Characteristics and cholinergic control of the 'minute rhythm' in ovine antrum, small bowel and gallbladder

Clinical application and research progress of extracellular slow wave recording in the gastrointestinal tract

The physiological function of the gastrointestinal (GI) tract is based on the slow wave generated and transmitted by the interstitial cells of Cajal. Extracellular myoelectric recording techniques are often used to record the characteristics and propagation of slow wave and analyze the models of slow wave transmission under physiological and pathological conditions to further explore the mechanism of GI dysfunction. This article reviews the application and research progress of electromyography, bioelectromagnetic technology, and high-resolution mapping in animal and clinical experiments, summarizes the clinical application of GI electrical stimulation therapy, and reviews the electrophysiological research in the biliary system.

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.

Analysis of the excitatory motor response evoked by nicotinic and muscarinic blockade of ovine small bowel

It has been reported that the administration of anticholinergic drugs evokes inhibitory and excitatory responses, but the precise character of the latter has not yet been defined. This study was thus devoted to analyzing its occurrence following various doses of hexamethonium (Hx) and atropine (At) administration in the course of different phases of the small-intestinal migrating motor complex (MMC) in fasted and non-fasted sheep and to further characterize the excitatory responses in comparison with individual phases of the MMC. Two basic types of excitatory response were found. In the course of chronic experiments, various doses of Hx and At evoked rebound excitation (RE, i.e., irregular contractions or spike bursts evoked in response to the anticholinergic drug) alternating with phase 3-like activity (not the organized phase 3 of the MMC or its parts). The intensity of these changes varied and was related to the drug dose. Thus intense and non-intense RE activity were distinguished. In non-fasted sheep, these alterations were slightly less pronounced than in fasted animals. When the drug was given during phase 1 of the MMC, RE did not occur or was greatly reduced and its arrival was delayed. Hx triggered RE mostly in the duodenum, while the action of At was most effective in the jejunum. It is concluded that Hx and At initially hamper small-intestinal motility and just after that evoke a secondary stimulatory response, i.e., phase 3-like activity and RE of different intensity, duration, and repeatability in fasted and non-fasted sheep. These stimulatory effects may resemble unorganized phases of the MMC.

Dose-related effects of cholecystokinin octapeptide administered during various phases of the migrating motor complex on small-intestinal motility in sheep

Cholecystokinin (CCK) may affect intestinal motility, but in ruminants its precise effects have not been entirely explored. The aim of this study was to examine the effects of CCK-octapeptide (CCK-OP) on small-intestinal myoelectric activity in rams in the course of chronic experiments. Five rams underwent implantation of bipolar platinum electrodes to the duodenal bulb, distal duodenum, and jejunum as well as a strain gauge force transducer attached near the duodenal electrode. During continuous myoelectric recordings, 0.15 M NaCl or CCK-OP were injected slowly into the jugular vein. Injections of CCK-OP at doses of 20 (over 30 s), 200 (over 30 or 60 s) and 2000 (over 30, 60 or 120 s) ng/kg of body weight were each administered 5 or 30-40 min after the onset of the duodenal phase 1 or phase 2 of the migrating myoelectric complex (MMC), respectively. Most of these CCK doses were considered physiological. Injections of the smallest dose of CCK-OP exerted a slight and mostly insignificant inhibitory effect on the duodenal bulb and the duodenal myoelectric activity index (MAI) values. In the duodenal bulb, the effects of CCK-OP on myoelectric activity were dose dependent and closely related to the phase of the MMC. In the duodenum, the high dose of the hormone evoked short stimulatory and longer inhibitory biphasic effects on the MAI. These effects were inversely related to the duration of the hormone injection. It is concluded that CCK evokes a physiological stimulatory and inhibitory (biphasic) effect on the duodenal bulb and duodenal motility in sheep, with the inhibitory effect of the hormone being more pronounced in the duodenal bulb than in the duodenum. These effects were related to the CCK dose and the MMC phase. Therefore, CCK is an important regulator of upper small bowel motility in sheep.

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.

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

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.