Mediators of non-adrenergic non-cholinergic inhibitory neurotransmission in porcine jejunum.

The purpose of this study was to determine the non-adrenergic non-cholinergic inhibitory neurotransmitter in pig jejunum. Intracellular electrical activity was recorded from circular smooth muscle cells. Inhibitory junction potentials (IJPs) evoked by electrical field stimulation were inhibited by tetrodotoxin (1 micromol L(-1)), omega-conotoxin GVIA (0.1 micromol L(-1)) tetrodotoxin, apamin (1 micromol L(-1)), 1-[6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione (U-73122; 10 micromol L(-1)) but not by N omega-nitro-l-arginine (l-NNA; 100 micromol L(-1)), haemoglobin (10 micromol L(-1)), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 10 micromol L(-1)) or 9-(tetrahydro-2-furyl)adenine (SQ-22536; 10 micromol L(-1)). S-nitroso-N-acetylpenicillamine (SNAP) hyperpolarized the membrane potential. This was inhibited by ODQ (3 micromol L(-1)) and charybdotoxin (0.1 micromol L(-1)). Adenosine-5-triphosphate (ATP; 100 micromol L(-1)) and 2-methylthio ATP (2-MeS-ATP; 100 micromol L(-1)) did not hyperpolarize the membrane potential and 6-N-N-diethyl-beta- gamma -dibromomethylene-d-adenosine-5'-triphosphate (ARL67156; 100 micromol L(-1)) did not modify IJPs. Carbon monoxide (CO; 10%) and tricarbonyl dichlororuthenium dimer ([Ru(CO3Cl2)]2; 100 micromol L(-1)) hyperpolarized the membrane potential however zinc, copper and tin protoporphyrin IX (100 micromol L(-1)) did not alter IJPs. Vasoactive intestinal peptide (VIP) hyperpolarized the membrane potential but 4-Cl-d-Phe6-Leu17-VIP (1 micromol L(-1)) did not modify IJPs. Pituitary adenylate cyclase activating peptide (PACAP)38 (0.5 micromol L(-1)) hyperpolarized the membrane potential. This was inhibited by apamin (1 micromol L(-1)) but not by tetrodotoxin (1 micromol L(-1)). Pituitary adenylate cyclase activating peptide6-38 (1 micromol L(-1)) inhibited IJPs. These data suggest that inhibitory neurotransmission in pig jejunum is mediated partly by PACAP.

Aging, esophageal motility, and gastroesophageal reflux.

OBJECTIVES: To compare esophageal motility and gastroesophageal reflux characteristics in young, middle-aged, and older healthy volunteers. DESIGN: Comparison of conventional esophageal manometry and scintigraphic study of gastroesophageal reflux in volunteers aged 20 to 30 years, 50 to 60 years, and 70 to 80 years. SETTING: Gastroenterology and nuclear medicine laboratories of a tertiary care university hospital. PARTICIPANTS: Forty healthy adult volunteers recruited from the community, 20 aged 20 to 30 years, 10 aged 50 to 60 years, and 10 aged from 70 to 80 years. MEASUREMENTS: Each volunteer underwent conventional esophageal manometry and scintigraphic study of gastroesophageal reflux. Contractile wave amplitude, duration, velocity, and lower esophageal sphincter relaxation duration, as well as the presence of abnormal peristalsis, were correlated with the proportion of volunteers with gastroesophageal reflux and the number and duration of gastroesophageal reflux episodes. RESULTS: Quantitative manometric parameters showed no correlation with gastroesophageal reflux patterns. Abnormal peristalsis was found more frequently in the older volunteers. The number of gastroesophageal reflux episodes per volunteer was similar in the three age groups, but the duration of gastroesophageal reflux episodes was longer in the older volunteers. CONCLUSION: Healthy older persons have impaired clearance of refluxed materials associated with a high incidence of defective esophageal peristalsis. This may explain the higher severity of reflux esophagitis in older people.

In vitro and in vivo effects of nitric oxide synthase inhibitors and nitric oxide inactivators on the South American opossum ileocolonic junction.

The potential role of nitrergic nerves in the regulation of the South American (SA) opossum ileocolonic junction (ICJ) function was investigated. In vitro, the effects of nitric oxide (NO) synthase inhibitors and NO inactivators on the non-adrenergic non-cholinergic (NANC) nerve-mediated relaxations of the circular muscle of the SA opossum ICJ were determined by employing isolated strips. Electrical field stimulation (0.2-8.0 Hz) caused frequency-dependent NANC relaxations. Nicotine and ATP also induced concentration dependent NANC relaxations that were abolished by tetrodotoxin (TTX). The relaxation response induced by NANC nerve activation was reduced in a dose dependent manner by NO synthase inhibitors while vasoactive intestinal peptide (VIP) and sodium nitroprusside (SNP) induced relaxations were uninfluenced by these drugs. In vivo, the NO synthase inhibitor, L-NAME, administered into the local artery caused a raise in intraluminal pressure of the ICJ in anaesthetized SA opossums in a L-arginine-preventable manner. Hydroquinone and pyrogallol, while being able to reduce, in a superoxide dimutase (SOD) reversible manner, the relaxations induced by exogenous NO failed to affect the NANC nerve-induced relaxations. Finally, neurones and nerve fibres in the myenteric plexus as well as varicose nerve fibres on the circular smooth layer were positive for NADPH-diaphorase activity. These findings indicate that nitrergic nerves inhibit ICJ circular smooth muscle in vitro and in vivo but cast doubts on the neuromediator being the NO radical.

Nonadrenergic-noncholinergic relaxations of isolated circular muscle from South American opossum esophagogastric junction: is nitric oxide the inhibitory mediator?

Nonadrenergic-noncholinergic (NANC) inhibitory nerves are responsible for most of the nerve induced relaxations of gastrointestinal muscle. It has recently been proposed that NANC nerves may release nitric oxide (NO) or a related compound derived from L-arginine. We have recently shown that the South American (SA) opossum is another suitable model to elucidate the mechanism involved in these NANC relaxations. In the present study the effect of NO synthase inhibitors as well as NO inactivators on the NANC-nerve induced relaxations of the circular muscle of the esophagogastric junction (EGJ) of the SA opossum was investigated. It was observed that the NO synthase inhibitors, L-NOARG and L-NAME, caused a concentration-dependent reduction of NANC-nerve induced relaxations which was reversed by L- but not D-arginine. The NO-donors sodium nitroprusside and hydroxilamine as well as NO caused concentration-dependent relaxations of the EGJ circular muscle. In the myenteric plexus of this region, NADPH-diaphorase positive neurons and nerve fibers were observed while in the circular muscle layer only numerous positive fibers were found. The NO inactivators, hydroquinone, pyrogallol and carboxy-PTIO, reduced NO-induced relaxations but failed to affect NANC nerve- and sodium nitroprusside-induced relaxations. Taken together, these findings indicate that NANC nerve induced relaxation of the SA opossum EGJ circular muscle is dependent on neural NO synthase activity and suggest that the neurotransmitter being released is a superoxide resistant molecule, which is unlikely to be the NO radical, or that the activity of NO synthase is required for the release of the actual neurotransmitter rather than for synthesizing the neuromediator.

Characterization of nerve-induced relaxation of gastrointestinal sphincteric smooth muscle in a South American opossum (Didelphis albiventris).

The presence of inhibitory nonadrenergic noncholinergic (NANC) intrinsic innervation of the circular muscle of the gastrointestinal sphincters of the South American (SA) opossum was investigated in vitro. Isolated circular muscle strips from the esophagogastric and ileocolonic junctions but not from the gastroduodenal(pylorus)region developed spontaneous tension. Tetrodotoxin (TTX, 1 microM) augmented the spontaneous tension only in the ileocolonic junction strips. Electrical field stimulation of esophagogastric and ileocolonic junction strips caused frequency-dependent responses consisting of a relaxation at lower frequencies (< 1 Hz) and a biphasic response or contraction field stimulation abolished the spontaneous activity at lower frequencies and induced contractions at higher frequencies. The responses elicited by electrical field stimulation in the three sphincters were abolished by TTX (1 microM). Electrical field-induced contractions were reduced while relaxations were enhanced by atropine (1 microM). In the presence of atropine (1 microM) and guanethidine (3 microM), electrical field stimulation, nicotine and ATP induced frequency- or concentration-dependent relaxations of the three sphincters that were abolished by TTX (1 microM). Isoproterenol and sodium nitroprusside caused concentration-dependent relaxations which were TTX-resistant. These findings indicate that the sphincteric circular muscle of the SA opossum gastrointestinal tract is relaxed by the activation of intrinsic NANC nerves and therefore can be used as a model for the study of the mechanisms involved in these responses.

Characterization of nerve-induced relaxation of gastrointestinal sphincteric smooth muscle in a South American opossum (Didelphis albiventris)

The presence of inhibitory nonadrenergic noncholinergic (NANC) intrinsic innervation of the circular muscle of the gastrointestinal sphincters of the South American (SA) opossum was investigated in vitro. Isolated circular muscle strips from the esophagogastric and ileocolonic junctions but not from the gastroduodenal (pylorus) region developed spontaneous tension. Tetrodotoxin (TTX, 1 muM) augmented the spontaneous tension only in the ileocolonic junction strips. Electrical field stimulation of esophagogastric and ileocolonic junction strips caused frequency-dependent responses consisting of a relaxation at lower frequencies (<1 Hz) and a biphasic response or contraction at higher frequencies. In the strips from the pyloric region electrical field stimulation abolished the spontaneous activity at lower frequencies and induced contractions at higher frequencies. The responses elicited by electrical field stimulation in the three sphincters were abolished by TTX (1 muM). Electrical field-induced contractions were reduced while relaxations were enhanced by atropine (1 muM). In the presence of atropine (1 muM) and guanethidine (3 muM), electrical field stimulation, nicotine and ATP induced frequency-or concentration-dependent relaxations of the three sphincters that were abolished by TTX (1 muM). Isoproterenol and sodium nitroprusside caused concentration-dependent relaxations which were TTX-resistant. These findings indicate that the sphincteric circular muscle of the SA opossum gastrointestinal tract is relaxed by the activation of intrinsic NANC nerves and therefore can be used as a model for the study of the mechanisms involved in these responses.

Effect of isosorbide dinitrate on gastroesophageal reflux in healthy volunteers and patients with Chagas' disease.

The effect of isosorbide dinitrate (ISD) on gastroesophageal reflux and gastric emptying during the 24-min period following a liquid meal was studied in healthy volunteers, Chagas' disease patients with normal esophageal motility (CD-1 group), and Chagas' disease patients with esophageal dysmotility (CD-2 group) with dynamic scintigraphy. At random, on two separate days, the subjects received 5 mg isosorbide dinitrate or an identical-appearing placebo tablet, by the sublingual route, and ingested a liquid test meal containing [99mTc]phytate colloid before scintigraphic studies were performed. Gastroesophageal reflux episodes were more frequent (P = 0.016) and gastroesophageal reflux indexes were greater (P < 0.010) after isosorbide dinitrate than after placebo in CD-2 group (N = 15) but not in healthy volunteers (N = 14) or CD-1 group (N = 9); six of seven CD-2 patients presenting with gastroesophageal reflux after isosorbide dinitrate had abnormal clearance of refluxate. Gastric emptying was similar in healthy volunteers (N = 13), CD-1 patients (N = 6), and CD-2 patients (N = 13), and no effect of isosorbide dinitrate on it was detected in any of the groups. In separate studies, 5 mg isosorbide dinitrate reduced the lower esophageal pressure (P < 0.01) in seven CD-2 patients. These results indicate that ISD increases the tendency towards GER in CD-2 patients, but not in healthy volunteers or CD-1 patients. This effect is probably related to an exceedingly intense relaxation of the LES caused by ISD in CD-2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of sublingual isosorbide dinitrate and cardiomyotomy on esophageal emptying in patients with chagasic megaesophagus.

The effects of surgical cardiomyotomy and isosorbide dinitrate on esophageal emptying were compared in 18 patients with symptomatic chagasic megaesophagus. The esophageal emptying of a radiolabelled test meal was assessed three times in each patient by a scintigraphic technique, twice before and once 10-14 days after cardiomyotomy. Isosorbide dinitrate, 5 mg by the sublingual route 5 min before the meal, preceded one of the preoperative studies. Esophageal retention at the completion of the meal was significantly less (P < 0.01) after both isosorbide dinitrate and cardiomyotomy than after the preoperative study not preceded by any treatment. This difference persisted up to 10 minutes after the meal. The values measured in the isosorbide dinitrate-preceded study and after cardiomyotomy were not different (P > 0.10) even though esophageal retention at the completion of the meal was slightly less after cardiomyotomy than after isosorbide dinitrate. These results show that isosorbide dinitrate and cardiomyotomy cause similar enhancement of esophageal emptying in chagasic megaesophagus.

Short report: comparison of the effects of sublingual nifedipine and isosorbide dinitrate on oesophageal emptying in patients with Chagasic achalasia.

The effects of sublingual nifedipine and isosorbide dinitrate on oesophageal emptying were compared in 11 patients with Chagasic achalasia. The oesophageal emptying of a radiolabelled test meal was assessed three times in each patient by a scintigraphic technique. No treatment preceded one of the studies (basal study). Nifedipine (20 mg) by the sublingual route 30 min before the meal, preceded one study. Isosorbide dinitrate, 5 mg by the sublingual route 5 min before the meal, preceded the third study. The order of the studies was allocated randomly for each patient. Oesophageal retention at the completion of the meal was significantly less (P less than 0.01) after isosorbide dinitrate (median: 54%, range: 5-87%) than after sublingual nifedipine (median: 78%, range: 7-99%) or after the control study (median: 83%, range: 5-100%). This difference persisted up to 20 min after the meal. Values measured in the control study and after sublingual nifedipine were not different (P greater than 0.10). These results show that isosorbide dinitrate, but not sublingual nifedipine, enhances oesophageal emptying in Chagasic achalasia.

[Influence of age on lower esophageal sphincter pressure]. / Influência da idade na pressão do esfíncter inferior do esôfago.

We studied the effect of aging on lower esophageal sphincter (LES) pressure of 52 normal subjects, 129 patients with Chagas' disease and 63 patients with systemic sclerosis. Three groups were compared: with ages between 10 to 29 years, 30 to 49 years and 50 to 70 years. We used a perfused catheter and the station pull-through (SPT) technique, at end expiratory phase. There was no difference in LES pressure between the three groups in normal subjects (p = 0.72) and patients with systemic sclerosis (p = 0.33). In Chagas' disease the patients with ages between 50 to 70 years had LES pressure (17 +/- 8 mmHg, mean +/- SD) lower (p = 0.03) than patients with ages between 10 to 29 years (22 +/- 9 mmHg). We conclude that in Chagas' disease the patients with ages over 50 years have LES pressure lower than patients with ages under 30 years, what does not happen with normal subjects nor systemic sclerosis patients.

An AC biosusceptometer to study gastric emptying.

A simple AC susceptometer was developed to study the gastric emptying when test meals labeled with 10% of a harmless magnetic tracer were ingested. The instrument allows the determination of T 1/2 of the stomach emptying with good precision compared to measurements with gamma camera and 99m Tc in the test meal.

Evidence for the involvement of nitric oxide in the electrically induced relaxations of human lower esophageal sphincter and distal pylorus.

The aim of the present study was to investigate in vitro the effect of NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, on neurogenic relaxation of human lower esophageal sphincter (LES) and distal pylorus (DP) circular muscle strips induced by electrical field stimulation (EFS). Muscle strips obtained from 5 patients who underwent total gastrectomy were suspended in 10-ml organ baths containing Krebs solution for recording isometric tension. L-NAME (30 microM) reduced the amplitude of the EFS-induced relaxation by 85 +/- 9% (N = 3) in the LES and by 52 +/- 16% (N = 3) in the DP but did not affect sodium nitroprusside-induced relaxation. L-Arginine (300 microM) partially reversed the L-NAME inhibition in the LES and totally in the DP. These findings suggest a role for L-arginine-derived NO in the nerve-mediated NANC relaxation of the human LES and DP.

Evidence for the involvement of nitric oxide in the electrically induced relaxations of human lower esophageal sphincter and distal pylorus

The aim of the present study was to investigate in vitro the effect of Ng-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, on neurogenic relaxation of human lower esophageal sphincter (LES) and distal pylorus (DP) circular muscle strips induced by electr4ical field stimulation (EFS). Muscle strips obtained from 5 patients who underwent total gastrectomy were suspended in 10-ml organ baths containing Krebs solution for recording isometric tension. L-NAME(30 uM) reduced the amplitude of the EFS-induced relaxation by 85 ñ 9% (N=3) in the LES and by 52 ñ 16% (N=3) in the DP but did not affect sodium nitroprusside-induced relaxation. L-Arginine (300 uM) partially reversed the L-NAME inhibition in the LES and totally in the DP. These findings suggest a role for L-arginine-derived NO in the nerve-mediated NANC relaxation of the human LES and DP