Physiological regulation and NO-dependent inhibition of migrating myoelectric complex in the rat small bowel by OXA

M. Ehrström,1 E. Näslund,1 J. Ma,3 A. L. Kirchgessner,3,4 and P. M. Hellström2

1Division of Surgery, Danderyd Hospital, SE-182 88 Stockholm; 2Department of Gastroenterology and Hepatology, Karolinska Hospital, Karolinska Institutet, SE-171 Stockholm, Sweden; 3Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York 11203; and 4Neurology/Gastrointestinal CEDD, GlaxoSmithKline, Harlow, Essex, CM19 5 AW United Kingdom


    ABSTRACT
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 ABSTRACT
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Orexin A (OXA)-positive neurons are found in the lateral hypothalamic area and the enteric nervous system. The aim of this study was to investigate the mechanism of OXA action on small bowel motility. Electrodes were implanted in the serosa of the rat small intestine for recordings of myoelectric activity during infusion of saline or OXA in naive rats, vagotomized rats, rats pretreated with guanethidine (3 mg/kg) or N{omega}-nitro-L-arginine (L-NNA; 1 mg/kg). Naive rats were given a bolus of the orexin receptor-1 (OX1R) antagonist (SB-334867-A; 10 mg/kg), and the effect of both OXA and SB-334867-A on fasting motility was studied. Double-label immunocytochemistry with primary antibodies against OXA, neuronal nitric oxide synthase (nNOS), and OX1R was performed. OXA induced a dose-dependent prolongation of the cycle length of the migrating myoelectric complex (MMC) and, in the higher doses, replaced the activity fronts with an irregular spiking pattern. Vagotomy or pretreatment with guanethidine failed to prevent the response to OXA. The OXA-induced effect on the MMC cycle length was completely inhibited by pretreatment with L-NNA (P < 0.05), as did SB-334867-A. The OX1R antagonist shortened the MMC cycle length from 14.1 (12.0–23.5) to 11.0 (9.5–14.7) min (P < 0.05) during control and treatment periods, respectively. Colocalization of OXA and nNOS was observed in myenteric neurons of the duodenum and nerve fibers in the circular muscle. Our results indicate that OXA inhibition of the MMC involves the OX1R and that activation of a L-arginine/NO pathway possibly originating from OX1R/nNOS-containing neurons in the myenteric plexus may mediate this effect. Endogenous OXA may have a physiological role in regulating the MMC.

migrating motor complex; SB-334867-A; enteric ganglia; myenteric plexus


OREXINS ARE NOVEL NEUROPEPTIDES that appear to play a role in regulation of feeding, arousal, and energy homeostasis (9). Initial reports suggested that the orexins [orexin A (OXA) and B (OXB)] are produced exclusively by a small group of neurons in the lateral hypothalamic area, a region classically implicated in the control of feeding behavior (20). However, neurons in the submucosal and myenteric plexuses and endocrine cells in the intestinal mucosa and pancreatic islets in both the guinea pig and rat (11, 16) have recently been shown to display OXA and orexin receptor immunoreactivity. OXA stimulates motility in the guinea pig isolated colon (11) and modulates both insulin and glucagon release from the endocrine rat pancreas (16, 18). Moreover, orexin-positive neurons in the gut, similar to those in the hypothalamus, are activated by fasting, indicating a functional response to nutritional status in these cells (11).

Few studies have examined the peripheral effects of orexins. Plasma concentrations of OXA are increased during fasting in humans (12) and are lower in obese subjects compared with normal-weight subjects in the fasted state (1). We have recently demonstrated (16) that intravenous infusion of OXA and OXB in rats replaces the migrating myoelectric complex (MMC) by a pattern of irregular spiking; however, the mechanism behind this effect has not been clarified.

Recently, a selective orexin receptor 1 (OX1R; SB-334867-A) antagonist has been developed (23). Intraperitoneal administration of SB-334867-A results in decreased food intake and body weight gain as well as increased metabolic rate (7). There have been no studies on OX1R antagonists and gastrointestinal motility, although SB-334867-A has recently been shown to block OXA-induced contractions in the guinea pig small intestine (15).

The aim of this study was to investigate the mechanism of OXA action on small bowel motility and to determine whether OXA has a physiological role in the small bowel motor control of fasted conscious rats. We also determined whether OXA-containing neurons display nitric oxide (NO) synthase (NOS)-like immunoreactivity [neuronal NOS (nNOS)] in the rat duodenum.


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Preparation of rats for electromyography. Male Sprague-Dawley rats were used for the experiments. Animals were anesthetized with pentobarbital sodium (50 mg/kg ip; Apoteksbolaget, Umeå, Sweden) and, through a midline incision, three bipolar stainless steel electrodes (SS-5T, Clark Electro-medical Instruments, Reading, UK) were implanted into the muscular wall of the small intestine, 5 (D), 15 (J1), and 25 (J2) cm distal to the pylorus. A jugular vein catheter for administration of drugs was implanted in all animals at a separate surgical session. The electrodes and catheters were tunneled subcutaneously to exit at the back of the animals' neck. After surgery, the animals were housed singly and allowed to recover for at least 7 days before experiments were undertaken. During the recovery periods, rats were trained to comply with experimental conditions. Experiments were carried out in conscious animals after an 18-h fasting period in wire-bottomed cages, with free access to water. The rats were placed in Bollman cages, and the electrodes were connected to an EEG preamplifier (7P5B) operating a Grass Polygraph 7B (Grass Instruments, Quincy, MA). The time constant was set at 0.015 s, and the low and high cut-off frequencies were set at 10 and 35 Hz, respectively.

Fasting small bowel motility studies. All experiments started with a control recording of basal myoelectric activity, during which four activity fronts of the MMC propagated over all three recording sites during a period of 60 min. Infusion of OXA (Bachem AG, Bubendorf, Switzerland) was started immediately after the fifth activity front had passed the first electrode site, using a microinjection pump (model CMA 100; Carnegie Medicine, Stockholm, Sweden).

In a first set of dose-response experiments, OXA at doses of 50 (n = 8), 250 (n = 8), 500 (n = 13), 1,000 (n = 9), and 5,000 (n = 7) pmol·kg1·min1 was administered intravenously for 60 min, and the effect on small bowel motility was recorded.

In a second set of experiments, the effect of OXA on small bowel motility was studied in rats subjected to a bilateral surgical subdiaphragmatic vagotomy (n = 7). In addition to vagotomy, a pyloroplasty was performed and the animals were fed standard rat chow. After a 60-min control period, intravenous infusion with OXA (500 pmol·kg1·min1) was given for 60 min. The dose 500 pmol·kg1·min1 was chosen because this dose was the closet to the ED50 in dose-response experiments.

In a third set of experiments, the effect of pretreatment of guanethidine (Ismelin, CIBA-Geigy, Basel, Switzerland) was studied on the response to OXA on fasting motility (n = 7). An intravenous bolus of guanethidine (3 mg/kg1) was given 24 h before experiments. After a 1-h control period, OXA (500 pmol·kg1·min1) was given as intravenous infusion for 60 min. The dose 500 pmol·kg1·min1 was chosen for the same reasons as above.

In a fourth set of experiments, the effect of the NOS inhibitor N{omega}-nitro-L-arginine (L-NNA) (Sigma, St. Louis, MO) was studied on the response to OXA at doses of 500 and 5,000 pmol·kg1·min1 (each n = 7). After the control period, OXA was infused intravenously for 60 min. After propagated activity fronts were resumed, L-NNA at a dose of 1 mg/kg was given intravenously 10 min before infusion with OXA was repeated for another 60 min. In a separate experiment, L-NNA alone (1 mg/kg) was administered and myoelectric activity was recorded for 60 min. The dose of 1 mg/kg of L-NNA has in previous studies been shown to exert a reliable pharmacological blockade without disturbing unspecific stimulation of the MMC pattern (8, 13). The doses of 500 and 5,000 pmol·kg1·min1 were used to evaluate the dependence of half-maximal and maximal responses of OXA on NO.

Studies with the OX1R antagonist. In a first set of experiments, rats (n = 6) were prepared as above. After a 60-min control period, an intravenous bolus of the OX1R antagonist SB-334867-A [10 mg/kg dissolved in DMSO (Sigma) to 0.33 ml] was administered immediately after termination of an activity front at the duodenal level, and motor activity was studied for another 60 min. In a separate set of experiments, DMSO was given alone (n = 4).

In a second set of experiments, rats (n = 6) were prepared as above. After a 60-min control period, OXA was administered intravenously for 60 min at a dose of 500 pmol·kg1·min1. After a 30-min washout period and normal fasting motility resumed, an intravenous bolus of SB-334867-A (10 mg/kg) was given and intravenous infusion of OXA (500 pmol·kg1·min1) and SB-334867-A (0.1 mg·kg1·min1) was given for 60 min.

Tissue preparation for immunohistochemisty. Male Sprague-Dawley rats (300–350 g, n = 6) were killed with an intravenous overdose of pentobarbital sodium (Apoteksbolaget, Umeå, Sweden). Segments (1 cm) of duodenum (immediately distal to the pylorus) were removed, washed through the lumen, and placed in 4% formaldehyde in 0.1 M phosphate buffer (pH 7.4) for 24 h. After fixation, the preparations were washed and stored in PBS containing sodium azide (1%). Material to be sectioned was cryoprotected overnight (at 4°C) in PBS containing 30% (wt/vol) sucrose, embedded in optimal cutting temperature (Miles Scientific, Naperville, IL), frozen with liquid N2, and sectioned (10 µm) using a Leica cryostat-microtome (Leica Microsystems, Deerfield, IL).

For whole mount preparations, segments of duodenum were opened along the mesenteric border, and the resulting rectangular sheet of intestine was stretched, pinned flat on balsa wood, and fixed as above. After fixation, the preparations were washed in PBS and then dissected into layers. Two whole mounts, one containing the submucosal and the other the myenteric plexus, were prepared as previously described (10).

Immunocytochemistry. To locate OXA protein in the tissue by immunocytochemistry, preparations were exposed to PBS containing 0.5% Triton X-100 and 4% horse serum for 30 min and then incubated with primary antibodies against OXA (affinity-purified rabbit polyclonal, diluted 1:2,000, Alpha Diagnostic International, San Antonio, TX). After preparations were washed with PBS, they were incubated (for 3 h) with affinity-purified donkey anti-rabbit secondary antibodies conjugated to indocarbocyanine (Cy3; diluted 1:2,000; Jackson ImmunoResearch Laboratories, West Grove, PA) or FITC (1:500; Jackson ImmunoResearch Laboratories). Parallel control sections were included that were incubated with normal goat serum instead of primary antibodies. No immunostaining was observed when a control IgG was substituted for the primary antibody.

Double-label immunocytochemistry was used to identify the cells that displayed OXA immunoreactivity and OXR1-immunoreactivity (rabbit polyclonal, diluted 1:500, Chemicon International, Temecula, CA) using primary antibodies raised in different species in conjunction with species-specific secondary antibodies [donkey anti-sheep (Jackson ImmunoResearch Laboratories), diluted 1:200] coupled to contrasting fluorophores (FITC or Cy3, as above). Primary antibodies against nNOS (sheep polyclonal, diluted 1:5,000, Chemicon International) were also used. To enhance visualization of peptide immunoreactivity in nerve cell bodies, rats were injected with colchicine (5 mg/kg) intraperitoneally. Twenty-four hours later, the rats were killed.

The tissues were placed in coverslips in Vectashield (Vector Laboratories, Burlingame CA). Preparations were examined by using a Radiance 2000 laser scanning confocal microscope (BioRad, San Francisco, CA) attached to an Axioskop 2 microscope (Carl Zeiss, Thornwood, NY). Images of 512 x 512 pixels were obtained and processed by using Adobe Photoshop 6.0 (Adobe Systems, Mountain View, CA) and printed with a Kodak (XLS-8600) printer.

Ethics, data, and statistical analysis. The local Ethics committee for animal experimentation in Stockholm, Sweden approved the experimental protocol.

The main characteristic feature of myoelectric activity of the small intestine in the fasted state, the activity front (phase III) of the MMC, was defined as a period of clearly distinguishable intense spiking activity with an amplitude at least twice that of the preceding baseline, propagating aborally through the whole recording segment and followed by a period of quiescence. The MMC cycle length, duration, and propagation velocity of the activity fronts were calculated (2) as a mean of the 60-min study period. All statistical evaluations are against the control period for experiment; however, control (saline) results are shown as a mean for all control data for that set of experiments. When no activity front was observed during the 60-min infusion period, a value of 61 min was assigned as the measured value. When only one or two activity fronts were observed, followed by a long period of quiescence, the MMC cycle length was calculated from the activity front preceding the start of the infusion to the activity front observed and then from the observed activity front during the infusion to the end of the infusion period plus 1 min.

Data are expressed as median (range), unless otherwise stated. The data were assessed for statistical significance using the two-sided Mann-Whitney U-test or Wilcoxon signed rank test for matched pairs at P < 0.05, as appropriate.


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NO mediates the inhibitory effect of OXA on the MMC. As previously reported (16), infusion of OXA had an inhibitory effect on the MMC, replacing it with a diffuse, irregular spiking motility pattern. OXA increased the MMC cycle length in a dose-dependent fashion. No effect was seen on the duration or propagation velocity of activity fronts of the MMC in the gut segment under study (Table 1).


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Table 1. Effect of OXA on fasting motility in the rat

 

After bilateral subdiaphragmatic vagotomy or pretreatment with guanethidine, the response of the small intestine to OXA was not different from that seen in untreated rats. The duration or propagation velocity of activity fronts in the gut segment was not affected (Table 2).


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Table 2. Effect of OXA on fasting gastrointestinal motility in vagotomized or rats pretreated with guanethidine

 

Pretreatment with L-NNA (1 mg/kg) resulted in a significant reduction of the cycle length compared with control. Pretreatment with L-NNA abolished the response of the small intestine to OXA at both 500 and 5,000 pmol·kg1·min1, so that the addition of L-NNA to the intravenous infusion of OXA was not different from control but significantly different from OXA alone. Again, no effect was seen on the duration or propagation velocity of activity fronts in the gut segment (Table 3).


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Table 3. Effect of OXA on fasting gastrointestinal motility after pretreatment with Nw-nitro-L-arginine

 

OX1R antagonist induces activity fronts and decreases MMC cycle length. Thirty-six (18–48) seconds after a bolus of SB-334867-A, an activity front was induced in all animals. During the 60-min study period, the MMC cycle length decreased after administration of the OX1R antagonist compared with control. The OX1R antagonist did not affect the duration of the activity front or the propagating velocity. Administration of DMSO alone did not affect the MMC pattern (Fig. 1, Table 4).



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Fig. 1. Mean (±SE) migrating myoelectric complex (MMC) of fasted small bowel motility in rats during saline infusion or after a bolus administration of 10 mg/kg of an orexin 1 receptor (OXR1) antagonist (SB-334867-A; top) and a representative recording after administration of SB-334867-A (bottom). D, electrode placement 5; J1, electrode placement 15; J2, electrode placement 25.

 

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Table 4. Effect of a bolus dose of a selective OX1R antagonist on fasting gastrointestinal motility

 

The effect of OXA on fasting motility is OX1R specific. The concomitant administration of OXA and SB-334867-A resulted in a significant reduction of the MMC cycle length compared with OXA alone and not different from control. The duration of the activity front and propagating velocity were unchanged (Fig. 2, Table 5).



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Fig. 2. A representative recording a 60-min control period (saline) followed by intravenous orexin A (OXA; 500 pmol·kg1·min1) for 60 min followed by a washout period of 30 min during which normal motor activity was observed. This was followed by the administration of bolus of 10 mg/kg of an orexin 1 receptor antagonist (SB-334867-A) and intravenous infusion of SB-334867-A (0.1 mg·kg1·min1) combined with OXA 500 pmol·kg1·min1 for 60 min.

 

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Table 5. Effect of OXA and a selective OX1R antagonist on fasting gastrointestinal motility

 

Localization of OXA and nNOS in the duodenum. As previously reported (16), OXA immunoreactivity was found in nerve cell bodies and fibers in the rat duodenum (Fig. 3). OXA-immunoreactive neurons were found in submucosal (not illustrated) and myenteric (Fig. 3A) ganglia. The immunoreactivity in the cytoplasm of such cells was relatively low but higher in colchicine-treated animals. No immunoreactivity was found in control sections processed without the primary antisera (not illustrated).



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Fig. 3. Characterization of OXA- and OXR1-immunoreactive neurons in the rat duodenum. A, B: OXA-immunoreactive neurons in the myenteric plexus (arrow; A) contain neuronal nitric oxide synthase (nNOS; arrow; B). C, D: OXA-immunoreactive nerve fibers (arrow; C) encircle nNOS immunoreactive neuron in the myenteric plexus (D). E, F: subset of OXR1-immunoreactive neurons (arrow; E) in the myenteric plexus contains nNOS (arrow; F). Horizontal markers, 10 µm.

 

Further studies were done to determine whether the neurons with OXA immunoreactivity also contained nNOS. OXA-immunoreactive submucosal neurons did not contain nNOS (not illustrated); however, in the myenteric plexus, a subset of OXA-immunoreactive neurons (Fig. 3A) displayed nNOS immunoreactivity (Fig. 3B). Some nNOS-immunoreactive neurons in the myenteric plexus were encircled by OXA-immunoreactive nerve fibers (Fig. 3, C and D). A subset of OXR1-immunoreactive neurons (Fig. 3E) in the myenteric plexus also contains nNOS (Fig. 3F). OXA-immunoreactive nerve fibers also contained nNOS (data not shown).


    DISCUSSION
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This study demonstrates that the effect of peripherally administered OXA on fasting small bowel motility is partly dependent on activation of the L-arginine/NO pathway, possibly originating from OXA/nNOS-containing neurons in the myenteric plexus of the duodenum. This effect is not dependent on vagal or sympathetic signaling. Administration of a selective OX1R antagonist induced activity fronts of the MMC and shortened the MMC cycle length, and the combined administration of OXA and an OX1R antagonist abolished the OXA effect on fasting motility, suggesting that this effect is OX1R specific. The distribution of OXA- and nNOS-immunoreactivity extends our previous findings demonstrating expression of orexins in rat duodenum (11, 16).

Intravenous infusions of OXA at doses ranging between 50 and 5,000 pmol·kg1·min1 increased the MMC cycle length without affecting the duration or propagation velocity of the activity fronts in a dose-dependent manner. Yet, the effect of OXA at higher doses seemed to be slightly variable. In our previous study (16), quiescence was achieved at 500 pmol·kg1·min1. Similar results were seen with OXA 500 pmol·kg1·min1 in experiments with L-NNA, whereas in the dose-response experiments, quiescence was not seen in some animals even at 500 and 1,000 pmol·kg1·min1. The reason for this is not clear. The half-life and degradation of peripheral OXA is not known. An individual response variability to OXA might explain our findings, but no such variations have been described elsewhere.

The administration of the selective OX1R antagonist SB-334867-A induced an activity front in 30 s in all animals and shortened the MMC cycle length by 25% compared with control situation. This suggests that OXA and OX1R are involved in the regulation of fasting motility. Also, because the combined administration of OXA and SB-334867-A resulted in a significant reduction in MMC cycle length compared with OXA alone, this suggests that the effect of OXA on fasting motility is OX1R specific. Motilin has been suggested to be involved in the regulation of the MMC and plasma concentrations of motilin fluctuate with the different phases of the MMC in humans (24). Plasma concentrations of OXA have been shown to increase during fasting in rats (18) and humans (12); however, it is unknown whether plasma OXA fluctuates during the different phases of the MMC or postprandially. Previous work with SB-334867-A (7) suggests that the compound has anorectic and thermogenic properties and may be used as a potential treatment for non-insulin-dependent diabetes mellitus and obesity. Our data indicate that there may also be a role for the SB-334867-A and OXA in the treatment of gastrointestinal motor disorders.

Intravenous infusion of OXA produced a comparable inhibitory effect as did VIP on the MMC (13). Because OXA nerve fibers in the circular muscle of the duodenum also contain VIP (16), the inhibitory effect of orexins on the MMC may be mediated by VIP or, at least, involve similar mechanisms as VIP (16). We have previously shown (16) that in the rat duodenum, OXA immunoreactivity occurs in endocrine cells, nerve cell bodies, and nerve fibers that innervate myenteric and submucosal ganglia and circular muscle. We have also found that VIP and OXA are colocalized, implying that the OXA-immunoreactive neurons are secretomotor neurons, interneurons, and/or inhibitory motoneurons. The mucosa contained OXA-immunoreactive nerve fibers; however, the innervation of the mucosa was sparse compared with the dense OXA innervation of ganglia and muscle. Thus OXA neurons are more likely to be interneurons and/or motoneurons (16). About 45% of submucosal nerve cells in the rat ileum contain VIP (14). These cells include secretomotor neurons and interneurons projecting within the submucosal plexus and to neurons in the myenteric plexus (4, 19). Myenteric VIP-containing cells are thought to be inhibitory motoneurons that mediate relaxation of the circular muscle (5).

In this study, we extended our studies of OXA distribution in the rat duodenum to include nNOS. We demonstrated that a subset of OXA neurons in the myenteric plexus contains nNOS as well as numerous nerve fibers in the circular muscle. NO has been demonstrated to be a transmitter of inhibitory neurons of the enteric nervous system (21) and to mediate relaxations of the gut (3). In this paper, we demonstrate that the NOS inhibitor L-NNA diminished the response of OXA on fasting small bowel motility. Although L-NNA alone reduced the cycle length of the MMC by a median of 8 min, pretreatment with L-NNA before OXA infusion decreased the cycle length by 42 min. The present results suggest that OXA modulates duodenal and jejunal motility through peripheral actions of the peptide, at least partly through an L-arginine/NO pathway.

In support of our results, in vitro studies of OXA on mouse small intestine demonstrate that OXA partially mediates nonadrenergic, noncholinergic relaxation through the activation of NOS-containing myenteric neurons (22). The results of Satoh et al. (22) suggest that OXA activates NOS neurons directly or indirectly though activation of interneurons within the myenteric plexus. Furthermore, spontaneous relaxations of the rat duodenum in between activity fronts of the MMC are NO dependent, whereas relaxation of the duodenum during activity fronts seems to be modulated, but not directly mediated, by NO. Rather, ATP seems to be the mediator of relaxation during the activity front of the MMC (6). Thus, although somewhat speculative, it is possible that the inhibition of activity fronts of the MMC seen by OXA in this study may be the result of NO modulation of ATP-mediated relaxation of the rat duodenum during activity front of the MMC.

In summary, this study demonstrates that the inhibitory effect of OXA on fasting small bowel motility is at least partly dependent on an L-arginine/NO pathway and seems to be mediated by OX1R. OXA seems to have a physiological role regulating the MMC, because a selective OX1R antagonist shortened the MMC cycle length. On the basis of our findings, it seems likely that OXA plays a significant role in modulating gastrointestinal function and may be involved in the processing of nutrients and energy control in addition to the central stimulation of food intake.


    DISCLOSURES
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This study was supported by grants from National Institutes of Health (NS-27645; to A. L. Kirchgessner), The Swedish Research Council, the Swedish Medical Society, Funds of the Karolinska Institutet, the Professor Nanna Svartz Fund, the Magnus Bergvall Fund, the Tore Nilsson Fund, the Ruth and Richard Juhlin Fund, Jeanssons Foundation, Bengt Ihre Foundation, STINT, and Henning and Johan Throne Holst Foundation.


    FOOTNOTES
 

Address for reprint requests and other correspondence: M. Ehrström, Dept. of Surgery, Danderyd Hospital, SE-182 88 Stockholm, Sweden (E-mail: marcus.ehrstrom{at}kids.ki.se).

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


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  1. Adam JA, Menheere PP, van Dielen FM, Soeters PB, Buurman WA, and Greve JW. Decreased plasma orexin-A levels in obese individuals. Int J Obes Relat Metab Disord 26: 274–276, 2002.[Medline]
  2. Bränström RO and Hellström PM. Characteristics of fasting and fed myoelectric activity in the rat small intestine: evaluation by computer analysis. Acta Physiol Scand 158: 53–62, 1996.[ISI][Medline]
  3. Calignano A, Whittle BJR, Di Rosa M, and Moncada S. Involvement of endogenous nitric oxide in the regulation of rat intestinal motility in vivo. Eur J Pharmacol 229: 273–276, 1992.[ISI][Medline]
  4. Ekblad E, Winther C, Ekman R, Håkanson R, and Sundler F. Projections of peptide-containing neurons in rat small intestine. Neuroscience 20: 169–188, 1987.[ISI][Medline]
  5. Furness JB. Types of neurons in the enteric nervous system. J Auton Nerv Syst 81: 87–96, 2000.[ISI][Medline]
  6. Glasgow I, Mattar K, and Krantis A. Rat gastrointestinal motility in vivo: involvement of NO and ATP in spontaneous motor activity. Am J Physiol Gastrointest Liver Physiol 275: G889–G896, 1998.[Abstract/Free Full Text]
  7. Haynes AC, Chapman H, Taylor C, Moore GBT, Cawthorne MA, Tadayyon M, Clapman JC, and Arch JR. Anorectic, thermogenetic and anti-obesity activity of a selective orexin-1 receptor antagonist in ob/ob mice. Regul Pept 104: 153–159, 2002.[ISI][Medline]
  8. Hellström PM, Al-Saffar A, Ljung T, and Theordorsson E. Endotoxin actions on migrating myoelectric complex, transit and gut neuropeptides in the rat. Role of nitric oxide. Dig Dis Sci 42: 1640–1651, 1997.[ISI][Medline]
  9. Kirchgessner AL. Orexins in the brain-gut axis. Endocr Rev 23: 1–15, 2002.[Abstract/Free Full Text]
  10. Kirchgessner AL and Gershon MD. Projections of submucosal neurons to the myenteric plexus of the guinea pig intestine: in vitro tracing of microcircuits by retrograde and antegrade transport. J Comp Neurol 277: 487–498, 1988.[ISI][Medline]
  11. Kirchgessner AL and Liu M. Orexin synthesis and response in the gut. Neuron 24: 941–951, 1999.[ISI][Medline]
  12. Komaki G, Matsumoto Y, Nishikata H, Kawai K, Nozaki T, Takii M, Sogawa H, and Kubo C. Orexin-A and leptin change inversely in fasting non-obese subjects. Eur J Endocrinol 144: 645–651, 2001.[ISI][Medline]
  13. Ljung T and Hellström PM. Vasoactive intestinal peptide suppresses migrating myoelectric complex of rat small intestine independent of nitric oxide. Acta Physiol Scand 165: 225–231, 1999.[ISI][Medline]
  14. Mann PT, Furness JB, and Southwell BR. Choline acetyl-transferase immunoreactivity of putative primary afferent neurons in the rat ileum. Cell Tissue Res 297: 241–248, 1999.[ISI][Medline]
  15. Matsuo K, Kaibara M, Uezono Y, Hayashi H, Taniyama K, and Nakane Y. Involvement of cholinergic neurons in orexin-induced contractility of guinea pig ileum. Eur J Pharmacol 452: 105–109, 2002.[ISI][Medline]
  16. Näslund E, Ehrström M, Ma J, Hellström PM, and Kirchgessner AL. Localization and effects of orexin on fasting motility in the rat duodenum. Am J Physiol Gastrointest Liver Physiol 282: G470–G479, 2002.[Abstract/Free Full Text]
  17. Nowak KW, Mackowiak P, Switonska MM, Fabis M, and Malendowicz LK. Acute orexin effects on insulin secretion in the rat: in vivo and in vitro studies. Life Sci 66: 449–454, 2000.[ISI][Medline]
  18. Ouedrago R, Näslund E, and Kirchgessner AL. Glucose regulates the release of orexin-a from the endocrine pancreas. Diabetes 52: 111–117, 2003.[Abstract/Free Full Text]
  19. Porter AJ, Wattachow DA, Brookes SJ, and Costa M. Projections of nitric oxide synthetase and vasoactive intesinal polypeptide-reactive subsucosal neurons in the human colon. J Gastroenterol Hepatol 14: 169–188, 1999.
  20. Sakurai T, Amemiya A, Ishii M, Matsuzaki I, Chemelli RM, Tanaka H, Williams SC, Richardson JA, Kozlowski GP, Wilson S, Arch JR, Buckingham RE, Haynes AC, Carr SA, Annan RS, McNulty DE, Liu WS, Terrett JA, Elshourbagy NA, and Yanagiswa M. Orexin and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior. Cell 92: 573–585, 1998.[ISI][Medline]
  21. Sanders KM and Ward SM. Nitric oxide as a mediator of nonadrenergic noncholinergic neurotransmission. Am J Physiol Gastrointest Liver Physiol 262: G379–G392, 1992.[Abstract/Free Full Text]
  22. Satoh Y, Uchida M, Fujita A, Nishio H, Takeuchi T, and Hata F. Possible role of orexin A in nonadrenergic, noncholinergic inhibitory response of muscle of the mouse small intestine. Eur J Pharmacol 428: 337–342, 2001.[ISI][Medline]
  23. Smart D, Sabido-David C, Brough SJ, Jewitt F, Johns A, Portor RA, and Jerman JC. SB-334867-A: the first selective orexin-1 receptor antagonist. Br J Pharmacol 132: 1179–1182, 2001.[Abstract/Free Full Text]
  24. Vantrappen G, Janssens J, Peeters TL, Bloom SR, Christofides ND, and Hellemans J. Motilin and the interdigestive migrating motor complex in man. Dig Dis Sci 24: 497–500, 1979.[ISI][Medline]




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