The 
2-adrenergic receptor antagonist yohimbine improves endotoxin-induced inhibition of gastrointestinal motility in mice
Department of Anaesthesiology, Kansai Medical University, Osaka, Japan
* Corresponding author: Department of Anaesthesiology, Kansai Medical University, 10-15, Fumizono-cho, Moriguchi, Osaka 570-8507, Japan. E-mail: takefumi{at}wd5.so-net.ne.jp
Accepted for publication November 29, 2006.
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
Background: Sepsis inhibits gastrointestinal motility. Although the exact mechanism of this is unclear, lipopolysaccharide is known to activate macrophages in the gastrointestinal wall, which upregulate their expression of inducible nitric oxide synthase (iNOS). This leads to an increased production of nitric oxide, which relaxes the gastrointestinal muscles. We studied endotoxaemic mice to determine whether yohimbine improved delayed gastric emptying and gastrointestinal transit.
Methods: Male Balb/c mice (n = 49) were randomly allocated to two groups, and either yohimbine 25 µg or saline was injected s.c. Four hours later, mice in each group were further randomly allocated to two groups, and either lipopolysaccharide 100 µg or saline was injected intraperitoneally. Eight hours later, liquid containing fluorescent microbeads was infused into the stomach, and 30 min later, gastric emptying and gastrointestinal transit were measured using flow cytometry. We also studied whether yohimbine given after injection of lipopolysaccharide was effective (n = 22). In another group of mice (n = 32), iNOS in the gastrointestinal tract was measured using western blotting.
Results: Lipopolysaccharide significantly inhibited gastric emptying and gastrointestinal transit. Yohimbine, given before or after lipopolysaccharide, significantly attenuated the inhibitory effects of lipopolysaccharide. Lipopolysaccharide increased the expression of iNOS in the small intestine and yohimbine suppressed the effects of lipopolysaccharide.
Conclusions: In endotoxaemic mice, yohimbine improved delayed gastric emptying and gastrointestinal transit, possibly by downregulating lipopolysaccharide-induced increased expression of iNOS.
Keywords: complications, sepsis; critical care; gastrointestinal tract, emptying; gastrointestinal tract, transit; sympathetic nervous system, yohimbine
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Sepsis inhibits gastrointestinal motility.1–5 Retention of food in the gastrointestinal tract can cause gastric distension and bacterial overgrowth, leading to aspiration pneumonitis, bacterial translocation, and multiple organ failure.6–8
The exact mechanism of sepsis-induced reduced gastrointestinal motility is unclear, but inflammatory and neural mechanisms have been suggested.5 9 Inflammatory mechanisms include the production of nitric oxide.4 10–14 Lipopolysaccharide (the endotoxin of Gram-negative bacteria) or live bacteria can activate the gastrointestinal wall macrophages which then upregulate the expression of inducible nitric oxide synthase (iNOS). This leads to an increased production of nitric oxide, which relaxes gastrointestinal muscles. Neural mechanisms include endotoxin-induced stimulation of capsaicin-sensitive afferent neurons and of the dorsal vagal complex.15 Vagal efferent motor and postganglionic myenteric neurons are also involved.9 15–17
Several prokinetic drugs have been proposed to ameliorate endotoxin-induced gastrointestinal dysmotility, but clinically effective drugs have yet to be established. In horses, phenylbutazone18 or metoclopramide19 ameliorated endotoxin-induced delayed gastric emptying, but efficacies of these drugs during endotoxaemia in humans are unclear. Yohimbine has been reported to improve endotoxin-induced delayed gastric emptying of liquid (containing acetaminophen) in horses.20 However, whether this drug also ameliorates delayed intestinal transit, and the mechanisms of this effect, have not been studied.
Gastrointestinal motility is also inhibited after operation.21–23 One possible mechanism is that surgical manipulation of the gut activates macrophages in the intestinal wall and these stimulated macrophages produce nitric oxide, leading to an inhibition of intestinal motility.21 Alpha-2-adrenoceptors are identified on these macrophages and they may be involved in the production of nitric oxide.21 In one study, yohimbine ameliorated postoperative ileus in rats, which is due to a decreased production of iNOS (and thus nitric oxide) by intestinal macrophages via the blockade of the 
2-adrenoceptors.21
Because of the similarities in the pathophysiology between postoperative and septic ileus, we hypothesized that yohimbine might ameliorate septic gastrointestinal dysmotility through the effects on iNOS expression in the gastrointestinal tract.
The first aim of the study was to evaluate whether the 2-adrenoceptor antagonist yohimbine improved delayed gastric emptying and gastrointestinal transit in endotoxaemic mice. The second aim was to see whether there were differences in iNOS expression with and without yohimbine in endotoxaemic mice.
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
The study was approved by the Institutional Research Ethics Committee on Animal Research.
Part 1 study
Animals
Male Balb/c mice aged 6–7 weeks and weighing 23–28 g were purchased from Charles River (Yokohama, Japan). The mice were housed under standardized environmental conditions with a 12 h light/dark cycle. They had been fasted for 16–24 h, but allowed free access to water, until 20–30 min before being given a test liquid into the stomach. Each animal was individually housed in a wire-mesh cage to prevent coprophagy during fasting. These procedures were based on our previous studies.24–27 Mice were randomly allocated to two groups, and either yohimbine (Sigma Chemical Co., St Louis, MO, USA) 25 µg (in 100 µl saline), the dose which approximates to 1 mg kg – 1, or 100 µl saline was injected s.c. The route and dose were determined on the basis of previous studies.21 25 Four hours later, mice in each group were further randomly allocated to two groups, and either lipopolysaccharide (Escherichia coli O111:B4, Sigma Chemical Co.) 100 µg (in 200 µl saline) or 200 µl saline was injected intraperitoneally (i.p.).
Markers for measurement
Gastric emptying and gastrointestinal transit of liquid were measured using fluorescent microbeads, as described previously.26 27 The microbeads (Flow Check High Intensity Alignment Grade Particles, 6 µm; Polysciences, Inc., Warrington, PA, USA), used as markers, are 6 µm in diameter, labelled with a fluorescent yellow–green dye, and emit yellow–green fluorescence when excited with a 488 nm argon laser. The quantity of the fluorescent microbeads in each sample was measured with a flow cytometer (FACScan; BD Biosciences, San Jose, CA, USA). Smaller microbeads (2.14 µm in diameter) (Sphero UV fluorescent particles, BD Biosciences) were also included to the test fluid to increase the recovery of the 6 µm markers from the gastrointestinal tract.26 These smaller microbeads do not emit fluorescence when a 488 nm argon laser is applied. The manufacturers provided these microbeads in water: 1 µl contained 2 x 103 6 µm microbeads or 6 x 106 2.14 µm microbeads.
We have confirmed that the variability of gastric emptying and gastrointestinal transit measured using these microbeads is reasonably small, and values are similar to those measured using a conventional method with a radioactive isotope.24 25
Measurement of gastric emptying and gastrointestinal transit
All experiments measuring gastrointestinal motility were started between 6:00 and 9:00 a.m. Twelve hours after injection of yohimbine or saline (and 8 h after injection of lipopolysaccharide or saline), each mouse was lightly anaesthetized with halothane (2%) by placing the mouse in a clean container until it went to sleep. Saline 0.2 ml, containing the 6 µm fluorescent microbeads (60 µl) together with the 2.14 µm non-fluorescent microbeads (2 µl), was infused via a metal cannula (PS 7912, ISIS Co., Ltd, Osaka, Japan) into the stomach. Thirty minutes later, the mouse was killed by an overdose of halothane. The oesophagus, just proximal to the gastric fundus, and the duodenum, just distal to the pylorus, were cross-clamped (to prevent spillage of contents from the stomach), and the stomach was removed.24–27 The small intestinal tract was also removed with clamping of the tract at several locations to minimize the movements of contents.24 25 This time interval was chosen to obtain the geometric centre (GC) (discussed subsequently) of 6–7 and to prevent the leading edge of the test fluid from going beyond the ileocaecal junction;24–27 if there was chyme in either the stomach or the small intestinal tract, data were not used. The intestinal tract was placed on a ruled template and divided into 10 equal segments. The stomach and each segment of the intestinal tract were placed into individual tubes containing 5 ml of phosphate-buffered saline. Each tube was vortexed and 700 µl of the supernatant was filtered through a strainer (Cell-Strainer, BD Biosciences) and subjected to flow cytometry.
Using flow cytometry, the 6 µm microbeads were selected (gated) by their distinct forward light scatter (which reflects the size of particles) and by their side light scatter (which reflects the complexity of the internal structure of particles) profiles. The gated particles were further analysed for the presence of intense fluorescence. The number of particles with high fluorescence intensity was counted for 30 s at the high flow rate of the cytometer.26 27
Gastric emptying of liquids was calculated as below:
%Gastric emptying = [(total count – stomach count)/(total count)] x 100, where total count = stomach count + 
(count in each intestinal segment).
Gastrointestinal transit was assessed using the GC (centre of gravity). This was calculated by a method described previously:24–27
GC = (CiSi)/(Ci), where Ci = count in segment Si (Fig. 1).
|
Western blotting
The antrum of the stomach and mid-parts of the jejunum and ileum were frozen in liquid nitrogen, homogenized, and lysed using ice-cold lysis buffer (50 mM Tris hydrochloride (pH 8.0), 0.1% sodium dodecyl sulphate (SDS), 1% Nonidet P-40, 5 mM ethylenediamine-N,N,N',N'-tetraacetic acid, 150 mM sodium chloride, 2 mM dithiothreitol, 1 mM sodium orthovanadate (Sigma Chemical Co.), and protease inhibitor cocktail (complete, Roche Applied Science, Mannheim, Germany). The lysates (20 µg per lane) were then separated on a 10% SDS–polyacrylamide gel and transferred to a polyvinylidene fluoride (PVDF) membrane (Sequi-Blot PVDF Membrane, Bio-Rad Laboratories, Hercules, CA, USA). iNOS was detected with an anti-iNOS antibody (1:2500) (Pharmingen, San Diego, CA, USA) and actin was detected with an anti-actin antibody (1:10 000) (Santa Cruz Biotechnology, Inc., Santa Cruz, CA, USA). Actin expression was assessed to confirm that equal amounts of protein were applied for analysis. These proteins were then made visible using anti-IgG-horse radish peroxidase antibodies of appropriate species (Zymed Laboratories Inc., S. San Francisco, CA, USA) and Enhanced Chemiluminescence plus Western Blotting Detection Reagent (Amersham Biosciences, Buckinghamshire, UK).
Part 2 study
Here, we examined whether there was a difference in the effect of yohimbine at different doses. We compared the one-third (8 µg), and three times (75 µg), with the dose (25 µg) used in Part 1.
Part 3 study
In clinical practice, a treatment drug would be given after endotoxin-induced ileus has occurred. In this part, we studied whether yohimbine given after the onset of endotoxaemia would also improve delayed gastric emptying and gastrointestinal transit.
Lipopolysaccharide 100 µg was injected i.p. Thirty minutes later, mice were randomly allocated to two groups, and either yohimbine 25 µg (in 100 µl saline) or 100 µl saline was injected i.p. We decided to give yohimbine 30 min after injection of lipopolysaccharide, because a previous study has shown that the symptoms and signs of endotoxaemia develop as early as 30 min after i.p. injection.16 Gastric emptying and gastrointestinal transit were determined 8 h after injection of lipopolysaccharide.
Statistical analysis
One-way analysis of variance (ANOVA) was used to compare the percent gastric emptying and GC in Part 1 and Part 2 studies. If this showed significance, unpaired Student's t-test was used to compare two groups. Friedman's test (non-parametric two-way ANOVA) was used to compare the expression of iNOS. If this showed significance, Wilcoxon signed-rank test was used to compare two groups. Non-parametric test for ordered groups was used for the dose–response relationship. P < 0.05 was considered significant.
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Part 1 study
Gastric emptying and gastrointestinal transit
Lipopolysaccharide significantly inhibited gastric emptying and gastrointestinal transit (Fig. 2). Yohimbine, which in itself did not have any effect, significantly attenuated the inhibitory effect of lipopolysaccharide.
|
Expression of iNOS in the gastrointestinal tract
In most of the control mice, iNOS was not expressed. However, in some mice, iNOS was expressed in the ileum (Fig. 3). In yohimbine-treated mice (without lipopolysaccharide), iNOS expression was similar to control mice. Lipopolysaccharide significantly (P < 0.05) induced the expression of iNOS in the ileum and, in some mice, also in the jejunum. In the lipopolysaccharide-treated mice, yohimbine significantly (P < 0.05) reduced the iNOS expression in the small intestine. iNOS was not detected in the stomach of any animal.
|
Part 2 study
Yohimbine 8 µg did not significantly attenuate the inhibitory effect of lipopolysaccharide, whereas higher doses (25 and 75 µg) significantly attenuated the inhibitory effect of lipopolysaccharide (Fig. 4).
|
0.3, 1, and 3 mg kg– 1, respectively.Part 3 study
Yohimbine, given 30 min after injection of lipopolysaccharide, significantly attenuated the inhibitory effect of lipopolysaccharide (Fig. 5).
|
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
We have shown that the
2-adrenoceptor antagonist yohimbine improved delayed gastric emptying and gastrointestinal transit in endotoxaemic mice. We have also found that yohimbine significantly reduced iNOS expression in the small intestine in this model. In endotoxaemia, macrophages in the intestinal wall are activated. These activated macrophages upregulate iNOS expression, leading to an increased production of nitric oxide.5 11 In addition, the activated macrophages recruit leucocytes, primarily monocytes (the precursors of macrophages) from the circulation via a production of chemokines, such as the monocyte chemoattractant protein-1.28 These recruited leucocytes also produce nitric oxide and further aggravate ileus.28 Alpha-2-adrenoceptors are present on these macrophages29–31 and stimulation of these receptors increases iNOS expression and nitric oxide production,29 31 whereas the reverse is true with blockade of the receptor.21 Therefore, it is likely that yohimbine ameliorated ileus by reducing nitric oxide release from macrophages in the small intestine, via downregulation of lipopolysaccharide-induced increased expression of iNOS.
In some of control mice, iNOS was expressed in the ileum, and yohimbine downregulated this expression. The cluster of Peyer's patches in the ileum is the major lymphoid organ of the gut, which contains a large number of immune cells including macrophages. Therefore, it can be assumed that macrophages in the ileum are stimulated by the intestinal bacterial flora and upregulate iNOS expression and that yohimbine might have downregulated iNOS expression. Nevertheless, these results may not be clinically important, because yohimbine in itself did not affect gastrointestinal transit, as shown in previous studies.20 21 32
In the stomach, iNOS expression was not appreciably altered either by lipopolysaccharide or by yohimbine. Nevertheless, yohimbine ameliorated lipopolysaccharide-induced delayed gastric emptying. Several possibilities can be considered for improved gastric emptying. First, the expression of iNOS in the stomach was below the detection limit with the methods used in the present study. Second, as gastric emptying is affected by the relative pressures of the gastric antrum and the proximal small intestine, the improvement of small intestinal motility might consequently have improved gastric emptying. Third, yohimbine might have improved gastric emptying via neural mechanisms.33 34 Endotoxaemia increases catecholamines,35–38 which stimulate 2-adrenoceptors on vagal nerve terminals. This decreases the release of acetylcholine,33 34 39 leading to reduced gastrointestinal motility. Yohimbine might have improved gastric emptying by sustaining the release of acetylcholoine.
One limitation of the present study is that we studied gastrointestinal transit of liquids, and thus transit of semi-solid may differ. Another limitation is that the mechanisms of the improvement with yohimbine were not formally studied. Therefore, our study could not rule out that the endotoxaemia-induced ileus might have been ameliorated by altering inflammatory reactions or haemodynamics in response to yohimbine.29 31 40
Yohimbine has been approved by the Food and Drug Administration for clinical use in the treatment of erectile dysfunction.41 In addition, clinical trials are ongoing to test the effect of yohimbine in colon transit for treating constipation.42 On the basis of this animal study, we suggest that yohimbine could reasonably be used for the treatment of gastrointestinal dysmotility during sepsis in a clinical setting.
|
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
1 Takakura K, Hasegawa K, Goto Y, Muramatsu I. (1997) Nitric oxide produced by inducible nitric oxide synthase delays gastric emptying in lipopolysaccharide-treated rats. Anesthesiology 87:652–7.[CrossRef][Web of Science][Medline]
2 Ceregrzyn M, Kamata T, Yajima T, Kuwahara A. (2001) Biphasic alterations in gastrointestinal transit following endotoxaemia in mice. Neurogastroenterol Motil 13:605–13.[CrossRef][Web of Science][Medline]
3 Calatayud S, Barrachina MD, Garcia-Zaragoza E, Quintana E, Esplugues JV. (2001) Endotoxin inhibits gastric emptying in rats via a capsaicin-sensitive afferent pathway. Naunyn Schmiedebergs Arch Pharmacol 363:276–80.[CrossRef][Web of Science][Medline]
4 De Winter BY, Bredenoord AJ, De Man JG, Moreels TG, Herman AG, Pelckmans PA. (2002) Effect of inhibition of inducible nitric oxide synthase and guanylyl cyclase on endotoxin-induced delay in gastric emptying and intestinal transit in mice. Shock 18:125–31.[CrossRef][Web of Science][Medline]
5 Overhaus M, Togel S, Pezzone MA, Bauer AJ. (2004) Mechanisms of polymicrobial sepsis-induced ileus. Am J Physiol Gastrointest Liver Physiol 287:G685–94.
6 Inglis TJ, Sherratt MJ, Sproat LJ, Gibson JS, Hawkey PM. (1993) Gastroduodenal dysfunction and bacterial colonisation of the ventilated lung. Lancet 341:911–3.[CrossRef][Web of Science][Medline]
7 O'Dwyer ST, Michie HR, Ziegler TR, Revhaug A, Smith RJ, Wilmore DW. (1988) A single dose of endotoxin increases intestinal permeability in healthy humans. Arch Surg 123:1459–64.
8 Moore FA. (1999) The role of the gastrointestinal tract in postinjury multiple organ failure. Am J Surg 178:449–53.[CrossRef][Web of Science][Medline]
9 Fan YP, Chakder S, Gao F, Rattan S. (2001) Inducible and neuronal nitric oxide synthase involvement in lipopolysaccharide-induced sphincteric dysfunction. Am J Physiol Gastrointest Liver Physiol 280:G32–42.
10 Cullen JJ, Caropreso DK, Ephgrave KS, Hemann LL, Hinkhouse MM. (1997) The effect of endotoxin on canine jejunal motility and transit. J Surg Res 67:54–7.[CrossRef][Web of Science][Medline]
11 Eskandari MK, Kalff JC, Billiar TR, Lee KK, Bauer AJ. (1999) LPS-induced muscularis macrophage nitric oxide suppresses rat jejunal circular muscle activity. Am J Physiol 277:G478–86.
12 Helmer KS, West SD, Shipley GL, et al. (2002) Gastric nitric oxide synthase expression during endotoxemia: implications in mucosal defense in rats. Gastroenterology 123:173–86.[CrossRef][Web of Science][Medline]
13 Helmer KS, Chang L, Cui Y, Mercer DW. (2002) Induction of NF-kappaB, IkappaB-alpha, and iNOS in rat gastric mucosa during endotoxemia. J Surg Res 104:46–52.[CrossRef][Web of Science][Medline]
14 Gan HT and Chen JD. (2005) Roles of nitric oxide and prostaglandins in pathogenesis of delayed colonic transit after burn injury in rats. Am J Physiol Regul Integr Comp Physiol 288:R1316–24.
15 Wang B, Glatzle J, Mueller MH, Kreis M, Enck P, Grundy D. (2005) Lipopolysaccharide-induced changes in mesenteric afferent sensitivity of rat jejunum in vitro: role of prostaglandins. Am J Physiol Gastrointest Liver Physiol 289:G254–60.
16 Quintana E, Hernandez C, Alvarez-Barrientos A, Esplugues JV, Barrachina MD. (2004) Synthesis of nitric oxide in postganglionic myenteric neurons during endotoxemia: implications for gastric motor function in rats. FASEB J 18:531–3.
17 Calatayud S, Garcia-Zaragoza E, Hernandez C, et al. (2002) Downregulation of nNOS and synthesis of PGs associated with endotoxin-induced delay in gastric emptying. Am J Physiol Gastrointest Liver Physiol 283:G1360–7.
18 Valk N, Doherty TJ, Blackford JT, Abraha TW, Frazier DL. (1998) Phenylbutazone prevents the endotoxin-induced delay in gastric emptying in horses. Can J Vet Res 62:214–7.[Web of Science][Medline]
19 Doherty TJ, Andrews FM, Abraha TW, Osborne D, Frazier DL. (1999) Metoclopramide ameliorates the effects of endotoxin on gastric emptying of acetaminophen in horses. Can J Vet Res 63:37–40.[Web of Science][Medline]
20 Meisler SD, Doherty TJ, Andrews FM, Osborne D, Frazier DL. (2000) Yohimbine ameliorates the effects of endotoxin on gastric emptying of the liquid marker acetaminophen in horses. Can J Vet Res 64:208–11.[Web of Science][Medline]
21 Kreiss C, Toegel S, Bauer AJ. (2004) Alpha2-adrenergic regulation of NO production alters postoperative intestinal smooth muscle dysfunction in rodents. Am J Physiol Gastrointest Liver Physiol 287:G658–66.
22 Schwarz NT, Kalff JC, Turler A, et al. (2004) Selective jejunal manipulation causes postoperative pan-enteric inflammation and dysmotility. Gastroenterology 126:159–69.[CrossRef][Web of Science][Medline]
23 Uemura K, Tatewaki M, Harris MB, et al. (2004) Magnitude of abdominal incision affects the duration of postoperative ileus in rats. Surg Endosc 18:606–10.[CrossRef][Web of Science][Medline]
24 Asai T, Vickers MD, Power I. (1997) Clonidine inhibits gastric motility in the rat. Eur J Anaesthesiol 14:316–9.[CrossRef][Web of Science][Medline]
25 Asai T, Mapleson WW, Power I. (1997) Differential effects of clonidine and dexmedetomidine on gastric emptying and gastrointestinal transit in the rat. Br J Anaesth 78:301–7.
26 Inada T, Asai T, Yamada M, Shingu K. (2004) A new method using flow cytometry to measure the effects of drugs on gastric emptying and gastrointestinal transit in mice. Arzneimittelforschung 54:557–62.[Medline]
27 Inada T, Asai T, Yamada M, Shingu K. (2004) Propofol and midazolam inhibit gastric emptying and gastrointestinal transit in mice. Anesth Analg 99:1102–6.
28 Turler A, Schwarz NT, Turler E, Kalff JC, Bauer AJ. (2002) MCP-1 causes leukocyte recruitment and subsequently endotoxemic ileus in rat. Am J Physiol Gastrointest Liver Physiol 282:G145–55.
29 Shen HM, Sha LX, Kennedy JL, Ou DW. (1994) Adrenergic receptors regulate macrophage secretion. Int J Immunopharmacol 16:905–10.[CrossRef][Web of Science][Medline]
30 Lunemann JD, Buttgereit F, Tripmacher R, Baerwald CG, Burmester GR, Krause A. (2001) Norepinephrine inhibits energy metabolism of human peripheral blood mononuclear cells via adrenergic receptors. Biosci Rep 21:627–35.[CrossRef][Web of Science][Medline]
31 Weatherby KE, Zwilling BS, Lafuse WP. (2003) Resistance of macrophages to Mycobacterium avium is induced by alpha2-adrenergic stimulation. Infect Immun 71:22–9.
32 Fulop K, Zadori Z, Ronai AZ, Gyires K. (2005) Characterisation of alpha2-adrenoceptor subtypes involved in gastric emptying, gastric motility and gastric mucosal defence. Eur J Pharmacol 528:150–7.[CrossRef][Web of Science][Medline]
33 Tanila H, Kauppila T, Taira T. (1993) Inhibition of intestinal motility and reversal of postlaparotomy ileus by selective alpha 2-adrenergic drugs in the rat. Gastroenterology 104:819–24.[Web of Science][Medline]
34 Taira T, Tanila H, Jyvasjarvi E, Pertovaara A, Kauppila T. (1995) Activation of alpha 2-adrenergic receptors decreases nerve trauma-induced afferent barrage but not autotomy. Brain Res Bull 36:563–7.[CrossRef][Web of Science][Medline]
35 Feuerstein G, Dimicco JA, Ramu A, Kopin IJ. (1981) Effect of indomethacin on the blood pressure and plasma catecholamine responses to acute endotoxaemia. J Pharm Pharmacol 33:576–9.[Web of Science][Medline]
36 Jones SB and Romano FD. (1984) Plasma catecholamines in the conscious rat during endotoxicosis. Circ Shock 14:189–201.[Web of Science][Medline]
37 Palsson J, Ricksten SE, Delle M, Lundin S. (1988) Changes in renal sympathetic nerve activity during experimental septic and endotoxin shock in conscious rats. Circ Shock 24:133–41.[Web of Science][Medline]
38 Murray MJ, Offord KP, Yaksh TL. (1989) Physiologic and plasma hormone correlates of survival in endotoxic dogs: effects of opiate antagonists. Crit Care Med 17:39–47.[Web of Science][Medline]
39 Tack JF and Wood JD. (1992) Actions of noradrenaline on myenteric neurons in the guinea pig gastric antrum. J Auton Nerv Syst 41:67–77.[Medline]
40 Law WR, Mourelatos MG, Krahmer R, Dziki AJ, Lynch WH, Ferguson JL. (1997) Effects of phentolamine or yohimbine on naloxone's actions during endotoxin shock in rats. Shock 7:217–24.[Web of Science][Medline]
41 Dinsmore WW. (2005) Available and future treatments for erectile dysfunction. Clin Cornerstone 7:37–45.[Medline]
42 Clinical trial: effect of yohimbine on colon transit. 2005. Available from http://clinicaltrials.gov/show/NCT00217048.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||