Gender- and age-related differences in muscular and nerve-mediated responses in human colon.

BACKGROUND: Gender- and age-related differences in muscular and nerve-mediated responses in human colon are poorly characterized. We studied carbachol-induced motor responses and electrically evoked contractions in sigmoid circular muscle from adult and elderly patients of different gender. METHODS: Sigmoid colon segments were obtained from 24 men and 16 women undergoing left hemicolectomy for colon cancer. Isometric tension was measured on muscle strips exposed to increasing carbachol concentrations. The effects of atropine, guanethidine, L-nitro arginine methyl ester (L-NAME), and tetrodotoxin on electrically evoked contractions were also studied. RESULTS: Female patients showed higher maximal response to carbachol than male patients, elderly females being the most sensitive to carbachol among all patient groups. Electrically evoked contractions were linearly related to stimulation frequency and abolished by tetrodotoxin. Electrically evoked contractions were significantly more pronounced in elderly male patients; they were reduced by atropine and guanethidine and increased by L-nitro arginine methyl ester in the presence of atropine and guanethidine (P < 0.05). The effect of L-NAME was most marked in elderly male patients and least pronounced in elderly females. CONCLUSIONS: The response to carbachol and the role of nitrergic pathways differ according to age and gender; this may depend on muscarinic receptor upregulation or humoral factors affecting nitric oxide release, respectively.

Vasoactive intestinal peptide receptor subtypes and signalling pathways involved in relaxation of human stomach.

Vasoactive intestinal peptide (VIP) relaxes smooth muscle by interacting with receptors coupled to cAMP- or cGMP-signalling pathways. Their relative contribution to human gastric relaxation is unknown. This study aimed at investigating, in terms of biological activity, receptor expression and related signalling pathways, the action of VIP separately on the human fundus and the antrum. VIP caused greater relaxation of smooth muscle cells (SMC) and strips of the antrum presenting on the former a higher efficacy and potency (ED(50): 0.53 +/- 0.17 nmol L(-1)) than on the fundus (ED(50): 3.4 +/- 1.4 nmol L(-1)). On both fundus and antrum strips, its effect was tetrodotoxin insentitive. Reverse transcriptase-polymerase chain reaction analysis showed the sole expression of VPAC2 and natriuretic peptide clearance receptors, with VPAC2 being more abundant in the antrum. Functional regional differences in receptor-related signalling pathways were found. Activation of the cAMP-pathway by forskolin or its inhibition by adenylate cyclase (2'5'-dideoxyadenosine) or kinase (Rp-cAMPs) inhibitors had more pronounced effects on antrum SMC. Activation of the cGMP-pathway by sodium nitroprusside or its inhibition by guanylate cyclase (LY83583) or kinase (KT5823) inhibitors had more effects on fundus SMC, on which a higher expression of endothelial nitric oxide synthase was found. In conclusion, regional differences in VIP action on human stomach are related to distinct myogenic properties of SMC of the antrum and the fundus.

Gallbladder motility before and after Billroth II gastric resection.

The aim of this study was to determine the effect of Billroth II gastric resection (BII) without vagotomy on gallbladder contraction in response to meal and CCK-OP infusion. Fourteen duodenal ulcer patients were studied before surgery and six months postoperatively. Gallbladder volume was measured by real-time ultrasonography. After surgery, there was a significant increase in fasting gallbladder volume (P < 0.05). Postprandial gallbladder emptying was not significantly affected by gastrectomy apart from a trend towards a shorter t1/2 and a larger ejection volume. In addition, postoperative gallbladder relaxation was more pronounced at time 120 min. In response to cholecystokinin-octapeptide (CCK-OP) infusion, there was a significant decrease of t1/2 after BII and a prolonged contraction with a significantly reduced gallbladder volume. Our data show that the gallbladder response both to meal and CCK-OP infusion is modified after BII and a larger postoperative gallbladder volume may play a role in the pathogenesis of gallstone disease after gastric surgery.

Effect of somatostatin on human gallbladder motility: an in vitro study.

In vivo studies have demonstrated that somatostatin induces human gallbladder relaxation. To determine whether this polypeptide acts directly on the gallbladder muscle, its effect on strips of human gallbladder was studied in vitro. Strips of gallbladder were set up isometrically in an organ bath containing oxygenated Krebs' solution. Dose-response curves to cholecystokinin-octapeptide and carbachol were first established. The ability of somatostatin to cause relaxation under basal conditions and during 50% maximal stimulation by cholecystokinin-octapeptide (7.2 x 10(-8) M) and carbachol (3.5 x 10(-6) M) was assessed in 32 strips at 4.3 x 10(-6) M concentration which mimics the plasma concentrations found in patients with somatostatinoma and in 12 additional strips at 4.3 x 10(-8) M concentration. Somatostatin action on the intrinsic innervation by using electrical field stimulation (EFS) (200 mA 5 msec in duration, 30 Hz; 400 mA, 1 msec in duration, 10 Hz) was also evaluated in 39 strips. Somatostatin had no effect on the basal or carbachol-generated tensions. On the contrary, somatostatin (4.3 x 10(-6) M) reduced cholecystokinin-octapeptide-generated tensions by 8% (P < 0.001) and reduced EFS-generated tensions at 30 Hz by 7.7% (P < 0.01) and those at 10 Hz by 41.2% (P < 0.01). All responses to cholecystokinin-octapeptide and carbachol were abolished by dibutyryl-guanosine 3', 5'-cyclic monophosphate (5 x 10(-3) M) and atropine (10(-5) M), respectively (P < 0.0002 and P < 0.0002). All responses to electrical field stimulation were reduced or abolished by tetrodotoxin (2 x 10(-6) M) (P < 0.001 and P < 0.0001, respectively). Our findings show that somatostatin exerts its inhibitory action on the response to cholecystokinin-octapeptide and on the intrinsic innervation of the gallbladder smooth muscle. The probable neurotransmitter is the acetylcholine.

Gallbladder motility in vitro in men with gallstones following Billroth II gastric resection.

Gastric surgery induces an increased incidence of gallstones. To investigate the changes in gallbladder kinetics after gastric resection, 20 male patients were studied: ten patients undergoing cholecystectomy for gallstones developed after Billroth II gastric resection and ten patients undergoing cholecystectomy for cholelithiasis without previous abdominal surgery. Longitudinal strips from the gallbladder wall were suspended in an organ bath and the isometric tension recorded. Dose-response curves to cholecystokinin-octapeptide and carbachol were obtained. Half the maximal response to cholecysto-kinin-octapeptide was 0.50 +/- 0.11 x 10(-7) M in the first group and 1.36 +/- 0.37 x 10(-7) M in the second group (P < 0.05). The ED50 to carbachol was 24.33 +/- 2.69 x 10(-7) M in the gastrectomy group and 40.39 +/- 5.01 x 10(-7) M in the control group (P < 0.01). There was no significant difference in the maximal contractile response either to cholecystokinin-octa-peptide or carbachol in the two groups. Our study shows an increased gallbladder sensitivity to cholecystokinin-octapeptide and carbachol in patients with gallstones developed after Billroth II gastric resection.

Ultrasonic vocalization in response to unavoidable aversive stimuli in rats: effects of benzodiazepines.

The effects of two benzodiazepine derivatives (diazepam, 0.5-1 mg/kg; alprazolam, 1.25-2.5 mg/kg) on ultrasonic calling elicited in adult rats by unavoidable aversive stimuli (footshocks) were investigated. The results show that either diazepam or alprazolam affected the duration of ultrasonic calls. In particular, a significant decrease in the length of ultrasounds was found in the group of animals treated with these benzodiazepines. The effects of diazepam were counteracted by the benzodiazepine-antagonist Ro 15-1788. On the other hand, neither a neuroleptic agent, such as haloperidol (0.5-1 mg/kg), nor an antidepressant, such as desipramine (5-10 mg/kg) influenced the parameters of ultrasonic emission in this experimental situation. The present results suggest that ultrasonic vocalization in response to unavoidable aversive stimuli could be considered as a potential new tool for studying drugs with antianxiety properties.

Colonic smooth muscle responses in patients with diverticular disease of the colon: effect of the NK2 receptor antagonist SR48968.

BACKGROUND: Little is known about the pathophysiology of diverticular disease. AIM: To compare passive and active stress and the response to carbachol of colonic smooth muscle specimens from patients with diverticular disease and patients with colon cancer. The effect of the NK2 receptor antagonist, SR48968, on electrically evoked contractions of circular muscle was also investigated. PATIENTS: Sigmoid colon segments were obtained from 16 patients (51-83 years) undergoing elective sigmoid resection for diverticular disease and 39 patients (50-88 years) undergoing left hemicolectomy for non-obstructive sigmoid colon cancer. METHODS: Isometric tension was measured on circular or longitudinal taenial muscle. Strips were stretched gradually to Lo (length allowing the development of optimal active tension with carbachol) and were also exposed to increasing carbachol concentrations. The effects of atropine, tetrodotoxin and SR48968 on electrically evoked (supramaximal strength, 0.3 ms, 0.1-10 Hz) contractions of circular strips from 8 patients with diverticular disease and 19 patients with colon cancer were also studied. RESULTS: Both passive and active stress in circular muscle strips obtained from patients with diverticular disease was higher than in patients with colon cancer (P < 0.05). Electrically evoked contractions were significantly reduced by atropine in all preparations and were virtually suppressed by combined SR48968 and atropine. Tetrodotoxin suppressed electrically evoked contractions only in patients with colon cancer, whereas a tetrodotoxin-resistant component was identified in patients with diverticular disease. CONCLUSIONS: The changes in both passive and active stress in specimens from patients with diverticular disease may reflect circular smooth muscle dysfunction. Acetylcholine and tachykinins are the main excitatory neurotransmitters mediating electrically evoked contractions in human sigmoid colon circular muscle.

Ultrasonic calling in rodents: a new experimental approach in behavioural toxicology.

Ultrasonic calls are emitted by many species of rodents in a variety of situations. In particular, infants commonly emit such calls when removed from the nest; the rate and intensity of calling are related to the degree of development of homoiothermy. The relevant biological significance of these signals is documented by their capability to promote parental behaviour, such as maternal retrieval. There is recent evidence that ultrasonic vocalization in rodent pups could be valuable as a bioassay in Behavioural Toxicology. In particular, the results of our recent studies together with those of other authors suggest that ultrasonic calls emitted by infant rats could be considered a useful test in detecting subtle effects of adverse treatment during development.

CCK1 receptor antagonist, dexloxiglumide: effects on human isolated gallbladder. Potential clinical applications.

Cholecystokinin is the main hormonal regulator of gallbladder motility. Dexloxiglumide, the active enantiomer of loxiglumide, interacts competitively with CCK1 receptors as determined in preclinical studies, such as specific radioligand binding assays or functional studies on isolated guinea pig gallbladder, where it inhibited smooth muscle cell contractions induced by cholecystokinin-octapeptide (CCK-8), the most prominent active forms of cholecystokinin. Dexloxiglumide has a potent antagonistic effect, of a competitive nature, on human gallbladder cholecystokinin type 1 receptors. In isolated human gallbladder, dexloxiglumide produced a concentration-dependent rightward shift of the cholecystokinin-octapeptide curve, without affecting its maximal response. Gallbladder motility was evaluated in clinical studies. Dexloxiglumide, orally administered to healthy volunteers at putative therapeutic doses, did not interfere with post-prandial gallbladder kinetics, despite an increase of fasting gallbladder volume. At present, dexloxiglumide is in an advanced stage of clinical research in gastroenterology. Overall, clinical observations suggest that dexloxiglumide may become an effective treatment in several gastrointestinal disorders. Moreover, the beneficial effects can be obtained without increasing the risk of gallstones formation, a potential hazard subsequent to the inhibition of gallbladder contractions and the resulting bile stasis. The potent and selective antagonist dexloxiglumide may offer a possible therapeutic tool for use not only in functional gastrointestinal disorders, such as irritable bowel syndrome, constipation, gastroesophageal reflux disease and functional dyspepsia, but also in other pathologies, such as biliary colics, pancreatic diseases and gastrointestinal tumors.

Tauroursodeoxycholic acid reduces damaging effects of taurodeoxycholic acid on fundus gastric mucosa.

We investigated the effects of tauroursodeoxycholic acid (TUDCA) to assess whether this acid may also have "protective" effects similar to those found with ursodeoxycholic acid (UDCA). We used a well-known amphibian model of gastric mucosa, and studied the effects of taurodeoxycholic acid (TDCA) on electrical transepithelial parameters, acid secretion and histology in absence or in presence of TUDCA. Mucosal exposure to TDCA, after stimulation with histamine, caused a reduction in transepithelial potential difference (V(t)) and transepithelial resistance (R(t)) and a decrease in acid secretion while mucosal exposure to TUDCA did not cause a significant change in the electrical parameters. Moreover, TDCA primarily affected the neck cells, while TUDCA affected only oxyntic cells, causing a similar degree of injury to that observed in controls. Mucosal exposure to TUDCA plus TDCA caused a reduction in short circuit current (I(sc)) and R(t), whereas acid secretion did not change. These results suggest that: (1) TUDCA reduces the damaging effects of TDCA on fundus gastric mucosa; (2) TUDCA may play an important role in the treatment of gastritis associated with bile reflux.

The tripeptide ZAMI-420 inhibits thromboxane-induced gastric vasoconstriction and ischaemia.

The tripeptide ZAMI-420 has been shown by Gervasi et al. (4) to be able to prevent experimentally-induced gastric damage, possibly by interfering with the synthesis and the action of thromboxane A2 (TXA2), a potent vasoconstrictor and platelet aggregator. Further studies on a canine stomach wedge preparation, supplied with a fixed flow of 10 ml/min-1 of arterial blood from the same dog have been designed to investigate this hypothesis. Bolus injection of arachidonic acid (AA) through a 30-sec incubation coil that allows the production of TXA2 resulted in a dose-related increase in resistance to flow in the stomach wedge vasculature and blanching of the gastric mucosa. This was progressively inhibited by ZAMI-420 perfused through the delay coil. Similar results were obtained with 1-benzylimidazole (BI). ZAMI-420, but not BI, produced a partial inhibition of TXA2-induced vasoconstriction when infused close to the stomach. Investigations of the antagonistic action of ZAMI-420 on the pharmacological effect of the formed TXA2 were carried out using strips of celiac and mesenteric artery from rabbits and gastric artery from dogs. Preincubation of these vascular preparations with ZAMI-420 led to progressive inhibition of the contraction induced either by the stable endoperoxide U-46619 or by CaCl2. Whittle et al. (3) reported that TXA2 may be involved in the pathogenesis of ulcerative disorders of the stomach; if so, both the inhibition of the synthesis and the antagonism of TXA2-induced effects could be of value in the prevention of experimentally-induced gastric disorders.

[Therapy of non-ulcer dyspepsia]. / Terapia della dispepsia non ulcerosa.

The authors describe the gastro-kinetic drugs that act on functional dyspepsia including metoclopramide, domperidone, clebopride cisapride. Moreover, in some forms of non-ulcer dyspepsia it is useful to give sulglicotide, a cytoprotective drug that has been shown to induce marked improvement of clinical symptoms and endoscopic findings.

Modulatory effect of three antibiotics on uterus bovine contractility in vitro and likely therapeutic approaches in reproduction.

This in vitro study investigates the modulatory effect of three antibiotics (amoxicillin, enrofloxacin, and rifaximin) on contractility of the bovine uterine tissue in follicular and luteal phases. The effects of these antibiotics at three single doses (10(-6), 10(-5), and 10(-4) M) on their basal contractility were evaluated in isolated organ bath. The functionality of the strip throughout the experiment was evaluated by a dose of carbachol (10(-5) M); the obtained effect had to be repeatable (difference of ≤20%) that is comparable to that induced by the previous administration of the same substance. The results demonstrate the different modulatory activities of these antibiotics on uterine contractility in follicular and luteal phases. The effects induced by amoxicillin and enrofloxacin are opposite: the first relaxes and the second increases the uterine contractility in both cycle phases. Instead, the activity of rifaximin varies depending on the phase of estrous cycle: it increases in the follicular phase and relaxes in the luteal phase. The obtained data provide the hypothesis of possible implications of these drugs in the pharmacologic modulation of uterine contractions. Their action at this level, associated with their specific antimicrobial effects, could suggest using these antibiotics for the treatment of diseases related to postpartum or infections that may occur in pregnant cattle, by virtue of their effects on myometrial contractility too.

Myogenic regional responsiveness to cholinergic and vipergic stimulation in human colon.

BACKGROUND: Differences in the actions of enteric neurotransmitters on colonic circular and longitudinal muscle layers have not been clearly determined, nor the possible existence of intrinsic myogenic phenotypes that might contribute to regional differences in human colon motor activity. The aim of this study was to analyze the direct pharmaco-mechanical coupling of carbachol (CCh) and vasoactive intestinal polypeptide (VIP) on human colonic smooth muscle strips and cells. METHODS: Circular and longitudinal muscle strips and cells were obtained from 15 human specimens of ascending and sigmoid colon. Both isometric tension on muscle strips and contraction and relaxation on cells were measured in response to increasing CCh and VIP concentrations. KEY RESULTS: Circular muscle strips of ascending colon were more sensitive to the effect of CCh than that of sigmoid colon, EC(50) values being, respectively, 4.15µmolL(-1) and 8.47µmolL(-1) (P<0.05), although there were no differences in maximal responses. No regional differences were observed in longitudinal muscle strips or in smooth muscle cells. Maximal responses to CCh were higher on circular than longitudinal muscle strips and cells throughout the colon. A greater sensitivity to VIP was observed in ascending colon compared with sigmoid colon, both in circular (EC(50:) 0.041 and 0.15µmolL(-1) , respectively, P<0.01) and longitudinal (EC(50:) 0.043 and 0.09µmolL(-1) , respectively, P<0.05) strips, and similar differences were observed in longitudinal smooth muscle cells (EC(50:) 44.85 and 75.24nmolL(-1) , respectively, P<0.05). CONCLUSIONS & INFERENCES: Regional myogenic differences in pharmaco-mechanical coupling between the enteric neurotransmitters and smooth muscle contribute to the complex regional motor patterns of human colon.

Gastric electrical dysrhythmia following cholecystectomy in humans.

In order to observe the incidence of dysrhythmia in 20 patients who had undergone cholecystectomy, we recorded gastric electrical activity by means of serosal electrodes from the day of surgery to the 6th postoperative day. The difference between the incidence of dysrhythmia on the day of the operation and the other days is statistically significant (t test: p less than 0.001). Bradygastria was the most frequently observed dysrhythmia, both on the day of surgery and on the following days. It had a frequency of around 1.0-1.5 cpm and the episodes lasted for a minimum of 10 min to a maximum of 105 min (mean duration 32.6 min). Episodes of tachygastria were of varying duration, ranging from a minimum of 3 min to a maximum of 60 min (mean duration 18.5 min), whereas episodes of gastric tachyarrhythmia lasted between 2 min and 21 min (mean duration 5.4 min). Only 1 patient had an episode of nausea and biliary vomiting, associated with an episode of gastric tachyarrhythmia on the 1st postoperative day. None of the other patients had symptoms of impaired gastric function, such as nausea, vomiting, bloating and epigastric pain, at any time during the recording sessions. These findings suggest that in most cases, gastric electrical rhythm returns to normal within 24 h of cholecystectomy and further that gastric dysrhythmia is not related to symptoms of impaired gastric function. The etiological mechanism and clinical significance of gastric dysrhythmia, therefore, are still unclear.

Electrical activity recorded from abdominal surface before and after right hemicolectomy in man.

To explain the origin of the electrical signals obtained from the abdominal cutaneous surface (electrosplanchnogram, ESG), the ESG was recorded in 6 patients with carcinoma of the right colon without obstruction before and after right hemicolectomy. The analysis of colonic electrical activity was performed by means of spectral analysis that utilized fast Fourier transform method. Since the colonic electrical signal is highly complex and it may contain several frequencies concurrently the spectral frequency components were subdivided in ranges and the dominant frequency and power were calculated for each range before and after surgery. The pattern obtained from power profile, expressed as differences in power percentages before and after surgery, demonstrated that there were significant differences in power data from right hemicolectomized patients compared to cholecystectomized ones (p = 0.00001 and p = 0.001 in 2.5-3.5 and 3.6-7.5 cpm range, respectively). In particular, hemicolectomized patients showed a slight increase of power percentage in the 2.6-3.5 cpm range and a clear reduction in the 3.6-7.5 cpm range. These data suggest that there are several components of colonic origin in the cutaneous ESG signal which, in the right colon, are identifiable in the 3.6-7.5 cpm range.

Electrical activity recorded from abdominal surface after gastrectomy or colectomy in humans.

The visceral electrical activity recorded from the abdominal surface was studied before and after either total gastrectomy or colectomy. The patterns obtained from fast Fourier transform analysis demonstrated the disappearance of the power peak of approximately 3 cpm after gastrectomy, whereas colectomy did not result in the disappearance of the power peak of approximately 3 and 8-12 cpm. Only the frequencies of approximately 3.5-7.5 cpm were not present after colon surgery. These data demonstrate that the spectral power peaks at frequencies of approximately 3 cpm are entirely related to the stomach because they disappear after gastrectomy; the power peaks between 3.5 and 7.5 cpm are related to the colon because they are present after gastrectomy but not after colectomy; the power peaks between 7.5 and 11 cpm are related to the small intestine because they are present after either gastrectomy or colectomy. The authors conclude that the electrical activity recorded from the abdominal surface and analyzed by fast Fourier transform gives reliable information concerning the electrical activity of the stomach and small intestine, although it is less reliable concerning the electrical activity of the colon.

Effect of cimetidine and ranitidine on gastric electrical activity in man.

Electrical activity was recorded in six post-cholecystectomy patients using bipolar serosal electrodes. Three patients were treated with intravenous cimetidine bolus in doses of 200 mg every four hours. Another three patients were treated with intravenous ranitidine bolus in doses of 50 mg every six hours. The frequency and the amplitude of the gastric electrical control activity (ECA) and the incidence of electrical response a activity (ERA) were evaluated before and after the administration of the drugs. The administration of cimetidine and ranitidine did not produce any statistically significant variation in the frequency and amplitude of the gastric ECA and the incidence of ERA. These results show that the effects of the H2-antagonists on gastric electrical activity had no clinical relevance.

In vitro electro-mechanical activity of the human colon. Simultaneous recording of the electrical patterns of the two muscle layers.

Electrical and mechanical activity on longitudinal and circular layers of the human sigmoid colon were simultaneously studied. Recordings were obtained from two electrode sites spaced 3 cm apart in a piece of colon which had been resected surgically and perfused in an organ bath. Spontaneous electrical activity of the colon showed slow waves and spikes. Slow waves were present for only 24.5% and 12% of the recording time on the longitudinal and circular layers, respectively, and they appeared as localized activity which was irregular in amplitude and varying in frequency. Electrical coupling between the two muscle layers was rarely seen and slow waves were not associated with pressure changes. Spiking activity were recorded as short and long spike bursts on both muscle layers. Short spike bursts were localized activity superimposed on slow waves. The associated mechanical activity, which consisted of single weak pressure changes or prolonged contractions with summation, was determined by slow wave frequency. Long spike bursts were seen at irregular intervals and were either propagated or not propagated activity associated with electrical oscillations ranging from 24 to 46 cpm. Mechanical activity consisted of sustained tonic contractions propagated or not propagated in the same way as the electrical pattern. Coordinated electrical activity of the two muscle layers seldom occurred when spontaneous activity was being recorded. Electrical activity on both muscle layers was very sensitive to stretching and could be initiated or modulated by pharmacological agents. In particular, our findings showed that stimulation induced coordinated spiking activity on the two muscle layers and caused mechanical activity, propagated orally or aborally, which consisted of long lasting, high amplitude contractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II: a releaser of PGI2 from fetal and newborn rabbit lungs.

Angiotensin II (AII) induces generation of prostacyclin (PGI2) in rabbit lung in vitro at different ages, i.e., fetus, newborn and adult. Particularly, neonatal rabbit lungs display a pattern of sensitivity to AII in producing PGI2, measured as 6-oxo-PGF1 alpha, which seems to be higher than that observed in fetal lungs. The PGI2 release appears to be specific for AII stimulation since the vasoconstriction induced by noradrenaline and ergotamine was not associated with generation of this lipidic material. The inability of PGI2 to relax the extralobar pulmonary artery in the newborn suggests that the lung microcirculation is the most likely site where the vasodilating and antiaggregatory functions of PGI2 may have a physiological role.