Inhibition of intestinal motility and reversal of postlaparotomy ileus by selective alpha 2-adrenergic drugs in the rat

Sterilization of free-ranging female capybaras (Hydrochoerus hydrochaeris): a comparison between two surgical techniques

This study evaluated two surgical sterilization techniques in free-ranging female capybaras (n = 21). The first group underwent uterine horn ligature (HL; n = 11), while the second was subjected to partial salpingectomy (S; n = 10). We assessed total operative time, incision length, the ease of identifying reproductive structures, the adequacy of exposure for surgical performance through flank or midline approaches, and the extent of abdominal viscera manipulation for each method. The HL method emerged as faster, with an average operative time difference of 16 minutes. In the S group, a flank mini-laparotomy over the ovarian topography facilitated easy exposure of the ipsilateral ovary and uterine tube, enabling ligature and partial resection of the uterine tube but not the uterine horn exposure. However, accessing the contralateral uterine tube without a bilateral incision was impractical, thus prolonging the total operative time due to the need for patient repositioning and new antisepsis procedures. Conversely, a post-umbilical approach for the HL method necessitated only one mini-laparotomy incision, offering ample uterine exposure for hysterotomy in pregnant females. Both methods involved minimal abdominal viscera manipulation and resulted in no fatalities or postoperative complications. Although direct comparison is limited by the distinct sterilization techniques and surgical approaches, this study underscores the challenges and surgical access of each method. Our findings endorse the HL technique as an effective contraception method for female capybaras to prevent the birth of seronegative offspring that could amplify Rickettsia sp., the causative agent of Brazilian spotted fever.

Magnetic Resonance Imaging of Gastric Motility in Conscious Rats

Introduction

Gastrointestinal (GI) magnetic resonance imaging (MRI) can simultaneously capture gastric peristalsis, emptying, and intestinal filling and transit. Performing GI MRI with animals requires anesthesia, which complicates physiology and confounds interpretation and translation from animals to humans. This study aims to enable MRI in conscious rats, and for the first time, characterize GI motor functions in awake versus anesthetized conditions.

Methods

We acclimated rats to remain awake, still, and minimally stressed during MRI. We scanned 14 Sprague-Dawley rats in both awake and anesthetized conditions after voluntarily consuming a contrast-enhanced test meal.

Results

Awake rats remained physiologically stable during MRI, showed gastric emptying of 23.7±1.4% after 48 minutes, and exhibited strong peristaltic contractions propagating through the antrum with a velocity of 0.72±0.04 mm/s, a relative amplitude of 40.7±2.3%, and a frequency of 5.1±0.1 cycles per minute. In the anesthetized condition, gastric emptying was about half of that in the awake condition, likely due to the effect of anesthesia in halving the amplitudes of peristaltic contractions rather than their frequency (not significantly changed) or velocity. In awake rats, the intestine filled more quickly and propulsive contractions were more occlusive.

Conclusion

We demonstrated the effective acquisition and analysis of GI MRI in awake rats. Awake rats show faster gastric emptying, stronger gastric contraction with a faster propagation speed, and more effective intestinal filling and transit, compared to anesthetized rats. Our protocol is expected to benefit future preclinical studies of GI physiology and pathophysiology.

Delayed Acetaminophen Absorption Resulting in Acute Liver Failure

Introduction. Acetaminophen is a common medication involved in deliberate and accidental self-poisoning. The acetaminophen treatment nomogram is used to guide acetylcysteine treatment. It is rare to develop hepatotoxicity with an initial acetaminophen concentration below the nomogram line. We present a case of acetaminophen ingestion with an initial concentration below the nomogram line that developed hepatic failure, due to a delayed peak acetaminophen concentration secondary to coingesting medications that slow gastric emptying. Case Report. A 43-year-old (55 kg) female presented after ingesting an unknown quantity of acetaminophen, clonidine, and alcohol. Her acetaminophen level was 41 mg/L (256 μmol/L) at 4.5 h post-ingestion, well below the nomogram line, and ALT was 25 U/L. Hence, acetylcysteine was not commenced. She was intubated for decreased level of conscious. A repeat acetaminophen level 4 h later was 39 mg/L (242 μmol/L), still below the nomogram line. She was extubated 24 h later.At 38 h post-ingestion she developed abdominal pain, the repeat acetaminophen level was 85 mg/L (560 μmol/L), ALT was 489 U/L, and acetylcysteine was commenced. The patient developed hepatic failure with a peak ALT of 7009 U/L and INR of 7.5 but made a full recovery. It was discovered that she had ingested a combination acetaminophen product containing dextromethorphan and chlorphenamine. Acetaminophen metabolites were measured, including nontoxic glucuronide and sulfate conjugates and toxic cytochrome P450 (CYP) metabolites. The metabolite data demonstrated increasing CYP metabolites in occurrence with the delayed acetaminophen peak concentration. Discussion. Opioids and antimuscarinic agents are known to delay gastric emptying and clonidine may also have contributed. These coingested medications resulted in delayed acetaminophen absorption. This case highlights the issue of altered pharmacokinetics when patients coingest gut slowing agents.

Postoperative ileus-An ongoing conundrum

BACKGROUND

Postoperative ileus is common and is a major clinical problem. It has been widely studied in patients and in experimental models in laboratory animals. A wide variety of treatments have been tested to prevent or modify the course of this disorder.

PURPOSE

This review draws together information on animal studies of ileus with studies on human patients. It summarizes some of the conceptual advances made in understanding the mechanisms that underlie paralytic ileus. The treatments that have been tested in human subjects (both pharmacological and non-pharmacological) and their efficacy are summarized and graded consistent with current clinical guidelines. The review is not intended to provide a comprehensive overview of ileus, but rather a general understanding of the major clinical problems associated with it, how animal models have been useful to elucidate key mechanisms and, finally, some perspectives from both scientists and clinicians as to how we may move forward with this debilitating yet common condition.

DA-9701 (Motilitone): A Multi-Targeting Botanical Drug for the Treatment of Functional Dyspepsia

Functional dyspepsia (FD) is the most common functional gastrointestinal disorder (FGID). FD is characterized by bothersome symptoms such as postprandial fullness, early satiety, and epigastric pain or burning sensations in the upper abdomen. The complexity and heterogeneity of FD pathophysiology, which involves multiple mechanisms, make both treatment and new drug development for FD difficult. Current medicines for FD targeting a single pathway have failed to show satisfactory efficacy and safety. On the other hand, multicomponent herbal medicines that act on multiple targets may be a promising alternative treatment for FD. DA-9701 (Motilitone), a botanical drug consisting of Corydalis Tuber and Pharbitidis Semen, has been prescribed for FD since it was launched in Korea in 2011. It has multiple mechanisms of action such as prokinetic effects, fundus relaxation, and visceral analgesia, which are mediated by dopamine D₂ and several serotonin receptors involved in gastrointestinal (GI) functions. In clinical studies, DA-9701 has been found to be beneficial for improvement of FD symptoms and GI functions in FD patients, while showing better safety compared to that associated with conventional medicines. In this review, we provide updated information on the pharmacological effects, safety, and clinical results of DA-9701 for the treatment of FGIDs.

DA-9701: A New Multi-Acting Drug for the Treatment of Functional Dyspepsia

Motilitone^® (DA-9701) is a new herbal drug that was launched for the treatment of functional dyspepsia in December 2011 in Korea. The heterogeneous symptom pattern and multiple causes of functional dyspepsia have resulted in multiple drug target strategies for its treatment. DA-9701, a compound consisting of a combination of Corydalis Tuber and Pharbitidis Semen, has being developed for treatment of functional dyspepsia. It has multiple mechanisms of action such as fundus relaxation, visceral analgesia, and prokinetic effects. Furthermore, it was found to significantly enhance meal-induced gastric accommodation and increase gastric compliance in dogs. DA-9701 also showed an analgesic effect in rats with colorectal distension induced visceral hypersensitivity and an antinociceptive effect in beagle dogs with gastric distension-induced nociception. The pharmacological effects of DA-9701 also include conventional effects, such as enhanced gastric emptying and gastrointestinal transit. The safety profi le of DA-9701 is also preferable to that of other treatments.

Both α2B- and α2C-adrenoceptor subtypes are involved in the mediation of centrally induced gastroprotection in mice

α(2)-adrenoceptors are known to mediate gastroprotective effect in both acid-dependent and acid-independent ulcer models. The aim of the present study was to determine, which of the three α(2)-adrenoceptor subtypes (α(2A), α(2B) or α(2C)) is responsible for this protection. Various α(2)-adrenoceptor agonists and antagonists were administered intracerebroventricularly (i.c.v.) to C57BL/6 mice with deletion of genes encoding the different subtypes. The gastric mucosal damage was induced by orally injected acidified ethanol. Both the non-selective α(2)-adrenoceptor agonist clonidine (0.3-2.8 nmol) and the α(2B/C)-adrenoceptor subtype preferring agonist ST-91 (0.5-11.5 nmol) induced dose-dependent gastroprotective effect in wild type, α(2A)-, α(2B)- and α(2C)-KO mice. In contrast, the α(2A)-adrenoceptor subtype agonist oxymetazoline (0.07-84 nmol i.c.v.) reduced only slightly the development of ethanol-induced ulcers. The effect of clonidine was antagonized by the non-selective antagonist yohimbine (25 nmol) and the α(2B/C)-adrenoceptor antagonist ARC 239 (10.4 nmol), but not by the α(2A)-adrenoceptor antagonist BRL 44408 (7.5 nmol). ARC 239 also reversed the effect of clonidine in α(2A)-, α(2B)- and α(2C)-KO mice, while the selective α(2C)-adrenoceptor antagonist JP 1302 (52 nmol) antagonized that only in α(2B)-KO, but not in α(2A)- and α(2C)-KO mice. These results suggest that α(2B)- and α(2C)-adrenoceptor subtypes can equally contribute to the mediation of gastroprotective effect induced by α(2)-adrenoceptor agonists in mice.

Postoperative ileus: pathogenesis and treatment

Surgical manipulation of the intestines activates intestinal macrophages that release cytokines and nitric oxide, which results in inhibition of intestinal motility. Subsequent infiltration of circulating leukocytes into the intestinal wall contributes to cytokine and nitric oxide release and exacerbates ileus. Other factors contributing to ileus are endotoxemia; edema of the intestine wall subsequent to excessive fluid therapy; hypocalcemia; and long abdominal incisions. Because treatment of ileus with prokinetic drugs has not proven to be very effective, efforts should be directed at reducing its severity. Strategies which reduce the severity of ileus include pretreatment with a nonsteroidal anti-inflammatory drug, minimizing the length of the abdominal incision, reducing intestinal manipulation, intraoperative lidocaine infusion, correction of hypocalcemia, limiting the volume of intravenous fluids to prevent intestinal edema, and administration of alpha(2) antagonists.

Inhibition of sympathetic pathways restores postoperative ileus in the upper and lower gastrointestinal tract

BACKGROUND AND AIM

Postoperative ileus (POI) is a transient bowel dysmotility following abdominal surgery. The effects of adrenergic blocking agents and celiac ganglionectomy were studied in rats to investigate the possible involvement of the adrenergic pathway in whole gastrointestinal (GI) transit in the early and late phases of POI.

METHODS

After laparotomy, the terminal ileum was manipulated for 10 min. (51)Cr was administered into the stomach or colon immediately after surgery. In another group, (51)Cr was administered 24 h after surgery. Three hours after (51)Cr was administered, the rats were killed, and GI and colonic transit was calculated as a geometric center (GC).

RESULTS

Gastrointestinal transit was significantly delayed 3 h after intestinal manipulation, compared with GI transit in rats that had anesthesia only. Three hours after intestinal manipulation, guanethidine (5 mg/kg) and yohimbine (3 mg/kg) significantly improved delayed GI transit. Celiac ganglionectomy also significantly improved delayed GI transit. Twenty-seven hours after intestinal manipulation, guanethidine, yohimbine and celiac ganglionectomy improved delayed GI transit induced by intestinal manipulation. Colonic transit was delayed 3 h after intestinal manipulation, and delayed colonic transit was partially restored within 27 h of intestinal manipulation. Guanethidine, yohimbine and celiac ganglionectomy improved delayed colonic transit 3 h and 27 h after intestinal manipulation.

CONCLUSIONS

Adrenoceptors activated by intestinal manipulation impair the motility of the entire GI tract in both the early and the late phase of POI.

The alpha2-adrenergic receptor antagonist yohimbine improves endotoxin-induced inhibition of gastrointestinal motility in mice

BACKGROUND

Sepsis inhibits gastrointestinal motility. Although the exact mechanism of this is unclear, lipopolysaccharide is known to activate macrophages in the gastrointestinal wall, which upregulate their expression of inducible nitric oxide synthase (iNOS). This leads to an increased production of nitric oxide, which relaxes the gastrointestinal muscles. We studied endotoxaemic mice to determine whether yohimbine improved delayed gastric emptying and gastrointestinal transit.

METHODS

Male Balb/c mice (n = 49) were randomly allocated to two groups, and either yohimbine 25 microg or saline was injected s.c. Four hours later, mice in each group were further randomly allocated to two groups, and either lipopolysaccharide 100 microg or saline was injected intraperitoneally. Eight hours later, liquid containing fluorescent microbeads was infused into the stomach, and 30 min later, gastric emptying and gastrointestinal transit were measured using flow cytometry. We also studied whether yohimbine given after injection of lipopolysaccharide was effective (n = 22). In another group of mice (n = 32), iNOS in the gastrointestinal tract was measured using western blotting.

RESULTS

Lipopolysaccharide significantly inhibited gastric emptying and gastrointestinal transit. Yohimbine, given before or after lipopolysaccharide, significantly attenuated the inhibitory effects of lipopolysaccharide. Lipopolysaccharide increased the expression of iNOS in the small intestine and yohimbine suppressed the effects of lipopolysaccharide.

CONCLUSIONS

In endotoxaemic mice, yohimbine improved delayed gastric emptying and gastrointestinal transit, possibly by downregulating lipopolysaccharide-induced increased expression of iNOS.

Characterisation of alpha2-adrenoceptor subtypes involved in gastric emptying, gastric motility and gastric mucosal defence

The effect of clonidine on ethanol-induced gastric mucosal damage, gastric emptying and gastric motility was compared. The clonidine-induced gastroprotective effect (0.03-0.09 micromol/kg, s.c.) was antagonised by yohimbine (5 micromol/kg, s.c.), prazosin (0.23 micromol/kg; alpha2B-adrenoceptor antagonist) and naloxone (1.3 micromol/kg, s.c.). Clonidine also inhibited the gastric emptying of liquid meal (0.75-3.75 micromol/kg, s.c.) and gastric motor activity (0.75 micromol/kg, i.v.) stimulated by 2-deoxy-D-glucose (300 mg/kg, i.v.). Inhibition of gastric emptying and motility was reversed by yohimbine (5 and 10 micromol/kg, s.c., respectively), but not by prazosin (0.23 micromol/kg, s.c.) or naloxone (1.3 micromol/kg, s.c.). Oxymetazoline-an alpha2A-adrenoceptor agonist-inhibited both gastric emptying (0.67-6.8 micromol/kg, s.c.) and motility (0.185-3.4 micromol/kg, i.v.), whereas it failed to affect gastric mucosal lesions. The results indicate that in contrast to the gastroprotective effect, which is mediated by alpha2B-adrenoceptor subtype, alpha2A-adrenoceptor subtype may be responsible for inhibition of gastric emptying and motility. However, the site of action (central, peripheral, both) remains to be established.

Role of oxidative stress in the pathogenesis of septic ileus in mice

We investigated the role of oxidative stress in the pathogenesis of septic ileus. Sepsis was induced by intraperitoneal (i.p.) injection of lipopolysaccharides (LPS, 20 mg kg(-1)) in mice. The effect of two i.p. injections of superoxide dismutase [polyethylene glycol (PEG)-SOD, 4000 U kg(-1)] and catalase (PEG-CAT, 15,000 U kg(-1)) was investigated on gastric emptying, intestinal transit and total nitrite plasma concentrations. We also performed immunohistochemical experiments on gastric and ileal tissue. LPS significantly delayed gastric emptying and intestinal transit while plasma nitrite levels increased. Polyethylene glycol (PEG)-SOD reversed the endotoxin-induced delay in gastric emptying and improved the delay in intestinal transit without effect on plasma nitrite levels. PEG-CAT slightly improved the delay in gastric emptying without effect on intestinal transit. Immunohistochemistry showed the presence of nitrotyrosine (NT) and 4-hydroxy-2-nonenal (HNE) in the gastric and ileal mucosa of LPS-treated mice. Treatment with PEG-SOD or PEG-CAT of LPS mice diminished the presence of NT or HNE in both tissues. In addition, LPS induced a significant increase in inducible nitric oxide synthase (iNOS)-positive residential macrophages in the external musculature of stomach and ileum, which significantly decreased after PEG-SOD or PEG-CAT treatment. The present results support a role for oxidative and nitrosative stress in the pathogenesis of septic ileus in mice.

Distribution of mRNA that codes for subtypes of adrenergic receptors in the gastrointestinal tract of dairy cows

OBJECTIVE

To describe the distribution of mRNA that codes for 9 subtypes of adrenergic receptors in the digestive tract of dairy cows.

SAMPLE POPULATION

Fresh full-thickness wall specimens from the abomasum (fundus, corpus, and antrum), ileum, cecum, proximal loop of ascending colon, and 4 locations of the spiral colon collected from 10 healthy cows at slaughter.

PROCEDURE

Concentrations of mRNA that code for 9 subtypes of adrenergic receptors in the bovine gastrointestinal tract (alpha1A, alpha1B, alpha1D, alpha2AD, alpha2B, alpha2C beta1, beta2, and beta3) were measured by use of a quantitative real-time reverse transcription-polymerase chain reaction assay. Results were reported in relation to mRNA expression of the housekeeping gene glyceraldehyde phosphate dehydrogenase (GAPDH).

RESULTS

Mean mRNA contents of adrenergic receptors in the bovine digestive tract were low (range, 0.00006% to 5.04% of GAPDH). Distribution of receptor subtypes was similar in all tissues, with lowest expression of alpha1D receptors, followed by alpha2B, alpha2C, beta3, alpha1B, alpha1A, beta1, and beta2 in the abomasum, whereas alpha2AD and beta2 in the intestines were highest. In comparison with the intestines, relative concentrations of mRNA for receptors beta2 and beta3 were significantly lower in the abomasum.

CONCLUSIONS AND CLINICAL RELEVANCE

Relative concentrations of mRNA that code for adrenergic receptors differed among receptor subtypes and among locations in the bovine gastrointestinal tract. Comparison of these values established in healthy cattle with results for cows with motility disorders, such as abomasal displacement and cecal dilatation, may lead to improved therapeutic or prophylactic approaches for these diseases.

Alpha2-adrenergic regulation of NO production alters postoperative intestinal smooth muscle dysfunction in rodents

Alpha2-adrenergic receptor activation plays an important role in the development of postoperative ileus. Alpha2-adrenergic receptors also regulate nitric oxide (NO) production by the mononuclear phagocyte system. We have previously shown that intestinal manipulation leads to a significant increase in NO production by infiltrating monocytes within the intestinal muscularis. The purpose of this study was to investigate whether alpha2-adrenergic blockade with yohimbine would alter postsurgical intestinal smooth muscle dysfunction and NO production by infiltrating monocytes and macrophages within the intestinal muscularis. Rats underwent small bowel intestinal manipulation with or without yohimbine. In vivo gastrointestinal transit and in vitro jejunal circular muscle contractility was measured 24 h postoperatively. RT-PCR was used to detect inducible NO synthase (iNOS) expression. NO levels in tissue culture supernatants were measured. Immunohistochemistry was used to localize alpha2-adrenergic receptor expression in the intestinal muscularis. Yohimbine significantly decreased manipulation-induced delay in gastrointestinal transit and reversed the postoperative decrease in intestinal muscle contractility. Intestinal manipulation resulted in significant iNOS mRNA induction in the intestinal muscularis, which was markedly attenuated after yohimbine treatment. Yohimbine also significantly decreased the postoperative increase in NO released into intestinal muscularis tissue culture supernatant. Immunohistochemistry identified alpha2-adrenergic receptors on monocytes recruited postoperatively into the intestinal muscularis. This study demonstrates that alpha2-adrenergic receptor stimulation of the inflamed postoperative intestinal muscularis plays a significant role in aggravating postoperative ileus through an enhanced induction of iNOS mRNA and increased release of NO from manipulated intestinal muscularis.

Effect of ghrelin and growth hormone-releasing peptide 6 on septic ileus in mice

Ghrelin is an orexigenic peptide with prokinetic effects in the rat. We investigated the effect of ghrelin and growth hormone-releasing hormone 6 (GHRP-6) on gastric emptying and transit in control and septic mice. Mice were injected i.p. with lipopolysaccharides (LPS) or saline (control). After 16-17 h mice were pretreated with saline, ghrelin or GHRP-6 1 h before intragastric administration of Evans blue. Fifteen minutes later, after assessment of the behaviour scale, mice were killed and gastric emptying, transit and rectal temperature were measured. In control mice, ghrelin (100 microg kg(-1)) and GHRP-6 (20-100 microg kg(-1)) accelerated gastric emptying, whereas ghrelin and GHRP-6 failed to increase transit significantly. Septic mice developed a delay in gastric emptying and transit, hypothermia and a deterioration of the behaviour scale. In septic mice, ghrelin (20 microg kg(-1)) accelerated gastric emptying without effect on transit while GHRP-6 significantly accelerated gastric emptying dose-dependently and failed to increase transit significantly. Ghrelin and GHRP-6 had no effect on the endotoxin-induced hypothermia or deterioration of behaviour scale. Therefore, the beneficial prokinetic effect of ghrelin but mainly of GHRP-6 offers potential therapeutic options in the treatment of septic gastric ileus.

Effects of peritoneal injury and endotoxin on myoelectric activity and transit

BACKGROUND

The combined effects of peritoneal injury and intraabdominal infection on gastrointestinal motility in postoperative ileus are poorly understood

MATERIALS AND METHODS

Sprague Dawley rats underwent placement of three electrodes on the small intestine and a tube gastrostomy. Animals were divided into four groups: a control (n = 12), a peritoneal injury (PI, n = 12), a peritoneal injection of lipopolysaccharide (LPS, n = 12), and a LPS + PI group (n = 12). After myoelectric activity recording on postoperative day (POD) 1, half of the rats in each group underwent intestinal transit studies. The remainder of the rats underwent another myoelectric activity recording as well as intestinal transit study at 48 h after operation

RESULTS

Although six to eight of rats in the control, PI, and LPS groups recovered migrating myoelectric complex (MMC) on POD 1, no rats in the LPS + PI group recovered MMC by POD 1. The transit distance on POD 1 in the PI (36 +/- 2.5 cm) and LPS + PI group (38 +/- 2.8 cm) was shorter than that in the control group (53 +/- 2.0 cm, P < 0.05)

CONCLUSIONS

Full recovery of liquid intestinal transit precedes the return of MMC activity after abdominal surgery in the rats. Peritoneal injury causes decreased intestinal transit and when combined with intraabdominal injection of LPS may cause the delayed recovery of MMC activity.

The effect of intrathecal medetomidine on small bowel transit in the rat

BACKGROUND AND OBJECTIVE

Gastrointestinal motility is influenced by abdominal trauma, laparotomy and particularly by intestinal ischaemia. The reflex inhibition of gastrointestinal motility is mediated mainly by the sympathetic nervous system. There are reports on the effects of systemically applied alpha2-adrenoceptor agonists on gastric emptying and recovery of bowel motility, but the effect of spinally applied alpha2-adrenoceptor agonists on intestinal motility has not been studied. The aim of this study was to investigate the effects of intrathecal medetomidine on gastrointestinal transit in rats after transient intestinal ischaemia.

METHODS

Forty rats were randomly assigned to four groups of 10 each. Intrathecal catheter insertion and laparotomy were performed on each rat. Saline (10 microL) was injected intrathecally in Groups A and B. Medetomidine (10 microg in 10 microL) was injected intrathecally in Groups C and D. Intestinal ischaemia was induced in Groups B and D. Gastrointestinal transit was determined by measuring the length that a standardized marker meal of activated charcoal had travelled. Intrathecal medetomidine was compared to intrathecal saline in their effect on intestinal motility after 30 min period of bowel ischaemia.

RESULTS

Laparotomy and intestinal ischaemia slowed gastrointestinal transit. Intrathecal medetomidine accelerated transit in both ischaemia and non-ischaemia groups.

CONCLUSION

Intrathecal medetomidine markedly accelerated small intestinal transit and may also hasten the recovery from post-ischaemic paralytic ileus.

Postoperative ileus is maintained by intestinal immune infiltrates that activate inhibitory neural pathways in mice

BACKGROUND AND AIMS

Postoperative ileus after abdominal surgery largely contributes to patient morbidity and prolongs hospitalization. We aimed to study its pathophysiology in a murine model by determining gastric emptying after manipulation of the small intestine.

METHODS

Gastric emptying was determined at 6, 12, 24, and 48 hours after abdominal surgery by using scintigraphic imaging. Intestinal or gastric inflammation was assessed by immune-histochemical staining and measurement of tissue myeloperoxidase activity. Neuromuscular function of gastric and intestinal muscle strips was determined in organ baths.

RESULTS

Intestinal manipulation resulted in delayed gastric emptying up to 48 hours after surgery; gastric half-emptying time 24 hours after surgery increased from 16.0 +/- 4.4 minutes after control laparotomy to 35.6 +/- 5.4 minutes after intestinal manipulation. The sustained delay in gastric emptying was associated with the appearance of leukocyte infiltrates in the muscularis of the manipulated intestine, but not in untouched stomach or colon. The delay in postoperative gastric emptying was prevented by inhibition of intestinal leukocyte recruitment. In addition, postoperative neural blockade with hexamethonium (1 mg/kg intraperitoneally) or guanethidine (50 mg/kg intraperitoneally) normalized gastric emptying without affecting small-intestinal transit. The appearance of intestinal infiltrates after intestinal manipulation was associated with increased c-fos protein expression in sensory neurons in the lumbar spinal cord.

CONCLUSIONS

Sustained postoperative gastroparesis after intestinal manipulation is mediated by an inhibitory enterogastric neural pathway that is triggered by inflammatory infiltrates recruited to the intestinal muscularis. These findings show new targets to shorten the duration of postoperative ileus pharmacologically.

Methods for decreasing postoperative gut dysmotility

Postoperative disturbances of gastrointestinal function (postoperative ileus) are among the most significant side-effects of abdominal surgery for cancer. Without specific treatment, major abdominal surgery causes a predictable gastrointestinal dysfunction which endures for 4-5 days and results in an average hospital stay of 7-8 days. Ileus occurs because of initially absent and subsequently abnormal motor function of the stomach, small bowel, and colon. This disruption results in delayed transit of gastrointestinal content, intolerance of food, and gas retention. The aetiology of ileus is multifactorial, and includes autonomic neural dysfunction, inflammatory mediators, narcotics, gastrointestinal hormone disruptions, and anaesthetics. In the past, treatment has consisted of nasogastric suction, intravenous fluids, correction of electrolyte abnormalities, and observation. Currently, the most effective treatment is a multimodal approach. Median stays of 2-3 days after removal of all or part of the colon (colectomy) are now achievable. Recent discoveries have the potential to significantly reduce postoperative ileus in patients with cancer who have had abdominal surgery.

Differential salutary effects of nonselective and selective COX-2 inhibitors in postoperative ileus in rats

BACKGROUND

Postoperative ileus (PI) is a common surgical complication, the treatment of which consists of supportive measures.

AIM

The effects of several cyclooxygenase (COX) inhibitors and their interaction with L-arginine/nitric oxide synthase (NOS) pathway were tested in a rat PI model.

METHODS

Intestinal transit was measured as Evans blue migration after skin incision, laparotomy, or laparotomy followed by evisceration and gut handling.

RESULTS

In contrast to a selective inducible NOS (iNOS) blocker, L-N(6)-(1-iminoethyl)lysine hydrochloride (L-NIL), N(omega)-nitro-L-arginine methyl ester (L-NAME) reversed the additional inhibitory effects of gut manipulation after laparotomy on the gastrointestinal transit (GI) in a dose-dependent, L-arginine-sensitive manner. Laparotomy and manipulations of small intestine increased blood plasma nitrites and nitrates level (NOx), an effect preventable by L-NAME. Indomethacin, resveratrol (selective COX-1 blocker), and COX-2 antagonists, nimesulide, NS-398, DuP-697, and L-752860, attenuated the additional inhibitory effects of gut manipulation following laparotomy in a dose-dependent manner. In contrast, only nimesulide, NS-398, DuP-697, and L-752860 partly, but significantly, reversed the effects of laparotomy on the intestinal transit. Administration of L-NAME subsequent to COX inhibitors abolished the salutary effects of the latter, implying that at least the synthesis of either NO or prostanoids must remain unaffected to enable a return of GI transit during the postoperative period.

CONCLUSION

In addition to NO synthesized by constitutive NOS (cNOS), prostaglandins produced by both COX-1 and COX-2 participate in the pathogenesis of PI, albeit in different pathological mechanisms. Thus laparotomy stimulated COX-2 activity, whereas gut manipulation led to an excessive cNOS activity and prostaglandin synthesis by COX-1.

Effect of inhibition of inducible nitric oxide synthase and guanylyl cyclase on endotoxin-induced delay in gastric emptying and intestinal transit in mice

Nitric oxide (NO) is postulated to play a role in endotoxin-induced ileus. We investigated the effect of selective blockade of inducible NO synthase (iNOS) and guanylyl cyclase on endotoxin-induced ileus in mice. Thirty minutes before injection of lipopolysaccharides (LPS), mice were pretreated with L-NAME (N omega-nitro-L-arginine methyl ester, non-selective NOS inhibitor), 1400W (N-(3-(aminomethyl)benzyl)acetamide, selective iNOS inhibitor), ODQ (1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one, guanylyl cyclase inhibitor), dimethyl sulfoxide (DMSO, vehicle), or dexamethasone. After 18 h, general well being deteriorated and the mice developed hypothermia and a significant delay in gastric emptying and intestinal transit as measured by Evans blue. 1400W completely reversed the endotoxin-induced delay in gastric emptying, while L-NAME did not have these beneficial effects. On the contrary, even in control mice, L-NAME delayed gastric emptying. Dexamethasone, DMSO, and ODQ mimicked the effect of 1400W on endotoxin-induced delay in gastric emptying. The endotoxin-induced delay in transit was significantly improved only by 1400W. None of the drugs reversed the hypothermia. In LPS mice treated with L-NAME, the behavior scale increased even further, while it decreased after treatment with 1400W. In conclusion, selective inhibition of iNOS reverses the endotoxin-induced delay in gastric emptying and transit and improves general well being. The pathway used by NO, derived from iNOS, may involve inhibition of guanylyl cyclase or radical scavenging.

Inhibition of stress-stimulated colonic propulsion by alpha 2-adrenoceptor antagonists in rats

Alpha2-adrenoceptor antagonists have been reported to stimulate colonic motor activity, but the effect on colonic motor dysfunction is unclear. We have investigated the effect of alpha 2-adrenoceptor antagonists on wrap-restraint stress-stimulated and normal colonic propulsion in rats. Colonic propulsion was evaluated by the transit of a charcoal marker along the colon. Faecal pellets output was also measured. A 30-min exposure to wrap-restraint stress starting 120 min after infusion of the charcoal marker significantly stimulated colonic transit with a concomitant increase in faecal pellets. Yohimbine and idazoxan, alpha 2-adrenoceptor antagonists, clonidine, an alpha 2-adrenoceptor agonist, and atropine suppressed wrap-restraint stress-stimulated colonic transit and faecal excretion in a dose-dependent manner. Ondansetron and YM060, 5-hydroxytryptamine3 (5-HT3) receptor antagonists, potently inhibited wrap-restraint stress-stimulated colonic transit, but only weakly inhibited faecal excretion. Neither alpha 2-adrenoceptor antagonists nor atropine had any significant effect on normal colonic transit, whereas clonidine and the 5-HT3 receptor antagonists inhibited it. alpha 2-Adrenoceptor antagonists as well as clonidine, atropine and 5-HT3 receptor antagonists inhibit the stress-induced colonic motor dysfunction in rats.

Functional gut disorders: from motility to sensitivity disorders. A review of current and investigational drugs for their management

Functional gut disorders include several clinical entities defined on the basis of symptom patterns (e.g., functional dyspepsia, irritable bowel syndrome, functional abdominal pain, functional abdominal bloating), for which there is no established pathophysiological mechanism. Because there is no well-defined pathophysiological target, treatment should be aimed at symptom improvement. Prokinetics and antispasmodics have been widely used in the treatment of functional gut disorders on the assumption that disordered motility is the underlying cause of symptoms, and symptom improvement is indeed achievable with these compounds in some, but not all, patients with features of hypo- or hypermotility, respectively. In the first part of this review, we cover the basic pharmacology and discuss the rationale for the clinical use of prokinetics and antispasmodics. On the other hand, in the past few years, the explosive growth in the research focusing on visceral sensitivity and visceral reflexes has suggested that at least some patients with functional gut disorders have altered visceral perception. Thus, the second part of the review covers these developments and focuses on studies addressing the issue of drugs modulating visceral sensitivity.

Role of VIP1/PACAP receptors in postoperative ileus in rats

1. Vasoactive intestinal polypeptide (VIP) is an inhibitory neurotransmitter in the enteric nervous system. We investigated the role of VIP1/PACAP receptors in postoperative ileus in rats. 2. Different degrees of inhibition of the gastrointestinal transit, measured by the migration of Evans blue, were achieved by skin incision, laparotomy or laparotomy plus mechanical stimulation of the gut. 3. The transit after skin incision or laparotomy was not altered by the VIP1/PACAP receptor antagonist Ac-His1,D-Phe2, K15, R16, VIP(3-7), GRF(8-27)-NH2 nor by the VIP1/PACAP receptor agonist K15, R16, VIP(1-7), GRF(8-27)-NH2 and the VIP2/PACAP receptor agonist RO 25-1553 (5 microg kg(-1)). 4. However, the transit after laparotomy plus mechanical stimulation was significantly enhanced by the VIP1/PACAP receptor antagonist, whereas it was further inhibited by the VIP1/PACAP receptor agonist. The combination of the VIP1/PACAP receptor agonist and antagonist counteracted the effect of both drugs alone. The VIP2/PACAP receptor agonist did not alter the effect of the VIP1/PACAP receptor antagonist. 5. The combination of the VIP1/PACAP receptor antagonist plus the nitric oxide (NO) synthase inhibitor L-nitroarginine had no effect on the transit after laparotomy plus mechanical stimulation, while the transit after skin incision was significantly decreased. 6. These findings suggest the involvement of VIP1/PACAP receptors, next to NO, in the pathogenesis of postoperative ileus. However, the combination of the VIP1/PACAP antagonist and the NO synthase inhibitor abolished the beneficial effect of each drug alone, suggesting the need for one of the inhibitory neurotransmitters to enable normal gastrointestinal transit.

Differential effect of indomethacin and ketorolac on postoperative ileus in rats

The effect of two prostaglandin biosynthesis inhibitors and their interaction with the L-arginine/nitric oxide (NO) pathway was investigated in a rat model of experimental ileus. The gastrointestinal transit was measured as the migration of Evans blue after three different operations. Indomethacin completely reversed the additional inhibition of the transit induced by mechanical stimulation of the gut. Ketorolac completely reversed the inhibition of the transit induced by the laparotomy, but had no additional effect on the inhibition induced by mechanical stimulation of the gut. Administration of indomethacin plus L-nitroarginine or L-arginine could not enhance or prevent the effect of indomethacin alone. Administration of ketorolac and L-nitroarginine completely reversed the transit after the laparotomy plus manipulation whereas ketorolac plus L-arginine had no additional effect as compared to ketorolac alone. From these findings we conclude that in addition to NO, prostaglandins are involved in the pathogenesis of postoperative ileus in the rat. However, indomethacin and ketorolac differentially affect postoperative ileus suggesting that prostaglandins are involved in different pathogenic mechanisms leading to postoperative ileus.

A model to investigate postoperative ileus with strain gauge transducers in awake rats

BACKGROUND

Postoperative ileus influences patients well-being, hospital stay, and health cost, and postoperative inhibition of colonic motility is a major contributor to postoperative ileus. Experimental models for investigating postoperative ileus are needed. In particular, recording of postoperative colonic motility in awake rats has not been described yet.

MATERIAL AND METHODS

Gastric, small intestinal, and colonic motility were recorded with strain gauge transducers in awake rats, and the effects of anesthesia and abdominal surgery on gastrointestinal motility were investigated.

RESULTS

Ether anesthesia increased gastric motility and inhibited small intestinal motility, while enflurane anesthesia had only minor effects on gastrointestinal motility. Abdominal surgery inhibited gastric, small intestinal, and colonic motility, and a detailed analysis of gastrointestinal motility in our postoperative ileus model is given.

CONCLUSIONS

We established a model to record gastric, small intestinal, and colonic motility in awake rats postoperatively. We could demonstrate that enflurane anesthesia had little effect on gastrointestinal motility, while laparotomy and short manipulation of the cecum produced a prolonged inhibition of gastrointestinal motility. Our model could be used to investigate postoperative ileus, particularly of the colon, in awake rats.

Effects of mu- and kappa-opioid receptors on postoperative ileus in rats

In a rat model of postoperative ileus, induced by abdominal surgery, we investigated the effect of mu- and kappa-opioid receptors. Different degrees of inhibition of the gastrointestinal transit, measured by the migration of Evans blue, were achieved by skin incision, laparotomy or laparotomy plus manipulation of the gut. Morphine (1 mg/kg), a preferential mu-opioid receptor agonist, significantly inhibited the transit after skin incision, while the transit after the laparotomy with or without manipulation was not significantly affected. Fedotozine (5 mg/kg), a peripheral kappa-opioid receptor agonist, enhanced the transit after laparotomy plus manipulation, while naloxone (1 mg/kg), a non-specific opioid receptor antagonist, further inhibited the transit after laparotomy plus manipulation. Naloxone and fedotozine alone had no effect on the transit after skin incision or laparotomy without manipulation. However, naloxone prevented the effect of morphine on the transit after skin incision and of fedotozine on the laparotomy plus manipulation. These results support a role for peripheral kappa-opioid receptors in the pathogenesis of postoperative ileus induced by abdominal surgery.

Effect of adrenergic and nitrergic blockade on experimental ileus in rats

1. In a rat model of experimental ileus, the effect of blockade of adrenergic and nitrergic neurotransmission was studied on the intestinal transit of Evans blue. 2. Ether anaesthesia and skin incision had no influence on the transit. Laparotomy significantly inhibited the transit of Evans blue. This inhibition was even more pronounced when the small intestine was manipulated. 3. Reserpine (5 mg kg-1), a drug that blocks adrenergic neurotransmission, completely reversed the inhibition of the transit induced by laparotomy but only partially reversed that induced by laparotomy with manipulation of the small intestine. 4. N omega-nitro-L-arginine (L-NOARG, 5 mg kg-1), a nitric oxide synthase inhibitor, completely reversed the reserpine-resistant inhibition induced by laparotomy with manipulation of the small intestine. The effect of L-NOARG was prevented by concomitant administration of L-arginine. L-Arginine itself slightly, but significantly enhanced the inhibition. S-methylisothiourea and aminoguanidine, selective inhibitors of the inducible NO synthase, had no effect on the transit after the three operations. 5. Treatment of the rats with reserpine plus L-NOARG had no additional effect on the transit after laparotomy as compared to reserpine alone. However, reserpine plus L-NNA completely reversed the inhibition of the transit induced by laparotomy with manipulation of the small intestine. 6. These findings support the involvement of adrenergic pathways in the pathogenesis of ileus and suggest that the additional inhibitory effect of mechanical stimulation results from an enhanced release of NO by the constitutive NO synthase.

Cisapride reduces postoperative gastrocaecal transit time after cardiac surgery in children

OBJECTIVE

To investigate the influence of the prokinetic drug cisapride on gastrocaecal transit time (GCTT) in children after open heart surgery.

DESIGN

Prospective, randomized and controlled study.

SETTING

Interdisciplinary paediatric intensive care unit in a tertiary-care children's hospital.

PATIENT

Twenty-one children with a median age of 6.2 years on day 1 after uncomplicated open heart surgery for isolated septal defects, acquired mitral or aortic valve disease or tetralogy of Fallot. Control group consisting of 10 healthy children with a median age of 8.1 years.

INTERVENTIONS

Ten children were randomized to receive cisapride 0.2 mg/kg body weight, 30 min prior to measurement of GCTT.

MEASUREMENTS AND RESULTS

GCTT was measured using hydrogen breath testing with a test solution containing lactulose and mannitol (0.4 g/kg and 0.1 g/kg body weight respectively). GCTT was markedly delayed in all patients compared to the control group. Within 8 h 8/10 patients in the treatment group versus 4/11 patients in the non-cisapride group achieved gastrocaecal transit. No adverse side-effects were observed.

CONCLUSIONS

Cisapride accelerates gastrocaecal transit after open heart surgery in children. In intensive care patients on inotropic support or opioid medication, it may facilitate the earlier reintroduction of enteral feeding.

Assessment of orocaecal transit time in cats by the breath hydrogen method: the effects of sedation and a comparison of definitions

Oro-caecal transit times (OCTTs) were assessed in 10 healthy adult cats by the lactulose breath hydrogen method with either no sedation (group A), or after the intramuscular administration of three sedative regimens: a combination of acetylpromazine at 0.1 mg kg-1 with buprenorphine at 10 micrograms kg-1 (group B), ketamine at 5 mg kg-1 with midazolam at 0.1 mg kg-1 (group C), or medetomidine at 50 micrograms kg-1 (group D). For each test, the OCTT was defined by four methods: a visual assessment, the first maintained 4 ppm increase in hydrogen production, and the first maintained 0.5 ml hr-1 increase in hydrogen production assessed by two cumulative sum methods. Depending on the definition, the median OCTTs of the cats were between 113 and 131.5 minutes in group A, 86.5 and 97.5 minutes in group B, 218 and 235.5 minutes in group C and 86.5 and 97.5 minutes in group D. By two of the definitions, the median OCTTs in group C were significantly longer than in group A (P < or = 0.037) and approached significance by the other two definitions. The use of sedatives significantly increased the inter-individual variability of the OCTTs, particularly in groups C and D. There were significant differences between the median OCTTs defined by the four different methods, but all the methods were very highly and significantly correlated (rs < or = 0.9503, P < 0.0001).

Adrenergic mechanisms in the control of gastrointestinal motility: from basic science to clinical applications

Over the years, a vast literature has accumulated on the adrenergic mechanisms controlling gut motility, blood flow, and mucosal transport. The present review is intended as a survey of key information on the relevance of adrenergic mechanisms modulating gut motility and will provide an outline of our knowledge on the distribution and functional role of adrenoceptor subtypes mediating motor responses. alpha1-Adrenoceptors are located postsynaptically on smooth muscle cells and, to a lesser extent, on intrinsic neurons; alpha2-adrenoceptors may be present both pre- and postsynaptically, with presynaptic auto- and hetero-receptors playing an important role in the modulation of neurotransmitter release; beta-adrenoceptors are found mainly on smooth muscle cells. From a clinical standpoint, adrenoceptor agonists/antagonists have been investigated as potential motility inhibiting (antidiarrheal/antispasmodic) or prokinetic agents, although at present their field of application is limited to select patient groups.