Involvement of alpha-1 and alpha-2 adrenoceptors in the postlaparotomy intestinal motor disturbances in the rat

Classics in Chemical Neuroscience: Xylazine

Xylazine (also known as "tranq") is a potent nonopioid veterinary sedative that has recently experienced a surge in use as a drug adulterant, most often combined with illicitly manufactured fentanyl. This combination may heighten the risk of fatal overdose. Xylazine has no known antidote approved for use in humans, and age-adjusted overdose deaths involving xylazine were 35 times higher in 2021 than 2018. In April 2023, the Biden Administration declared xylazine-laced fentanyl an emerging drug threat in the United States. In 2022, the Drug Enforcement Agency (DEA) reported nearly a quarter of seized fentanyl powder contained xylazine. This dramatic increase in prevalence has solidified the status of xylazine as an emerging drug of abuse and an evolving threat to public health. The following narrative review outlines the synthesis, pharmacokinetics, pharmacodynamics, and adverse effects of xylazine, as well as the role it may play in the ongoing opioid epidemic.

Comparison of the effects of dexmedetomidine and remifentanil on perioperative hemodynamics and recovery profile of patients undergoing laryngeal microsurgery: A prospective randomized double-blinded study

BACKGROUND

Laryngeal microsurgery (LMS) causes hemodynamic instability and postoperative agitation, cough, pain, nausea, and vomiting. Moreover, because of a short operation time, it is associated with challenging anesthetic management. The aim of this study was to compare the usefulness of continuous administration of dexmedetomidine and remifentanil in inducing general anesthesia in patients undergoing LMS.

METHODS

This is a prospective randomized control design. Continuous intravenous infusion of dexmedetomidine (group D) or remifentanil (group R) was administered from 10 minutes before the induction of anesthesia to the end of surgery. In both groups, 1.5 mg/kg propofol and 0.5 mg/kg rocuronium were administered for the induction of anesthesia, and desflurane were titrated during the measurement of the bispectral index. We recorded hemodynamic data, recovery time, grade of cough, pain score, and analgesic requirements during the perioperative period.

RESULTS

61 patients were finally analyzed (30 for group D, 31 for group R). The incidence of moderate to severe postoperative sore throat was higher in group R than in group D (42% vs 10%, P = .008), and the quantity of rescue fentanyl used in post-anesthesia care unit was significantly higher in group R than in group D (23.2 ± 24.7 mg vs 3.3 ± 8.6 mg; P < .001); however, the time required for eye opening was significantly longer in group D than in group R (599.4 ± 177.9 seconds vs 493.5 ± 103.6 seconds; P = .006). The proportion of patients with no cough or single cough during extubation was comparable between the 2 groups (group D vs group R: 73% vs 70%) as was the incidence of hemodynamic instability.

CONCLUSION

Although there was a transient delay in emergence time, dexmedetomidine reduced postoperative opioid use and the incidence of sore throat. Dexmedetomidine may be used as an alternative agent to opioids in patients undergoing LMS.

Neuronal innervation of the intestinal crypt

Mucosal damage is a key feature of inflammatory bowel diseases (IBD) and healing of the mucosa is an endpoint of IBD treatment that is often difficult to achieve. Autonomic neurons of the parasympathetic and sympathetic nervous system may influence intestinal epithelial cell growth and modulating epithelial innervation could for that reason serve as an interesting therapeutic option to improve mucosal healing. Understanding of the biological processes triggered by nonspecific and specific epithelial adrenergic and cholinergic receptor activation is of key importance. At present, with rising technological advances, bioelectronic neuromodulation as treatment modality has gained momentum. We discuss the current view on state-of-the-art innervation of the intestinal crypt and its impact on epithelial cell growth and differentiation. Furthermore, we outline bioelectronic technology and review its relevance to wound healing processes.

Muscle relaxant induced pancreatitis leading to hyperosmolar hyperglycemic state

Muscle relaxants are commonly prescribed in the United States but may have deleterious side effects that are unrecognized by physicians. Here, we report a 55-year-old Caucasian man who developed pancreatitis and a subsequent hyperosmolar hyperglycemic state after being prescribed tizanidine. The patient had untreated hypertriglyceridemia, unbeknownst to the prescribing physician. While hypertriglyceridemia is a widely understood risk factor for pancreatitis, its incidence with tizanidine is not. As an alpha-2 agonist, tizanidine slows gastrointestinal motility by inhibiting gastrointestinal smooth muscle contraction, which could lead to ileus which occurred in this patient. Alpha-2 agonists further contract the hepato-pancreatic sphincter, which may result in obstruction of pancreatic enzyme flow via the pancreatic duct. This patient’s case of pancreatitis was precipitated by 2 factors: (i) his use of tizanidine and (ii) hypertriglyceridemia. This case demonstrates that patients presenting with severe hypertriglyceridemia, or other potential risk factors for pancreatitis, should not be prescribed tizanidine.

Morphological and Molecular Characterization of Human Dermal Lymphatic Collectors

Millions of patients suffer from lymphedema worldwide. Supporting the contractility of lymphatic collectors is an attractive target for pharmacological therapy of lymphedema. However, lymphatics have mostly been studied in animals, while the cellular and molecular characteristics of human lymphatic collectors are largely unknown. We studied epifascial lymphatic collectors of the thigh, which were isolated for autologous transplantations. Our immunohistological studies identify additional markers for LECs (vimentin, CCBE1). We show and confirm differences between initial and collecting lymphatics concerning the markers ESAM1, D2-40 and LYVE-1. Our transmission electron microscopic studies reveal two types of smooth muscle cells (SMCs) in the media of the collectors with dark and light cytoplasm. We observed vasa vasorum in the media of the largest collectors, as well as interstitial Cajal-like cells, which are highly ramified cells with long processes, caveolae, and lacking a basal lamina. They are in close contact with SMCs, which possess multiple caveolae at the contact sites. Immunohistologically we identified such cells with antibodies against vimentin and PDGFRα, but not CD34 and cKIT. With Next Generation Sequencing we searched for highly expressed genes in the media of lymphatic collectors, and found therapeutic targets, suitable for acceleration of lymphatic contractility, such as neuropeptide Y receptors 1, and 5; tachykinin receptors 1, and 2; purinergic receptors P2RX1, and 6, P2RY12, 13, and 14; 5-hydroxytryptamine receptors HTR2B, and 3C; and adrenoceptors α2A,B,C. Our studies represent the first comprehensive characterization of human epifascial lymphatic collectors, as a prerequisite for diagnosis and therapy.

Effect of chewing gum on the postoperative recovery of gastrointestinal function

Postoperative gastrointestinal dysfunction remains a source of morbidity and the major determinant of length of stay after abdominal operation. There are many different reasons for postoperative gastrointestinal dysfunction such as stress response, perioperative interventions, bowel manipulation and so on. The mechanism of enhanced recovery from postoperative gastrointestinal dysfunction with the help of chewing gum is believed to be the cephalic-vagal stimulation of digestion which increases the promotability of neural and humoral factors that act on different parts of the gastrointestinal tract. Recently, there were a series of randomized controlled trials to confirm the role of chewing gum in the recovery of gastrointestinal function. The results suggested that chewing gum enhanced early recovery of bowel function following abdominal surgery expect the gastrointestinal surgery. However, the effect of chewing gum in gastrointestinal surgery was controversial.

Sham feeding with chewing gum after elective colorectal resectional surgery: a randomized clinical trial

OBJECTIVE

To determine whether sham feeding with chewing gum improved gastrointestinal recovery after colorectal resection surgery, in the presence of routine postoperative feeding.

BACKGROUND

Sham feeding with chewing gum has been shown to accelerate the return of gut function after colorectal surgery. This study sought to determine whether sham feeding with gum, after colorectal resection, accelerates return of gastrointestinal function in patients on a rapid feeding enhanced recovery program.

METHODS

A randomized "two armed" controlled clinical trial was performed. Equal groups of open and laparoscopic colorectal resection surgical patients were recruited. Patients in the intervention arm received chewing gum 4 times a day postoperatively. All patients in the trial were placed on an established, standardized Enhanced Recovery After Surgery program. The primary outcome was time to return of gut function, assessed by time to flatus and first bowel motion. Secondary outcomes were time to tolerate diet, symptoms of ileus in the form of nausea, vomiting and distension, pain as assessed by analgesic consumption and visual analogue scales, complications, and length of hospital stay.

RESULTS

A total of 161 patients were recruited. Postoperative morbidity was equivalent between groups, with no complications related to gum chewing. There was no difference between groups with respect to the primary outcomes of time to flatus and bowel motion. There was less perception of pain in the intervention group on days 2 to 5, and no difference with respect to all other secondary outcomes.

CONCLUSIONS

Sham feeding with gum, after open and laparoscopic colorectal resectional surgery is safe, but does not hasten the return of gastrointestinal function in patients who receive accelerated postoperative feeding. (ACTRN12607000538448).

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.

Gum chewing reduces postoperative ileus? A systematic review and meta-analysis

BACKGROUND

An important cause of delayed recovery from intestinal surgery is postoperative ileus. Gum chewing is a form of sham feeding, which could encourage gastrointestinal motility through cephalic-vagal stimulation.

METHODS

We sought to identify all randomized controlled trials comparing gum chewing with standard care after elective intestinal surgery. We searched electronic databases (Cochrane, Embase, and PubMed), reference lists and contacted authors to obtain further data. We assessed the identified trials for quality and performed a meta-analysis and systematic review. The main outcome measures examined were time to flatus and stool postoperatively and length of hospital stay, which were analysed using random effect models. We also examined clinical complication rates.

RESULTS

We identified nine eligible trials that had enrolled a total of 437 patients. The intervention was well tolerated and complication rates were low. There was statistical evidence of heterogeneity for the three main outcomes. Pooled estimates showed a reduction in time to flatus by 14 h (95% CI: -20 to -8h, p=0.001), time to bowel movement by 23 h (95% CI: -32 to -15 h, p<0.001) and a reduction in length of hospital stay by 1.1 days (95% CI: -1.9 to -0.2 days, p=0.016).

CONCLUSIONS

Chewing sugarless gum following elective intestinal resection is associated with improved outcomes. Insufficient data were available to demonstrate a reduced rate of clinical complications or reduced cost. An adequately powered, methodologically rigorous trial of gum chewing is required to confirm if there are any benefits and if these result in differences in clinical outcomes such as infection.

Methylnaltrexone in the treatment of opioid-induced constipation

Constipation is a significant problem related to opioid medications used to manage pain. This review attempts to outline the latest findings related to the therapeutic usefulness of a μ opioid receptor antagonist, methylnaltrexone in the treatment of opioid-induced constipation. The review highlights methylnaltrexone bromide (Relistor™; Progenics/Wyeth) a quaternary derivative of naltrexone, which was recently approved in the United States, Europe and Canada. The Food and Drug Administration in the United States approved a subcutaneous injection for the treatment of opioid bowel dysfunction in patients with advanced illness who are receiving palliative care and when laxative therapy has been insufficient. Methylnaltrexone is a peripherally restricted, μ opioid receptor antagonist that accelerates oral-cecal transit in patients with opioid-induced constipation without reversing the analgesic effects of morphine or inducing symptoms of opioid withdrawal. An analysis of the mechanism of action and the potential benefits of using methylnaltrexone is based on data from published basic research and recent clinical studies.

Role of selective alpha and beta adrenergic receptor mechanisms in rat jejunal longitudinal muscle contractility

Gut motility is modulated by adrenergic mechanisms. The aim of our study was to examine mechanisms of selective adrenergic receptors in rat jejunum. Spontaneous contractile activity of longitudinal muscle strips from rat jejunum was measured in 5-ml tissue chambers. Dose-responses (six doses, 10(-7) -3 x 10(-5)M) to norepinephrine (NE, nonspecific), phenylephrine (PH, alpha1), clonidine (C, alpha2), prenalterol (PR, beta1), ritodrine (RI, beta2), and ZD7714 (ZD, beta3) were evaluated with and without tetrodotoxin (TTX, nerve blocker). NE(3 x 10(-5)M) inhibited 74 +/- 5% (mean +/- SEM) of spontaneous activity. This was the maximum effect. The same dose of RI(beta2), PH(alpha1), or ZD(beta(3)) resulted in an inhibition of only 56 +/- 5, 43 +/- 4, 33 +/- 6, respectively. The calculated concentration to induce 50% inhibition (EC50) of ZD(beta3) was similar to NE, whereas higher concentrations of PH(alpha1) or RI(beta2) were required. C(alpha2) and PR(beta1) had no effect. TTX changed exclusively the EC50 of RI from 4.4 +/- 0.2 to 2.7 +/- 0.8% (p < 0.04). Contractility was inhibited by NE (nonspecific). PH(alpha1), RI(beta2), and ZD(beta3) mimic the effect of NE. TTX reduced the inhibition by RI. Our results suggest that muscular alpha1, beta2, and beta3 receptor mechanisms mediate adrenergic inhibition of contractility in rat jejunum. beta2 mechanisms seem to involve also neural pathways.

Role of bile in intestinal motility after massive liver resection in conscious rats

AIM

To investigate the effect of 90% partial hepatectomy (90% PHx) and the involvement of bile on ileal motility in conscious rats.

METHODS

Two strain gauge force transducers were chronically implanted in the ileum of each of 20 rats. The rats were divided into four groups, three of which underwent 90% PHx. The experiments were performed with the rats in a conscious, fasted state. After ileal motility was recorded, bile or saline was perfused into the duodenum of each rat in two of the 90% PHx groups. The effects of the perfusion on ileal motility were observed and recorded using the motility index (MI), defined as the area under the contraction cues after surgery and expressed as the ratio to the MI in the preoperational motility. The time of the first passage of stool after surgery was recorded.

RESULTS

A typical migrating motor complex (MMC) pattern was observed in normal fasted rats. Increased MMC cycle lengths and a decreased MI at 1 day and 3 days after 90% PHx were observed. The MMC after 90% PHx was characterized by an increased duration of Phase 2-like activity. The MMC cycle length, the MI, and the time of the first passage of stool after 90% PHx were improved by perfusion of bile into the duodenum through the biliary cannula but were not influenced by perfusion of saline into the duodenum through the biliary cannula.

CONCLUSION

The MMC cycle length and the MI were inhibited after 90% PHx, with the involvement of decreased bile flow into the gastrointestinal tract by liver resection.

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.

Postoperative ileus: a review

PURPOSE

Postoperatively, some patients experience a prolonged inhibition of coordinated bowel activity, which causes accumulation of secretions and gas, resulting in nausea, vomiting, abdominal distension, and pain. This prolonged inhibition can take days or weeks to resolve and often is referred to as postoperative paralytic ileus lasting more than three days after surgery. This article reviews the etiology, pathophysiology, and treatment options of postoperative ileus.

METHODS

The relevant literature from 1965 to 2003 was identified and reviewed using MEDLINE database of the U.S. Medical Library of Medicine. Both retrospective and prospective studies were included in this review.

RESULTS

The pathophysiology of postoperative ileus is multifactorial. The duration of postoperative ileus correlates with the degree of surgical trauma and is most extensive after colonic surgery. However, postoperative ileus can develop after all types of surgery including extraperitoneal surgery. A variety of treatment options have been used to decrease the duration of postoperative ileus. However, it is difficult to compare these studies because of small sample sizes and differences in operations performed, anesthesia protocols provided both intraoperatively and postoperatively, patient comorbidities, and in the measured end points, such as the time to the presence of bowel sounds, flatus, or bowel movements, tolerance of solid food, or discharge from the hospital. However, despite these drawbacks, some conclusions can be made.

CONCLUSIONS

Paralytic postoperative ileus continues to be a significant problem after abdominal and other types of surgery. The etiology is multifactorial and is best treated with a combination of different approaches. Currently, the important factors that could effect the duration and recovery from postoperative ileus include limitation of narcotic use by substituting alternative medications such as nonsteroidals and placing a thoracic epidural with local anesthetic when possible. The selective use of nasogastric decompression and correction of electrolyte imbalances also are important factors to consider.

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.

COX-2 dependent inflammation increases spinal Fos expression during rodent postoperative ileus

BACKGROUND AND AIMS

Cyclooxygenase 2 (COX-2) and prostaglandins (PGs) participate in the pathogenesis of inflammatory postoperative ileus. We sought to determine whether the emerging neuronal modulator COX-2 plays a significant role in primary afferent activation during postoperative ileus using spinal Fos expression as a marker.

METHODS

Rats, and COX-2(+/+) and COX-2(-/-) mice underwent simple intestinal manipulation. The effect of intestinal manipulation on Fos immunoreactivity (IR) in the L(5)-S(1) spinal cord, in situ circumference, and postoperative leucocytic infiltrate of the intestinal muscularis was measured. Postoperative PGE(2) production was measured in peritoneal lavage fluid. The dependence of these parameters on COX-2 was studied in pharmacological (DFU, Merck- Frosst, selective COX-2 inhibitor) and genetic (COX-2(-/-) mice) models.

RESULTS

Postoperative Fos IR increased 3.7-fold in rats and 2.2-fold in mice. Both muscularis leucocytic infiltrate and the circumference of the muscularis increased significantly in rats and COX-2(+/+) mice postoperatively, indicating dilating ileus. Surgical manipulation markedly increased PGE(2) levels in the peritoneal cavity. DFU pretreatment and the genetic absence of COX-2(-/-) prevented dilating ileus, and leucocytic infiltrate was diminished by 40% with DFU and by 54% in COX-2(-/-) mice. DFU reversed postsurgical intra- abdominal PGE(2) levels to normal. Fos IR after intestinal manipulation was attenuated by approximately 50% in DFU treated rats and in COX-2(-/-) mice.

CONCLUSIONS

Postoperatively, small bowel manipulation causes a significant and prolonged increase in spinal Fos expression, suggesting prolonged primary afferent activation. COX-2 plays a key role in this response. This activation of primary afferents may subsequently initiate inhibitory motor reflexes to the gut, contributing to postoperative ileus.

Small intestinal transit does not adequately represent postoperative paralytic ileus in rats

Small intestinal transit (SIT) has often been regarded as an index of pathophysiological state of postoperative ileus (PI) in rats. The reliability of SIT as an index of PI was examined in the present study. PI was induced via abdominal surgery (i.e., laparotomy with evisceration and manipulation) in rats. For one group of PI-induced rats, SIT of a charcoal test meal was measured. When necessary, the physical state (i.e., severity and site of distension) of the gastrointestinal (GI) tract in each rat was visually examined. For another group of PI-induced rats, abdominal X-ray radiographs were obtained after introducing the barium sulfate suspension. The abdomen was then opened and the physical state of the GI tract was visually examined. The SIT was decreased in most of the PI-induced rats, and the GI distension was observed, with substantial intersubject variations, in all of the PI-induced rats. However, no linear relationship was evident between the SIT and the severity of GI distension (e.g., at 20 h after PI induction). Instead, the severity and site of GI distension could be monitored by the X-ray radiology. Therefore, the use of SIT as an index of Pi should be substantially limited.

Preoperative intraluminal application of capsaicin increases postoperative gastric and colonic motility in rats

In a model to investigate postoperative gastrointestinal motility with strain gauge transducers in awake rats, we tested the effects of intraluminal capsaicin infusion into the cecum 2 days or 14 days prior to abdominal surgery. Acute infusion of capsaicin into the cecum for 30 minutes increased the gastric, small intestinal, and colonic motility index by up to 115%, 34%, and 59%, respectively, compared to vehicle infusion. Intraluminal capsaicin infusion 2 days prior to abdominal surgery significantly increased the intraoperative gastric and colonic motility index by 166% and 100%, respectively, compared to vehicle, but had no effect on small intestinal motility. The postoperative decrease in gastric or colonic motility was completely prevented by capsaicin pretreatment, representing a 73% and a 72% increase in the motility index during the first postoperative hour and a 40% and a 29% increase in the motility index during the second postoperative hour compared to vehicle, whereas the postoperative decrease in small intestinal motility was not altered by capsaicin pretreatment. In contrast, intraluminal capsaicin infusion 14 days prior to abdominal surgery had no effect on postoperative inhibition of gastrointestinal motility. Our results suggest that capsaicin-sensitive visceral afferent C-fibers, presumably of the submucosa, play an important role in mediating postoperative ileus. Intraluminal capsaicin does probably ablate these nerve fibers temporarily, with no systemic side effects observed with the use of the tail flick test as a measure of skin nociception.

Role of NK2 receptors in gastric barosensitivity and in experimental ileus in rats

This study was performed to evaluate the role of tachykinin NK2 receptors in gastric barosensitivity and in postsurgical intestinal atony, using a selective NK2 antagonist (MEN 11420). Gastric distensions were performed in rats equipped with a gastric balloon and electrodes implanted in the neck muscles. Ileus was produced by laparotomy and caecum palpation in rats previously prepared with electrodes implanted on the proximal jejunum. Fifteen minutes before gastric distension or laparotomy, the animals received MEN 11420 (10, 100 or 200 microg kg-1 intravenously) or saline. The first distending pressure to increase the integrated neck electromyogram > 100% was considered the pain threshold. MEN 11420 (100 microg kg-1) increased significantly pain threshold (20.5 +/- 1.2 vs. 17.0 +/- 0.8 mm Hg) but did not modify gastric volumes at the three doses tested. Abdominal surgery was followed by a total inhibition of jejunal spiking activity lasting 80.4 +/- 18.7 min. MEN 11420 (10 and 100 microg kg-1) shortened the duration of motor inhibition by 36 and 39%, and induced a premature recovery of the phase III of migrating myoelectric complex at the lowest dose tested (130 +/- 32 vs. 192 +/- 28 min). We conclude that NK2 receptors, probably located on afferent fibres, are involved in gastric barosensitivity and in postsurgical intestinal atony.

Evidence for VIP(1)/PACAP receptors in the afferent pathway mediating surgery-induced fundic relaxation in the rat

We previously reported activation of an inhibitory adrenergic and a non-adrenergic non-cholinergic (NANC) pathway during abdominal surgery relaxing the rat gastric fundus. In the present study, we investigated the possible role of nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) in the NANC part of the surgery-induced fundic relaxation. The effect of the NO biosynthesis inhibitor N(G)-nitro-L-arginine (L-NOARG), the non-selective VIP receptor antagonist [D-p-Cl-Phe(6),Leu(17)]-VIP and the selective VIP(1) receptor antagonist [Acetyl-His(1),D-Phe(2),Lys(15),Arg(16), Leu(17)]-VIP was investigated on the non-adrenergic fundic relaxation induced by manipulation of the small intestine followed by resection of the caecum. Guanethidine partly reduced the manipulation-induced fundic relaxation. Addition of L-NOARG reduced this non-adrenergic component, whereas the non-selective VIP receptor antagonist had no significant effect. Combination of L-NOARG and the non-selective VIP antagonist however further reduced the relaxation to manipulation. The selective VIP(1) receptor antagonist reduced the mean and maximal relaxation induced by abdominal surgery in the presence of guanethidine. When combined with L-NOARG, the relaxation of the gastric fundus was almost completely abolished. The VIP(1) receptor antagonist alone had no significant effect on the mean and maximal relaxation, but enhanced recovery of fundic tone. In conclusion, as VIP(1) receptors are not present in the rat gastric fundus, these results suggest that the NANC inhibitory pathway activated during abdominal surgery involves VIP(1) receptors, most likely in the afferent limb. The inhibitory neurotransmitters released at the level of the gastric fundus smooth muscle are NO and a substance different from VIP.

Yohimbine ameliorates the effects of endotoxin on gastric emptying of the liquid marker acetaminophen in horses

The effect of yohimbine pretreatment on gastric emptying of a liquid marker in horses was evaluated by measuring serum concentrations of acetaminophen. Gastric emptying was determined in normal, fasted horses, in horses given endotoxin (E. coli 055 B5; 0.2 microg/kg) intravenously, and in horses given yohimbine (0.25 mg/kg, IV, over 30 minutes) plus endotoxin. Acetaminophen (20 mg/kg) was given by stomach tube 15 minutes after the endotoxin infusion. Blood samples for acetaminophen analysis were collected, and time to reach the peak serum concentration (Tmax), the maximum serum concentration (Cmax) and the area under the acetaminophen serum concentration versus time curve (AUC) were determined for each treatment group. Endotoxin significantly increased Tmax, indicating a profound delay in gastric emptying and yohimbine pretreatment significantly (P < or = 0.05) prevented this effect.

Activation of an adrenergic and vagally-mediated NANC pathway in surgery-induced fundic relaxation in the rat

The aim of this study was to pharmacologically characterize and investigate the possible contribution of adrenergic and nonadrenergic noncholinergic (NANC) pathways involved in the relaxation of the rat gastric fundus following abdominal surgery. Using an intragastric balloon, the effect of skin incision (SI), laparotomy (LT) and manipulation of the small intestine followed by caecal resection (M + R) on fundic pressure was evaluated. SI resulted in a brief relaxation of the gastric fundus abolished by guanethidine and blocked by hexamethonium and the combination of phentolamine, propranolol and atropine (PPA). LT induced a longer lasting relaxation which was abolished by guanethidine and hexamethonium. It was blocked by PPA and the combination of ganglionectomy and vagotomy, but unaffected by atropine, vagotomy or ganglionectomy. M + R induced a long-lasting relaxation which was only partly blocked by guanethidine or PPA, illustrating an inhibitory NANC component. Vagotomy combined with guanethidine completely abolished the relaxation following M + R, whereas it was significantly blocked by hexamethonium and the combination of ganglionectomy with vagotomy. These results indicate that SI, LT and M + R induce inhibition of fundic motility via an adrenergic mechanism. During M + R, an additional vagally mediated inhibitory NANC pathway is activated. Finally, we suggest that LT and M + R inhibit the gastric fundus via both a splanchnic and a vagal reflex pathway.

Adrenoceptors and colocolonic inhibitory reflex

The colocolonic inhibitory reflex is characterized by inhibition of proximal colonic motility induced by distal colonic distension. The aim of this study was to investigate the underlying neural mechanisms of this reflex, in vivo, using an isolated loop of canine colon. In five beagle dogs, motility was recorded from an exteriorized colonic loop via a serosal strain gauge connected to a digital data logger and chart recorder. Inflation of a balloon in the distal colon resulted in inhibition of motility in the isolated loop. Inhibition of motor activity persisted following injection of propranolol (100 microg/kg intravenously), a beta-adrenoceptor antagonist, but was abolished following administration of the alpha2-adrenoceptor antagonist yohimbine (200 microg/kg intravenously). This study confirms that the colocolonic inhibitory reflex is mediated via the extrinsic nerves to the colon. As the reflex was abolished by alpha2-, but not beta-adrenoceptor blockade, this indicates that the reflex pathway involves alpha2-adrenoceptors.

Effects of escins Ia, Ib, IIa, and IIb from horse chestnuts on gastrointestinal transit and ileus in mice

The effects of saponin fraction and its principal constituents escins Ia (1), Ib (2), IIa (3), and IIb (4) from horse chestnuts on gastrointestinal transit (GIT) and ileus were investigated in mice. Ileus was induced by acetic acid peritoneal irritation or by laparotomy with manipulation. One hour after the oral administration, the saponin fraction (12.5-100 mg/kg) and 14 (12.5-50 mg/ kg, except for 3 at 12.5 mg/kg) dose-dependently accelerated GIT. The optimal effects of the saponin fraction (25 mg/kg) occurred 5-240 min (applied intervals between the fraction and the charcoal meal) after the oral administration. The fraction (12.5-100 mg/ kg) and 1-4 (12.5-50 mg/kg, except for 1 and 2 at 12.5 mg/kg) dose-dependently prevented the inhibition of GIT induced by the acetic acid peritoneal irritation. They (12.5-100mg/kg) also dose-dependently prevented the inhibition of GIT induced by the laparotomy with manipulation. Desacylescins I (5) and II (6) (50 mg/kg) showed no such effects. These results demonstrated that the saponin fraction and 1-4 accelerated GIT and prevented the experimental ileus, and indicate that the 21, 22-acyl groups are essential for the accelerative effects of 1-4. The accelerations of GIT by 1-4 were completely abolished by the pretreatment with streptozotocin (100 mg/kg, iv), but not by the pretreatment with capsaicin (75 mg/kg in total, sc) or atropine (10 mg/kg, sc). These results imply that the sympathetic nervous system may be, but neither capsaicin-sensitive sensory nerves nor the cholinergic mechanism, involved in the accelerations of GIT by escins 1-4.

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.

Calcitonin gene-related peptide and spinal afferents partly mediate postoperative colonic ileus in the rat

BACKGROUND

Calcitonin gene-related peptide (CGRP) is a widely distributed neuropeptide contained in intrinsic and extrinsic neurons of the gastrointestinal wall that has been shown to be released by noxious stimulation, to be involved in nociception, to inhibit gastrointestinal motility, and to partly mediate postoperative gastric ileus. We hypothesized that abdominal surgery-induced release of CGRP might inhibit postoperative colonic motility and food intake.

METHODS

Colonic transit, stool pellet number, stool pellet weight, and food intake were measured for 48 hours after induction of postoperative ileus in rats. CGRP was immunoneutralized by preoperative injection of CGRP monoclonal antibody, or visceral afferent nerve fibers containing CGRP were functionally ablated by topical capsaicin treatment of the vagus nerves or of the celiac/superior mesenteric ganglia before abdominal surgery.

RESULTS

Abdominal surgery increased colonic transit time and decreased 24-hour cumulative stool pellet number, stool pellet weight, and food intake. CGRP immunoneutralization reversed postoperative inhibition of colonic transit, 24-hour cumulative stool pellet number, stool pellet weight, and food intake by 77%, 82%, 80%, and 52%, respectively. Whereas ablation of vagal afferent nerve fibers had no effect, spinal afferent nerve fiber ablation reversed postoperative inhibition of 24-hour cumulative stool pellet number, stool pellet weight, and food intake by 41%, 38%, and 19%, respectively.

CONCLUSIONS

CGRP and spinal afferent nerve fibers partly mediate postoperative colonic ileus and inhibition of food intake in the rat. By the magnitude of reversal of postoperative ileus, CGRP seems to be an important mediator of postoperative colonic ileus. Our results for the first time show involvement of a neuropeptide and spinal afferents in the mediation of postoperative colonic ileus and postoperative inhibition of food intake in rats.

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.

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.

Recovery of gastrointestinal motility from post-operative ileus in dogs: effects of Leu13-motilin (KW-5139) and prostaglandin F2 alpha

Cyclical motor activity of the gastrointestinal tract, normally occurring during the interdigestive period in several mammals, is disrupted in the post-operative ileus. We determined the recovery from the disappearance of cyclical motor activity, from the stomach to the colon, in dogs after laparotomy with the force transducers. Moreover, we examined the effects of Leu13-motilin (KW-5139) and prostaglandin F2 alpha (PGF2 alpha), administered in the early post-operative period, on the gastrointestinal motility. Following laparotomy, the cyclical motor activity reappeared firstly in the ileum and the colon, then in the jejunum and the duodenum, and finally in the stomach. The reappearance time of the phase III contractions in the stomach was 105.8 +/- 10.6 h (n = 4). In the early post-operative period, KW-5139 (0.5 microgram kg-1, i.v.) induced phase-III-like contractions, whereas PGF2 alpha (50 micrograms kg-1, i.v.) induced simultaneously occurring contractions over the whole gastrointestine. The treatment with KW-5139 (0.5 microgram kg-1, i.v.) four times (twice daily on the first and the second post-operative day) significantly (P < 0.05) shortened the time required to recover the phase III contractions in the stomach (64.2 +/- 2.2 h, n = 4), whereas that with PGF2 alpha (50 micrograms kg-1, i.v.) four times did not (111.3 +/- 17.2 h, n = 4). The present results indicate that, after laparotomy, the cyclical motor activity recovers faster in the distal intestine than in the proximal intestine and the stomach, and that KW-5139, but not PGF2 alpha, shortens the reappearance time of the phase III activity in the stomach.

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

BACKGROUND

The effects of selective alpha-agonist medetomidine and alpha 2-antagonist atipamezole on gastrointestinal motility were studied.

METHODS

The passage of intragastrically administered Evans blue in the small bowel of unanesthetized rats was followed, and the stomachs were weighted after killing the rats.

RESULTS

Subcutaneous medetomidine, 0.01-0.1 mg/kg, was found to delay small intestinal transit but not gastric emptying, with a maximal effect seen at 0.03 mg/kg. Atipamezole fully reversed the effect of 0.1 mg/kg of medetomidine with a dose of 2.5 mg/kg. Atipamezole alone did not affect small intestinal transit. Subcutaneous morphine, 6 mg/kg, delayed gastric emptying and small intestinal transit, whereas intraperitoneal morphine only delayed gastric emptying. Subcutaneous atipamezole, 0.06 mg/kg, was partially able to reverse the delayed intestinal transit but did not inhibit morphine-induced gastric retention. Subcutaneous atipamezole, 0.06 mg/kg, reversed laparotomy-induced ileus completely.

CONCLUSIONS

Atipamezole may provide a useful treatment for postlaparotomy ileus.

Fedotozine reverses ileus induced by surgery or peritonitis: action at peripheral kappa-opioid receptors

BACKGROUND

Fedotozine is a peripheral opioid agonist. Its effects were assessed in experimental ileus in rats.

METHODS

Ileus was induced by abdominal surgery (laparotomy and cecum palpation) or peritonitis (acetic acid, intraperitoneally). Digestive motility was recorded by electromyography and gastrointestinal transit estimated using a 51Cr-labeled test meal.

RESULTS

Surgery or peritonitis inhibited motility and migrating myoelectrical complexes for 2-3 hours. In both models, fedotozine (3 mg/kg, intravenously; 10 mg/kg, subcutaneously) restored a normal motility pattern. This action was reproduced by the kappa-agonist, U-50, and 488H and was blocked by subcutaneous naloxone, naloxone-methiodide, or nor-binaltorphimine, a selective kappa-antagonist. Peritonitis induced a 57% inhibition of gastric emptying and intestinal transit that was reversed by fedotozine (1-10 mg/kg, subcutaneously) or kappa-agonists (U-50, 488H, bremazocine) but not delta-agonists (DPDPE, [D-Ala2]-deltorphin-II), whereas mu-agonists (morphine, fentanyl) potentiated ileus. Fedotozine restoration of transit was blocked by subcutaneous naloxone, naloxone-methiodide, or norbinaltorphimine but not by intracerebroventricular naloxone. Fedotozine was inactive up to 300 micrograms/rat when given intracerebroventrically or intrathecally.

CONCLUSION

Fedotozine reverses experimental ileus via an action at peripheral kappa-opioid receptors.

The effect of adrenoceptor antagonists on the ileal brake mechanism in the rat

1. Studies were carried out in the rat to investigate the effect of adrenoceptor antagonists on stomach to caecum transit time under control conditions and during ileal infusion of Intralipid. Stomach to caecum transit time (SCTT) of the head of the meal was measured by use of environmental hydrogen analysis and the distribution of the meal was assessed by a scintigraphic technique. 2. Four adrenoceptor antagonists were used in these studies, the alpha 1 antagonist prazosin, the alpha 2 antagonist, idazoxan, the beta 1 antagonist atenolol and the beta 2 antagonist ICI 118551. 3. None of the antagonists affected SCTT of the head of the meal during ileal infusion of saline. However, the alpha 1 and beta 1 antagonists significantly reversed (P less than 0.05) the delay in SCTT induced by ileal infusion of Intralipid whereas the alpha 2 antagonist, idazoxan, potentiated this delay (P less than 0.05). 4. Study of the distribution of the radiolabelled meal showed that the Intralipid delayed SCTT by slowing both gastric emptying (P less than 0.05) and small bowel transit (P less than 0.05). 5. Prazosin delayed gastric emptying under control conditions (P less than 0.001) but did not alter significantly the effect of ileal lipid on the distribution of the meal, 100 min or 200 min after gavage.6. The meal distribution was more compatible with the hydrogen analysis after administration of the ,beta-adrenoceptor antagonists. The reversal of the lipid-induced delay in SCTT caused by atenolol was associated with more radioactivity in the large intestine 200min after the gavage. ICI 118551 had no significant effects on either the distribution of the meal or the SCTT of the head of the meal.7. In conclusion, the data confirm that the sympathetic nervous system normally modulates or mediates the mechanisms that influence gastrointestinal transit in the rat and suggest that these mechanisms may be involved in the ileal brake effect. Nevertheless the data also suggest that simple measurement of the transit of the head of the meal by use of environmental hydrogen analysis may sometimes give a misleading impression of the action of drugs on gastrointestinal transit of the bulk of a test meal.

Effects of atipamezole, a novel alpha 2-adrenoceptor antagonist, in open-field, plus-maze, two compartment exploratory, and forced swimming tests in the rat

The behavioral effects of atipamezole (0.5-4.5 mg/kg), a new and highly selective alpha 2-adrenoceptor antagonist, were studied in four behavioral models: open-field, elevated plus-maze, two compartment exploratory test and forced swimming test. Atipamezole (1.5 and 4.5 mg/kg) produced a dose-dependent suppression of locomotor activity in the open field test. In the two compartment exploratory test, the same doses of atipamezole decreased locomotor activity in a 5 min test but not in a 10 min test. The numbers of transitions between the compartments were not significantly affected by atipamezole. Doses of 0.5-4.5 mg/kg did not significantly change the time spent in the open arms or the total number of arm entries in the plus-maze, and doses of 1.5 and 4.5 mg/kg decreased defecation marginally. Vocalization during the forced swimming test was increased by atipamezole (1.5 mg/kg) but the duration of immobility was not increased over the dose range (0.5-1.5 mg/kg) of atipamezole used. Our results suggest that, in the rat, atipamezole decreases motor activity in the early phase of the exploration of new surroundings. In the doses used, atipamezole may suppress defecation and increase vocalization in rats.

Duration of intravenous fluid replacement after abdominal surgery: a prospective randomised study

This prospective randomised study examined the possibility of early resumption of oral hydration and discontinuation of intravenous fluid replacement after emergency or elective abdominal surgery. Following elective cholecystectomy alone or with a choledocholithotomy or an emergency Hartmann's procedure for large bowel obstruction, patients were randomised to early oral hydration (sips of water for 12 h followed by free fluids by mouth for 24 h, when oral intake of food was allowed--intravenous hydration was discontinued 6 h after starting the intake of free fluids orally) or conventional intravenous hydration (intravenous hydration and an oral regimen of water as follows: sips every hour for 12 h, 30 ml every hour for 24 h, 60 ml every hour for 24 h, 90 ml every hour for 24 h, free fluids for 12 h, when food was allowed--intravenous hydration was discontinued 6 h after starting the free fluids). The two regimens were equally effective in maintaining fluid balance and normal plasma and urinary electrolytes without any observed differences in biochemical or metabolic values. Each of free fluids by mouth, discontinuation of intravenous hydration, and consumption of solid food were achieved in the patients on early oral hydration at time periods significantly shorter than those attained with the conventional regimen (P less than 0.001). Similarly, patients on the latter regimen were hospitalised for significantly longer times than those on early oral hydration (P less than 0.001). Early oral hydration after biliary surgery or a Hartmann's procedure effectively maintains fluid balance and has advantages over the conventional intravenous hydration regimen.

On the relevance of non-steroidal anti-inflammatory drugs in the prevention of paralytic ileus in rodents

In the mouse, the gastrointestinal transit of a charcoal marker, halved following the intraperitoneal administration of acetic acid, was no longer inhibited after pretreatment with the non-steroidal anti-inflammatory drugs (NSAIDs), indomethacin, ketoprofen, piroxicam or ximoprofen (0.25-2.5 mg kg-1 orally). In the fasted rat, the migrating myoelectric complex pattern of the small intestine which was disrupted for about one hour by acetic acid was unaltered by pretreatment with indomethacin or ximoprofen (0.5 mg kg-1 i.p.). In the anaesthetized rat, the inhibition by about 50% of the gastrointestinal transit due to laparotomy, did not occur following treatment with NSAIDs. It is concluded that NSAIDs prevent the occurrence of chemically-induced and postoperative ileus in rodents, an effect probably related to the analgesic properties of NSAIDs.