Role of Serotonin in the Recovery of Electrical Activity in the Stomach and Small Intestine of Rats during the Early Postsurgery Period

The effects of serotonin and 5-HT₄ receptor agonist cisapride on electrical activity of the stomach and small intestine were studied in rats with postoperative ileus. Postoperative ileus was accompanied by the absence of the migrating myoelectric complex in the stomach and small intestine. All phases of the migrating myoelectric complex were successively recovered in the jejunum, duodenum, and stomach. Administration of serotonin and 5-HT₄ receptor agonist cisapride into the jejunum was followed by the appearance of spike activity, which spread from the stomach to the jejunum. Intraintestinal treatment with cisapride and serotonin shortened the period to recovery of the migrating myoelectric complex to 3 and 4 days, respectively. Our results suggest that serotonin plays a role in the regulation of the migrating myoelectric complex at the early postoperation period. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 11, pp. 511–514, November, 2005     

Functional heterogeneity of damaged gastroduodenal complex

Peculiarities of myoelectric activity in the gastric corpus, pylorus, and duodenum during acute damage to the stomach and simulated partial intestinal obstruction were studied on cats. During adaptation, the functional systems of digestion organs are characterized by disruption of the relationships between their elements. Disturbances of adaptive processes were accompanied by strengthening of these relationships, which made the whole system more vulnerable. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 2, pp. 149–151, February, 2007     

Ghrelin Induces Fasted Motor Activity of the Gastrointestinal Tract in Conscious Fed Rats

Ghrelin is a newly discovered orexigenic peptide originating from the stomach. However, its action in regulating the fed and fasted motor activity of the digestive tract is not fully understood. In the present study, we examined the effects of intracerebroventricular ( i.c.v. ) and intravenous ( i.v. ) injection of ghrelin on the physiological fed and fasted motor activities in the stomach and duodenum of freely moving conscious rats. i.c.v. and i.v. injection of ghrelin induced fasted motor activity in the duodenum in normal fed rats, while i.v. injection of ghrelin induced fasted motor activity in both the stomach and duodenum in vagotomized rats. The effects of i.c.v. and i.v. injected ghrelin were blocked by growth hormone secretagogue receptor (GHS-R) antagonist given by the same route and also blocked by immunoneutralization of neuropeptide Y (NPY) in the brain. The effects of i.v. injected ghrelin were not altered by i.c.v. injection of GHS-R antagonist in vagotomized rats. Injection of GHS-R antagonist blocked the fasted motor activity in both the stomach and duodenum in vagotomized rats but did not affect the fasted motor activity in normal rats. Low intragastric pH inhibited the effect of ghrelin. The present results indicate that ghrelin is involved in regulation of fasted motor activity in the stomach and duodenum. Peripheral ghrelin may induce the fasted motor activity by activating the NPY neurons in the brain, probably through ghrelin receptors on vagal afferent neurons. Once the brain mechanism is eliminated by truncal vagotomy, ghrelin might be primarily involved in the regulation of fasted motor activity through ghrelin receptors on the stomach and duodenum. The action of ghrelin to induce fasted motor activity is strongly affected by intragastric pH; low pH inhibits the action.     

不同状态下家兔Oddi括约肌肌电活动实验模型的建立

目的建立不同状态下家兔Odd i括约肌(sph incter ofOdd i,SO)肌电活动实验模型。方法利用电生理方法记录家兔Odd i括约肌的肌电活动,并建立空腹、进食、药物兴奋和药物抑制等四种状态下Odd i括约肌肌电活动的实验模型。结果空腹状态下家兔SO肌电表现为规律的、单发性的锋电位(sp ike potentials of SO,SPSO);禁食18 h后,给予50 m l牛奶,SO肌电表现为规律的、间断的肌电簇(myoelectron ic activity of SO,MASO);静脉注射1 mg吗啡和2 mg新斯的明后,SO肌电活动首先表现为数个长时间、不间断的SPSO组成的肌电串,120~150 m in内完全抑制,抑制期过后又恢复单个SPSO;静脉给予山莨菪硷1 mg,SPSO随即消失。结论成功建立了四种状态下家兔Odd i括约肌肌电活动实验模型。     

An immunohistochemical study of endocrine cells in the alimentary tract of the grass lizard, Takydromus wolteri Fischer (Laceridae)

Distribution patterns and the relative frequency of different types of endocrine cells were demonstrated in the alimentary tract of the grass lizard, Takydromus wolteri, using nine specific antibodies raised against mammalian regulatory peptides. The alimentary tract of the lizard was divided into six portions from the esophagus to the rectum. Most endocrine cells were found in the epithelial lining and were generally spindle shaped with long cytoplasmic processes ending in the lumen (open cell type), whereas cells that were spherical in shape (closed cell type) were occasionally found in gastric, esophageal and intestinal glands. Endocrine cells were stained for the following regulatory peptides: bovine Sp-1/chromogranin (BCG), serotonin, somatostatin, gastrin, cholecystokinin (CCK)-8, glucagon, insulin, human pancreatic polypeptide (HPP) and secretin. Cells stained for BCG and serotonin were present throughout the entire gastrointestinal tract and they occurred with the highest frequency in stomach and pylorus, respectively. Somatostatin-positive cells were detected throughout the entire gastrointestinal tract except for the esophagus and large intestine, and were most predominant in pylorus and duodenum. Cells stained for gastrin were restricted to the pylorus and duodenum and occurred with a relatively low frequency. CCK-8-positive cells were observed from pylorus to small intestine and showed the highest frequency in the pylorus. Glucagon- and insulin-containing cells were located in duodenum and small intestine but were found only rarely. HPP-stained cells were detected in duodenum and small intestine with the highest frequency in duodenum. Cells stained for secretin were restricted to duodenum and were found only rarely. In conclusion, distribution patterns and the relative frequency of these endocrine cells correspond well with previous reports on distribution patterns of endocrine cells in reptile species but some deviating patterns were also observed.     

Incoordination of gastroduodenal myoelectric activity caused by immobilization stress in rabbits

Incoordination of gastroduodenal myoelectric activity in rabbits under immobilization stress was manifested, first, in an earlier resumption of spike activity in the duodenum than in the stomach and pyloric sphincter after its simultaneous suppression in these three parts of the gastrointestinal tract and, second, in the subsequent considerable increase of duodenal spike activity over its baseline level, while stomach and pyloric sphincter activities remained reduced. The incoordination of gastroduodenal myoelectric activity, which developed during the first hour of immobilization, was accompanied by the formation of erosive lesions in the gastric mucosa. The results of this study suggest that incoordination of gastroduodenal motor activity may be implicated in stressinduced gastric ulcers as a factor that damages the gastric mucosa by slowing down the evacuation of stomach contents and promoting duodenogastric reflux. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 3, pp. 239–242, March, 1995     

Effects of celiac and superior mesenteric ganglionectomy on interdigestive myoelectric complex in dogs.

The interdigestive myoelectrical activity of the stomach and small bowel has been studied before and after celiac and superior mesenteric ganglionectomy in four healthy, well-trained conscious dogs. The interdigestive myoelectric complex was present before and after the gangliomectomy in all dogs, but variability in the duration of its cycles was increased by ganglionectomy. The percentage of time that action potential activity was present during the interdigestive period in the stomach and orad half of the small bowel was also increased in all animals after the ganglionectomy. The duration of phase III, the activity front, was unaltered by the operation, but the timing of the other phases became more variable after ganglionectomy. The time required for migration of the complex from duodenum to terminal ileum was more variable after ganglionectomy in the three animals in which it could be measured, and in two of them the migration time was shorter. An abnormal electrical pattern occurred in all animals after ganglionectomy. Its duration ranged from 0.5--5 min. Electrically, it appeared to represent an elongated, nonmigrating activity front.     

An autoradiographic study of the distribution of the vagus nerve in the wall of the ferret stomach

In this study, the normal distribution of the dorsal and ventral vagal trunks in the wall of the stomach of the ferret was investigated by the method of partial acute vagotomy and analyzed by light autoradiography. The dorsal trunk is distributed to the dorsal surface of the body and both surfaces of the pylorus. The ventral trunk reaches principally to the body of the ventral surface of the stomach. Three months after partial vagotomy, tritiated leucine was injected into the vagal dorsal motor nucleus to map any anatomical changes in the gastric distribution of each abdominal vagal trunk. Three months after dorsal trunk vagotomy, the ventral trunk invaded the territory of the dorsal trunk close to the lesser curvature of the body of the stomach by reactive sprouting. Three months after ventral trunk vagotomy, the dorsal trunk spread to innervate the ventral surface of the stomach that formerly was innervated by the ventral trunk. Three months after ventral trunk vagotomy, regrown connection of the ventral trunk was observed crossing over the ligature to the denervated areas of the ventral surface of the stomach. This result was observed in the three animals of chronic ventral vagotomy only, and the histological examination of the regrown connection showed that it was neuronal. This phenomenon of the compensatory reactive sprouting of the surviving vagal nerve terminals, whether regenerative or terminal, may explain the recovery of gastric function. This could account for some of the failures of partial vagotomy in humans. © 1993 Wiley-Liss, Inc.     

Required neural involvement in control of canine migrating motor complex.

This study evaluated the effects of muscarinic, nicotinic, and adrenergic neuronal blockade on the migrating motor complex (MMC) in four unanesthetized dogs. Circular muscle contractile activity was recorded from eight strain gauge force transducers implanted on the stomach and small intestine of each dog. Both atropine sulfate and hexamethonium bromide significantly increased the period of the MMC. When the complex returned after hexamethonium administration, the period of the succeeding complexes was significantly decreased when compared to control. Guanethidine sulfate significantly increased contractile activity on the pylorus, duodenum, and jejunum with a corresponding disruption of the MMC pattern. The migrating motor complex requires the preganglionic release of acteylcholine and possibly an inhibitory input from the sympathetic nervous system for its normal appearance.     

Effects of ranitidine and oxmetidine on gastrointestinal motility in conscious dog

Two histamine H₂-receptor antagonists ranitidine and oxmetidine were tested for their effects on gastrointestinal motility in conscious fasted dogs chronically fitted with intraparietal electrodes on the antrum, duodenum and jejunum. Intravenous administration of ranitidine (3 mg/kg) stimulated gastrointestinal spiking activity through a cholinergic mechanism and increased the duration of the cycles of migrating myoelectric complexes. Oxmetidine at the same dose did not modify the gastrointestinal motor profile. These results showed clearcut differences in nonspecific effects of two H₂-antagonists equipotent on gastric acid secretion.To whom correspondence should be addressed.     

Effect of motilin on the opossum upper gastrointestinal tract and sphincter of Oddi

We studied the effect of motilin on myoelectric activity of the sphincter of Oddi (SO) and upper gastrointestinal tract in conscious opposums. In 17 animals, bipolar electrodes were implanted on the gastric antrum, SO, duodenum, and jejunum. Subsequent 8-h recordings reconfirmed our previous findings that SO spike burst rate changed with interdigestive cycles of the gastrointestinal migrating myoelectric complex (MMC), becoming maximal during passage of phase III activity through the duodenum. In eight animals, peak motilin levels were shown to occur concurrently with maximal SO spike burst rate and MMC phase III activity in the duodenum. Motilin infusion (0.3 and 0.9 micrograms X kg-1 X h-1), given for 30-60 min starting 10 min after duodenal phase III, elicited premature MMC activity that originated in the stomach. Maximal SO activity occurred coincident with passage of premature phase III activity through the duodenum. Pulse intravenous doses of motilin (25-1,600 ng/kg) generally caused an immediate increase in spike burst activity in the gastric antrum, duodenum, and SO that lasted 3-5 min and was often followed by a premature MMC, usually starting in the antrum and progressing through the duodenum and jejunum. Increases in SO spike burst rate also occurred concurrent with motilin-induced, premature duodenal phase III. Motilin given at 5-60% of the duodenal MMC cycle length elicited premature MMCs at 10-60% of the cycle, but no premature MMCs were elicited by any of the motilin doses at the 5% intervals.(ABSTRACT TRUNCATED AT 250 WORDS)     

A radiological study of gastric (abomasal) emptying in calves before and after vagotomy.

1. Gastric emptying has been studied in the conscious, standing calf by lateral radiography and fluoroscopy of radiopaque meals instilled into the abomasum before and after vagotomy. 2. Bilateral cervical vagotomy proved to be the only certain way of achieving total vagal transection. By instillation of milk into the abomasum through a cannula calves were maintained in normal, healthy condition for up to 36 days after vagotomy. 3. Motility of the antrum was not impaired by vagotomy so that some movement of gastric chyme to the duodenum occurred within minutes of instillation into the abomasum. Complete transference of the test meal was, however, delayed after vagotomy. 4. The greatest effect of vagotomy appeared to be on the abomasal body so that inadequate amounts of chyme were transferred to the antrum for pumping to the duodenum. 5. Delay in passage of contrast material through the intestine was related to delay in gastric emptying although vagotomy may have affected the intestine directly. 6. Following vagotomy the abomasum showed a resumption of normal motility and emptying after 7-29 days. This effect of vagotomy is similar to that seen in the simple stomach and is probably due to the establishment of intrinsic gastric control.     

Purified Shigella enterotoxin does not alter intestinal motility.

A purified Shigella enterotoxin (pST) and a cell-free lysate with pST removed (CFL-pST) from the whole-cell lysate of Shigella dysenteriae 60 R were used to study their effect on the myoelectric activity and mucosal integrity of rabbit ileal segments. We have previously defined two myoelectric patterns: the migrating action potential complex and repetitive bursts of action potentials that occur in response to certain bacteria and their enterotoxins. The in vivo model consisted of isolated ileal segments in male New Zealand White rabbits. The segments were infused with sterile saline (1 ml/h), pST (2.4-micrograms injection), or CFL-pST (1 ml/h). Myoelectric activity in the segments exposed to pST was similar to that with the saline infusion, but CFL-pST induced significant alterations in myoelectric activity in the form of repetitive bursts of action potentials. The mucosa of the segments exposed to pST showed only mild inflammatory changes. In contrast, CFL-pST caused moderate to severe inflammatory changes with enterocyte necrosis. These studies show that pST, a known enterotoxin, did not alter myoelectric activity and had no significant effect on the integrity of ileal mucosa, as determined by light microscopy. CFL-pST caused both inflammation and tissue necrosis with significant alterations in motor activity. These studies suggest that S. dysenteriae 60 R produces a substance or substances other than pST that cause florid in vivo cytotoxicity and alter myoelectric activity.     

Effect of vagotomy and serotomin on myoelectric activity and functional relationships in various subdivisions of the gastroduodenal complex

Serotonin significantly increases the amplitude of smooth muscle electrical activity in the stomach and duodenum and improves their functional coupling disturbed by vagotomy. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 4, pp. 384–386, April, 1999     

Motilin-independent ectopic fronts of the interdigestive myoelectric complex in dogs

We have studied in four conscious dogs the relationship between circulating concentrations of motilin and the activity front (phase III) of the interdigestive myoelectric complex. During fasting, cyclic peaks of motilin secretion were concomitant in every instance with the initiation of activity fronts that began in the stomach or duodenum. When somatostatin was administered at doses of 5, 2.5, or 0.625 microgram x kg-1 x h-1 for 3 h, motilin concentrations were stabilized at lowered levels and no activity fronts occurred in the duodenum. Somatostatin also inhibited the stimulatory effects of exogenous motilin on the entire small intestine. During somatostatin infusion, however, ectopic fronts began in the jejunum and were propagated to the cecum despite low motilin concentration. After a 100-g meat meal, the cyclic increase of motilin was interrupted and no activity fronts were observed in the duodenum, but ectopic fronts started lower in the small intestine. Our study supports the hypothesis that motilin induces activity fronts in the canine duodenum, but it shows that ectopic fronts are not controlled by motilin.     

Effect of serotonin-adipinate on the ultrastructure and synthetic activity of endotheliocytes of microhemocirculatory bed of human brain (autopsy material, early autopsies)

Electron-microscopic and radioautographic investigation showed the ability of brain capillary endotheliocytes for retaining functional activity in total ishemia. Administration of serotonin adipinate in an early postoperative period supports intracellular processes and plays a protective role.     

Tachykinins increase vascular permeability in the gastrointestinal tract of the rat

The occurrence of inflammation as indicated by extravasation of Evans blue bound to plasma proteins was examined in various parts of the gastrointestinal tract in the rat, following administration of tachykinins, capsaicin and hydrochloric acid. Intravenous neurokinin A dose-dependently induced extravasation in stomach, duodenum, jejunum, caecum and colon, but had no effect in ileum. Neurokinin B equipotently induced extravasation in the stomach but had no effect in other parts of the gut and substance P had no effects on extravasation of Evans blue in any of the examined parts of the gastrointestinal tract. Capsaicin given intraperitoneally increased vascular permeability in stomach and duodenum only, while extravasation of Evans blue after capsaicin given intraluminally did not differ from the effect of the vehicle alone. As a comparison, HCl given intraluminally in the duodenum was found to induce a prominent extravasation of Evans blue of a greater magnitude than that of tachykinins. We suggest that tachykinins, and in particular neurokinin A, may be of importance for extravasation of plasma proteins as part of inflammatory reactions in the upper and lower gastrointestinal tract.     

Stability of Myoelectric Slow Waves and Contractions Recorded from the Distal Colon

The stability of physiological activity in the distal colon was investigated by recording 5-6 hours in each of 6 healthy adults. Contractions and myoelectric slow waves were recorded from the sigmoid colon (25-30 cm from the skin surface) and rectum (10-15 cm), and pressure waves were recorded from the proximal small intestine. The activity index (sum of areas of all waves divided by recording time) varied by 200% to 800% across 4-min samples for all motility and myoelectric slow wave recordings. Spectral analysis indicated that contractile activity waxed and waned in a cycle with a period of 40-55 min in the colon and 64-80 min in the small intestine. Myoelectric slow wave activity in the colon cycled with a period of 30-40 min. Contractile activity in the sigmoid colon was correlated with similar activity in the rectum, but myoelectric slow wave activity in the colon was not correlated with myoelectric slow waves in the rectum. The frequency composition of contractions and slow waves was unstable over time.     

Direct effects of motilin on isolated smooth muscle from various regions of the human stomach

The effects of motilin on gastrointestinal muscles show great variations in different organs and different species. For a precise regional differentiation, we recorded the mechanical activity of longitudinal and circular strips from fundus, corpus and antrum and of circular preparations from the inner and outer layer of the pyloric sphincter and from the duodenum (20 human stomachs). Motilin produced excitatory effects on the mechanical activity of the circular muscle strips from all regions of the human stomach including the pylorus. The effects on longitudinal preparations and on duodenal strips were weak. The most striking effect was an increase of phasic activity (amplitude) in circular antrum preparations, which exceeded the acetylcholine- and bombesin-induced activity. In pylorus preparations, a strong stimulation of phasic activity was observed with a transition to tonic activity in the inner layer of the pyloric ring at high motilin concentrations. The motilin-induced activity of the pyloric preparations was greater than the acetylcholine-induced contractions and even exceeded the bombesin-induced responses in the outer pylorus. The responses of the muscle strips of the proximal stomach (fundus and corpus) were weaker and did not exceed the acetylcholine-induced activity. All effects remained unaltered by atropine and tetrodotoxin application. The study confirms that motilin can interact directly with the smooth muscle of human stomach.     

The effects of pressure and pharmacologically active substances on gastric peristalsis in a transmurally stimulated rat stomach-duodenum preparation

1. A rat stomach—duodenum preparation in which pressures in the body and the antrum and flow through the pylorus could be recorded simultaneously has been used to study the effects of pressure and pharmacologically active substances on the peristalsis induced by transmural stimulation.

2. Vagal and transmural stimulation produced vigorous peristalsis and episodic flow. Simultaneous stimulation of the peri-arterial nerves abolished peristalsis and relaxed the pylorus.

3. After repeated stimulation the preparation lost tone and peristalsis failed. Peristalsis and tone could then be improved by lowering intragastric pressure. Vigorous peristalsis could be restored in an inactive preparation by eserine and more transiently by 5-HT.

4. Drugs which increased smooth muscle tone improved peristalsis and, under the conditions used, they reduced flow. Eserine was more active in this respect than acetylcholine or 5-HT.

5. Adrenaline and hyoscine abolished peristalsis and caused the stomach and the pylorus to relax.

6. The results suggest that the peristaltic activity of the antrum is more important than the tone of the pylorus itself in controlling gastric emptying.