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Motilin was infused in this study with the aim of examining refractory characteristics for motilin stimulation of antral phase III and fasting gallbladder emptying. Moreover, interdigestive pyloric and small intestinal motility from duodenum to ileum were studied, as these may be target organs for motilin. Eight fasting, healthy male volunteers received, on separate subsequent days, repeated infusions of 13leucine-motilin (8 pmol (kg min)(-1) for 5 min) or saline at 30 min after phase IIIs in the duodenum. Interdigestive motility of the antrum, pylorus, duodenum, jejunum and ileum was measured for maximum 10 h by using a 21-lumen perfused catheter. Gallbladder motility was measured by ultrasonography. Motilin infusions induced antral phase IIIs, but only after a preceding phase III of duodenal origin. Under this condition, time-interval to phase III at the duodenal recording site was 30 +/- 13 (SEM) min after motilin, compared with 79 +/- 14 min after saline (P < 0.01), and compared with 121 +/- 13 min for motilin infusion following an antral phase III (P < 0.001). Motilin did not affect small intestinal motility or isolated pyloric pressure waves (IPPWs). However, the number of IPPWs was significantly affected by the origin of the preceding phase III, irrespective of whether motilin or saline was infused. Gallbladder volume decreased significantly within 10 min after each motilin infusion. We conclude that this study clearly demonstrates differential regional effects of motilin. Motilin initiates antral phase IIIs, but stimulation is subject to a refractory period which is clearly prolonged after a preceding antral phase III. Motilin induced gallbladder emptying, however, is not subject to a refractory state. Small intestinal phase IIIs as well as pyloric IPPWs are not affected by motilin.

A plasma motilin peak and a partial gallbladder emptying precede the antral phase III of the migrating motor complex (MMC). To clarify the causal relationship between these factors, we aimed to study the role of motilin in interdigestive gastrointestinal and gallbladder motility simultaneously. In addition, involvement of 5HT3 receptors in the action of motilin was studied. Eight fasting, healthy male volunteers received 13Leu-motilin or 0.9% NaCl i.v. for 30 min, in randomized order on two separate occasions, from 30 min after phase III. Seven of the eight subjects also received the 5HT3 receptor antagonist ondansetron in addition to motilin, on a third occasion. Antroduodenal motility, gallbladder volumes and plasma motilin were measured. The interval between the start of infusion and phase III was 95.0 (57.6-155.7) min for saline, 28.7 (21.0-33.2) min for motilin, and 39.3 (30.7-100.5) min for motilin + ondansetron (P < 0.05). Gallbladder volume decreased by one-third from 10 min after both motilin and motilin + ondansetron infusion (P < 0.05), and returned to baseline with duodenal passage of phase III. In two of the seven subjects phase III was absent after motilin + ondansetron, although gallbladder volume decreased and only refilled during a later spontaneous phase III. We conclude that motilin induces both partial gallbladder emptying and antral phase III. Indeed, although gallbladder emptying clearly precedes antral phase III, ondansetron only prevented phase III in some cases and had no effect on gallbladder emptying. Passage of phase III in the duodenum makes an important contribution to gallbladder refilling.

A plasma motilin peak and a partial gallbladder emptying precede the antral phase III of the migrating motor complex (MMC). To clarify the causal relationship between these factors, we aimed to study the role of motilin in interdigestive gastrointestinal and gallbladder motility simultaneously. In addition, involvement of 5HT3 receptors in the action of motilin was studied. Eight fasting, healthy male volunteers received 13 Leu-motilin or 0.9% NaCl i.v. for 30 min, in randomized order on two separate occasions, from 30 min after phase III. Seven of the eight subjects also received the 5HT3 receptor antagonist ondansetron in addition to motilin, on a third occasion. Antroduodenal motility, gallbladder volumes and plasma motilin were measured. The interval between the start of infusion and phase III was 95.0 (57.6–155.7) min for saline, 28.7 (21.0–33.2) min for motilin, and 39.3 (30.7–100.5) min for motilin + ondansetron (P < 0.05). Gallbladder volume decreased by one-third from 10 min after both motilin and motilin + ondansetron infusion (P < 0.05), and returned to baseline with duodenal passage of phase III. In two of the seven subjects phase III was absent after motilin + ondansetron, although gallbladder volume decreased and only refilled during a later spontaneous phase III. We conclude that motilin induces both partial gallbladder emptying and antral phase III. Indeed, although gallbladder emptying clearly precedes antral phase III, ondansetron only prevented phase III in some cases and had no effect on gallbladder emptying. Passage of phase III in the duodenum makes an important contribution to gallbladder refilling. [ABSTRACT FROM AUTHOR]

The role of interdigestive gallbladder emptying in gallstone formation is unknown. In fasting healthy subjects, gallbladder emptying is associated with antral phase III of the migrating motor complex (MMC) and high plasma motilin. Therefore, gallbladder volumes and motilin levels were measured during 13 MMC cycles in 10 cholesterol gallstone patients and compared with 20 MMC cycles in 10 healthy subjects. MMC cycle length was longer in gallstone patients than in healthy subjects (158.2 +/- 17.0 vs 105.5 +/- 10.4 min, respectively; P < 0.05), due to longer phase I (39.8 +/- 5.7 vs 17.2 +/- 3.7 min, respectively; P < 0.05). In contrast to healthy subjects, gallstone patients had no significant fluctuations of gallbladder volume during the MMC cycle, and motilin concentrations were not different in MMC cycles with phase III originating in antrum or duodenum. During MMC cycles with phase III originating in the duodenum, motilin levels were twice as high in gallstone patients as in healthy subjects (P < 0.002). In conclusion, cholesterol gallstone patients have an abnormal MMC and motilin release pattern. Their interdigestive gallbladder emptying is reduced and dissociated from the MMC. These disturbances may contribute to gallstone formation. [ABSTRACT FROM AUTHOR]

Background/Aims: The enterohepatic circulation of bile acids is related to normal inter-digestive gastrointestinal motility, with the gut peptide motilin also being involved. This study aimed to investigate the effect of intraduodenal artificial bile infusion on antroduodenal and gallbladder motility so as to further elucidate the controlling factors. Methods: Twelve fasting, healthy male volunteers received artificial bile (80 mol% bile acids; 15 mol% phospholipids; 5 mol% cholesterol) or placebo (saline) intraduodenally for 10 min starting 30 min after the end of phase III, according to a double-blind, randomised, cross-over design. Antroduodenal motility, gallbladder volumes, and plasma motilin levels were measured. All values are means ± SEM. Results: The interval between infusion and the subsequent phase III, as well as the origin of this phase III were not significantly different between bile and saline. Antral pressure waves were significantly more frequent during and immediately after bile infusion compared with saline infusion (p < 0.05). The duration of phase I following infusion was significantly longer after bile (24.8 ± 3.7 min) than after saline infusion (13.1 ± 1.7 min; p < 0.05). The mean gallbladder volume tended to increase in the hours following bile infusion, but to decrease after saline infusion (p = 0.06). Plasma motilin increased after bile and saline infusion in an almost identical way. Conclusion: This study provides no clear evidence for a role of intraduodenal artificial bile (i.e. its main constituents) in the regulation of migrating motor complex cycling or feedback inhibition of inter-digestive gallbladder emptying.Copyright © 2001 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]