Influence of various feeding conditions, the migrating myoelectric complex and cholinergic drugs on antral slow waves in sheep

Occurrence of the specific long spike burst pattern in the ovine proximal gallbladder as an indication of myoelectric regional variability

The myoelectrical activity of the ovine gallbladder has not been fully recognised. Five rams were fitted with six small intestinal and three gallbladder electrodes and a strain gauge force transducer was mounted near the gallbladder fundic electrode. In two series of successive experiments, the electromyographical and mechanical recordings were recorded over a period of 5–7 hours. The occurrence of the slow waves in the small bowel was regular, unlike those in the gallbladder. In the gallbladder infundibulum, the specific pattern, called the long spike burst pattern (LSBP), was observed. It comprised usually one or two parts of prolonged duration. The first part resembled the classical (short lasting) spike burst in the small bowel, and its amplitude was lower than that of the second part. The spike burst frequency of the second part was 2–3 times lower than that of the first part. During phase 1-like and phase 2a-like activities, the intensity of the gallbladder LSBP was reduced while enhanced after feeding. In fasted rams, the duration of a specific pattern, observed in the gallbladder infundibulum, was longer than in non-fasted animals and its amplitude was low. Similar events were recorded in the gallbladder corpus, but the specific pattern was shorter and irregular. In the gallbladder fundus, mostly irregular short spike bursts were recorded. It is concluded that in sheep, specific types of the long-lasting groups of spikes occur in the upper gallbladder areas exhibiting myoelectrical regional variability. The character of an LSBP depends on feeding conditions.

Regional differences in the effects of various doses of cerulein upon the small-intestinal migrating motor complex in fasted and non-fasted sheep

There are no precise data concerning the effect of cerulein on the small-intestinal migrating motor complex (MMC) in sheep. Thus, the effort was directed towards the elucidation of the role of cerulein, a cholecystokinin (CCK) amphibian analogue, in the regulation of MMC cycle in conscious fasted and non-fasted sheep in various regions of the small intestine. In six sheep, equipped with bipolar electrodes in the entire small intestine and with one duodenal strain gauge force transducer in four of these animals, the continuous myoelectric and motor activity recordings were performed. During control period, two normal consecutive MMC cycles were recorded in fasted and non-fasted animals and then cerulein was slowly injected at the dose 1 (during 30 s), 10 (during 30 s or 60 s) or 100 ng/kg (during 30 s, 60 s or 120 s) or infused at the dose 0.5 or 1.5 ng/kg/min during 60 min. After cerulein administration at least two consecutive MMC cycles were also recorded. It was found that cerulein in moderate and higher doses injected in both fasted and non-fasted animals, especially during phase 2a or 2b MMC, inhibited phase 3 in the duodenum in at least one-third of the experiments and significantly increased the MMC cycle duration. The application of 100 ng/kg of cerulein during 120 s in the course of phase 2b MMC prolonged cycle duration from 70 +/- 21 to 113 +/- 19 min (p < 0.05) or from 51 +/- 18 to 113 +/- 19 min (p < 0.01) in fasted and non-fasted sheep respectively. The first phase 3 MMC arriving after cerulein administration at the highest dose was usually abnormal in approximately 60% of the experiments. The second phase 3 observed following the hormone injection was abnormal much less frequently and to the lesser extent. Furthermore, both cerulein doses significantly shortened the duration of phase 3 MMC either in fasted (from approximately 5.5-6.5 cpm to 4-5 cpm) or in non-fasted sheep (from approximately 4.5-5.5 to 3-4.5 cpm). The effects of cerulein exhibited the dose-response character. They were more pronounced when cerulein was injected during phase 2b or 2a MMC when compared with phase 1 MMC. The effects of cerulein on the ileal MMC were less evident, although the inhibition of the ileal phase 3 in response to both higher injected doses was observed occasionally. Infusions of cerulein in non-fasted sheep exerted similar effects as cerulein injections. It was stated that cerulein exerts marked regulatory effect upon the small-intestinal MMC in sheep. Although it remains uncertain whether the efficient doses of cerulein used in the present study correspond to physiological or pharmacological doses of CCK it seems likely that most of these doses were physiological. Thus, it is concluded that cerulein participates in the control of MMC cycles in the digestive and interdigestive states in sheep. It is possible that CCK is a physiological regulator of the ovine small-intestinal MMC.

Effects of motilin and ursodeoxycholic acid on gastrointestinal myoelectric activity of different origins in fasted rats

AIM: To investigate gastrointestinal migrating myoelectric complex (MMC) and the effects of porcine motilin and ursodeoxycholic acid (UDCA) on MMC of gastrointestinal tract of different origins in fasted rats.

METHODS: Three bipolar silver electrodes were chronically implanted on the antrum, duodenum and jejunum. Seven days later 24 experimental rats were divided into 2 groups. One group was injected with porcine motilin via sublingual vein at a dose of 20 μg/kg, the other group was perfused into stomach with UDCA. The gastrointestinal myoelectric activity was recorded 1 h before and 2 h after the test substance infusions into the rats.

RESULTS: In all fasted rats a typical pattern of MMC was observed. Among the totally 68 activity fronts recorded in fasted rats under control, 67% started in duodenum, and 33% in antrum. MMC cycle duration and duration of phase III of antral origin were longer than those of duodenal origin. Administration of 20 μg/kg porcine motilin induced a premature antral phase III of antral origin. But perfusion into stomach with UDCA resulted in shorter MMC cycle duration, longer duration of phase III of duodenal origin, which were followed with shorter cycle duration and duration of antral phase III.

CONCLUSION: In fasted rats, MMC could originate from antrum and duodenum respectively. The characteristics of MMC of different origins may contribute to the large variations within subjects. The mechanisms of different origins of phase III may be different. Porcine motilin and UDCA could affect MMC of different origins of the gastrointestinal tract in fasted state, respectively.