Endotoxin pretreatment modifies peristalsis and attenuates the antipropulsive action of adrenoceptor agonists in the guinea-pig small intestine

Gastrointestinal motility in acute illness

Critical illness affects gastrointestinal motility - not only as a primary problem, which brings the patient to the intensive care unit (ICU), but also as a complication consecutive to the ICU stay. Motility disturbances may result from impaired function of gastrointestinal muscle, pacemaker cell function and nerve activity. The most important neural control system is the enteric nervous system that contains the largest collection of neurons (10(8) cells) outside the central nervous system. Through its organization it can operate independently of the brain and generate motility patterns according to need: a postprandial motility pattern starting after food intake, and an interdigestive motility pattern starting several hours after a meal. Undisturbed intestinal motility depends critically on a balanced interaction between inhibition and excitation, and a disturbance in this balance leads to severe derangements of intestinal motility. These motility disturbances differ in clinical appearance and location but can affect all parts of the gastrointestinal tract. This review focuses on select motility disturbances such as gastroparesis, postoperative ileus, and Ogilvie's syndrome. Generally effective methods to treat these conditions are given. Finally, we focus on special management options to prevent such motility disturbances or to reduce their severity.

Implication of neuropeptide-Y Y2 receptors in the effects of immune stress on emotional, locomotor and social behavior of mice

Neuropeptide Y (NPY) is involved in the regulation of emotional behavior, and there is indirect evidence for a role of NPY in the cerebral responses to peripheral immune challenge. Since the NPY receptors involved in these reactions are not known, we investigated the effect of Escherichia coli lipopolysaccharide (LPS) on emotional, locomotor and social behavior, body temperature and circulating corticosterone in female Y2 (Y2-/-) and Y4 (Y4-/-) receptor knockout mice. LPS (0.1mg/kg injected IP 2.5h before testing) increased rectal temperature in control and Y4-/- mice to a larger degree than in Y2-/- animals. Both Y2-/- and Y4-/- mice exhibited reduced anxiety-related and depression-like behavior in the open field, elevated plus-maze and tail suspension test, respectively. While depression-like behavior was not changed by LPS, anxiety-related behavior was enhanced by LPS in Y2-/-, but not control and Y4-/- animals. Y2-/- mice were also particularly susceptible to the effect of LPS to attenuate locomotor behavior and social interaction with another mouse. The corticosterone response to LPS was blunted in Y2-/- mice which presented elevated levels of circulating corticosterone following vehicle treatment. These data show that Y2-/- mice are particularly sensitive to the effects of LPS-evoked immune stress to attenuate locomotion and social interaction and to increase anxiety-like behavior, while the LPS-induced rise of temperature and circulating corticosterone is suppressed by Y2 receptor knockout. Our observations attest to an important role of endogenous NPY acting via Y2 receptors in the cerebral response to peripheral immune challenge.

Prevention of lipopolysaccharide-induced intussusception in mice by the COX2 inhibitor rofecoxib

Intussusception (IS), an invagination of a portion of the intestine into itself, has recently attracted considerable interest after the withdrawal of a rotavirus vaccine because of reports on increased risk of IS shortly after vaccination. The present study was designed to shed further light on the mechanism of IS formation and its prevention. Intussusception was induced in adult mice by intraperitoneal injection of lipopolysaccharide (LPS; 8 mg/kg) from salmonella typhimurium. The presence of IS was confirmed at laparotomy. The serum levels TNF-alpha were measured with ELISA. Six hours after LPS injection, 14.5% of the animals demonstrated IS. A total of 65 animals received rofecoxib (20 mg/kg), a selective COX2 inhibitor, 15-30 min before intraperitoneal injection of LPS, and only two (3%) in this group demonstrated IS 6 h later (P < 0.05 vs. control). We confirmed the well-known increase in serum TNF-alpha levels in response to LPS; however, this increase was not blocked by rofecoxib pretreatment. Notably, there was no correlation between the serum TNF-alpha levels and the development of IS. The results show that the occurrence of IS can be significantly decreased by pretreatment with a selective COX-2 inhibitor.

Stimulus-evoked opioid inhibition in guinea-pig longitudinal muscle-myenteric plexus strip is modulated by NMDA receptors

Longitudinal muscle-myenteric plexus (LMMP) strips of the guinea-pig ileum were used to investigate the stimulus-evoked endogenous opioid inhibition and its modulation by ionotropic glutamate receptors. Regular cholinergic twitch responses evoked by a short 3-s-field stimulation in intervals of 80s were found reduced after an interposed period of prolonged 40-s-field stimulation. In the presence of a peptidase-inhibitor-cocktail, the cholinergic twitch response following the period of prolonged stimulation was even further reduced as compared to normal Tyrode solution without peptidase inhibitors. In both instances, the impairment of the cholinergic twitch response was completely abolished by naloxone thus demonstrating its opioidergic nature. This endogenous inhibitory opioid effect was significantly mitigated by the NMDA-receptor antagonist MK-801, but not by the AMPA/kainate receptor antagonist CNQX. These results demonstrate by functional experiments that there is a significant opioid-mediated inhibition in guinea-pig LMMP preparations evoked by a prolonged electrical stimulation, and that an NMDA antagonist can mitigate the opioid inhibition.

The effects of tramadol and fentanyl on gastrointestinal motility in septic rats

In this study, we investigated the effects of tramadol and fentanyl on gastrointestinal transit (GIT) during acute systemic inflammation in an experimental model of cecal ligation and perforation (CLP). One-hundred-twenty male Swiss-Albino rats were divided randomly into 6 groups: Group I = sham-operated + saline; Group II = sham-operated + fentanyl; Group III = sham-operated + tramadol; Group IV = CLP + saline; Group V = CLP + fentanyl; Group VI = CLP + tramadol. Suspension of charcoal was administered as an intragastric meal to measure the GIT. GIT% (mean +/- sd) were 46.1% +/- 9.8%, 43.2% +/- 9.8%, 45.9% +/- 10.2%, 33.2% +/- 9.2%, 24.9% +/- 4.1%, and 31.8% +/- 8.4% in Groups I, II, III, IV, V, and VI, respectively. GIT% was significantly less in Group V than in Groups I, II, III, and IV (P < 0.05). The Group VI mean value was significantly lower than those of Groups I, II, and III (P < 0.05) but not different from those of Groups IV and V (P > 0.05). The antitransit effect of fentanyl was shown to have increased in the experimental sepsis model, but no decrease in GIT was obtained with tramadol. This was thought to be the result of an associated endogenic opioid system activation and receptor upregulation in sepsis.