Role of nitric oxide in non-adrenergic, non-cholinergic nerve-mediated relaxation in dog duodenal longitudinal muscle strips

Transmural electrical stimulation caused a relaxation in the dog duodenal longitudinal muscle strips treated with atropine, phentolamine and propranolol, which was abolished by tetrodotoxin. The relaxation was suppressed by oxyhemoglobin and L-NG-nitro-arginine (L-NA), but not influenced by D-NA. Inhibition by L-NA was reversed by L-arginine, but not by D-arginine. The response to transmural electrical stimulation was similar to that caused by nitric oxide or nitroglycerin. Nitric oxide appears to participate importantly in non-adrenergic, non-cholinergic nerve-mediated relaxation.

Cysteamine-induced duodenal ulcer and the hepatoduodenal branch of the vagus nerve

We investigated the role of the autonomic nervous system in gastric acid secretion, somatostatin concentration and PAS-positive mucus production in Brunner's glands in cysteamine-induced duodenal ulcer. Vagotomized rats were used. No ulcers occurred in the groups with vagotomies of the hepatoduodenal, truncal or gastric branches after cysteamine administration. However, in the hepatoduodenal branch vagotomized group, there was an increase in gastric acid secretion after cysteamine administration. A similar increase was observed in the control group, but the decreases in somatostatin concentration and PAS-positive mucus seen in the control group were not found in the hepatoduodenal vagotomized group. These results suggest that the hepatoduodenal branch of the vagus nerve might play an important role in the ulcerogenic process of cysteamine-induced duodenal ulcer.

Inhibitory effects of cholecystokinin develop through interaction with duodenal signals

I previously reported that cholecystokinin octapeptide (CCK-8) had little effect on feeding motivation as indexed by runway performance, but that substantial impairment resulted from the interaction of CCK-8 and prefeeding of sucrose. If the sucrose was sham-fed, potentiation of the effect of CCK-8 was seen only after large doses. The current experiments examined whether synergy between 1 microgram/kg CCK-8 and prefeeding could be reproduced using gastric, duodenal, or hepatic-portal infusions. Gastric and duodenal infusions of 30% sucrose were effective; in conjunction with CCK-8 they decreased running speed as substantially as prefeeding did. The duodenal effect was specific. Glucose appeared to be as effective as sucrose, whereas equi-osmotic saline and mannitol were not. Intraportal glucose was relatively ineffective; interaction with CCK-8 was seen only after very large infusions, and the resulting running speeds did not approach those seen after prefeeding or gastrointestinal infusions. These results suggest that decreased feeding motivation after 1 microgram/kg CCK-8 develops through synergy between this peptide and a carbohydrate-sensitive signal generated within the small intestine.

Blockade of bombesin receptors with [Leu14-psi(CH2NH)-Leu13]bombesin fails to suppress nutrient-induced CCK release from rat duodenojejunum

The present study was undertaken in order to delineate the contribution of enteric bombesin (BBS)-containing nerves in the food-induced release of intestinal cholecystokinin (CCK). For this purpose, the isolated vascularly perfused rat duodenojejunum model was used and the new compound [Leu14-psi(CH2NH)-Leu13]BBS was infused intraarterially at a concentration of 10(-6) M to block the BBS receptors. Vascular infusion of BBS alone (10(-8) M or 10(-9) M) provoked a dose-dependent release of CCK-like immunoreactivity (CCK-LI). The secretion pattern of CCK was biphasic and consisted of a transient peak (300-400% above basal) followed by a sustained response (200-300% above basal). Vascular coinfusion of the BBS analogue with BBS 10(-9) M completely abolished both phases of CCK release while only the second phase of CCK secretion was profoundly reduced upon coadministration of BBS 10(-8) M with the BBS receptor antagonist. Luminal administration of mixed nutrients induced a prompt and well-sustained release of CCK-LI which was unaffected upon arterial infusion of the BBS analogue. These data suggest that the intestinal supply in BBS-producing nerves is not involved in the food-induced release of intestinal CCK in the rat.

On the purinergic system in rat duodenum: existence of P1 and P2 receptors on the smooth muscle

In rat duodenum, in vitro, in the presence of atropine and guanethidine, ATP administration caused a tetrodotoxin-insensitive relaxation followed by a rebound contraction. A similar response was obtained also after electrical field stimulation (EFS) of non-adrenergic, non-cholinergic (NANC) nerves. alpha, beta-methylene-TP and theophylline antagonized the response to ATP, but they failed to affect the noradrenaline- and EFS-induced relaxation. These results suggest that P1 and P2 receptors are present in rat duodenum, but their activation is not responsible for the inhibitor effects due to the NANC nerves.

[Characteristics of cortical representation of the components of the gastroduodenal complex and role of the vagus nerve in the regulation of visceral afferentation]

Evoked potentials were registered at the cortex of both hemispheres of the brain during electrical stimulation of the body of the stomach, pylorus and duodenum pre and post bilateral vagotomy. It has been demonstrated that duodenum is represented at the cortex more widely in comparison with other parts of the gastroduodenal complex. Bilateral vagotomy increases amplitude of the evoked potentials, more substantially at the right hemisphere, that may be connected with enhancement of excitability of the irritating structure by exclusion of the efferent influence of vagal nerves, which take part in the regulation of visceral afferentation at the level of end organ nervous system.

Sphincter of Oddi cyclic motility. Effect of translocation of the papilla in opossums

The role of myoneural continuity between the sphincter of Oddi and duodenum in coordinating sphincter cyclic motility and the duodenal migrating myoelectric complex was studied in conscious opossums. Five animals underwent implantation of the duodenal papilla into the jejunum. Myoelectric recording was obtained from the sphincter, duodenum, and jejunum in these animals and from 5 other animals as controls. The mean spike frequency of the sphincter of controls was 1.6 per min during phase I, 4.2 per min during phase II, 11.0 per min during phase III, and 3.6 per min during phase IV of the duodenal migrating myoelectric complex. After translocation of the papilla, the spike rates during phase II (2.2 per min) and phase III (2.8 per min) were lower than in controls (p less than 0.02), while those during phases I and IV remained unchanged. Feeding disrupted the migrating myoelectric complex and increased sphincter spike activity in both groups; however, the plateau frequency after feeding was lower after the translocation. These data suggest that the duodenum does not control cyclicity of sphincter motility but sphincter-duodenal intrinsic myoneural continuity is important in the increase in sphincter spike activity during phases II and III and after feeding.

Vagal afferent innervation of the pylorus and the upper small intestine studied in the rat with the horseradish peroxidase technique

The neuronal tracer horseradish peroxidase was injected into different segments of the gastrointestinal in the rat, in order to study the vagal afferent innervation. In the nodose ganglia the extent of labeling was greater in the experiments on the gastric antrum and pylorus than in the experiments on the first part of the small intestine. Vagal afferents are scarce in the upper duodenum and originate mainly from the left nodose ganglion.

Neural control of duodenal motor inhibition by antral contractions in dogs

The mechanism of the inhibition of proximal duodenal motor activity by carbachol-induced antral contractions or by field stimulation was studied in anesthetized dogs that had strain gauges sutured 5 and 10 cm from the pylorus on the antrum and duodenum. The duodenum was excited by vagal stimulation or distal duodenal field stimulation. Duodenal inhibition was studied 1) during a control period and after the pylorus was transected followed by administration of phentolamine, 2) during control and after phentolamine followed by pyloric transection, 3) during control and after prazosin followed by yohimbine, and 4) during control and after yohimbine. Duodenal inhibition was greater when the antral stimulation or duodenal contractions were near the pylorus. Pyloric transection did not significantly reduce this inhibition; phentolamine then abolished it. Prazosin did not abolish inhibition but yohimbine did. In conclusion, antroduodenal inhibition under our experimental conditions was mediated primarily by sympathetic nerves modulating the activity of duodenal cholinergic nerves, which possess alpha 2-adrenoceptors, and to a less extent by intrinsic nerves crossing the pylorus.

The intimate association of nerve terminals with the lacteal endothelium in the canine duodenal villi observed by transmission electron microscopy of serial sections

A hitherto undescribed intimate association of the nerve fibers with the central lacteal endothelium in the canine duodenum was demonstrated by transmission electron microscopy of ultrathin serial sections. Around the proximal half of the entire extent of the central lacteal, there exist three to ten unmyelinated nerve fibers 0.1-0.15 microns in diameter. Some of these exhibit bulbar swellings (0.7-1.0 microns in diameter) which contain small clear vesicles (30-35 nm in diameter) and/or rather large vesicles (60-90 nm) with electron-dense cores (40-60 nm). Most of the bulbar structures of the nerve fibers are in contact with or surrounded by the central lacteal endothelial cells. These results suggest the existence of a neuronal control over the activity of the lacteal endothelial cells.

Nerve-mediated contractile and electrical activity of the guinea-pig choledocho-duodenal junction

The intrinsic motor innervation of the guinea-pig choledocho-duodenal junction was investigated by recording the contractile and intracellular electrical activity of smooth muscle from different regions of this tissue. Electrical transmural nerve stimulation evoked phasic contractions in rings of muscle from the ampulla (0.45 s-1) and tonic contractions in rings of muscle from the choledochal sphincter. Intracellular microelectrode recordings from muscle strips from these two regions revealed that excitatory junction potentials (peak amplitude 7 mV) evoked by transmural nerve stimulation were more conspicuous in muscle strips from the choledochal sphincter, but inhibitory junction potentials (peak amplitude 13 mV) were of larger amplitude in muscle strips from the ampulla. Contractions and membrane depolarization evoked by transmural nerve stimulation were sensitive to 1.4 microM atropine and abolished by 3.1 microM tetrodotoxin. Histological studies on the choledocho-duodenal junction also revealed that the distribution of smooth muscle was non-uniform along the tissue. These results suggest that the two regions may have different functions in the motility of the choledocho-duodenal junction.

Immunocytochemical study of peptidergic structures in Brunner's glands

Nervous and endocrine peptidergic structures in human Brunner's glands were studied by immunofluorescence. Endocrine cells storing immunoreactive components respectively similar to somatostatin 14, the amino-terminal portion (1-14) of somatostatin 28, gastrin-cholecystokinin, and peptide YY were distributed throughout the acini. Peptidergic nerve structures contained materials immunologically related to vasoactive intestinal peptide, peptide histidine methionine, substance P, neuropeptide Y, and gastrin-releasing peptide. The latter peptide was detected in discrete fibers running into the acini but within no cell body in the submucosa. All other neuropeptides were stored in fibers, isolated or grouped in bundles, and in perikarya of submucosal ganglia close to the acini. No immunoreactive structures were detected using antisera directed against pancreatic polypeptide, secretin, motilin, neurotensin, or calcitonin gene-related peptide. The results suggest that several regulatory peptides may be involved in the control of Brunner's glands in humans.

[Mechanical properties of the small intestine of rats in the normal state and after disturbed parasympathetic innervation]

In intact and vagotomized (in 14 and 30 days after the operation) rats by means of the dynamometric method values of maximal load and relative maximum elongation of the proximal and middle areas of the small intestine (SI) have been determined in vitro. Dependence of relative elongation of the SI fragments on the load applied has been investigated. The proximal part of the SI is the most firm to tearing in comparison to the middle one. Bilateral subdiaphragmatic+ truncal vagotomy results in an increased firmness to tearing and in relative maximal elongation of the SI proximal part in 14 days and in decrease of the former parameter in the same SI part in 30 days.

Ectopic jejunal pacemakers and enterogastric reflux after Roux gastrectomy: effect of intestinal pacing

The aims of this study were to determine whether ectopic pacemakers are present in the Roux limb of dogs after vagotomy and Roux gastrectomy, whether these pacemakers lead to enterogastric reflux, and whether abolishing the pacemakers with electric pacing might correct such reflex, were it to occur. In five dogs that had undergone gastric vagotomy and Roux gastrectomy and five dogs that had undergone gastric vagotomy and Billroth I gastrectomy (controls), myoelectric activity of the Roux limb or duodenum was recorded during saline infusion (154 mmol/L NaCl) or nutrient (Meritene) infusion into the limb or the duodenum. Reflux of infusate into the stomach was determined via a gastric cannula. Tests in Roux dogs were done with and without limb pacing. Roux dogs showed ectopic pacemakers in the Roux limb that drove the pacesetter potentials of the limb in a reverse, or orad, direction during 76% of the recordings; Billroth dogs rarely had such pacemakers (p less than 0.001). Enterogastric reflux occurred in both groups of dogs but was greater during phase III of the interdigestive migrating myoelectric complex in Roux dogs (12% +/- 6%) than in Billroth dogs (3% +/- 1%; p less than 0.05). Pacing abolished the ectopic pacemakers in the Roux dogs and reduced enterogastric reflux from 12% +/- 6% to 3% +/- 2% when phase III was present (p less than 0.05). In conclusion, the Roux limb was driven by ectopic pacemakers that contributed to, but were not solely responsible for, jejunogastric reflux. Pacing abolished the ectopic pacemakers and decreased reflux when phase III was present in the limb.

Relaxatory responses of canine proximal stomach to esophageal and duodenal distension. Importance of vagal pathways

The viscerovisceral reflex control of gastric tone remains poorly characterized. We have previously demonstrated physiological variations in gastric tone that occur during fasting and after feeding. These variations are neurally regulated. We have now compared the reflex mechanisms modulating gastric tone that are elicited by esophageal or duodenal distension in fasted, conscious dogs. To determine the pathways involved in these reflexes, we combined the technique of vagal blockade (by cooling the supradiaphragmatic vagi isolated within a surgically implanted cooling jacket) with the administration of autonomic drugs. Gastric tone was measured as the air volume within an intragastric bag maintained at a constant, low pressure by an electronic barostat. Standardized distensions were performed by means of an inflatable balloon-catheter positioned either in the mid-esophagus (in three dogs) or in the distal duodenum (in three dogs). A profound and consistent gastric relaxation was induced by distension of either the esophagus (247 +/- 21 ml delta volume, P less than 0.05) or the duodenum (238 +/- 29 ml, P less than 0.05). Supradiaphragmatic vagal cooling abolished the gastric relaxatory response to duodenal distension and significantly reduced, but did not completely suppress, the response to esophageal distension. Neither cholinergic stimulation (intravenous bethanechol) nor adrenergic blockade (combined intravenous phentolamine and propranolol) had any significant effect on either gastric relaxatory response. Combined adrenergic and cholinergic (intravenous atropine) blockade induced gastric relaxation, but failed to suppress the gastric responses. We conclude that both esophageal and duodenal distension elicit gastric relaxation by a noncholinergic vagal mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased tissue concentration of neuropeptide Y in the duodenal mucosa in coeliac disease

Neuropeptide Y (NPY) is localized to intestinal nerve fibres, of which there are few in normal duodenal mucosa. In the duodenal mucosa of 10 patients with coeliac disease and in a control group of 21 patients with other gastrointestinal symptoms but with normal function of the small intestine we studied the frequency of such fibres by immunohistochemistry and the tissue concentration of NPY by radioimmunoassay. Patients with coeliac disease had an increased number of NPY nerve fibres and significantly elevated tissue concentrations compared with the control group. The eluted fractions obtained by high-pressure liquid chromatography of duodenal extracts showed the same immunoreactive components in the two groups. This study therefore suggested proliferation of the peptide-containing nerve system in coeliac disease. The increased NPY levels in the duodenal mucosa may be of functional significance for the disease symptoms.

Spread of the single spike activity in the myenteric plexus of the guinea-pig duodenum

The spontaneous single spikes in the myenteric plexus of the guinea-pig duodenum were recorded extracellularly. The myenteric plexus neurones in the cardiac region of the stomach also exhibited the spontaneous single spike activity. The frequency of these spikes was at low level. By the treatment with a high Mg and Ca-free Krebs solution, the single spikes were abolished. The generation of the single spikes was also inhibited by d-tubocurarine. These results suggest the presence of nicotinic neurotransmission in the myenteric plexus. The field stimulation could not evoke the single spike activity. The single spike activities of the myenteric plexus neurones were recorded by two electrodes situated in a ganglion or at two different ganglia. The simultaneous recordings by two different spots showed that there were corresponded and non-corresponded spikes. The former may be due to the conduction of excitation. The values of the correspondence ratio were calculated and the values ranged from 39.1% to 69.6% in a ganglion and ranged from 55.2% to 94.2% in different ganglia. The single spikes may spread over 10 mm in a longitudinal direction. These results suggest that the intra- and interganglionic interactions appear within the myenteric plexus and ganglia are interconnected into a functional integrative circuitry.

Modulation of synaptic transmission in the rabbit coeliac ganglia by gastric and duodenal mechanoreceptors

The involvement of duodenal and gastric mechanoreceptors in the modulation of synaptic transmission was investigated in a rabbit sympathetic prevertebral ganglion. The present study was performed in vitro on the coeliac plexus connected to the stomach and the duodenum. The electrical activity of ganglionic neurons was recorded using intracellular recording techniques. The patterns of synaptic activation of these ganglionic neurons in response to the activation of mechanoreceptors by gastric or duodenal distension were investigated. Although gastric or duodenal distension was unable to elicit any fast synaptic activity in ganglionic neurons, it produced either an inhibition or a facilitation of the fast nicotinic excitatory postsynaptic potentials elicited by stimulation of the thoracic splanchnic nerves. In addition, this distension triggered long-lasting (3-11 min) modifications in the electrical properties of the ganglionic neurons, i.e. slow depolarizations (6-18 mV) or slow hyperpolarizations (3-6 mV), which were sometimes associated with a decrease in the input membrane resistance. After cooling of the nerves connecting the coeliac ganglia to the stomach, the activation of gastric or duodenal mechanoreceptors was no longer able to modify the fast synaptic activation or the electrical properties of the ganglionic neurons. The results demonstrate that gastric and duodenal mechanoreceptors project onto neurons of the coeliac ganglia and change their excitability as well as the central inputs they receive. The long duration of these modifications suggests that gastric and duodenal mechanoreceptors can modulate the activity of the neurons of the coeliac ganglia.

Role of extrinsic and intrinsic nerves in hormonal induction of the migrating motor complex in the jejunum

The mechanism of induction of the migrating motor complex (MMC) by neural or humoral agents and their role in the control of fasting motility are not well understood. Our aim was to determine the role of extrinsic and intrinsic nerves in mediating the induction of the MMC by motilin. Three groups of dogs were studied. Group I consisted of neurally intact control dogs. In group II, intrinsic neural continuity between the duodenum and the jejunum was interrupted by transection and reanastomosis of the distal duodenum. Dogs in group III underwent disruption of all intrinsic and extrinsic neural input to the entire jejunoileum. Serosal electrodes were sewn to duodenum and jejunum in all dogs. After a 2-week recovery, fasting myoelectric activity was recorded on four or more occasions. Motilin (0.1 microgram/kg iv) was given 30 min after a spontaneous duodenal phase III. In group I (controls), motilin induced a premature MMC, which originated in the duodenum and migrated along the small intestine. In group II (intrinsic neural disruption), motilin induced a premature MMC, which began simultaneously in the proximal duodenum and proximal jejunum. In group III (intrinsic and extrinsic neural disruption), motilin induced a premature MMC in the duodenum but not in the jejunum; rather, a short, nonmigrating burst of spike potentials occurred simultaneously in all jejunal electrodes. These observations suggest that extrinsic innervation is necessary for motilin to induce phase III activity in the jejunum. Extrinsic neural pathways appear to mediate motilin-induced MMC activity in the jejunum.

Mechanical visceral pain model: chronic intermittent intestinal distention in the rat

Animal models designed to test the effectiveness of analgesic agents against viceral pain typically rely on a noxious chemical irritation of the peritoneum, e.g., acetic acid and phenylquinone writhing tests. While useful, this type of assay depends upon an acute inflammation and the release of local alogens. Further, ethical and scientific constraints prevent repeated assessments in a single animal, thereby compounding the difficulty of assessing tolerance development to analgesic agents. To overcome these constraints we developed a model for mechanical visceral pain (VPM) based on a repeatable and reversible duodenal distention in the rat. A chronic indwelling intraduodenal balloon catheter is well tolerated and upon inflation produces a writhing response graded in proportion to distention. This response is inhibited by morphine in a dose dependent manner.

Splanchnic nerve stimulation inhibits duodenal HCO3- secretion in the rat

Sympathoadrenergic inhibition of HCO3- secretion by the duodenal mucosa was studied in chloralose anesthetized rats. Duodenal HCO3- secretion was measured in situ by pH-stat titration. Direct efferent electrical stimulation of the cut splanchnic nerves (10 Hz, supramaximal intensity) inhibited the duodenal alkaline output by approximately 50%. This inhibitory response was blocked by the administration of either the adrenolytic agent guanethidine or the alpha 2-adrenoceptor antagonist yohimbine. However, neither the alpha 1-adrenoceptor antagonist prazosin nor the beta-adrenoceptor antagonist propranolol blocked the response to splanchnic nerve stimulation. The present data suggest that electrical splanchnic nerve stimulation inhibits duodenal HCO3- secretion via activation of adrenergic nerve fibers and alpha 2-adrenoceptors within the peripheral nervous system.