Effects of Cholera Toxin on Small Intestinal Motor Activity in the Fasted State

We sought to determine the effect of cholera toxin on small intestinal motor activity in the fasted state and relate it to secretion in conscious dogs. Motor activity was recorded by strain gauge force transducers and secretion was measured by diverting it to the outside through a two-way cannula. Inoculation of the study segment with cholera toxin resulted in a 10-fold increase in fluid output by 120 minutes postinjection. At the same time that fluid output increased Significantly changes in fasting motor activity occurred. The cycle length of the migrating motor complex was significantly reduced, the percentage of phase II activity was significantly increased, and migrating clustered contractions were inhibited. Perfusion of the study segment by a nonabsorbable electrolyte solution at a rate similar to the rate of secretion induced by cholera toxin did not change the cycle length of migrating motor complexes, but the percentage of phase II activity was significantly increased as with cholera toxin, and migrating clustered contractions were inhibited. The reduction in the cycle length of migrating motor complexes seems to be a direct effect of cholera toxin on the gut wall while the increase in percentage of phase II activity and inhibition of migrating clustered contractions appear to be indirect effects due to fluid accumulation.     

Activity Fronts of Migrating Myoelectric Complex: Initiation by Luminal Bile Acids in Rat Small Intestine

The aim of the present study was to investigate the possible role of bile in regulation of fasting small intestinal motility in the rat. Myoelectric activity was recorded by bipolar electrodes implanted in the jejunum, 15, 25, and 35 cm distal to the pylorus. After recording migrating myoelectric complexes (MMCs), total biliary drainage was performed by cannulating the bile duct of 15 rats. After biliary drainage for 267 (222–312) minutes (mean and 95% confidence interval), a characteristic continuous irregular spiking activity appeared at all recording sites. When continuous irregular spiking had persisted for 2 hours, a mixture of 20 mM taurocholic and 10 mM taurochenodeoxycholic acid was infused into the duodenum (0.5 μ/mol/min for 90 min) of seven rats. Bile acid infusion induced three to six activity fronts within 25 to 47 minutes in all animals. Maximal bile acid secretion in response to bile acid infusion was obtained about 1 hour after the last induced activity front, when the motility pattern had returned to irregular spiking. In eight rats with biliary drainage but without bile acid infusion, irregular spiking activity persisted for at least 10 hours. In sham-operated rats, regular activity fronts started after 221 (146–296) minutes. Thus drainage of bile changes the motility pattern from MMC to continuous irregular spiking, while duodenal bile acid infusion after biliary drainage reinstates the MMC pattern in rat small intestine.     

High-resolution analysis of the duodenal interdigestive phase III in humans

To study the spatial organization of the propagating pressure waves of duodenal phase III, we performed fasting antroduodenal high-resolution manometry with a 16-channel catheter in 12 healthy subjects. The phase III pressure waves diverged in an anterograde and retrograde direction from the start site of each pressure wave. The pressure waves maintained this configuration as the activity front moved distally in the duodenum. The start site of the pressure waves moved gradually to a point approximately 12 cm (median) distal to the pylorus and remained at this point for about 40% of the phase III time before moving further distally. The length of retrograde pressure wave propagation increased to 6 cm (median) as the pressure wave origin moved aborally to a point 10-14 cm distal to the pylorus, and then decreased when the origin of pressure waves reached the distal end of the duodenum. Bidirectional pressure waves dominated in both retrograde and anterograde activity fronts. Three pressure-wave mechanisms behind the duodenal phase IV were observed. Isolated pyloric pressure waves were absent during late duodenal phase III retroperistalsis. Thus, a number of new features of the duodenal phase III-related motility were observed using high-temporospatial resolution recordings.     

Development and validation of microcomputer analysis of gastric and small-bowel manometry

A novel microcomputer method for analysis of gastric and small-bowel motility was developed for recognition and measurement of inter-digestive migrating motor complexes (MMC) and associated features as well as fed-state contraction characteristics. Facilities for removal of signal artefacts were also provided. This microcomputer method was validated against observer findings in 24-h ambulatory gastric and small-bowel motility studies of six volunteers. No significant differences were found between microcomputer and observer motility analysis relating to MMC number, MMC migration velocity, fed-state contraction characteristics or artefact recognition. This method provides an accurate automated method for measurement of gastric and small-bowel motor physiology.     

Human postprandial gastric emptying of indigestible solids can occur unrelated to antral phase III

According to animal experiments, postprandial gastric emptying of indigestible solids is mainly related to the antral phase III activity of the migrating motor complex. Gastric emptying of indigestible solids in humans has not been directly correlated to pressure recordings. The aim of the present study was to investigate the postprandial emptying pattern of indigestible solids in humans and its relation to fed and fasted antral motility. Ten healthy volunteers participated. After an overnight fast they had a standard breakfast. Two sizes of radiopaque markers (ROMs) were given with the test meal; ten cubes each of side measurement 1.5 mm and 3 mm, respectively. Emptying of the ROMs from the stomach was followed by fluoroscopy with simultaneous antral manometry. In six of the subjects, fasting antral manometry was performed on one day and on another day, the emptying of 7 mm cylindrical particles together with 3 mm cubes, in the absence of a gastric tube was recorded. All ROMs were emptied within 5 h (range 1.5-4.5 h). In all subjects, the smaller particles (1.5 mm) showed a slight, insignificant tendency to move from the stomach more rapidly than the larger (3 mm) particles. None of the subjects had an antral phase III before all ROMs were emptied from the stomach. Instead, the typical irregular postprandial pressure activity was present in all subjects until the emptying was completed. Furthermore, the highest postprandial motility index during the emptying study was far below the motility index during phase III, but comparable to the motility index during late phase II. Emptying of the 7 mm particles occurred significantly more slowly at 1.5-2.5 h, but otherwise was similar to the emptying of the smaller particles. There was no difference between emptying of the 3 mm cubes with or without the presence of the tube. Contrary to common opinion, gastric emptying of indigestible solids after a meal can occur unrelated to the antral phase III, at least up to a particle size of 3 mm and perhaps even 7 mm. These findings are of great importance for the evaluation of gastric emptying of indigestible solids, including the pharmacodynamics of orally administered drugs.     

Distinctive motor responses to human acute salmonellosis in the jejunum and ileum

Given the differences that normally exist in jejunal and Heal motility patterns, we wished to determine whether these regions respond differently to acute enteric infections. In 10 patients with acute gastroenteritis induced by Salmonella infection and 12 healthy individuals jejunal and Heal motility was recorded at eight equidistant sites by a manometric system for 6 h during fasting. All were healthy individuals, but only three of 10 patients exhibited the cyclic inter digestive motor complex; 82 ± 9 min duration in healthy individuals (mean ± SE). In the jejenum, patients exhibited short bursts of intense activity (6.3 ± 1.6 bursts/subject in patients vs. 1.8 ± 0.5 in controls; P < 0.05); burst activity was scarce in the ileum. In contrast to healthy subjects, patients exhibited prolonged periods (64 ± 3 min duration) of Heal motor quiescence, that accounted for 32 ± 11% of recording time; such silent periods were not observed in the jejunum. Prolonged propagated ileal contractions were observed only in two healthy subjects, but in seven out of 10 patients. These data indicate that acute Salmonella infection magnifies the motor differences between the jejunum and the ileum; both regions generate aberrant and markedly different dysmotility patterns.     

Neural Contribution to Interdigestive Lower Esophageal Sphincter Pressure Phenomena in the Conscious Opossum

The genesis of lower esophageal sphincter (LES) pressure in anesthetized opossums is a myogenic phenomenon without excitatory neural input. The mechanism responsible for generating phasic LES pressure phenomena in unanesthetized opossums, however, is not established. In this study, we evaluated the effects of potential pharmacological antagonists on LES pressure phenomena in unanesthetized opossums. We also compared LES responses to pharmacological excitatory agonists in anesthetized and unanesthetized animals. In awake animals the LES exhibited substantial tone as well as characteristic phasic activity. The tonic, or basal, LES pressure did not change during cycling of the migratory motor complex (MMC). However, atropine, 4-diphenylacetoxy-N-methylpiperidine methiodide, and hexamethonium abolished the phasic, MMC-related LES contractions while having no effect on basal pressure. Pirenzepine, prazosin, propranolol, pyrdamine, naloxone, and haloperidol did not affect either phasic or tonic LES pressure phenomena. Anesthesia substantially reduced the excitatory LES response to motilin but not to bethanechol, cholecystokinin-octapeptide, pentagastrin, or phenylephrine. The results suggest that phasic LES contractions related to the MMC cycle are mediated by postganglionic cholinergic nerves with nicotinic ganglionic transmission. Basal LES tone, however, is maintained by a myogenic phenomenon. Anesthesia reduces excitatory LES responses induced by motilin, which acts via excitatory nerves, but has no effect on excitatory responses induced by agents that act mainly or exclusively on LES smooth muscle.     

Reproducibility of antroduodenal motility during prolonged ambulatory recording

Ambulatory recording of antroduodenal manometry is a novel technique with several advantages over standard stationary manometry recording. Although the feasibility of this technique in clinical practice has been demonstrated, reproducibility of antroduodenal motility recorded by means of ambulatory manometry has not been investigated. To test whether antroduodenal motility recorded by ambulatory manometry is reproducible, we performed two 24-h ambulatory antroduodenal manometry recordings in 18 healthy subjects according to an identical protocol with a 1-week interval. Motility was recorded with a five-channel solid-state catheter. Postprandial motility was recorded after consumption of two test meals and interdigestive motility was recorded nocturnally. Postprandial antroduodenal motor characteristics were identical between the separate recordings. The number and duration of nocturnal cycles of the interdigestive migrating motor complex were also in the same range. Phase III characteristics in general were not different between the two recordings. Only minor alterations were observed in the duration of phase III motor fronts with duodenal onset and in the number of interdigestive cycles concluded by duodenal onset phase III. Parameters obtained by qualitative analysis were comparable between the two recordings. The antroduodenal motility pattern, when measured by ambulatory recording with solid state catheters under standardized conditions, is very reproducible.     

Sham feeding disrupts phase III of the duodenal migrating motor complex in humans

The role of the vagus nerve in the control of the intestinal migrating motor complex (MMC) is unclear. This study aimed to evaluate the effect of physiological vagal stimulation with sham feeding on phase III of the MMC. Antroduodenal motility was recorded in six healthy volunteers. The first phase III was used as a control, and sham feeding was performed during the second phase III. The MMC was disrupted within 1.5 ± 0.4 min of sham feeding and its duration was shorter than the control phase III. Phase III propagation was inhibited in all subjects, most of them exhibiting no propagation beyond the third duodenal recording site. During sham feeding, the antrum exhibited transient phasic contractions in five out of six subjects. The duodenal motility index recorded for up to 30 min after the onset of the sham feeding was unchanged in five out of six subjects. We conclude that sham feeding consistently interrupted phase III of the duodenal MMC and induced antral contractions, but failed to provoke significant motor events in the duodenum.     

Analysis of motor patterns in the isolated guinea-pig large intestine by spatio-temporal maps

We investigated and quantified the spontaneous patterns of motility in the isolated guinea-pig proximal and distal colon taken from adult animals. During spontaneous emptying, profiles of proximal and distal colon were recorded with a video camera, and image analysis was used to construct spatio-temporal maps of the motions of the intestinal wall. Four patterns of motility were recorded. In the proximal colon there were neurally mediated contractions that propagated in the aboral direction at 4.1 mm s(-1), gently pushing the soft contents aborally; these are likely to represent spontaneous peristaltic behaviour. A second pattern, insensitive to tetrodotoxin (TTX; 0.6 microM), consisted, in both oral and aboral propagation, of shallow contractions of the circular muscle (ripples). These contractions propagated aborally at 2.8 +/- 0.45 mm s(-1) and orally at 2.03 +/- 0.31 mm s(-1) (n=10). Of these TTX-resistant contractions, 22.5% propagated both orally and aborally from a common origin. The orally propagated component of these myogenic contractions is likely to correspond to the antiperistalsis widely described in the proximal colon. In the distal colon, two patterns of motor activity were observed. One, induced by natural or artificial pellets, consisted of peristaltic contractions that pushed the pellets aborally at 0.8 mm s(-1) and expelled a pellet every 108 s. In the interval between pellet propulsion and after the distal colon had emptied all of its pellets a second, nerve-mediated pattern of motor activity, consisting of clusters of annular circular muscle contractions separated by short dilated regions, slowly propagated aborally at 0.3 mm s(-1). Both of these motor patterns were abolished by TTX (0.6 microM). A latex balloon, inserted at the oral end of the empty isolated distal colon and inflated to a size similar to faecal pellets, was propelled at 1.4 mm s(-1). Epoxy resin-covered natural pellets were propelled at a similar speed of 1.6 mm s(-1).Our data revealed that myogenic and neurogenic patterns of propagated contractions in the colon occur in isolated preparations and are involved in emptying the colon.     

Characteristic motor patterns of phase II and behaviour of phase III in the fed state

The motor pattern of the phase II of the migration motor complex (MMC) is poorly characterized and it remains to be determined whether it differs from the fed motor-pattern. Furthermore, discrepancy exists on the disruption of ongoing MMCs by feeding, and finally, the understanding of the behaviour of phase Ills during enteral nutrition is incomplete. Therefore, canine intestinal motility was studied after meal and during enteral infusion of nutrients (elemental diet, glucose, maltose, amino acids) or of hypertonic saline (300–1520 mosmol kg^?1). Motility of the proximal, mid- and distal jejunum was recorded with strain-gauge transducers. The motor patterns of the interdigestive phase II, after feeding and during enteral nutrition were analysed by a computer. Additionally, the disruption of the MMC by food and by enteral infusion of nutrients or hypertonic saline was investigated. The inter digestive phase II consisted of three different contractile patterns, clustered contractions, a mixed contractile pattern and non-migrating bursts of propagated contractions (NBPCs). NBPCs differed significantly from the phase III activity in several motility parameters and by the lack of aboral migration. Only small differences existed between the motor patterns of phase II and of the fed state, whereas the motor pattern induced by enteral infusion of an elemental diet differed significantly from that of phase II. Ongoing MMCs of the proximal jejunum often continued to migrate to the mid- and distal jejunum. During enteral infusion of nutrients or of hypertonic saline, phase Ills recurred. The migration of ongoing phase Ills and the recurrence of subsequent phase Ills decreased with increasing caloric or osmotic loads. The following conclusions were reached, (a) The phase II of the MMC is a complex motor-pattern. NBPCs represent a new contractile pattern, (b) The MMC is a characteristic feature of the empty gut. After meal and during enteral nutrition, phase Ills are usually suppressed but they can recur during the digestive period.     

Inhibition of the migrating motor complex by duodenal drainage in man

Abstract The effect of varying bile acid output on fasting small intestinal motility was investigated in healthy male volunteers. Biliary output was manipulated by jejunal infusion of isotonic mannitol, which resulted in increased output, and by prolonged drainage of duodenal contents, which resulted in decreased output. Intestinal motility was measured by manometric recordings performed at four levels in the proximal small intestine. A marker dilution technique was used to measure pancreatico-biliary output. There were three experimental groups: duodenal drainage, non-drainage and control. Both duodenal drainage and non-drainage groups underwent jejunal saline infusion, followed by mannitol infusion. The control group did not receive drainage or infusions. In the drainage group, 0.41 (0.13-0.68) activity fronts of the migrating motor complex (MMC) per hour were recorded during saline infusion, but only 0.06 (0-0.19) activity fronts per hour were observed during mannitol infusion. In the nondrainage group, 0.71 (0.61-0.81) activity fronts per hour were observed during saline infusion and 0.50 (0.18-0.82) activity fronts per hour were recorded during mannitol infusion. In the control group, 0.58 (0.33–0.84) activity fronts per hour were recorded during the first 4-h session and 0.58 (0.45-0.71) activity fronts per hour during the second session. There was no difference between the number of activity fronts per hour observed in the control group and those observed in the saline infusion of the drainage group. In contrast, there was a significant decrease in the number of activity fronts per hour in the drainage group during mannitol infusion, compared to both non-drainage group during mannitol infusion (P < 0.01) and controls (P < 0.05). In conclusion, decreased biliary output caused by duodenal drainage in combination with mannitol infusion is associated with inhibition of the cyclic activity of MMC in the proximal small intestine in man.     

Effects of duodenal flow on interdigestive patterns of small bowel myoelectric activity

Factors regulating the conversion of the interdigestive migrating motor complex (MMC) to postprandial patterns of motility are not completely understood. This study assessed the effects of varying rates of nonnutrient duodenal flow on patterns of interdigestive motility before and after abdominal vagotomy. Six neurally intact dogs were prepared with serosal intestinal electrodes and a duodenal infusion catheter. After recovery, the dogs were studied by infusing an isosmolar, noncaloric, balanced electrolyte solution at rates of 0, 3, 6, 9, or 12 ml/min for 5 hours into the proximal duodenum. With increasing rates of duodenal infusion, the duration of phase I decreased progressively (P < 0.05), while the period of the MMC remained unchanged. The MMC was eventually inhibited at rates of 9 or 12 ml/min with establishment of a pattern of intermittent spike activity. These findings were similar in 3 of these dogs after transthoracic total abdominal vagotomy. Our findings suggest that increases in duodenal infusion rate, independent of caloric or nutrient content, modulate patterns of intestinal motility during the postprandial period; this effect does not appear to be vagally mediated.     

Twenty-four hour ambulatory antroduodenal manometry in normal subjects (co-operative study)

Circadian antroduodenal motor activity was studied in 40 normal subjects by means of a portable recording system consisting of a computerized data logger and a probe with microtransducers. The quantitative and qualitative characteristics of contraction events during the interdigestive and digestive periods, as well as during the awake and asleep periods, were analysed. The composition and timing of meals and night recumbence were standardized. In spite of the high interindividual variability in motor parameters, significant differences in the characteristics of interdigestive and digestive periods between waking and sleep states were found. This paper confirms the existence of a circadian variation in antroduodenal motor activity and provides reference values from a large series of normal subjects that can be used for statistical comparisons with those obtained from patients recorded with the same method.     

Comparative analysis of phase III migrating motor complexes in stomach and small bowel using wireless motility capsule and antroduodenal manometry

Background Assessment of phase III MMC is often not performed due to the invasive nature of antroduodenal manometry used to detect it. The aim of the study was to evaluate the ability of wireless motility capsule (WMC) to detect phase III MMC and correlate it with the simultaneous measurements by antroduodenal manometry (ADM). Methods Eighteen patients underwent simultaneous ADM and WMC. MMCs were identified first on ADM and then correlated with WMC events occurring simultaneously. Frequency of contractions per min, AUC, MI, and criteria for amplitude thresholds of contractions representing MCCs on WMC tracings were defined. Key Results In 18 patients, a total of 29 MMCs were recorded by ADM. WMC detected 86% of MMC events measured by ADM. Hundred percent (10/10) of MMCs in stomach were detected by WMC, whereas 79% (15/19) of MMCs were detected in SB. The sensitivity and specificity of WMC high amplitude contractions to represent phase III MMC were 90% and 71.8% in the stomach; 73.7% and 84.7% in SB, respectively, and negative predictive value was 99.9% in both regions. Conclusions & Inferences Wireless motility capsule was able to detect the phase III MMCs as the high amplitude contractions with good fidelity. WMC does not detect the propagation of MMC. Using the pressure thresholds, WMC can detect high amplitude contraction representing phase III MMC with favorable sensitivity/specificity profile and 99.9% negative predictive value. This observation may have clinical significance, as the absence of high amplitude contractions recorded by WMC during fasting state suggests absence of MMCs.     

Neuropeptide Y Inhibits the Migrating Myoelectric Complex and Delays Small Intestinal Transit in Rats

The effect of neuropeptide Y (NPY) on myoelectric activity of the small intestine was related to transit of a radioactive marker in fasted conscious rats. Myoelectric activity was recorded with bipolar electrodes implanted 5, 20, and 35 em distal to pylorus. A radioactive marker was administered luminally in the duodenum immediately after an activity front of a migrating myoelectric complex (MMC) had passed the first recording site. Intravenous infusion of NPY (50–100 pmol kg⁻¹ min ⁻¹) did not affect the MMC in the duodenum but interrupted its distal propagation and inhibited spiking in the jejunum. At higher doses, NPY (200–800 pmol kg⁻¹ min⁻¹) abolished the MMC at all recording sites. Effects of NPY on myoelectric activity were not prevented by guanethidine, phentolamine, propranolol, or naloxone. The effects of NPY on myoelectric activity corresponded to a dose-related slowing of transit of the marker. In controls, the peak of the marker was propagated ahead of the activity front over the three recording sites. NPY (100 pmol kg⁻¹ min⁻¹) slowed transit, with the peak of the marker proximal to the third electrode site. NPY (400 pmol kg⁻¹ min⁻¹) further delayed transit, with the peak of the marker proximal to the second electrode site. We conclude that the activity front of the MMC exerts a high propulsive capacity. NPY produced a dose-related nonadrenergic inhibition of the intestinal myoelectric activity, which may account for a delayed transit of intestinal contents.     

Motilin, erythromycin, and the gastric migrating motor complex: site of action

Motilin is a putative hormone which induces a premature migrating motor complex when administered exogenously, but the target organ for this hormonal effect is undetermined. Our aim was to determine whether motilin and the motilin agonist, erythromycin, induce a premature migrating motor complex via an effect directly on the stomach. Six dogs underwent splenectomy and ligation of all branches of the splenic artery except the left gastroepiploic and short gastric arteries to the proximal stomach. An intra-arterial catheter was placed in the proximal splenic artery for close intra-arterial injection of motilin and erythromycin directly to the gastric corpus/proximal antrum. After recovery, the minimum effective dose required to induce a premature migrating motor complex was determined for motilin and for erythromycin given close intra-arterially or intravenously (systemically) by monitoring upper gut myoelectric activity. Minimum effective doses of motilin and erythromycin were the same whether given intra-arterially or intravenously. The latency interval or the time to onset of a premature Phase III was less than 2 minutes for intra-arterial or intravenous administration (P > 0.05). The characteristics of induced-Phase HI activity (appearance, duration, velocity) did not differ from spontaneous Phase HI activity (P > 0.05). Although plasma motilin concentrations increased after threshold doses of both motilin and erythromycin, increases in plasma motilin occurred later after erythromycin (lOmin) than after exogenous motilin (3 min). Our findings suggest that motilin initiation of the migrating motor complex does not occur by independent stimulation of putative receptors in the gastric corpus or proximal antrum.     

The migrating motor complex modulates intestinal motility response and rate of gastric emptying of caloric meals

Abstract The present study elucidates whether the phase of the migrating motor complex (MMC) present at the moment of food intake modulates postprandial motor response and rate of gastric emptying of caloric meals. Eight healthy male volunteers with a mean age of 26 years were examined twice. During water-perfused gastroduodenal manometry, a liquid meal with paracetamol added as a marker was orally administered during phase I and late phase II. Paracetamol appeared in serum 14.1 ± 3.8 min and 9.1 ± 4.0 (mean ± SD) min, respectively, after intake of the meal (P < 0.02). The area under the curve of s-paracetamol until 25 min after intake was 232 ± 169 μmoll_-1 min and 362 ± 130 (P < 0.05), respectively. When taken during late phase II, a phase III-like activity occurred within 2.1 ± 1.3 min in the duodenum, and was succeeded by quiescence. During phase I, the meal invariably initiated irregular contractions within 4 min. The phase of MMC during which a caloric meal is ingested modulates duodenal motor response and rate of gastric emptying during the initial postprandial period. Initial postprandial motor activity thus represents the combined effect of nutrient stimulation and the underlying enteric biorhythm as reflected by phase of MMC.     

Role of Cholecystokinin in Gallbladder and Duodenal Motility in the Interdigestive State of Dogs

This study was designed to determine the role of cholecystokinin (CCK) in the motility patterns of duodenum and gallbladder in fasted conscious dogs. During the naturally occurring activity front in the duodenum a significant increase in the motility index, (MI) of the gallbladder was accompanied by a decrease in the gallbladder volume from about 28 ± 4 ml (control) to 21 ± 3 ml. Similar changes in the gallbladder were observed after intravenous bolus injections of motilin (20 to 40 ng/kg), which gave increments in plasma motilin comparable to those occurring spontaneously during the activity front but failed to affect plasma levels of CCK. Blocking of CCK receptors by L-364, 718 (0.5 to 1 mg/kg) delayed the occurrence of the spontaneous activity front in the duodenum and the accompanying alterations in the gallbladder motility. CCK receptor antagonism abolished the premature activity front induced by motilin in both the duodenum and the gallbladder, converted the fed-like pattern induced by exogenous CCK to a fasted motility pattern in the duodenum and prevented CCK-induced reduction in the gallbladder volume. Atropine (12.5 μg/kg) blocked the spontaneous activity front in the duodenum and accompanying alterations in the gallbladder motility and volume but failed to affect those induced by motilin. We conclude that the motility of the gallbladder in fasted dogs shows cyclic changes with typical reduction in the organ volume coinciding with the spontaneous or motilin-induced activity front in the duodenum, and that both CCK and muscarinic receptors are involved in the MMC-related alterations in the motor activity of the gallbladder.