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Biomedical subjects

V Schusdziarra

Publications and source records attributed to V Schusdziarra.

At least 19 recordsLinked to original sources
PubMed2005

[Bariatric surgery. Patient selection and indication].

Successful reduction of body weight in patients with morbid obesity (BMI >40 kg/m(2)) is difficult and on a long-term basis nearly impossible with non-interventional treatment modalities. Surgical therapy is an efficient alternative for these patients. Potential surgical treatment should be carefully evaluated during a 6-month preoperative treatment phase during which indications and contraindications should be evaluated. Qualified postoperative care must be provided.

Adult↗
PubMed2004

[Pharmacotherapy of obesity].

While the intentional modification of eating habits remains the most important measure for losing weight, pharmacological support, in particular with regard to the long-term outcome, can be helpful. Catacholaminergic substances, such as diethylpropion and phenylpropanolamine are restricted by their side effects to short-term application only, and their use makes little sense. The serotoninergic substance sibutramine, which acts on the central nervous system to curb the appetite or enhance the feeling of saturation, and orlistat, which inhibits the assimilation of fat from the bowel, are approved for longer-term treatment of obesity, and lead to an additional loss of 3-5% of the patient's initial weight after one year of use. Thereafter, however, this benefit decreases. Further substances involving new, possibly combinable, approaches are currently under development.

Appetite Depressants↗
PubMed2004

Cholesterol lowering effect of dietary weight loss and orlistat treatment--efficacy and limitations.

BACKGROUND: Orlistat reduces energy uptake by the impairment of fat digestion and some evidence indicates it also lowers plasma cholesterol. AIM: To examine total, low-density lipoprotein- and high-density lipoprotein cholesterol during a weight reducing regimen, and assess the effect of orlistat in lowering cholesterol levels independent of its weight reducing efficacy. METHODS: A total of 448 patients with elevated cholesterol according to cardiovascular risk factors entered a 2 week single-blind run-in period on a hypocaloric diet. Of 384 patients were subsequently assigned double-blind treatment with orlistat (3 x 120 mg/day) or placebo for 6 months in conjunction with the hypocaloric diet. RESULTS: Weight loss in the orlistat group was 7.4 kg vs. 4.9 kg with placebo. Total and low-density lipoprotein cholesterol decreased by 25-30 mg/dL vs. 10-15 mg/dL with placebo. Reduction of cholesterol with orlistat was significantly greater than anticipated from weight loss alone. In patients with cardiovascular risk factors entering the study with lower cholesterol values orlistat was also superior to placebo. On the contrary, reduction of cholesterol concentrations never exceeded 20%. CONCLUSION: Orlistat has a cholesterol lowering efficacy independent of its weight reducing effect. Because of the limited therapeutic effectiveness, patients at high cardiovascular risk should receive rather early additional cholesterol lowering medication during weight loss programmes.

Adolescent↗
PubMed2003

Cannabinoid receptor type 1 modulates excitatory and inhibitory neurotransmission in mouse colon.

The effects of cannabinoid receptor agonists and antagonists on smooth muscle resting membrane potentials and on membrane potentials following electrical neuronal stimulation in a myenteric neuron/smooth muscle preparation of wild-type and cannabinoid receptor type 1 (CB1)-deficient mice were investigated in vitro. Double staining for CB1 and nitric oxide synthase (neuronal) was performed to identify the myenteric CB1-expressing neurons. Focal electrical stimulation of the myenteric plexus induced a fast (f) excitatory junction potential (EJP) followed by a fast and a slow (s) inhibitory junction potential (IJP). Treatment of wild-type mice with the endogenous CB1 receptor agonist anandamide reduced EJP while not affecting fIJP and sIJP. EJP was significantly higher in CB1-deficient mice than in wild-type littermate controls, and anandamide induced no effects in CB1-deficient mice. N-arachidonoyl ethanolamide (anandamide), R-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3,-de]- 1,4-benzoxazin-6-yl]-1-naphtalenylmethanone, a synthetic CB1 receptor agonist, nearly abolished EJP and significantly reduced the fIJP in wild-type mice. N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-caroxamide (SR141716A), a CB1-specific receptor antagonist, was able to reverse the agonist effects induced in wild-type mice. SR141716A, when given alone, significantly increased EJP in wild-type mice without affecting IJP in wild-type and EJP in CB1-deficient mice. Interestingly, SR141716A reduced fIJP in CB1-deficient mice. In the mouse colon, nitrergic myenteric neurons do not express CB1, implying that CB1 is expressed in cholinergic neurons, which is in line with the functional data. Finally, excitatory and inhibitory neurotransmission in the mouse colon is modulated by activation of CB1 receptors. The significant increase in EJP in CB1-deficient mice strongly suggests a physiological involvement of CB1 in excitatory cholinergic neurotransmission.

Animals↗
PubMed2003

Endogenous CCK depresses contractile activity within the ascending myenteric reflex pathway of rat ileum.

The ascending excitatory reflex is an important part of the myenteric reflex. In order to study the ascending neural pathways, isolated segments of rat ileum were stimulated by electrical stimulation of the gut wall (20 V, 3 pulses per second, 1 ms) using platinum electrodes. The excitatory contractile response was recorded using perfused manometric side-hole tubing located 2 and 4 cm orally to the stimulation site. The contractile response to electrical stimulation was abolished by atropine (10(-6) M) or hexamethonium (10(-4) M). The excitatory response increased after administration of the cholecystokinin A (CCK(A)) receptor antagonists lorglumide (3x10(-6) M: +44.1%), devazepide (10(-8) M: +19.4%; 10(-7) M: +30.0%) and SR-27897 (10(-10) M: +21.8%, 10(-8) M: +47.0%, P<0.05, n=8). However, the CCK(B) receptor antagonist L-365,260 also caused a significant increase in the oral excitation (10(-6) M: +27.4%). sCCK-8 caused a significant reduction in the ascending response (10(-8) M: -11.5%) and induced spontaneously occurring contractions at doses ranging from 10(-10)-10(-6) M. CCK-9 significantly increased the ascending response (10(-7) M: +10.9%, P<0.05). However, caerulein (10(-10) M: -25.9%, 10(-8) M: -26.8%; P<0.01) and pentagastrin (10(-10) M: -20.2%, P<0.05; 10(-8) M: -23.7%, P<0.01; 10(-6) M: -28.3%, P<0.001) reduced the ascending contractile response significantly. These data, obtained with potent and highly specific CCK receptor antagonists, demonstrate an inhibitory role of endogenously released CCK within the ascending neural pathway. The data further suggest that exogenously applied CCK-related peptides have different effects on the myenteric reflex which might be due to excitation of the different involved neurons (short and long ascending inter- and motorneurons) in an unphysiological order. Thus in experiments investigating more complex neuronal circuits, experiments with antagonists should be regarded as more specific.

Animals↗
PubMed2003

Impact of carbohydrate and fat intake on weight-reducing efficacy of orlistat.

BACKGROUND: Orlistat treatment of obesity results in a poor long-term weight loss (< 5%) in about 30% of patients. AIM: Total energy and macronutrient intake were examined to assess the effect of a change in eating habits on weight loss. METHODS: Sixty-two patients consumed a hypocaloric diet, together with orlistat (3 x 120 mg/day), for 72 weeks, with a maximal fat allowance of 30% of the energy intake. At regular intervals, food diaries were recorded. RESULTS: Fifty-six patients completed the study and lost 8.5 +/- 0.88 kg (P < 0.001). Energy intake was approximately 1500 kcal/day during the entire study period. In three sub-groups established according to weight loss (1, < 5%; 2, > 5% and < 10%; 3, > 10%), fat intake was within the recommended range in all groups during the first 6 months, but thereafter only in group 3. All groups increased their carbohydrate consumption, with the greatest increase in group 1, which could account for the rapid regain of initially lost body weight in this group. CONCLUSION: At the beginning of a weight management programme in conjunction with orlistat, a low fat intake is advised for an efficient reduction in body weight. Subsequently, in patients with poor long-term weight loss, dietary recommendations must also consider carbohydrate restriction to ensure an adequate hypocaloric diet.

Adolescent↗
PubMed2002

Endomorphins 1 and 2 reduce relaxant non-adrenergic, non-cholinergic neurotransmission in rat gastric fundus.

It is now well established that opioids modulate cholinergic excitatory neurotransmission in the gastrointestinal tract. The aim of the present study was to characterize a possible effect of endomorphins on nonadrenergic, noncholinergic (NANC) relaxant neurotransmission in the rat gastric fundus in vitro. The drugs used in the experiments were the endogenous mu-opioid receptors (MORs) endomorphin 1 and 2 and the mu-opioid receptor antagonist CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2). CTAP left the basal tonus and the spontaneous activity of the preparation unchanged. Electrical field stimulation (EFS) under NANC conditions at frequencies ranging from 0.5 to 16 Hz caused a frequency-dependent relaxant response on the 5-hydoxytryptamine (5-HT) (10(-7) M) precontracted smooth-muscle strip. Both endomorphin 1 and endomorphin 2 significantly reduced this relaxation in a concentration-dependent manner. Endomorphin 1 proved to be more potent in reducing the relaxant responses. The endomorphin effects were significantly reversed by the MOR antagonist CTAP. CTAP itself did not influence the EFS-induced relaxation. In summary, these data provide evidence that the endogenous MOR agonists endomorphin 1 and 2 can reduce nonadrenergic, noncholinergic neurotransmission in the rat gastric fundus smooth muscle via a pathway involving MORs. The physiological relevance of these findings remains to be established, since the data presented suggest that the endomorphins act as neuromodulators within NANC relaxant neurotransmission.

Analgesics, Opioid↗
PubMed2002

Melatonin reduces non-adrenergic, non-cholinergic relaxant neurotransmission by inhibition of nitric oxide synthase activity in the gastrointestinal tract of rodents in vitro.

The aim of the present study was to investigate the effects of melatonin on non-adrenergic, non-cholinergic (NANC) relaxant neurotransmission in the gastrointestinal tract, which is mainly mediated by nitrergic and peptidergic mechanisms. Melatonin (10(-7)-10(-3) M) had no effect on the basal tonus of the rat gastric fundus smooth muscle. Relaxant responses following electrical stimulation(40 V; 0.5 ms pulse duration; 10 s stimulation duration) under NANC conditions on a 5-hydroxytryptamine (5-HT, 10(-7) M) contraction plateau were elicited at frequencies in the range of 0.5-16 Hz. Melatonin significantly reduced these inhibitory NANC responses (16 Hz without melatonin: -103 +/- 6.3%; melatonin 10(-5) M: -80.4 +/- 7.5%; melatonin 10(-4) M: -39.1 +/- 17.1%). Intracellular recording was carried out in a mouse colonic preparation. Electrical neural stimulation of the mouse colonic neurons caused biphasic intracellular hyperpolarization in smooth-muscle cells. The initial fast component is apamin-sensitive, and the following slow component is dependent on nitrergic mechanisms, as it is abolished in the presence of NG-nitro-L-arginine (L-NNA). Melatonin significantly reduced the nitric oxide-dependent slow component of neurally transmitted hyperpolarization, whereas the initial fast component was left unchanged. In a synaptosomal preparation of the enteric nervous system of rat intestine, enzymatic nitric oxide synthase (NOS) activity was significantly reduced by melatonin at concentrations ranging from 10(-7) to 10(-4) M (basal preparation including cofactors: 61.2 +/- 9.4 fmol/mg; melatonin 10(-4) M: 39.2 +/- 6.9 fmol/mg). Reverse transcriptase-polymerase chain reaction (RT-PCR) studies were conducted to investigate the melatonin receptors (mt(1), MT(2) and MT(3)) present in the esophagus, stomach and ileum of the rat. The presence of mt1 mRNA expression alone, but not of mRNA expression for MT(2) or MT(3), was demonstrated in the tissues. In conclusion, this study demonstrates that melatonin reduces the functional inhibitory NANC response. It shows that this effect may be the result of a reduction of the nitrergic component of the smooth-muscle inhibitory junction potential (IJP) and related to direct inhibition of NOS activity in enteric synaptosomes. The presence of mt1 receptor transcripts adds supportive evidence for a possible physiological role of melatonin within the enteric nervous system.

Adrenergic Agents↗
PubMed2002

Okadaic acid inhibits relaxant neural transmission in rat gastric fundus in vitro.

The aim of the present study was to characterize the influence of the phosphatase type 1 and 2A inhibitor okadaic acid on non-adrenergic, non-cholinergic (NANC) neurotransmission in the rat gastric fundus. Okadaic acid (10-6 M), an inhibitor of protein phosphatases 1 and 2A, did not show any influence on the basal tonus or on a contraction plateau induced by 5-HT (10-7 M) within 30 min of observation. When okadaic acid (10-6 M) was applied 10 min prior to 5-HT (10-7 M), the contraction plateau of serotonin was unchanged. To investigate the inhibitory neurotransmission, the muscle strips were pre-contracted using 5-HT (10-7 M), and inhibitory stimuli were applied at the contraction plateau, which was stable over 30 min. The inhibitory effects of vasoactive intestinal peptide (VIP), nitric oxide (NO) and electrical field stimulation (EFS, 40 V, 0.5 ms, frequencies ranging from 0.5 to 16 Hz) were examined. When okadaic acid (10-6 M) was applied prior to EFS-induced NANC relaxation, significant attenuation of the inhibitory response was demonstrated (16 Hz: control: -92.4 +/- 1.9%; okadaic acid 10-7 M: -60.7 +/- 6.1%; okadaic acid 10-6 M: -25.3 +/- 3.4%; n=11; P < 0.01). By contrast, neither the concentration-dependent inhibitory actions of VIP (10-11-10-8 M) (VIP 10-8 M: -100%; VIP 10-8 M + okadaic acid 10-6 M: -89.9 +/- 8.3%; n=8; n.s) nor that of diethylamine nitric oxide (DEA-NO) (3 x 10-7-10-4 M) (DEA-NO 10-4 M: -95.3 +/- 8.4%; DEA-NO 10-4 M + okadaic acid 10-7 M: -98.3 +/- 6.3%; DEA-NO 10-4 M + okadaic acid 10-6 M: 96.5 +/- 7.6%; n=9; n.s.) on 5-HT induced contraction were altered by pre-incubation with okadaic acid (10-6 M). This is the first report that supports the concept that protein phosphatases 1 and 2A may contribute to the regulation of rat gastric fundus motility. The protein phosphatase inhibitor okadaic acid significantly reduces electrically induced inhibitory NANC responses, while leaving direct muscular effects of the inhibitory NANC neurotransmitters VIP and NO unaffected - suggesting a neural site of action. The potential roles of protein phosphatases on NANC neurotransmission remain to be clarified in detail, as this might offer a new pathway for modulating smooth-muscle function.

Animals↗
PubMed2002

Endoscopic treatment of chronic pancreatitis: a multicenter study of 1000 patients with long-term follow-up.

BACKGROUND AND STUDY AIMS: Endoscopic ductal decompression therapy has become an established method of treating patients with painful obstructive chronic pancreatitis. Smaller series, mostly with a medium-term follow-up period, have reported encouraging results. The present analysis presents long-term follow-up data from a large multicenter patient cohort. PATIENTS AND METHODS: Patients with painful chronic pancreatitis and with ductal obstruction due to either strictures and/or stones treated endoscopically at eight different centers underwent follow-up after 2 - 12 years (mean 4.9 years). The patients' clinical data, the rate of technical success, and complications were recorded from the charts. Follow-up data were prospectively obtained using structured questionnaires; the main parameter for evaluating treatment success was a significant reduction in pain (no pain or only weak pain). RESULTS: Follow-up data were obtained from 1018 of 1211 patients treated (84%) with mainly strictures (47%), stones (18%), or strictures plus stones (32%). At the long-term follow-up, 60% of the patients had their endotherapy completed, 16% were still receiving some form of endoscopic treatment, and 24% had undergone surgery. The long-term success of endotherapy was 86% in the entire group, but only 65% in an intention-to-treat analysis. There were no significant differences between the patient groups with regard to either strictures, stones, or both. Pancreatic function was not positively affected by endoscopic therapy. CONCLUSIONS: Endoscopic ductal decompression therapy offers relief of pain in two-thirds of the patients when it is used as the only form of treatment. One-quarter of the patients have to undergo surgery.

Adolescent↗
PubMed2002

Monitoring of tumour glucose metabolism by PET in a phase I study evaluating hormonal therapy in advanced pancreatic cancer.

BACKGROUND: Positron emission tomography (PET) determines therapy-induced changes in tumour glucose utilization. Experimental data indicate that cholecystokinin (CCK) stimulates pancreatic cancer growth. In this study in patients with advanced pancreatic cancer, we evaluated the use of fluorodeoxyglucose (FDG) PET compared with magnetic resonance imaging (MRI) in monitoring hormonal therapy using a highly selective, non-peptide CCK receptor antagonist (SR 27897B). METHODS: Nineteen patients were enrolled on a 28-day course of SR 27897B. Initially, 4 patients received 20 mg of SR 27897B; 9 patients received 40 mg; and 6 patients 80 mg. Imaging studies, including FDG-PET and MRI, were performed at baseline and on days 14 and 28. RESULTS: No significant changes in FDG uptake by the primary tumours were observed. Rate of progression of disease was 11 (61%) of 18 evaluable patients by MRI. Median survival of all patients enrolled was 2.7 months. SR 27897B was fairly well tolerated at all doses tested. The most common side effects were gastrointestinal disorders such as diarrhoea, flatulence and nausea. CONCLUSION: SR 27897B, when used alone at the limited doses employed, led neither to an impairment of tumour glucose metabolism nor to a reduction of tumour size in advanced pancreatic cancer.

Adenocarcinoma↗
PubMed2002

You get what you expect? A critical appraisal of imaging methodology in endosonographic cancer staging.

BACKGROUND AND AIMS: After an initial period of excellent results with newly introduced imaging procedures, the accuracy of most imaging methods declines in later publications. This effect may be due to various methodological factors involved in the research. Using the example of endoscopic ultrasound (EUS), this study aimed to elucidate one of the factors possibly concerned--namely, the extent to which the examiners are adequately blinded. METHODS: Well documented videotapes of EUS examinations of 101 patients with resected tumours of the oesophagus (n=32), stomach (n=33), or pancreas (n=36) were evaluated in three different ways: firstly, retrospective analysis under routine clinical conditions; secondly, evaluation of EUS videotapes in a strictly blinded fashion; and thirdly, evaluation of the same videotapes but with additional information from the video endoscopic appearance (oesophageal/gastric cancer) or from computed tomography results (pancreatic cancer). Histopathological T staging was used as the reference method. RESULTS: The accuracy of EUS in T staging was 73% under routine conditions. This value fell significantly to 53% for the blinded evaluation but increased again to 62% for the unblinded evaluation. The sensitivity of staging T1/T2 tumours was 72% (routine EUS), 59% (blinded EUS), and 70% (unblinded EUS). The respective values for advanced tumours were 85%, 74%, and 72%. CONCLUSIONS: The accuracy of EUS for T staging in clinical practice appears to be lower than has previously been reported. In addition, blinded analysis produced significantly poorer results, which improved when another test was added. It may be speculated that better results with routine EUS obtained in a clinical setting are due to additional sources of information.

Digestive System Neoplasms↗
PubMed2002

Effect of cannabinoids on neural transmission in rat gastric fundus.

The purpose of this study was to examine the possible role of cannabinoids on the neuromuscular function of rat gastric fundus. In addition to possible direct effects on smooth muscle, the influence of cannabinoids on contractile (cholinergic) and relaxant (non-adrenergic, non-cholinergic (NANC)) neural innervation of the rat gastric fundus was investigated in vitro. Neither anandamide (an endogenous cannabinoid receptor agonist) nor Win 55,212-2 and methanandamide (synthetic cannabinoid receptor agonists) nor AM 630 (a cannabinoid receptor antagonist) showed any effect on smooth muscle activity at baseline or after precontraction with 5-hydroxytryptamine (5-HT; 10(-7) M). Electrical field stimulation (EFS) of the smooth muscle preparation (40 V; 5 Hz) caused cholinergically mediated twitch contractions that were abolished by atropine (10(-6) M) or tetrodotoxin (TTX; 10(-6) M). Anandamide and Win 55,212-2 reduced these twitch contractions in a concentration-dependent manner, an effect that could be reversed by the cannabinoid receptor antagonist AM 630 for anandamide, but not for Win 55,212-2. When NANC relaxant neural responses (presence of atropine (10(-6) M) and guanethidine (10(-6) M)) were induced by EFS, the cannabinoid receptor agonists anandamide and Win 55,212-2 reduced the relaxant response, an effect that could be reversed by the cannabinoid receptor antagonist AM 630 for anandamide, but not for Win 55,212-2. When given alone AM 630 caused an increase in the EFS-induced relaxant response. The presence of CB1 and CB2 cannabinoid receptor mRNA within the rat stomach was demonstrated by reverse transcription polymerase chain reaction (RT-PCR). The results of this study indicate that cannabinoids modulate excitatory cholinergic and inhibitory NANC neurotransmission in the rat gastric fundus. Endogenous cannabinoids may play a physiological role only in NANC inhibitory transmission, as AM 630 did not modify the electrically induced cholinergic contraction. The involved cannabinoid receptors are most likely located on neuronal structures. The present study also provides evidence that more than one receptor type is involved.

Animals↗
PubMed2002

Characterizing voltage-dependent Ca(2+) channels coupled to VIP release and NO synthesis in enteric synaptosomes.

In enteric synaptosomes of the rat, the role of voltage-dependent Ca(2+) channels in K(+)-induced VIP release and nitric oxide (NO) synthesis was investigated. Basal VIP release was 39 +/- 4 pg/mg, and cofactor-substituted NO synthase activity was 7.0 +/- 0.8 fmol. mg(-1). min(-1). K(+) depolarization (65 mM) stimulated VIP release Ca(2+) dependently (basal, 100%; K(+), 172.2 +/- 16.2%; P < 0.05, n = 5). K(+)-stimulated VIP release was reduced by blockers of the P-type (omega-agatoxin-IVA, 3 x 10(-8) M) and N-type (omega-conotoxin-GVIA, 10(-6) M) Ca(2+) channels by ~50 and 25%, respectively, but not by blockers of the L-type (isradipine, 10(-8) M), Q-type (omega-conotoxin-MVIIC, 10(-6) M), or T-type (Ni(2+), 10(-6) M) Ca(2+) channels. In contrast, NO synthesis was suppressed by omega-agatoxin-IVA, omega-conotoxin-GVIA, and isradipine by ~79, 70, and 70%, respectively, whereas Ni(2+) and omega-conotoxin-MVIIC had no effect. These findings are suggestive of a coupling of depolarization-induced VIP release primarily to the P- and N-type Ca(2+) channels, whereas NO synthesis is presumably dependent on Ca(2+) influx not only via the P- and N- but also via the L-type Ca(2+) channel. In contrast, none of the Ca(2+) channel blockers affected VIP release evoked by exogenous NO, suggesting that NO induces VIP secretion by a different mechanism, presumably involving intracellular Ca(2+) stores.

Animals↗
PubMed2001

Characterization of vagal input to the rat esophageal muscle.

There is recent morphological evidence for an interaction of autonomic nerve fibers and extrinsic motor nerves of the rat esophagus. The aim of the present study was to investigate a possible functional role of this autonomic innervation of vagal motor fibers on rat esophageal smooth and striated muscle function in vitro. The entire esophagus with both Nn vagi, including the Nn recurrentes, was dissected and placed in an organ bath with oxygenated Krebs-Ringer buffer. Contractile activity was measured in longitudinal direction with a force transducer. Both Nn vagi were placed on a bipolar platinum electrode 2 cm apart from the esophagus. Vagal stimulation, applied for 1 s (40 V, 0.5 ms, 20 Hz) resulted in a biphasic contractile response, which was completely blocked by tetrodotoxin (10(-6) M). The first part consisted of a tetanic striated muscle contraction, which was abolished by tubocurarin (10(-5) M) but unaffected by atropine (10(-6) M) or hexamethonium (10(-4) M). In contrast, the second part was completely abolished by hexamethonium (10(-4) M) and atropine (10(-6) M), whereas tubocurarine (10(-5) M) showed no influence, suggesting a stimulation of preganglionic nerve fibers supplying esophageal smooth muscle (muscularis mucosae). In order to characterize possible autonomic transmitters of the ENS of the esophagus, the following experiments were carried out. The magnitude of the striated muscle response was unaffected by VIP (10(-7) M), 5-HT (10(-6) M) and galanin (10(-8) - 10(-7) M), whereas they caused an inhibition of the smooth muscle response (VIP: -53.8 +/- 4.2%; galanin 10(-8) M: - 18.5 +/- 2.2%; 10(-7) M: -40.4 +/- 2.9%; 5-HT: -78.2 +/- 2.1%). The inhibitory effects of VIP and galanin on smooth muscle were reversible by the antagonists VIP 10-28 and galanin 1-15. In the presence of the nitric oxide synthase (NOS) inhibitor L-NNA (10(-4) M), the smooth and striated muscle contraction were not significantly influenced. Exogenous application of the NO-donor DEA-NO (10(-4) M) reduced the smooth muscle contraction by -81.6 +/- 7.4%, but had no significant effect on the striated muscle contraction. Though immunohistochemical findings are highly suggestive of an nitrergic autonomic modulation of striated muscle contraction by enteric neurons, we could not demonstrate a NO-mediated action on striated muscle activity. Therefore, the physiological relevance of the immunohistochemical findings remain unclear.

Animals↗
PubMed2001

Functional coupling between nitric oxide synthesis and VIP release within enteric nerve terminals of the rat: involvement of protein kinase G and phosphodiesterase 5.

1. The subcellular mechanisms involved in the effect of nitric oxide (NO) on the release of vasoactive intestinal polypeptide (VIP) were examined in synaptosomes isolated from rat small intestine. 2. VIP release was stimulated by the NO donor SNAP (10(-7)-10(-4) M) in an oxyhaemoglobin-sensitive manner. The presence of the guanylate cyclase inhibitor ODQ (10(-5) M), or inhibition of protein kinase G (PKG) by KT 5823 (3 x 10(-6) M) or Rp-8Br-PET-cGMPS (5 x 10(-7) M), antagonized the SNAP-induced VIP release, suggesting a regulatory role of PKG, confirming previously published data from enteric ganglia. This finding was further supported by the fact that direct PKG activation by the stable cGMP analogue 8-pCPT-cGMP stimulated VIP secretion to the same extent as SNAP. 3. Basal VIP secretion was enhanced in the presence of zaprinast, an inhibitor of cGMP-dependent phosphodiesterase 5 (PDE 5), suggesting a functional role of PDE 5 in NO-cGMP signalling. Supportive evidence for this finding was obtained by demonstration of the presence of PDE 5 using RT-PCR. 4. Stimulation of endogenous NO production by L-arginine was also effective in releasing VIP. The effect was abolished in the presence of KT 5823, but was insensitive to oxyhaemoglobin (10(-3) M), suggesting that an interaction between NO and VIP is likely to occur within the same nerve terminal rather than between terminals. 5. NO synthesis was not affected by VIP (10(-8)-10(-5) M), suggesting that there is no feedback regulation between the NO and the VIP pathways. 6. These findings support the notion that an anatomical and functional interrelationship exists between NO and VIP in enteric nerve terminals and that complex signalling mechanisms involving PKG and PDE 5 contribute to NO-induced VIP release.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Distinct expression of splice variants of neuronal nitric oxide synthase in the human gastrointestinal tract.

BACKGROUND & AIMS: Changes of neuronal nitric oxide synthase (nNOS) expression have been linked to several human gastrointestinal disorders such as achalasia, diabetic gastroparesis, and hypertrophic pyloric stenosis. They could be caused by differential transcriptional control or alternative splicing generating different nNOS proteins. The aims of this study were to characterize 5'-splice variants, promoter usage, and site-specific expression of nNOS in the human gastrointestinal tract. METHODS: 5'-Splice variants were characterized by immunoblotting, reverse-transcription polymerase chain reaction, 5'-rapid amplification of complementary DNA ends, and Southern blotting. Genomic analysis was performed by rapid amplification of genomic ends, followed by reporter gene assays. RESULTS: Six different 5'-splice variants of nNOS-messenger RNA were identified showing specific expressions at various sites of the human gastrointestinal tract. Three variants encode for nNOSalpha, which has a specific N-terminal PDZ/GLGF domain and interaction sites for regulatory proteins. Two variants encode for nNOSbeta and 1 for nNOSgamma, which both lack the protein-binding domains of nNOSalpha. In addition to 2 known first exons, a novel first exon of human nNOS with a separate functionally active downstream promoter and multiple binding sites for transcription factors was identified and characterized. CONCLUSIONS: Six 5'-mRNA splice variants of nNOS encoding 3 different nNOS proteins are expressed in the human gut. The differential expression of these proteins could be implicated in different biological functions.

Alternative Splicing↗