摘要:

To define the variations in gastric tone associated with the intestinal motor correlates of vomiting, we studied the effects of intracerebroventricular pharmacological manipulation in four fasting, conscious dogs with an injection catheter implanted into the fourth cerebral ventricle. Simultaneous monitoring of gastric tone and duodenal motility allowed us to study the correlation between gastric and duodenal motor events. We compared the effects of i.c.v. morphine (0.1 to 1 μLg/kg), apomorphine (0.003 to 0.03 (μg/kg), and the α2‐adrenoceptor agonist ST91 (0.1 to 1 μg/kg). These agonists, by the i.c.v. route all induced gastric relaxation accompanied by a retrograde power contraction in the duodenum and, at the highest doses, emesis; subsequently, a burst of intense phasic pressure activity developed in the duodenum. However, at a dose that was fully effective i.c.v., they had no effect when given intravenously. Naloxone or domperidone, at doses that had no effect per se, blocked the effects of morphine and apomorphine, respectively, except for a residual gastric relaxation. Idazoxan failed to block the effects of ST91. We conclude that a common pattern of motor events is triggered in the upper gut by different drugs by activation of receptors involved in the mechanism of vomiting and probably located in the central nervous system, and that the effects of morphine and apomorphine are mediated respectively by opioid and dopamine rece

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00001.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The extent and nature of colonic and anorectal motility responses to S2, S3, and S4 anterior nerve root stimulation were studied in seven paraplegic patients with a Brindley electromicturition sacral implant. After sequential S2, S3 and S4 stimulation wave height activity was increased above basal from the transverse colon to the rectum. The mean motility index response to sequential stimulation was greatest at the splenic flexure. The greatest peak wave height and mean motility index response to individual anterior nerve root stimulation was to S3, which could empty the left colon by a distal motility gradient. S4 anterior root stimulation increased the intrarectal pressure and also raised the anal canal pressure to high levels.

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

This work evaluated the effects of 20‐minute exposures to acoustic stress, cold (10°C), or immobilization on gastric emptying of test meals containing51Cr sodium chromate in rats and mice. Four diets were studied: one consisting of reconstituted cow's milk (diet A), a synthetic diet containing arabic gum, glucose, and casein (diet B), diet B with arachis oil (diet C), and a nonnutritive diet containing methylcellulose and saline (diet D). Test‐meal volumes were 0.5 ml in mice and 3 ml in rats. Gastric emptying, expressed as percentage of meal emptied, was measured 30 minutes after gavage with the test meal. Acoustic stress and cold, applied after gavage, increased (p>.05) the rate of gastric emptying of diet A by 46.8% and 70.7%, respectively, in mice and by 13.4% and 22.0% in rats. Immobilization did not affect (p>.05) the gastric emptying of diet A in either species. Cold significantly increased (p ≤ .05) the emptying rate of diets C and D in mice but not in rats. Gastric emptying of diet D was unaffected by the three stressors in mice but was increased (45.7%) by cold in rats. This study shows that the effects of stress on gastric emptying of a nutritive meal depend mainly on the type of stressor. Of the three tested, cold was the most powerful. These results also support the conclusion that stressor, diet, and species are all important in gastric em

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The genesis of lower esophageal sphincter (LES) pressure in anesthetized opossums is a myogenic phenomenon without excitatory neural input. The mechanism responsible for generating phasic LES pressure phenomena in unanesthetized opossums, however, is not established. In this study, we evaluated the effects of potential pharmacological antagonists on LES pressure phenomena in unanesthetized opossums. We also compared LES responses to pharmacological excitatory agonists in anesthetized and unanesthetized animals. In awake animals the LES exhibited substantial tone as well as characteristic phasic activity. The tonic, or basal, LES pressure did not change during cycling of the migratory motor complex (MMC). However, atropine, 4‐diphenylacetoxy‐N‐methylpiperidine methiodide, and hexamethonium abolished the phasic, MMC‐related LES contractions while having no effect on basal pressure. Pirenzepine, prazosin, propranolol, pyrdamine, naloxone, and haloperidol did not affect either phasic or tonic LES pressure phenomena. Anesthesia substantially reduced the excitatory LES response to motilin but not to bethanechol, cholecystokinin‐octapeptide, pentagastrin, or phenylephrine. The results suggest that phasic LES contractions related to the MMC cycle are mediated by postganglionic cholinergic nerves with nicotinic ganglionic transmission. Basal LES tone, however, is maintained by a myogenic phenomenon. Anesthesia reduces excitatory LES responses induced by motilin, which acts via excitatory nerves, but has no effect on excitatory responses induced by agents that act mainly or exclusively on LES smoo

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Fasting activity seen as migrating myoelectric complexes and postprandial activity was recorded from eight conscious dogs with monopolar electrodes implanted on the serosa of the small bowel. A basal period was recorded, after which the 5‐hydroxytryptamine (5‐HT) antagonists methysergide, ketanserin, ICS 205–930, cyproheptadine, or MDL 72222 were administered by intravenous infusion. In other fasted experiments the same antagonists were administered in combination with a 5‐HT infusion. Ketanserin did not change the fed or fasted pattern in the intestine. Methysergide induced irregular spiking activity at all electrode sites in both preprandial and postprandial experiments which continued to the end of recording. Cyproheptadine prevented the distal propagation of phase III of the complex beyond the jejunum. Antagonists of the 5‐HT3receptor abolished phase II of the complex in some experiments. In postprandial experiments these antagonists increased the spiking activity recorded. 5‐HT itself produced irregular spiking, which in the proximal electrodes only was reduced by concurrent ketanserin administration. These data indicate a role for endogenous 5‐HT in the production of phase II of the migrating myoelectric complex and in its distal migration. The stimulatory action of 5‐HT in the proximal intestine is mediated by 5‐HT2receptors. Distally 5‐HT3receptors can play an inhibitory role in the c

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

This study was designed to determine the role of cholecystokinin (CCK) in the motility patterns of duodenum and gallbladder in fasted conscious dogs. During the naturally occurring activity front in the duodenum a significant increase in the motility index, (MI) of the gallbladder was accompanied by a decrease in the gallbladder volume from about 28 ± 4 ml (control) to 21 ± 3 ml. Similar changes in the gallbladder were observed after intravenous bolus injections of motilin (20 to 40 ng/kg), which gave increments in plasma motilin comparable to those occurring spontaneously during the activity front but failed to affect plasma levels of CCK. Blocking of CCK receptors by L‐364, 718 (0.5 to 1 mg/kg) delayed the occurrence of the spontaneous activity front in the duodenum and the accompanying alterations in the gallbladder motility. CCK receptor antagonism abolished the premature activity front induced by motilin in both the duodenum and the gallbladder, converted the fed‐like pattern induced by exogenous CCK to a fasted motility pattern in the duodenum and prevented CCK‐induced reduction in the gallbladder volume. Atropine (12.5 μg/kg) blocked the spontaneous activity front in the duodenum and accompanying alterations in the gallbladder motility and volume but failed to affect those induced by motilin. We conclude that the motility of the gallbladder in fasted dogs shows cyclic changes with typical reduction in the organ volume coinciding with the spontaneous or motilin‐induced activity front in the duodenum, and that both CCK and muscarinic receptors are involved in the MMC‐related alterations in the motor activity of the

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Although the sympathetic nervous system influences intestinal motility and intestinal fluid and electrolyte transport, the role of sympathetic nerves in the relationship between the two processes has not been characterized. We investigated the effect of sympathetic nerve stimulation of intestinal function by monitoring concurrently predominantly longitudinal smooth muscle activity and transmural potential difference as an on‐line marker of intestinal ion transport. In a segment of rabbit small intestine in vitro, perivascular nerve stimulation inhibits spontaneous phasic motor activity and reduces transmural potential difference, which reflects enhanced absorption of fluids and electrolytes. The aim of this study was to investigate the particular adrenoceptors involved in both the smooth muscle and epithelial responses. Using the selective antagonists for the α1‐(prazonsin), α2‐(idazoxan), β1‐(atenolol), and β2‐adrenoceptors (butoxamine), we demonstrated that the enhanced fluid absorption, as shown by a fall in transmural potential difference, is α‐mediated with both α1‐and α2‐adrenoceptors being involved. However, there was considerable variation with regard to the type of α‐adrenoceptor subtype exerting the dominant effect. The sympathetically induced loss of spontaneous smooth muscle motor activity was found to be predominantly β1‐mediated, with the remainder of the respons

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

We used [3H] nitrendipine binding to isolated smooth muscle cells and isometric tension studies of muscle strips to characterize the calcium channels from rabbit proximal and distal colon. At 25°C [3H] nitrendipine binding was rapid, saturable, reversible, specific, and linearly proportional to cell number. The affinity of the ligand for its receptor was similar in proximal and distal colon (KD129 ± 21 pM and 124 ± 17 pM, respectively). In the proximal colon there were 68,000 receptors per cell, compared to 58,000 receptors per cell in the distal colon (p>.1). The Hill coefficient for nitrendipine was close to unity, suggesting binding to a single receptor. Although nitrendipine and nifedipine competitively inhibited [3H]nitrendipine binding, verapamil did not alter [3H] nitrendipine binding, suggesting the presence of at least two discrete, noninteracting sites for the binding of drugs that block calcium channels. In studies with muscle strips nitrendipine competitively inhibited isometric tension stimulated by both bethanechol and high extracellular potassium concentration. There were no significant differences in response from proximal and distal colon. These results suggest that calcium antagonist binding characteristics to calcium channels are similar in proximal and distal colon, and do not explain previously observed differences in the function of muscle in these tissu

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Transit through the bypassed intestine is initially depressed in rats that have 70% of their jejunoileum bypassed. In this study, the influence of intraluminal infusion of the mucolytic N‐acetyl‐L‐cysteine on the depressed transit was determined. Beginning on the first postoperative day, the bypassed intestines were infused continuously with either saline or a 6% solution of acetylcysteine. In one group of animals, transit was determined on the third day after operation. In another group, segments of intestine were evaluated morphometrically on the twelfth day. Transit rates in bypassed intestines of those animals infused with acetylcysteine were higher than those in bypassed intestines of animals infused with saline. Compared to saline infusion, acetylcysteine infusion resulted in the following structural changes in the bypassed intestine: decreases in the total cross‐sectional area of the gut, the wet weight and cross‐sectional area of the intestinal muscle, and the thickness of the circular muscle layer. These findings support the hypothesis that the reduced transit and muscular hypertrophy seen in the uninfused bypassed intestine of rats early after operation may be due to alterations in intestinal contents which incl

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Neuronal stimulation of most isolated precontracted gastrointestinal smooth muscle results in relaxation. This study examined the changes in cyclic nucleotide content associated with neuronally induced relaxation in sphincteric and nonsphincteric smooth muscle of the gut. Electrical field stimulation produced a frequency‐dependent relaxation of the guinea pig proximal colon (EF50= 1.6 Hz) and taenia coli (EF50= 2.4 HZ), and the canine proximal colon (EF50= 3.1 Hz) and internal anal sphincter (EF50= 3.0 Hz). Changes in cyclic nucleotide content occurred during EFS‐induced relaxation. Cyclic AMP levels were significantly increased in the guinea pig poximal colon and taenia coli and in the canine proximal colon. No change in cyclic GMP occurred in these smooth muscles. Conversely, in the canine internal anal sphincter the cyclic GMP content increased significantly with no change in cyclic AMP. These effects in this sphincter are similar to those identified previously in the lower esophageal sphincter of opossum, dog, and man. Tetrodotoxin blocked the EFS‐induced relaxation and the associated accumulation of cyclic nucleotides of all tissues. Therefore, EFS‐induced relaxation is mediated by the activation of neurons and the release of inhibitory neurotransmitter(s). Also, EFS‐induced relaxation is closely associated with increases in smooth muscle cyclic nucleotide content. Most importantly, the change in cyclic nucleotide accumulation that occurs during EFS‐induced relaxation is different for sphincteric and nonsphincteric smooth muscle, (i.e., different cyclic nucleotides are generated in sphincteric and nonsphincteric smooth muscle in response to stimulation of nonadrenergic, nonchohnergic, inhibitory enter

ISSN:1350-1925    

DOI:10.1111/j.1365-2982.1990.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY