg/ml) diluted in glucose (5%) was also given. The sacrifice was performed 10, 20 or 30 min after the latter to determine in a spectrophotometer the gastric empty. In another experimental setting, glibenclamide (3 or 10 mg/Kg, v.o.) or capsazepine (10 mg/kg, i.p) were injected 1h previously to the L-cysteine (50 mg/kg, p.o) or H2S donors (NaHS 150 Âmol/kg or LawessonÂs reagent 27Âmol/kg, p.o) instillation. In order to study the role of capsaicin-sensitive afferent neurons, high neurotoxic doses of capsaicin was instilled into the animals. On the 8th day post capsaicin injection, NaHS or LawessonÂs reagent was administered. The protocol for ethanol administration, sacrifice, and dosages were repeated for these conditions as described previously. Finally, the spontaneous contraction of isolated gastric fundus to KCl (control contraction) and growing doses of NaHS was determined in vitro through and isometric force transducer connected to an acquisition system. RESULTS: L-cysteine, NaHS and LawessonÂs reagent prevented, in a dose dependent manner, the ethanol-induced gastric injury. Besides, high and low levels of GSH and MDA were found respectively in comparison to the control group given only ethanol. Glibenclamide (10 mg/kg) and capsazepine completely reversed the protective effect of the H2S donors. The animals that undergone afferent neuronal ablation also developed gastric lesions despite the injection of L-cysteine and H2S donors. NaHS, LawessonÂs reagent and L-cysteine all accelerated gastric empty in comparison to the control group and in a dose-dependent manner. Such prokinetic effect was abolished in glibenclamide and capsazepine pre-treated mice. The NaHS was also able to induce an increase in gastric fundus basal tonus in vitro presenting a ceiling effect in the concentration of 300ÂM when compared with the standard KCl contraction. CONCLUSIONS: The H2S prevented the ethanol-induced gastric damage, GSH consumption, and lipid peroxidation processes in the stomach mucosa of mice. The H2S also revealed a prokinetic effect leading to a higher liquid gastric empty in mice. Such results seem to be dependent on KATP channels, sensory afferent neurons, and TRPV1 receptors activation.

Adolescents with type 1 diabetes (T1DM) are given nutritional education, but the knowledge about their adherence to the food recommendations and associations between dietary intake and metabolic control is poor. Gastrointestinal symptoms are more prevalent in adults with T1DM than in healthy controls, which may be due to disturbed gastrointestinal motility. The meal content affects the gastric emptying rate and the postprandial glycaemia in healthy adults and adults with type 2 diabetes. Meal ingestion also elicits several postprandial hormonal changes of importance for gastrointestinal motility and glycaemia. Eating disorders are more prevalent in young females with T1DM than in healthy females, and are associated with poor metabolic control. The prevalence of eating disorders in adolescent boys with T1DM is not known.  This thesis focuses on eating and gastrointestinal function in adolescents with T1DM. Three population-based, cross-sectional studies demonstrated that adolescents with T1DM consume healthy foods more often and have a more regular meal pattern than age- and sex-matched controls. Yet both boys and girls are heavier than controls. The intake of saturated fat is higher and the intake of fibre is lower than recommended in adolescents with T1DM. Patients with poor metabolic control consume more fat and less carbohydrates than patients with better metabolic control. Gastrointestinal symptoms are common in adolescents with T1DM, but the prevalence is not increased compared with controls. Gastrointestinal symptoms in patients are associated with female gender, daily cigarette smoking, long duration of diabetes, poor metabolic control during the past year, and an irregular meal pattern. Adolescent boys with T1DM are heavier and have higher drive for thinness than healthy boys, but do not differ from them in scales measuring psychopathology associated with eating disorders.   In a randomized, cross-over study, we found that a meal with a high fat and energy content reduces the initial (0–2 hours) postprandial glycaemic response and delays gastric emptying in adolescents with T1DM given a fixed prandial insulin dose compared with a low-fat meal. The glycaemic response is significantly associated with the gastric emptying rate. Both a high- and a low-fat meal increase the postprandial concentrations of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) and suppress the postprandial ghrelin levels in adolescents with T1DM. The postprandial changes of these hormones are more pronounced after the high-fat meal. Insulin-like growth factor binding-protein (IGFBP) –1 concentrations decrease after insulin administration irrespective of meal ingestion. The GLP-1 response is negatively associated with the gastric emptying rate. The fasting ghrelin levels are negatively associated with the postprandial glycaemic response, and the fasting IGFBP-1 levels are positively associated with the fasting glucose levels.  We conclude that nutritional education to adolescents with T1DM should focus more on energy intake and expenditure to prevent and treat weight gain. It should also focus on fat quality and fibre intake to reduce the risk of macrovascular complications and improve glycaemia. Gastrointestinal symptoms in adolescents with T1DM should be investigated and treated as in other people irrespective of having diabetes. However, adolescents with long duration of diabetes, poor metabolic control, and symptoms from the upper gut should have their gastric emptying rate examined during euglycaemia. There may be an increased risk for development of eating disorders in adolescent males with T1DM since they are heavier than healthy boys and have higher drive for thinness. This should be investigated in future, larger studies.  For the first time, we showed that a fat-rich meal delays gastric emptying and reduces the initial glycaemic response in patients with T1DM. The action profile of the prandial insulin dose to a fat-rich meal may need to be postponed and prolonged compared with the profile to a low-fat meal to reach postprandial normoglycaemia. Circulating insulin levels affect postprandial GIP, GLP-1, and ghrelin, but not IGFBP-1, responses less than the meal content. The pronounced GIP-response to a fat- and energy-rich meal may promote adiposity, since GIP stimulates lipogenesis. Such an effect would be disadvantageous for adolescents with T1DM since they already have increased body fat mass and higher weights compared with healthy adolescents. Adolescents with T1DM may have subnormal postprandial ghrelin suppression, which may be due to their increased insulin resistance or elevated growth hormone levels. This needs to be investigated in future, controlled studies.

nÃo hà / Està bem estabelecido que a regulaÃÃo dos lÃquidos corporais seja garantida pela interaÃÃo funcional entre os sistemas cardiovascular e renal. Atualmente, evidÃncias clÃnicas e experimentais sugerem que o trato gastrintestinal (TGI) ajusta seu padrÃo motor e absortivo apÃs variaÃÃes agudas da volemia. Embora a insuficiÃncia renal parcial ou total promova variaÃÃes dos volumes corporais circulantes, poucos estudos apontam a relaÃÃo entre a insuficiÃncia renal e o funcionamento do trato gastrintestinal. Neste trabalho, estudamos o efeito da dieta salina sobre a motilidade gastrintestinal [esvaziamento gÃstrico (EG) e o trÃnsito gastrintestinal (GI) de lÃquidos] e transporte intestinal (IT) de Ãgua e eletrÃlitos (Na+, K+ e Cl-) em ratos nefrectomizados parcialmente (nefre5/6) ou falso-operados (FO) em condiÃÃes de hidrataÃÃo e desidrataÃÃo. Para tanto, 138 ratos Wistar, machos (180-220g), submetidos à nefrectomia parcial (nefre5/6) em duas etapas (0 e 7 dias). ApÃs nefre 5/6 ou FO, os animais foram distribuÃdos em dois grupos diferentes, a saber: raÃÃo e salina 1% ou raÃÃo e Ãgua. ApÃs 3d e, sob jejum de 24h com livre acesso à salina ou Ãgua, 1,5ml da refeiÃÃo teste (vermelho fenol 0,5mg/ml e glicose 5%) foi administrada por gavagem em animais acordados. Decorridos 10, 20 ou 30min, os animais foram sacrificados por deslocamento cervical, seguidos da exÃrese das vÃsceras abdominais para determinaÃÃo da taxa de EG e trÃnsito GI. AlÃm disso, um experimento semelhante foi realizado utilizando 5ml de polietilenoglicol-PEG (30% - 20.000 DA) injetado por via subcutÃnea em ratos quatro horas antes do inÃcio do experimento, a fim de simular as condiÃÃes de desidrataÃÃo. Para os estudos do transito intestinal de Ãgua e eletrÃlitos, os animais anestesiados, foram submetidos à perfusÃo ileal com Ringer + vermelho fenol durante 60min. Para todos os experimentos, monitoramos os parÃmetros hemodinÃmicos (pressÃo arterial-PA, pressÃo venosa central-PVC, frequÃncia cardÃaca-FC e volume sanguÃneo-VS) e ainda as concentraÃÃes bioquÃmicas plasmÃticas de Ur, Cr, Na+, K+ e Cl- foram determinadas. Em relaÃÃo ao grupo FO a dieta salina nÃo modificou o EG ou transito GI, nem os parÃmetros hemodinÃmicos ou bioquÃmicos, porÃm promoveu secreÃÃo ileal de Ãgua e eletrÃlitos. Por outro lado, a dieta salina nos animais nefre5/6 promoveu: i) aumento da retenÃÃo gÃstrica de 47%, 26% e 38% (10, 20 e 30 minutos de tempo pÃs-prandial, respectivamente), ii aceleraÃÃo do trÃnsito GI, iii) aumento na secreÃÃo ileal de Ãgua e eletrÃlitos e, iv) aumento da PA, PVC, FC, BV. A desidrataÃÃo aguda com PEG preveniu as alteraÃÃes da motilidade, da secreÃÃo GI e dos parÃmetros hemodinÃmicos secundÃrios hipervolemia crÃnica à custa da nefrectomia 5/6 associada à dieta salina. A motilidade gastrintestinal e o ajuste da absorÃÃo, devido à dieta salina sobre os animais submetidos à nefrectomia parcial, estÃo relacionados aos nÃveis do volume do sangue e pode ser revertida por desidrataÃÃo aguda. Em conclusÃo, trato gastrointestinal pode ajustar tanto o seu motor, bem como atividades de absorÃÃo apÃs desequilÃbrios crÃnicos volume de sangue. / It is well established that the regulation of the corporal fluids is guaranteed by functional interaction between cardiovascular and renal systems. Currently, clinical and experimental evidences suggest that gastrointestinal (GI) tract (GIT) adjust their motor and absorptive activities due to acute changes in the blood volume. Although total or partial renal failure promotes corporal fluids changing. Several studies indicate a relationship among renal failure and GIT functions. In this work, we study the effect of a salt diet on GIT motility [gastric emptying (GE) and GI transit of liquids] and intestinal transport (IT) of H2O and electrolytes (Na+, K+ and Cl-) in partial nephrectomized (nefre5/6) or false-operated (FO) rats under hydrated and dehydrate conditions. For that, 138 male Wistar rats (180-220g) submitted to partial nephrectomy (nefre5/6) in two steps (0 and 7 days). After nefre5/6 or FO procedures, animals were distributed into 2 different experiments both containig two groups as follows: feed+1% saline or feed+water. For the hydrate conditions experiment, after 3d and under 24-hour fasting with free access to water or saline, 1.5ml of the test meal (phenol red 0.5 mg/mL containg 5% glucose) was gavaged in the awake animals. Next 10, 20 or 30 minutes, the animals were sacrificed by cervical dislocation. Following, excision of the abdominal viscera was performed in order to determine the GE rate and GI transit. Additionally, similar experiment were performed using 5mL of polyethylene glycol-PEG (30% - 20,000 DA) injected subcutaneous in the rats 4 hours before the beginning of the experiment in order to simulate the dehydrate conditions. For IT studies, anesthetized animals underwent ileal perfusion with Ringer+phenol red solution and were monitored along 60 min. For all experiments, mean arterial pressure - MAP, central venous pressure-CVP, heart rate-HR and blood volume-BV were monitored. Also, plasmatic concentrations of Ur, Cr, Na+, K+ and Cl- were determined. Compared with FO group, nefre5/6 did not change the GE or GI transit, neither hemodynamic or biochemical parameters, but promotes ileal secretion of water and electrolytes. On the other hand, comparing the salt diet and standard diet, the nefre5/6 animals caused: i) increases on the gastric retention of 47%, 26% and 38% (at 10, 20 and 30 minutes of postprandial time, respectively), ii) acceleration of the GI transit, iii) increases on the ileal secretion of water and electrolytes and, iv) increases BP, CVP, HR and BV. However, changes on the other plasmatic biochemical parameters were not observed in this study. The acute dehydration with PEG prevented gut motility and hemodynamic changes and the increase of gastrointestinal secretions. Gastrointestinal motility and absorptive adjustments due to salt diet on the partial nephrectomized animals, is related to blood volume levels and, can be reversed by acute dehydration. In conclusion, gastrointestinal tract can adjust both their motor as well as absorptive activities after chronic blood volume imbalances.

This work has tried to provide better insight in some pathophysiological factors involved in functional dyspepsia. We have identified several experimental evidences supporting the hypothesis that activation of transducers of wall tension at the level the proximal stomach might be the key to the genesis of at least some of the symptoms. One of the mechanisms by which this activation may be enhanced in patients is the presence of defective accommodation of the proximal stomach in response to a meal. This abnormality was present in a large subgroup of patients and was associated to the presence of early satiety. Pharmacological modulation of the gastric wall tension resulted in concomitant changes in symptom severity, both in health and in functional dyspepsia patients. Special attention has been given to provide the clinician with better tools to investigate his patient, in the perspective of the prescription of a treatment aimed at restoring a defective mechanism. / Ce travail a tenté d'améliorer la compréhension de certains mécanismes physiopathologiques de la dyspepsie fonctionnelle. Nous avons identifié plusieurs arguments expérimentaux soutenant l'hypothèse disant que c'est l'activation de mécanorécepteurs sensibles à la tension pariétale qui est reponsable d'au moins un des symptômes de l'affection. Un des mécanismes par lesquels cette activation peut accrue chez les patients est la présence d'un défaut de l'accommodation gastrique post-prandiale. Cette anomalie a été retrouvée dans une large proportion des patients et est associée à la présence de satiété précoce. Les modifications du tonus gastrique ont résulté dans de modifications concomitantes des symptômes aussi bien chez les volontaires que chez les patients atteints de dyspepsie fonctionnelle.Une attention particulière a été portée sur le développement de nouveaux outils permettant de caractériser les patients dans la perspective de la prescription d'un traitement visant à corriger un mécanisme défectueux.

This work has tried to provide better insight in some pathophysiological factors involved in functional dyspepsia. We have identified several experimental evidences supporting the hypothesis that activation of transducers of wall tension at the level the proximal stomach might be the key to the genesis of at least some of the symptoms. One of the mechanisms by which this activation may be enhanced in patients is the presence of defective accommodation of the proximal stomach in response to a meal. This abnormality was present in a large subgroup of patients and was associated to the presence of early satiety. Pharmacological modulation of the gastric wall tension resulted in concomitant changes in symptom severity, both in health and in functional dyspepsia patients. Special attention has been given to provide the clinician with better tools to investigate his patient, in the perspective of the prescription of a treatment aimed at restoring a defective mechanism. / Ce travail a tenté d'améliorer la compréhension de certains mécanismes physiopathologiques de la dyspepsie fonctionnelle. Nous avons identifié plusieurs arguments expérimentaux soutenant l'hypothèse disant que c'est l'activation de mécanorécepteurs sensibles à la tension pariétale qui est reponsable d'au moins un des symptômes de l'affection. Un des mécanismes par lesquels cette activation peut accrue chez les patients est la présence d'un défaut de l'accommodation gastrique post-prandiale. Cette anomalie a été retrouvée dans une large proportion des patients et est associée à la présence de satiété précoce. Les modifications du tonus gastrique ont résulté dans de modifications concomitantes des symptômes aussi bien chez les volontaires que chez les patients atteints de dyspepsie fonctionnelle.Une attention particulière a été portée sur le développement de nouveaux outils permettant de caractériser les patients dans la perspective de la prescription d'un traitement visant à corriger un mécanisme défectueux.

Background Transthyretin amyloid (ATTR) amyloidosis is a systemic disorder caused by amyloid deposits formed by misfolded transthyretin (TTR) monomers. Two main forms exist – wild-type and hereditary ATTR amyloidosis, the latter associated with TTR gene mutations. Wild-type ATTR amyloidosis has a late onset and primarily cardiac manifestations, whereas hereditary ATTR amyloidosis is a rare autosomal dominant condition with a considerable phenotypic diversity. Both disorders are present all over the world, but endemic areas of the hereditary form are found in Sweden, Portugal, Brazil and Japan. Gastrointestinal (GI) complications are common in hereditary ATTR amyloidosis and play an important role in the patients’ morbidity and mortality. Malfunction of the autonomic and enteric nervous systems has been proposed to contribute to the GI disturbances, but the underlying mechanisms have not been fully elucidated. The aims of this thesis were to assess the prevalence of GI disturbances for different subtypes of ATTR amyloidosis, to further explore the mechanisms behind these disturbances, and to evaluate the outcome of the patients’ GI function after liver transplantation, which currently is the standard treatment for hereditary ATTR amyloidosis. Methods The Transthyretin Amyloidosis Outcomes Survey (THAOS) is the first global, multicenter, longitudinal, observational survey that collects data on patients with ATTR amyloidosis. THAOS enrollment data were used to assess the prevalence of GI symptoms and to evaluate their impact on nutritional status (mBMI) and health-related quality of life (EQ-5D Index Score). Data from routine investigations of heart-rate variability and cardio-vascular response to tilt tests were utilized to evaluate the impact of autonomic neuropathy on the scintigraphically measured gastric emptying half-times in Swedish patients with hereditary ATTR amyloidosis. Gastric wall autopsy specimens from Japanese patients with hereditary ATTR amyloidosis and Japanese non-amyloidosis controls were analyzed with immunohistochemistry and computerized image analysis to assess the densities of interstitial cells of Cajal (ICC) and nervous tissue. Data from gastric emptying scintigraphies and validated questionnaires were used to evaluate the outcome of Swedish patients’ GI function after liver transplantation for hereditary ATTR amyloidosis. Results Sixty-three percent of the patients with TTR mutations and 15 % of those with wild-type ATTR amyloidosis reported GI symptoms at enrollment into THAOS. Subsequent analyses focused on patients with TTR mutations and, among them, unintentional weight loss was the most frequent symptom (32 %) followed by early satiety (26 %). Early-onset patients (&lt;50 years of age) reported GI symptoms more frequently than late-onset cases (70 % vs. 50 %, p &lt;0.01), and GI symptoms were more common in patients with the V30M mutation than in those with non-V30M mutations (69 % vs. 56 %, p &lt;0.01). Both upper and lower GI symptoms were significant negative predictors of nutritional status and health-related quality of life (p &lt;0.01 for both). Weak but significant correlations were found between gastric emptying half-times and the function of both the sympathetic (rs = -0.4, p &lt;0.01) and parasympathetic (rs = -0.3, p &lt;0.01) nervous systems. The densities of c-Kit-immunoreactive ICC were significantly lower in the circular (median density 0.0 vs. 2.6, p &lt;0.01) and longitudinal (median density 0.0 vs. 1.8, p &lt;0.01) muscle layers of the gastric wall in patients compared to controls. Yet, no significant differences in protein gene product 9.5-immunoreactive nervous cells were found between patients and controls either in the circular (median density 3.0 vs. 6.8, p = 0.17) or longitudinal (median density 1.4 vs. 2.5, p = 0.10) muscle layers. Lastly, the patients’ GI symptoms scores had increased slightly from before liver transplantation to the follow-ups performed in median two and nine years after transplantation (median score 7 vs. 10 vs. 13, p &lt;0.01). However, their gastric emptying half-times (median half-time 137 vs. 132 vs. 125 min, p = 0.52) and nutritional statuses (median mBMI 975 vs. 991 vs. 973, p = 0.75) were maintained at follow-ups in median two and five years after transplantation. Conclusion GI disturbances are common in hereditary ATTR amyloidosis and have a negative impact on the patients’ nutritional status and health-related quality of life. Fortunately, a liver transplantation appears to halt the progressive GI involvement of the disease, although the patients’ GI symptoms tend to increase after transplantation. An autonomic neuropathy and a depletion of gastrointestinal ICC seem to contribute to the GI disturbances, but additional factors must be involved.

Inadequate delivery of nutrition to the critically ill is common, and may adversely affect clinical outcomes, including survival. This thesis reports studies designed to characterise the gastrointestinal dysfunction underlying feed intolerance in the critically ill, as well as the pathophysiology of these dysfunctions, and investigate potential therapeutic measures. While it has been established that enteral nutrition is frequently unsuccessful in the critically ill, assessment of the success of feeding in an Australian intensive care unit (ICU) had not been performed previously. A prospective survey examined the incidence of, and risk factors for, feed intolerance in the ICU at the Royal Adelaide Hospital and demonstrated that, in 40 patients receiving enteral feeding, only about 60% of their nutritional requirements were met at the end of the first week. The main cause for this lack of success was large gastric residual volumes, indicative of delayed gastric emptying (GE). This study, accordingly, quantified the limitations of nutritional delivery in contemporary practice in a local ICU. The results suggest that a better understanding of the pathogenesis underlying this problem is warranted in order to direct research into improved therapies. Scintigraphy is the most accurate technique to measure GE, but is difficult to perform in the ICU. A simpler, more convenient, test would increase the accessibility of GE measurement for both research and clinical purposes. A study comparing a breath test technique and gastric residual volume measurement to the scintigraphic measurement of GE in 25 mechanically ventilated patients demonstrated that GE measured by a breath test technique closely correlated with that measured by scintigraphy. While the breath test had a specificity of 100% it only had a sensitivity of about 60% in the prediction of delayed GE. Similarly, gastric residual volume measurement correlated with scintigraphic measurement of GE but also lacked sensitivity. The breath test has previously been demonstrated to be highly reproducible and it represents a useful option for repeated measurement of GE in the same patient. It is therefore likely to be useful to determine changes in GE over time or in response to a therapeutic intervention. There is a lack of information about the prevalence and determinants of delayed GE in the critically ill. Previous studies have substantial limitations and scintigraphic measurement of GE has only rarely been used. A study comparing GE measured by scintigraphy in 25 patients to 14 healthy subjects demonstrated that GE was delayed in approximately 50% of the ICU patients (>10% retention at 4h) and markedly delayed in about 20% (>50% retention at 4h). Patients with trauma and sepsis appeared to have a relatively higher prevalence of delayed GE (80% and 75% respectively). In addition, the longer the patient had been in ICU the more normal the rate of GE. Quantification of delayed GE may prove useful by defining patients who may benefit from preventative or therapeutic options. The abnormalities in gastrointestinal motility underlying delayed GE in the critically ill are poorly characterised. Simultaneous manometric and gastric emptying measurements were performed in 15 mechanically ventilated patients and 10 healthy subjects. These studies demonstrated that delayed GE was associated with reduced antral activity, increased pyloric activity and increased retrograde duodenal activity in the patients. Persistent fasting motility during feeding was also frequently observed. Furthermore, the feedback response to small intestinal nutrients was enhanced. This latter observation may provide an explanation for the delayed GE and warrants further investigation. Recent studies suggest that the hormone cholecystokinin may be a mediator of increased small intestinal feedback and, if confirmed, this has clear therapeutic implications. Nutrient absorption has rarely been measured in the critically ill. GE and glucose absorption (using 3-O-methyl glucose) were measured simultaneously in 19 ICU patients and compared to 19 healthy subjects. Glucose absorption was shown to be markedly reduced in the patients. Slow GE was associated with delayed, and reduced, absorption. However, glucose absorption was also reduced in patients with normal GE suggesting that reduced glucose absorption in critical illness is only partly due to delayed GE. Accordingly, measures to improve the effectiveness of GE and thereby improve overall nutritional status may be compromised by abnormal small intestinal absorption. The mechanisms underlying this warrant further investigation. A number of therapeutic options directed at improving the delivery of nutrition were examined. In a study involving 20 mechanically ventilated patients, administration of 200mg erythromycin intravenously was shown to be superior to placebo for treating feed intolerance. The optimal dose of erythromycin, however, was unclear. In a subsequent study involving 35 ICU patients, GE was measured using a breath test technique, before and after 2 different doses of erythromycin or placebo and a ‘low’ intravenous dose (70mg) of erythromycin appeared to be as effective as a ‘moderate’ dose (200mg). Both doses were only effective in subjects who had delayed GE at baseline. Based on the outcome of these studies, low doses of erythromycin have subsequently been routinely used to treat feed intolerance in the critically ill patients at the Royal Adelaide Hospital. Animal and human studies suggested that the antibiotic, cefazolin, may have a prokinetic effect. Cefazolin, however, did not demonstrate similar prokinetic activity at a ‘low’ dose (50mg) in a critically ill cohort. The results of this study do not support the use of this agent, at this dose, as a prokinetic, in this population. If nasogastric administration of nutrition proves unsuccessful an alternative is to infuse nutrient directly into the small intestine. However, the placement of feeding tubes distal to the pylorus is technically difficult. A novel technique for postpyloric tube insertion was examined with promising results. In summary, the studies described in this thesis have provided a number of insights relevant to the management of the critically ill by quantifying the prevalence of feed intolerance and delayed GE, characterising some of the disturbances in gastrointestinal motility underlying this problem, and evaluating a number of therapeutic interventions. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1345143 / Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2008

Inadequate delivery of nutrition to the critically ill is common, and may adversely affect clinical outcomes, including survival. This thesis reports studies designed to characterise the gastrointestinal dysfunction underlying feed intolerance in the critically ill, as well as the pathophysiology of these dysfunctions, and investigate potential therapeutic measures. While it has been established that enteral nutrition is frequently unsuccessful in the critically ill, assessment of the success of feeding in an Australian intensive care unit (ICU) had not been performed previously. A prospective survey examined the incidence of, and risk factors for, feed intolerance in the ICU at the Royal Adelaide Hospital and demonstrated that, in 40 patients receiving enteral feeding, only about 60% of their nutritional requirements were met at the end of the first week. The main cause for this lack of success was large gastric residual volumes, indicative of delayed gastric emptying (GE). This study, accordingly, quantified the limitations of nutritional delivery in contemporary practice in a local ICU. The results suggest that a better understanding of the pathogenesis underlying this problem is warranted in order to direct research into improved therapies. Scintigraphy is the most accurate technique to measure GE, but is difficult to perform in the ICU. A simpler, more convenient, test would increase the accessibility of GE measurement for both research and clinical purposes. A study comparing a breath test technique and gastric residual volume measurement to the scintigraphic measurement of GE in 25 mechanically ventilated patients demonstrated that GE measured by a breath test technique closely correlated with that measured by scintigraphy. While the breath test had a specificity of 100% it only had a sensitivity of about 60% in the prediction of delayed GE. Similarly, gastric residual volume measurement correlated with scintigraphic measurement of GE but also lacked sensitivity. The breath test has previously been demonstrated to be highly reproducible and it represents a useful option for repeated measurement of GE in the same patient. It is therefore likely to be useful to determine changes in GE over time or in response to a therapeutic intervention. There is a lack of information about the prevalence and determinants of delayed GE in the critically ill. Previous studies have substantial limitations and scintigraphic measurement of GE has only rarely been used. A study comparing GE measured by scintigraphy in 25 patients to 14 healthy subjects demonstrated that GE was delayed in approximately 50% of the ICU patients (>10% retention at 4h) and markedly delayed in about 20% (>50% retention at 4h). Patients with trauma and sepsis appeared to have a relatively higher prevalence of delayed GE (80% and 75% respectively). In addition, the longer the patient had been in ICU the more normal the rate of GE. Quantification of delayed GE may prove useful by defining patients who may benefit from preventative or therapeutic options. The abnormalities in gastrointestinal motility underlying delayed GE in the critically ill are poorly characterised. Simultaneous manometric and gastric emptying measurements were performed in 15 mechanically ventilated patients and 10 healthy subjects. These studies demonstrated that delayed GE was associated with reduced antral activity, increased pyloric activity and increased retrograde duodenal activity in the patients. Persistent fasting motility during feeding was also frequently observed. Furthermore, the feedback response to small intestinal nutrients was enhanced. This latter observation may provide an explanation for the delayed GE and warrants further investigation. Recent studies suggest that the hormone cholecystokinin may be a mediator of increased small intestinal feedback and, if confirmed, this has clear therapeutic implications. Nutrient absorption has rarely been measured in the critically ill. GE and glucose absorption (using 3-O-methyl glucose) were measured simultaneously in 19 ICU patients and compared to 19 healthy subjects. Glucose absorption was shown to be markedly reduced in the patients. Slow GE was associated with delayed, and reduced, absorption. However, glucose absorption was also reduced in patients with normal GE suggesting that reduced glucose absorption in critical illness is only partly due to delayed GE. Accordingly, measures to improve the effectiveness of GE and thereby improve overall nutritional status may be compromised by abnormal small intestinal absorption. The mechanisms underlying this warrant further investigation. A number of therapeutic options directed at improving the delivery of nutrition were examined. In a study involving 20 mechanically ventilated patients, administration of 200mg erythromycin intravenously was shown to be superior to placebo for treating feed intolerance. The optimal dose of erythromycin, however, was unclear. In a subsequent study involving 35 ICU patients, GE was measured using a breath test technique, before and after 2 different doses of erythromycin or placebo and a ‘low’ intravenous dose (70mg) of erythromycin appeared to be as effective as a ‘moderate’ dose (200mg). Both doses were only effective in subjects who had delayed GE at baseline. Based on the outcome of these studies, low doses of erythromycin have subsequently been routinely used to treat feed intolerance in the critically ill patients at the Royal Adelaide Hospital. Animal and human studies suggested that the antibiotic, cefazolin, may have a prokinetic effect. Cefazolin, however, did not demonstrate similar prokinetic activity at a ‘low’ dose (50mg) in a critically ill cohort. The results of this study do not support the use of this agent, at this dose, as a prokinetic, in this population. If nasogastric administration of nutrition proves unsuccessful an alternative is to infuse nutrient directly into the small intestine. However, the placement of feeding tubes distal to the pylorus is technically difficult. A novel technique for postpyloric tube insertion was examined with promising results. In summary, the studies described in this thesis have provided a number of insights relevant to the management of the critically ill by quantifying the prevalence of feed intolerance and delayed GE, characterising some of the disturbances in gastrointestinal motility underlying this problem, and evaluating a number of therapeutic interventions. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1345143 / Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2008

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Estudamos o efeito do citrato de sildenafil (ViagraÂ), vasodilatador largamente utilizado na terapÃutica da disfunÃÃo erÃtil, sobre o comportamento motor do trato gastrintestinal (TGI) de ratos Wistar. Para tanto, utilizamos 175 animais machos, pesando entre 200 a 350g, distribuÃdos nos quatro seguintes grupos de estudo: efeitos do citrato de sildenafil sobre o i) esvaziamento gÃstrico (EG) e os trÃnsitos gastrintestinal (GI) e ii) intestinal de lÃquido em ratos acordados; iii) a complacÃncia gÃstrica de ratos anestesiados e iv) a contratilidade de tiras isoladas do duodeno de ratos ex vivo. i) Avaliamos, em 64 ratos acordados sob jejum e livre acesso à Ãgua por 24h, o efeito da injeÃÃo (0,2mL; e.v.) de sildenafil (4mg/Kg) ou veÃculo (HCl 0,01N) sobre o EG e o trÃnsito GI de lÃquido, bem como sobre a pressÃo arterial (PA). Mediante gavagem, 1,5mL da refeiÃÃo-teste (vermelho de fenol - 0,5mg/mL em glicose a 5%) foi injetada no estÃmago. Depois de 10, 20 ou 30min, sacrificamos os animais e, apÃs laparotomia, obstruÃmos o piloro, o cÃrdia e o Ãleo terminal. Removemos e dividimos o TGI em: estÃmago e segmentos consecutivos do intestino delgado (40% iniciais; 30% mediais e 30% terminais). ApÃs o processamento destas porÃÃes viscerais, determinamos as absorbÃncias das amostras a 560nm. A retenÃÃo fracional de vermelho fenol em cada segmento permitiu o cÃlculo do EG e trÃnsito GI. Em um grupo separado de animais, a PA foi monitorada continuamente por meio de um sistema digital de aquisiÃÃo de dados durante 20min antes e 30min apÃs o tratamento com sildenafil ou diluente. Comparado ao grupo controle, houve aumento significativo da retenÃÃo gÃstrica (44,2Â2,0 vs 53,2Â2,1; 25,4Â1,3 vs 37,3Â1,6; 20,9Â2,5 vs 32,5Â2,9%) nos animais tratados com sildenafil e sacrificados aos 10, 20, ou 30min, respectivamente, bem como retarde significativo no trÃnsito GI. Embora o sildenafil tenha provocado hipotensÃo, a PA retoma nÃveis basais logo apÃs 10min. O prÃ-tratamento com omeprazol (bloqueador da secreÃÃo Ãcida estomacal) nÃo modificou o efeito do sildenafil sobre os valores de retenÃÃo gÃstrica e intestinal nem nos nÃveis de PA. ii) Noutros animais (n=44), sob jejum de 24h e dotados previamente (3d) de uma cÃnula crÃnica no bulbo duodenal, estudamos o efeito do sildenafil sobre a progressÃo ao longo do intestino delgado de uma refeiÃÃo teste (10MBq de TecnÃcio ligado a fitato e diluÃdo em 1mL de salina 0,9%). Decorridos 20, 30 ou 40min da injeÃÃo (0,2mL e.v.) de sildenafil (4mg/Kg) ou diluente (HCL 0,01N), sacrificamos os animais e, apÃs laparotomia e remoÃÃo do TGI, dividimo-o em: estÃmago, cinco segmentos congruentes e consecutivos de intestino delgado e o intestino grosso. A contagem da radiatividade foi determinada num colimador de gama-cÃmara. O sildenafil promoveu retarde (p<0,05) do TI, indicado pelos retardes dos centros geomÃtricos da refeiÃÃo de 2,8&#61617; 0,2 vs 3,3&#61617; 0,1; 3,0&#61617; 0,2 vs 3,7&#61617; 0,1 e 3,4&#61617; 0,1 vs 4,2&#61617; 0,2 em relaÃÃo ao grupo controle, aos 20, 30 ou 40min. iii) Os estudos de complacÃncia gÃstrica foram conduzidos em 39 ratos anestesiados, sob jejum de 24h. As variaÃÃes do volume gÃstrico (VG), foram medidas por pletismografia, enquanto a PA foi monitorada continuamente por um sistema digital de aquisiÃÃo de dados. Em relaÃÃo aos valores basais (2,91Â0,19mL) o sildenafil (3mg/Kg â e.v.) aumentou (p<0,05) o VG apÃs 10, 20 e 30min (3,08Â0,18; 3,10Â0,17 e 3,09Â0,17mL). A PA basal (105,8Â2,28mmHg) caiu significativamente com o sildenafil (59,8Â3,2; 64,8Â3,7 e 59,3Â4,6mmHg) enquanto o diluente (HCl 0,01N) nÃo modificou seja o VG ou a PA. O prÃ-tratamento mediante esplancnotomia ou injeÃÃo e.v. com azul de metileno (3mg/Kg-bloqueador da guanilato ciclase), L-NNA (3mg/Kg-bloqueador da NO sintetase) ou propranolol (2mg/Kg-Ã-bloqueador) preveniram o aumento do VG pelo sildenafil; jà o pÃs-tratamento com nitroprussiato de sÃdio (1mg/Kg - e.v.) o ampliou significativamente. iv) Avaliamos ainda o efeito do sildenafil sobre a contratilidade de tiras isoladas do duodeno de ratos ex vivo (n=28), sacrificados por deslocamento cervical. Tiras dissecadas do duodeno foram suspensas longitudinalmente em cuba de vidro (10mL), plena de soluÃÃo de Tyrode (37oC e pH 7,4), e submetidas a uma tensÃo inicial de 1g. ApÃs 1h de estabilizaÃÃo, a contratilidade espontÃnea ou induzida das tiras foi registrada continuamente por um sistema digital de aquisiÃÃo de dados. O sildenafil em doses crescentes e cumulativas (0,1 a 300Âmol/L) relaxou (EC50 de 9,6Âmol/L) o duodeno, mais atà que o zaprinaste ou a papaverina (bloqueadores de FDEs) (EC50 91,6 e 78,5Âmol/L, nesta ordem). Observamos ademais que o sildenafil inibiu as contraÃÃes induzidas por acetilcolina ou carbacol (IC50 26,7 e 16,2Âmol/L, respectivamente). Jà o prÃ-tratamento com azul de metileno, ODQ (bloqueador da guanilato ciclase) ou L-NAME (bloquedor da NO sintetase), mas nÃo o D-NAME (isÃmero inativo da NO sintetase) preveniram o efeito do sildenafil. O efeito mio-relaxante do sildenafil foi ampliado pela L-arginina (substrato do NO sintetase) ou nitroprussiato de sÃdio (doador de NO). O prÃ-tratamento com forskolina (estimulador da adenilato ciclase) tambÃm aumentou o efeito mio-relaxante do sildenafil. Em resumo, observamos que o sildenafil diminui a motilidade gastrintestinal, retardando o EG, os trÃnsitos GI e intestinal de lÃquido em ratos acordados; aumenta a complacÃncia gÃstrica em ratos anestesiados alÃm de apresentar efeitos antiespasmÃdico e mio-relaxante sobre tiras isoladas de duodeno de ratos ex vivo; por estimulaÃÃo do sistema nervoso simpÃtico e tendo como provÃvel mecanismo de aÃÃo ao nÃvel do miÃcito gastrintestinal a via do NO/GMP cÃclico. / We evaluated the effect of sildenafil citrate (ViagraÂ) a vasodilator largely used for the treatment of male erectile dysfunction, on the gastrointestinal motility in rats. Experiments were performed on 175 male, Wistar rats, weighing 200-350g. Four groups of study were done: the sildenafil effects on the: i) Gastric emptying (GE) and gastrointestinal (GI) transit and ii) Intestinal transit (IT) of liquid in awake rats; iii) Gastric compliance in anesthetized rats and iv) Contractility of rat duodenal isolated strips. i) In 64 rats fasted for 24h with previous vascular access (right jugular vein and left carotid artery), we studied the effect of an i.v. injection (0.2mL) of sildenafil (4mg/Kg) or vehicle (0.01N HCl) on GE and GI transit of a liquid meal, as well as on arterial pressure (AP) in a separated group of rats. Animals were gavage-fed with 1.5mL of a test meal (0.5mg/mL of phenol red in 5% glucose). After 10, 20 or 30min, animals were sacrificed and submitted to a laparotomy to obstruct the pylorus, cardia and terminal ileus. The gut was removed and then divided into: stomach and consecutive three small intestine segments (40% proximal; 30% medial and 30% terminal). After processing these segments, the dye retention was determined at 560nm. The percentage of dye retention in each segment permitted to evaluate GE and GI transit. Arterial pressure was continuously monitored by a digital acquisition system during 20min before and 30min after sildenafil injection. We observed a significant increase of gastric retention in sildenafil treated rats at 10, 20, or 30min after the test meal (44,2Â2,0 vs 53,2Â2,1; 25,4Â1,3 vs 37,3Â1,6; 20,9Â2,5 vs 32,5Â2,9%, respectively), as well as a significant GI transit delay. Despite of sildenafil inducing hypotension, AP returned to basal levels 10min afterwards. Acid gastic secretion blocking pre-treatment with omeprazol did not modify the sildenafil effect on gastric retention, GI transit or AP. ii) In another group we evaluated the sildenafil (4mg/Kg) or diluente (0.01N HCl, 0.2mL) effects on the IT in awake rats, fasted for 24h. Animals were studied 3d after the insertion of a silastic cannula (0.6cm ID) into the duodenal bulb. We evaluated the progression of a radioactive liquid test meal fed (10MBq of 99mTc â 1mL of saline 0,9%) administered through the inserted cannula into the small intestine. After 20, 30 or 40min, animals were sacrificed by anesthetic overdose. After laparotomy, we removed and divided the gut in: stomach, five congruent and consecutive segments of the small intestine and the large intestine. Radioactivity counting was obtained in a gamma-chamber collimator. Sildenafil promoted an IT delay (p<0.05), indicated by shifting the center of mass to the proximal portions of the TGI (2.8Â0.2 vs 3.3Â0.1; 3.0Â0.2 vs 3.7Â0.1 and 3.4Â0.1 vs 4.2Â0.2) in relation to control group. iii) Gastric compliance study was performed on 39 anesthetized rats after 24h of fasting. Gastric volume (GV) variations were measured by plethysmography while AP was continuously monitored. We have also observed that GV increased (p<0.05) after sildenafil treatment (3mg/Kg - e.v) (3.08Â0.18; 3.10Â0.17 and 3.09Â0.17mL vs 2.91Â0.19mL) at 10, 20 and 30min after drug administation, respectively. Basal AP (105.8Â2.28mmHg) dropped by the sildenafil injection (59.8Â3.2; 64.8Â3.7 and 59.3Â4.6mmHg-p<0.05) while vehicule (0.01N HCl) did not change either GV or AP. After splanchnotomy or pre-treatments (e.v.) with methylene blue (3mg/Kg-guanilate cyclase blocker), L-NNA (3mg/Kg - NO synthase blocker) or propranolol (2mg/Kg - Ã-blocker) prevented GV increase due to sildenafil; while post-treatment with sodium nitroprusside (1mg/Kg - NO donor) raised it. iv) The in vitro contractility studies were performed on isolated duodenal strips obtained from rats (n=28) killed by cervical dislocation. Duodenal strips were suspended longitudinally in a glass chamber (10mL), filled with Tyrode solution (37oC and pH 7.4). After 1h of stabilization under 1g of initial tension, the spontaneous or induced contractility were continuously recorded by a digital acquisition system. Increasing and cummulative doses of sildenafil (0.1 to 300Âmol/L) relaxed (9.6Âmol/L of EC50) the duodenal strips. This effect was more intense than those displayed by zaprinast or papaverine (PDEs blockers) (91.6 and 78.5Âmol/L of EC50, in this order). Sildenafil showed significant antispasmodic and myorelaxant effects on the duodenal contractions induced by acetylcholine or carbamylcholine (IC50 26.7 and 16.2Âmol/L, respectively). Pre-treatment with methylene blue, ODQ (guanilato cyclase blocker) or L-NAME (NO synthase blocker) also prevented these sildenafil effects, but D-NAME (an inactive substrate for NO synthase) did not. Myorelaxant sildenafil effect was reverted by L-arginine (substrate for NO synthase) and contrarily it was largely increased by sodium nitroprusside. Forskolin adenylate cyclase activation pre-treatment also increased the myorelaxant effect of sildenafil. In summary, we have observed that sildenafil slowed down the gastrointestinal motility, delaying GE, GI and intestinal transits of a liquid meal in awake rats; Gastric compliance was also increased in anesthetized rats treated with sildenafil. Sildenafil also exhibited both antispasmodic and myorelaxant effects on isolated strips of duodenum of ex vivo rats. Besides central or peripheral sympathetic nervous system activation, sildenafil possibly acts at the gastrointestinal myocite level by activating the NO/GMPc system.