[Quality of health worker-patient communication: What are the benefits of integrating mental health into front-line services in Guinea?] / Qualité de la communication soignant-patient : quels apports de l'intégration de la santé mentale dans des services de première ligne en Guinée ?

BACKGROUND: Patient-centred care presupposes communication based on empathy, active listening and dialogue. Our study examines the effects of integrating mental health in multi-purpose health centres on health workers' communication with patients who consult for problems unrelated to mental health. The objective is to compare the quality of communication in health centres where staff have received specific training in the management of mental disorders (SM+) compared to those without such training (SM-). METHODS: The study was conducted among 18 health workers in charge of primary curative consultations in 12 non-governmental health centers in Guinea: 7 health workers in 4 SM+ health centers and 11 health workers in 8 SM- health centres. The study is based on mixed methods: observation, semi-structured and group interviews. The Global Consultation Rating Scale (GCRS) was applied to assess patient-centered communication. RESULTS: The SM+ GCRS scores obtained by SM+s during observations are generally higher than the SM- scores. The odds of having a "good quality" consultation are almost 3 times higher in SM+ than in SM- for some steps in the consultation process. The SM+ discourse is more patient-centered, and differs from the more biomedical discourse of SM-. SM- health workers do not consider all of the stages of a patient-centred consultation to be applicable and recommend "leapfrogging". On the contrary, SM+ health workers consider all stages to be important and are convinced that the integration of mental health has improved their communication through the training they have received and the practice of caring for persons with mental disorders. CONCLUSION: The integration of mental health into primary care provision represents an opportunity to improve the quality of care in its "patient-centred care" dimension. That said, optimal development of patient-centred care presupposes favorable structural conditions.

Inhibition of the spindle assembly checkpoint kinase TTK enhances the efficacy of docetaxel in a triple-negative breast cancer model.

BACKGROUND: Triple-negative breast cancers (TNBC) are considered the most aggressive type of breast cancer, for which no targeted therapy exists at the moment. These tumors are characterized by having a high degree of chromosome instability and often overexpress the spindle assembly checkpoint kinase TTK. To explore the potential of TTK inhibition as a targeted therapy in TNBC, we developed a highly potent and selective small molecule inhibitor of TTK, NTRC 0066-0. RESULTS AND CONCLUSIONS: The compound is characterized by long residence time on the target and inhibits the proliferation of a wide variety of human cancer cell lines with potency in the same range as marketed cytotoxic agents. In cell lines and in mice, NTRC 0066-0 inhibits the phosphorylation of a TTK substrate and induces chromosome missegregation. NTRC 0066-0 inhibits tumor growth in MDA-MB-231 xenografts as a single agent after oral application. To address the effect of the inhibitor in breast cancer, we used a well-defined mouse model that spontaneously develops breast tumors that share key morphologic and molecular features with human TNBC. Our studies show that combination of NTRC 0066-0 with a therapeutic dose of docetaxel resulted in doubling of mouse survival and extended tumor remission, without toxicity. Furthermore, we observed that treatment efficacy is only achieved upon co-administration of the two compounds, which suggests a synergistic in vivo effect. Therefore, we propose TTK inhibition as a novel therapeutic target for neoadjuvant therapy in TNBC.

Epidemiological characteristics of a population visiting a patient-centered informative website about irritable bowel syndrome.

Background and aims: Irritable bowel syndrome (IBS) is a chronic disorder characterized by abdominal pain and an altered bowel habit. The aim of this study was to evaluate the characteristics of a population visiting a patient-centered informative website about IBS. Methods: Five digital surveys were used to assess the Rome IV criteria, red flag symptoms, healthcare use, psychological comorbidities, quality of life, symptom severity, diet, physical activity. Patients were divided into a Rome positive and negative population with the Rome positive population being further subtyped based on dominant stool pattern. Results: Red flag symptoms (42%) and comorbid psychological disorders (65% anxiety and 39% depression) were common. Despite consulting health care professionals and therapy, most patients (96%) still experienced moderate to severe symptoms with an average impact on quality of life. 73% performed regular physical exercise and 25% of the Rome positive population followed the FODMAP diet. Almost all participants consulted a health care professional at one point in time and used some form of therapy. 54% of the patients believed there is generally sufficient information available and 57% thinks that their physician takes IBS seriously. However, only 41% thinks that their physician has sufficient knowledge about IBS. Conclusions: This study underlines the importance of a thorough characterization of IBS patients. Furthermore, patients expressed an urgent need for high quality information and education for both health care professionals and patients.

Light and electron microscopic radioautography of hepatic cell nucleoli in mice treated with actinomycin d.

Nucleolar partition induced by actinomycin D was used to demonstrate some aspects of nucleolar RNA synthesis and release in mouse hepatic cells, with light and electron microscopic radioautography. The effect of the drug on RNA synthesis and nucleolar morphology was studied when actinomycin D treatment preceded labeling with tritiated orotic acid. Nucleolar partition, consisting of a segegration into granular and fibrillar parts was visible if a dosage of 25 microg of actinomycin D was used, but nucleolar RNA was still synthesized. After a dosage of 400 microg of actinomycin D, nucleolar RNA synthesis was completely stopped If labeling with tritiated orotic acid preceded treatment with 400 microg of actinomycin D, labeled nucleolar RNA was present 15 min after actinomycin D treatment while high resolution radioautography showed an association of silver grains with the granular component. At 30 min after actinomicyn D treatment all labeling was lost. Since labeling was associated with the granular component the progressive loss of label as a result of actinomycin D treatment indicated a release of nucleolar granules. The correlation between this release and the loss of 28S RNA from actinomycin D treated nucleoli as described in the literature is discussed.

TRPV1 receptors on unmyelinated C-fibres mediate colitis-induced sensitization of pelvic afferent nerve fibres in rats.

Patients with inflammatory bowel disease often suffer from gastrointestinal motility and sensitivity disorders. The aim of the current study was to investigate the role of transient receptor potential of the vanilloid type 1 (TRPV1) receptors in the pathophysiology of colitis-induced pelvic afferent nerve sensitization. Trinitrobenzene sulphate (TNBS) colitis (7.5 mg, 30% ethanol) was induced in Wistar rats 72 h prior to the experiment. Single-fibre recordings were made from pelvic nerve afferents in the decentralized S1 dorsal root. Fibres responding to colorectal distension (CRD) were identified in controls and rats with TNBS colitis. The effect of the TRPV1 antagonist N-(4-tertiarybutylphenyl)-4-(3-chlorophyridin-2-yl)tetrahydropyrazine-1(2H)carboxamide (BCTC; 0.25-5 mg kg(-1)) or its vehicle (hydroxypropyl-beta-cyclodextrin) was tested on the afferent response to repetitive distensions (60 mmHg). Immunocytochemical staining of TRPV1 and NF200, a marker for A-fibre neurons, was performed in the dorsal root ganglia L6-S1. TNBS colitis significantly increased the response to colorectal distension of pelvic afferent C-fibres. BCTC did not significantly affect the C-fibre response in controls, but normalized the sensitized response in rats with colitis. TNBS colitis increased the spontaneous activity of C-fibres, an effect which was insensitive to administration of BCTC. TNBS colitis had no effect on Adelta-fibres, nor was their activity modulated by BCTC. TNBS colitis caused an immunocytochemical up-regulation of TRPV1 receptors in the cell bodies of pelvic afferent NF200 negative neurons. TRPV1 signalling mediates the colitis-induced sensitization of pelvic afferent C-fibres to CRD, while Adelta-fibres are neither sensitized by colitis nor affected by TRPV1 inhibition.

Study on the cyclic GMP-dependency of relaxations to endogenous and exogenous nitric oxide in the mouse gastrointestinal tract.

BACKGROUND AND PURPOSE: cGMP mediates nitrergic relaxations of intestinal smooth muscle, but several studies have indicated that cGMP-independent mechanisms may also be involved. We addressed this contention by studying the effect of ODQ and ns2028, specific inhibitors of soluble guanylate cyclase, on nitrergic relaxations of the mouse gut. EXPERIMENTAL APPROACH: Mouse gastric fundus and small intestinal muscle preparations were mounted in organ baths to study relaxations to exogenous NO, NO donors and electrical field stimulation (EFS) of enteric nerves. KEY RESULTS: In gastric fundus longitudinal muscle strips, ODQ and NS2028 abolished the L-nitroarginine-sensitive relaxations to EFS and the relaxations to NO and NO donors, glyceryl trinitrate (GTN), SIN-1 and sodium nitroprusside (SNP). EFS of intestinal segments and muscle strips showed L-nitroarginine-resistant relaxations, which were abolished by the purinoceptor blocker suramin. In the presence of suramin, ODQ and NS2028 abolished all relaxations to EFS in intestinal segments and strips. ODQ and NS2028 abolished the relaxations to exogenous NO and to the NO donors GTN, SIN-1 and SNP in circular and longitudinal intestinal muscle strips. Intestinal segments showed residual relaxations to NO and GTN. CONCLUSIONS AND IMPLICATIONS: Our results indicate that relaxations to endogenous NO in the mouse gastric fundus and small intestine are completely dependent on cGMP. ODQ and NS2028 incompletely blocked nitrergic relaxations to exogenous NO in intact intestinal segments. However, it is unlikely that this is due to the involvement of cGMP-independent pathways because ODQ and NS2028 abolished all relaxations to endogenous and exogenous NO in intestinal muscle strips.

Experimental pancreatitis disturbs gastrointestinal and colonic motility in mice: effect of the prokinetic agent tegaserod.

Acute pancreatitis remains a potentially life-threatening disease associated with gastrointestinal motility disturbances. Prokinetic agents may be useful to overcome these motility disturbances. In this study, we investigated the effect of acute necrotizing pancreatitis (ANP) on gastrointestinal motility in female mice and evaluated the effect of tegaserod, a prokinetic 5-hydroxytryptamine-4 (5HT4) receptor agonist. ANP was induced by feeding mice a choline-deficient ethionine-supplemented diet during 72 h. In vivo intestinal motility was measured as the geometric centre (GC) of 25 glass beads 30-120-360 min after gavage. Colonic peristaltic activity was studied using a modified Trendelenburg set-up. ANP significantly decreased GC 30-120-360 min after bead gavage, associated with a significant increase of myeloperoxidase in the proximal small intestine and colon, but not in the stomach or distal small intestine. Tegaserod significantly ameliorated GC 360 min after bead gavage in control and pancreatitis mice. In isolated colonic segments, ANP significantly decreased the amplitude of peristaltic waves and increased the interval between peristaltic contractions. Tegaserod normalized the disturbed interval. In conclusion, ANP impairs gastric, small intestinal and colonic motility in mice. Tegaserod improves ANP-induced motility disturbances in vivo and in vitro, suggesting a therapeutic benefit of prokinetic 5HT4 receptor agonists in the treatment of pancreatitis-induced ileus.

Novel nervous system mechanisms in visceral pain.

Visceral hypersensitivity is an important factor underlying abdominal pain in functional gastrointestinal disorders such as irritable bowel syndrome (IBS) and can result from aberrant signaling from the gut to the brain or vice versa. Over the last two decades, research has identified several selective, intertwining pathways that underlie IBS-related visceral nociception, including specific receptors on afferent and efferent nerve fibers such as transient receptor potential channels (TRP) channels, opioid, and cannabinoid receptors. In this issue of Neurogastroenterology and Motility Gil et al. demonstrate that in an animal model with reduced descending inhibitory control, the sympathetic nervous system outflow is enhanced, contributing to visceral and somatic hypersensitivity. They also provide evidence that interfering with the activation of adrenergic receptors on sensory nerves can be an interesting new strategy to treat visceral pain in IBS. This mini-review places these findings in a broader perspective by providing an overview of promising novel mechanisms to alter the nervous control of visceral pain interfering with afferent or efferent neuronal signaling.

Irritable bowel syndrome and visceral hypersensitivity : risk factors and pathophysiological mechanisms.

Irritable bowel syndrome (IBS) is a common functional gastro-intestinal disorder, characterized by abdominal pain and altered intestinal motility. Visceral hypersensitivity is an important hallmark feature of IBS and is believed to underlie abdominal pain in patients with IBS. The two main risk factors associated with the development of IBS are gastrointestinal inflammation and psychological distress. On a peripheral level, visceral sensitivity seems to be modulated by several mechanisms. Immune cells in the mucosal wall, such as mast cells, and enterochromaffin cells may sensitize afferent nerves by release of their mediators. Furthermore, increased mucosal permeability, altered intestinal microflora and dietary habits may contribute to this feature. On a central level, an increased prevalence of psychiatric comorbidities is demonstrated in IBS patients, alongside alterations in the hormonal brain-gut axis, increased vigilance towards intestinal stimuli and functional and structural changes in the brain. The pathogenesis of IBS is complicated and multifactorial and the treatment remains clinically challenging. Dietary measures and symptomatic control are the cornerstones for IBS treatment and may be sufficient for patients experiencing mild symptoms, alongside education, reassurance and an effective therapeutic physician-patient relationship. New pharmacological therapies are aimed at interfering with mediator release and/or blockade of the relevant receptors within the gut wall, while modulation of the intestinal flora and diet may also be of therapeutic benefit. Tricyclic anti-depressants and serotonin reuptake inhibitors act both on a central and peripheral level by modulating pain signalling pathways.

Regional differences in gastrointestinal motility disturbances during acute necrotising pancreatitis.

Patients with acute pancreatitis often suffer from intestinal motility disturbances but the mechanism of this dysfunction is largely unknown. We studied the effect of acute necrotising pancreatitis (ANP) on in vivo gastrointestinal motility and in vitro intestinal contractility in mice. ANP was induced non-invasively by feeding young female mice a choline-deficient ethionine-supplemented (CDE) diet during 72 h. Gastric emptying and intestinal transit were measured in vivo 15 min after intragastric gavage of a semiliquid Evans blue bolus. Gastric and intestinal neuromuscular function was determined in vitro on isolated muscle strips. ANP significantly decreased gastric emptying from 61.2 +/- 9.8 to 34.9 +/- 7.1% and intestinal transit from 63.4 +/- 5.6 to 32.5 +/- 5.4%. ANP did not affect receptor-dependent and receptor-independent gastric muscle contractions except the contractions to substance P, which were slightly inhibited. In intestinal muscle strips, ANP significantly decreased contractions to EFS, carbachol, PGF(2alpha), substance P and KCl. Our results show that ANP delays gastric emptying in vivo, associated with a specific reduction in substance P contractility in vitro. ANP also impairs intestinal transit in vivo, associated with a non-specific reduction of intestinal contractility in vitro. We conclude that ANP impairs gastrointestinal motility in mice with underlying regional differences in the pathogenic mechanisms.

Role of oxidative stress in the pathogenesis of septic ileus in mice.

We investigated the role of oxidative stress in the pathogenesis of septic ileus. Sepsis was induced by intraperitoneal (i.p.) injection of lipopolysaccharides (LPS, 20 mg kg(-1)) in mice. The effect of two i.p. injections of superoxide dismutase [polyethylene glycol (PEG)-SOD, 4000 U kg(-1)] and catalase (PEG-CAT, 15,000 U kg(-1)) was investigated on gastric emptying, intestinal transit and total nitrite plasma concentrations. We also performed immunohistochemical experiments on gastric and ileal tissue. LPS significantly delayed gastric emptying and intestinal transit while plasma nitrite levels increased. Polyethylene glycol (PEG)-SOD reversed the endotoxin-induced delay in gastric emptying and improved the delay in intestinal transit without effect on plasma nitrite levels. PEG-CAT slightly improved the delay in gastric emptying without effect on intestinal transit. Immunohistochemistry showed the presence of nitrotyrosine (NT) and 4-hydroxy-2-nonenal (HNE) in the gastric and ileal mucosa of LPS-treated mice. Treatment with PEG-SOD or PEG-CAT of LPS mice diminished the presence of NT or HNE in both tissues. In addition, LPS induced a significant increase in inducible nitric oxide synthase (iNOS)-positive residential macrophages in the external musculature of stomach and ileum, which significantly decreased after PEG-SOD or PEG-CAT treatment. The present results support a role for oxidative and nitrosative stress in the pathogenesis of septic ileus in mice.

Histamine H4 receptors in the gastrointestinal tract.

Histamine is a well-established mediator involved in a variety of physiological and pathophysiological mechanisms and exerts its effect through activation of four histamine receptors (H1-H4). The histamine H4 receptor is the newest member of this histamine receptor family, and is expressed throughout the gastrointestinal tract as well as in the liver, pancreas and bile ducts. Functional studies using a combination of selective and non-selective H4 receptor ligands have rapidly increased our knowledge of H4 receptor involvement in gastrointestinal processes both under physiological conditions and in models of disease. Strong evidence points towards a role for H4 receptors in the modulation of immune-mediated responses in gut inflammation such as in colitis, ischaemia/reperfusion injury, radiation-induced enteropathy and allergic gut reactions. In addition, data have emerged implicating H4 receptors in gastrointestinal cancerogenesis, sensory signalling, and visceral pain as well as in gastric ulceration. These studies highlight the potential of H4 receptor targeted therapy in the treatment of various gastrointestinal disorders such as inflammatory bowel disease, irritable bowel syndrome and cancer.

Mechanisms contributing to visceral hypersensitivity: focus on splanchnic afferent nerve signaling.

BACKGROUND: Visceral hypersensitivity is a main characteristic of functional bowel disorders and is mediated by both peripheral and central factors. We investigated whether enhanced splanchnic afferent signaling in vitro is associated with visceral hypersensitivity in vivo in an acute and postinflammatory rat model of colitis. METHODS: Trinitrobenzene sulfonic acid (TNBS)-colitis was monitored individually by colonoscopy to confirm colitis and follow convalescence and endoscopic healing in each rat. Experiments were performed in controls, rats with acute colitis and in postcolitis rats. Colonic afferent mechanosensitivity was assessed in vivo by quantifying visceromotor responses (VMRs), and by making extracellular afferent recordings from splanchnic nerve bundles in vitro. Multiunit afferent activity was classified into single units identified as low threshold (LT), wide dynamic range (WDR), high threshold (HT), and mechanically insensitive afferents (MIA). KEY RESULTS: During acute TNBS-colitis, VMRs were significantly increased and splanchnic nerve recordings showed proportionally less MIA and increased WDR and HT afferents. Acute colitis gave rise to an enhanced spontaneous activity of both LT and MIA and augmented afferent mechanosensitivity in LT, WDR and HT afferents. Postcolitis, VMRs remained significantly increased, whereas splanchnic nerve recordings showed that the proportion of LT, WDR, HT and MIA had normalized to control values. However, LT and MIA continued to show increased spontaneous activity and WDR and HT remained sensitized to colorectal distension. CONCLUSIONS & INFERENCES: Visceral hypersensitivity in vivo is associated with sensitized splanchnic afferent responses both during acute colitis and in the postinflammatory phase. However, splanchnic afferent subpopulations are affected differentially at both time points.

T-cell membrane characteristics of "mycosis cells" in the skin and lymph node.

In some patients with mycosis fungoides atypical cells ("mycosis cells") are found in the blood. Recently the T-cell membrane characteristics of these atypical cells have been described. In this paper the results of a study of the atypical cells isolated from the lymph nodes and the skin lesions of three patients with mycosis fungoides are presented. Using electron microscopy, it could be demonstrated that the atypical cells formed rosettes with uncoated sheep red blood cells, but not with antibody-complement-coated sheep erythrocytes, indicating the T-cell membrane characteristics of the atypical cells.

Effect of potassium channel blockade and alpha 2-adrenoceptor activation on the release of nitric oxide from non-adrenergic non-cholinergic nerves.

1. Using a superfusion bioassay cascade, we studied the effect of K+ channel blockers and alpha 2-adrenoceptor agents on the release of a transferable factor, previously characterized as nitric oxide (NO) or a nitric oxide-related substance (NO-R), in response to non-adrenergic non-cholinergic (NANC) nerve stimulation in the canine ileocolonic junction (ICJ). 2. The non-selective K+ channel blockers, 4-aminopyridine (4-AP, 50 microM) and tetraethylammonium (TEA, 1 mM) and the more selective blocker of Ca(2+)-activated K+ channels, charybdotoxin (Leiurus quinquestriatus venom (LQV), 0.4 microgram ml-1), significantly enhanced the release of NO-R induced by low frequency stimulation (2-4 Hz). In the presence of 4-AP and TEA, the release of NO-R was nearly abolished by tetrodotoxin (2 microM), and by L-NG-nitroarginine (L-NOARG, 0.1 mM). Relaxations induced by direct injection of exogenous NO (5-50 pmol) or nitroglycerin (GTN, 10-30 pmol) onto the rabbit aortic detector ring were not affected. 3. The alpha 2-adrenoceptor agonist, UK-14,304 (0.3 microM) inhibited the release of NO-R induced by low (2-4 Hz), but not that induced by high (16 Hz), frequency stimulation. This inhibitory effect was completely reversed by the alpha 2-adrenoceptor antagonist, yohimbine (0.3 microM). Neither UK-14,304 nor yohimbine affected the relaxations induced by exogenous NO (5 pmol) or GTN (10 pmol) on the aortic detector ring.3+

Prejunctional modulation of the nitrergic innervation of the canine ileocolonic junction via potassium channels.

1. The effects of different K+ channel blockers were studied on nitric oxide (NO)-mediated non-adrenergic non-cholinergic (NANC) relaxations in the canine ileocolonic junction. 2. The non-selective blockers of K+ channels, 4-aminopyridine (4-AP) and tetraethylammonium (TEA) and the blocker of large conductance Ca(2+)-activated K+ channels, charybdotoxin, potently enhanced the NANC relaxations induced by low frequency stimulation. The blocker of small conductance Ca(2+)-activated K+ channels, apamin, had no effect on electrically-induced NANC relaxations. 3. NANC nerve-mediated relaxations induced by adenosine 5'-triphosphate (ATP), acetylcholine (ACh) and gamma-aminobutyric acid (GABA) were significantly enhanced by 4-AP and charybdotoxin but not by apamin. TEA significantly enhanced the NANC relaxations in response to GABA and ATP while that in response to ACh was abolished. 4. None of the K+ channel blockers had an effect on the dose-response curve to NO, on the noradrenaline-induced contraction or on the relaxation to nitroglycerine (GTN). 5. From these results we conclude that inhibition of prejunctional K+ channels increases the nitrergic relaxations induced by electrical and chemical receptor stimulation of NANC nerves and thus suggests a regulatory role for these prejunctional K+ channels in the release of NO from NANC nerves in the canine ileocolonic junction.

Alpha 2-adrenoceptor-mediated modulation of the nitrergic innervation of the canine isolated ileocolonic junction.

1. The effects of specific alpha-adrenoceptor agonists and antagonists on electrically-evoked non-adrenergic non-cholinergic (NANC) relaxations, previously demonstrated as nitrergic, were investigated in isolated circular muscle strips of the canine ileocolonic junction. 2. During a substance P-induced contraction and in the presence of atropine and guanethidine, the specific alpha 1-adrenoceptor agonist, phenylephrine and antagonist, prazosin, as well as the specific alpha 2-adrenoceptor antagonist, yohimbine, had no effect on the NANC relaxations evoked by electrical field stimulation. In contrast, clonidine and the more specific alpha 2-adrenoceptor agonist, UK-14,304, significantly reduced the electrically-induced relaxations, preferentially those in response to low frequency stimulation. The inhibitory effect of UK-14,304 on these relaxations was antagonized by yohimbine. 3. During a noradrenaline-induced contraction, clonidine, but not UK-14,304 significantly augmented the relaxations to electrical stimulation. 4. The adrenoceptor agonists and antagonists used had no effect on concentration-response curves to NO or on the relaxation induced by nitroglycerin. 5. These results indicate that stimulation of prejunctional alpha 2-adrenoceptors inhibits the nitrergic NANC relaxations induced by field stimulation and thus suggest prejunctional regulation of nitric oxide release via alpha 2-adrenoceptors in the canine ileocolonic junction.

Bioassay of nitric oxide released upon stimulation of non-adrenergic non-cholinergic nerves in the canine ileocolonic junction.

1. The release and the nature of the inhibitory non-adrenergic non-cholinergic (NANC) neurotransmitter was studied in the canine ileocolonic junction. A circular muscle strip of the canine ileocolonic junction served as donor tissue in a superfusion bioassay in which rings of rabbit aorta with the endothelium removed served as detector tissue. 2. The ileocolonic junction released a labile factor with vasodilator activity upon stimulation of non-adrenergic non-cholinergic (NANC) nerves in response to electrical impulses and the nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium (DMPP). This release was respectively frequency- and concentration-dependent. 3. The release was reduced by the blocker of neuronal conductance, tetrodotoxin, and by the inhibitor of the nitric oxide (NO) biosynthesis NG-nitro-L-arginine. The biological activity was enhanced by superoxide dismutase and eliminated by haemoglobin. Hexamethonium abolished only the release in response to DMPP. 4. Injection of adenosine 5'-triphosphate (ATP) or vasoactive intestinal polypeptide (VIP) onto the cascade induced relaxations of the rabbit aorta but they were different from those induced by NO or the transferable factor. 5. Based on organ bath experiments in which the reactivity of different parts of the circular smooth muscle layer of the ileocolonic junction was investigated, a muscle strip of superficial circular muscle with submucosa was chosen as the detector strip in the bioassay cascade. 6. The ileocolonic junction dose-dependently relaxed in response to nitroglycerin and NO. NO was much more potent in the rabbit aorta than in the canine ileocolonic junction. 7. In conclusion, our results demonstrate the release of a transferable vasorelaxant factor in response to NANC nerve stimulation which behaves pharmacologically like NO but not like ATP or VIP. Therefore, we suggest that NO or a NO releasing substance is the inhibitory NANC neurotransmitter in the canine ileocolonic junction.

Comparison of the pharmacological profile of S-nitrosothiols, nitric oxide and the nitrergic neurotransmitter in the canine ileocolonic junction.

1. In organ bath experiments, hydroquinone (30-100 microM) and hydroxocobalamin (30-100 microM) concentration-dependently inhibited the relaxations induced by NO (0.3-30 microM) but not those by nitroglycerin (GTN, 1 microM) in the canine ileocolonic junction (ICJ). Hydroxocobalamin reduced the relaxation to low frequency (2 Hz) stimulation of the non-adrenergic, non-cholinergic (NANC) nerves, whereas hydroquinone only reduced the NANC nerve-mediated relaxations to electrical stimulation at 16 Hz, 0.5 ms. 2. Relaxations to S-nitroso-L-cysteine (CysNO, 1-30 microM), or S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 1-30 microM) were not inhibited by hydroquinone (30-100 microM), hydroxocobalamin (30-100 microM), pyrogallol (30-100 microM) or L-cysteine (1-3 microM). Hydroquinone (100 microM) only reduced the relaxation to 10 microM CysNO. Hydroxocobalamin, but not hydroquinone, pyrogallol or L-cysteine, potentiated the relaxations to the lowest concentration (1 microM) of S-nitrosoglutathione (GSNO, 1-30 microM). 3. In the superfusion bioassay, hydroquinone (100 microM) and hydroxocobalamin (1 microM) concentration-dependently inhibited the biological activity of authentic NO (1-4 pmol) to the same extent as that of the transferable nitrergic factor, released from the canine ICJ in response to NANC nerve stimulation (8-16 Hz, 2 ms). Responses to GTN (10 pmol) or adenosine 5'-triphosphate (10 nmol) were not affected. 4. In conclusion, the nitrosothiols CysNO, SNAP and GSNO relax the canine ileocolonic junction, but these relaxations, pharmacologically, behave differently from the NANC nerve-mediated relaxations. From the bioassay experiments, we conclude that the nitrergic factor, released in response to NANCnerve stimulation of the canine ICJ, behaves pharmacologically like NO but not like a nitrosothiol.Therefore, we suggest NO, and not CysNO, SNAP or GSNO as the inhibitory NANC neurotransmitter in the canine ICJ.

Ca2+ dependency of the release of nitric oxide from non-adrenergic non-cholinergic nerves.

1. The role of Ca2+ in nitrergic neurotransmission was studied in the canine ileocolonic junction. 2. The specific N-type voltage-sensitive Ca2+ channel blocker omega-conotoxin GVIA (CTX, 10-100 nM) significantly reduced the electrically-evoked (2-16 Hz, 1-2 ms pulse width) non-adrenergic non-cholinergic (NANC) relaxations, preferentially affecting those to low frequency stimulation, in circular muscle strips of the ileocolonic junction. In contrast, the nerve-mediated NANC-relaxations in response to acetylcholine (30 microM), gamma-aminobutyric acid (100 microM) and adenosine 5'-triphosphate (100 microM), as well as the relaxations to nitric oxide (NO) (3-10 microM) and nitroglycerin (1 microM), remained unaffected. 3. A NO-related substance (NO-R), released from the ileocolonic junction in response to NANC nerve stimulation (4 and 16 Hz, 2 ms pulse width), was assayed with a superfusion bioassay cascade. CTX (50 nM) reduced the release of NO-R induced by electrical impulses (4 Hz: from 18 +/- 4% to 6 +/- 4%; 16 Hz: from 33 +/- 2% to 14 +/- 4%, n = 5), but not that in response to the nicotinic receptor agonist, 1,1-dimethyl-4-phenylpiperazinium (DMPP, 0.3 mM). In Ca(2+)-free medium, the release of NO-R evoked by electrical impulses or DMPP was inhibited. The L-type Ca2+ channel blockers verapamil (1-3 microM) and nifedipine (1 microM) had no effect. 4. From these results we conclude that the release of NO-R in response to NANC nerve stimulation is Ca(2+)-dependent. The electrically-evoked release of NO-R results from Ca2+ entry through CTX-sensitive N-type voltage-sensitive Ca2+ channels, whereas that induced by nicotinic receptor activation involves CTX-insensitive Ca2+ channels, different from the L- or N-type.