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.
The long-acting somatostatin analogue SMS 201-995, also called Sandostatin, is used in the treatment of acromegaly and peptide-secreting tumors. Little is known about its effect on gut motility, although such an effect might be expected considering the spectrum of activities of its parent molecule, somatostatin. We have studied the effect on the interdigestive motility of intravenous boluses of 0, 0.1, 0.5, 1.5, and 5.0 micrograms/kg of this analogue in 10 dogs with bipolar electrodes implanted along the entire small bowel. All doses induced, within 5 min of administration, premature phase-3 activity that was isolated to one segment, normally progressive, or simultaneous (stationary) in all channels. Only low doses induced isolated phase 3, whereas the frequency of the induction of stationary phase 3 increased with higher doses. In the next cycle of the migrating motor complex the duration of phase 1 was increased, although the duration of the whole cycle was not changed. This cycle ended with mostly ectopic phase-3 activity. During phase 2 of the following cycle ultra-rapid rushes of spiking activity progressing at a speed of 25 +/- 3 cm/sec in the upper jejunum were regularly observed. Although this pattern occurs very rarely under control conditions, it was present in 20%, 80%, and 100% of the experiments after doses of 0.5, 1.5, and 5.0 micrograms/kg, respectively. We conclude that gastrointestinal side effects observed during administration of SMS 201-995 might be related to these motility effects, which warrant further investigation. SMS 201-995 may be a tool to study the mechanism of the induction of ultra-rapid rushes and of stationary phase 3.
Cholecystokinin (CCK) can affect phasic contractions and the minute rhythm (MR) in ovine duodenum but its effect on the tonic component remains unclear. Thus, the aim of this study was to assess whether the hormone exerts significant changes on phasic and tonic components of the duodenal motor activity and on phasic and tonic components of the duodenal MR. Mechanical and electrical activities of the duodenum were recorded in four sheep before and after slow intravenous cholecystokinin octapeptide (CCK-OP, doses 20, 200 and 2000 ng/kg b.w.) and cerulein (doses 1, 10 and 100 ng/kg b.w.) administration in the course of phase 2b of the migrating motor complex. During 5-20-minute periods the area under contraction curve for phasic, tonic and total motor activity was measured for the whole curve and separately for the MR-related activity. It was found that both CCK peptides stimulate phasic and tonic components of the duodenal motor activity as well as both these components of the duodenal MR. The effect of CCK peptides on the tonic component was stronger than on the phasic component. These effects were similar in non-fasted and fasted animals. CCK-OP evoked slightly greater effect than cerulein. The effects of these CCK peptides on phasic and tonic components of the MR were similar. It is concluded that CCK-OP and cerulein stimulate both phasic and tonic components of the duodenal motor activity and phasic and tonic components related to the MR in sheep. , small bowel, myoelectrical and motor activity, cholecystokinin Ruminants
Cholecystokinin (CCK) can exert multiple actions on intestinal motility but its effect on the small-intestinal 'minute rhythm' (MR) is virtually unknown. Therefore, the electrical activity from the abomasal antrum, duodenal bulb, duodenum, jejunum and ileum was continuously recorded in six sheep before, during and after slow intravenous administration, of three doses each, of cholecystokinin-octapeptide (CCK-OP) and cerulein. In four of these sheep, two additional electrodes and the strain gauge force transducer were also inserted in the duodenum. Chronic experiments were performed in the fasted and non-fasted animals and saline or CCK peptides were injected during phases 1, 2a or 2b of the duodenal migrating myoelectric complex (MMC). The administration of both CCK peptides in various doses evoked an inhibitory effect mostly in the duodenal bulb, except for the lowest dose of cerulein. The effects of 20 times greater doses of CCK-OP than that of cerulein were more pronounced. The introduction of both CCK peptides during phase 1 of the MMC produced no marked or significant response. In non-fasted animals, the effects of both hormonal peptides, given during phase 2b of the MMC, were often stronger than those given during phase 2a, while in fasted animals the effects of CCK peptides, administered in the course of phases 2a and 2b of the MMC, were similar. Both higher doses of CCK peptides increased the number of spike bursts within the given MR pattern in the duodenum and decreased the incidence of MR mostly in the duodenal bulb. The inhibitory effects of both CCK peptides on the bulbar MR exhibited a dose-response character, though the lowest dose often evoked the slight stimulatory response. It is concluded that CCK principally exerts an inhibitory effect upon the MR in the duodenal bulb and modifies the MR in the duodenum by increasing the spike burst number in a given MR pattern. Both these actions of CCK peptides seem to be physiological. There is a positive relationship between the intensity of the refractory period and the demonstrated effect of CCK in the duodenum.
The presented study was designed to elucidate whether the cholinergic mechanisms control ovine antral slow waves in various physiological conditions, including feeding and various phases of migrating myoelectric complex (MMC). The investigations were carried out on six adult sheep of Polish Merino breed with seven bipolar electrodes surgically implanted onto the antral and small intestinal wall. In the course of chronic experiments, the myoelectric activity was recorded from these regions using the multichannel electroencephalograph. Experiments were performed on 48 h fasted and non-fasted animals. During some of these experiments, sheep were fed with standard fodder. During control experiments 0.15 M NaCl was slowly administered i.v. through the indwelling catheter and during other experiment, hexamethonium bromide (2.0 and 5.0 mg/kg). atropine sulfate (0.02; 0.1; 0.5 and 1.5 mg/kg) and pirenzepine dihydrochloride (0.02; 0.5 and 2.0 mg/kg) were administered i.v. during phase 1-2a or 2b MMC. The drugs were also given in combinations. The recordings were analysed and the antral slow wave amplitudes and frequencies were calculated. Unlike the slow wave amplitude, either feeding or the anticholinergic drugs significantly increased slow wave frequency, especially when the given procedure was started during phase 2b MMC. The most pronounced effects were observed after hexamethonium given alone or in combinations. Thus, the cholinergic system modulates antral slow wave frequency in sheep.
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