Influence of Various Feeding Conditions, the Migrating Myoelectric Complex and Cholinergic Drugs on Antral Slow Waves in Sheep

Abstract

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.

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

“…1). These criteria were very similar to those described earlier (Romański, 2002a,b). The percentage of slow waves with spikes was calculated considering the slow wave frequency (cpm) in the given region.…”

“…Secondly, the influence of endogenous CCK may interfere with cerulein action. Thus, cerulein affects the MMC in sheep and the weaker effects of the hormone administered during phase 1 MMC than during phase 2 MMC probably results from the refractory period present during phase 1 MMC as it was suggested earlier (Romański, 2002b). Furthermore, it seems likely that the nervous system may contribute in cerulein action on the MMC in sheep.…”

“…The recordings were visually analysed and the MMC and its phases were identified in the small intestine according to the criteria proposed by Code and Marlett (1975), including the division of phase 2 MMC into phase 2a and 2b (Dent et al, 1983, Romański, 2002a,b). The onset of phase 2a MMC was identified as the first 3‐min period of the myoelectric activity recording during which at least 10% of the slow waves were superimposed with the spike burst and which was followed by a period of not longer than 6 min when the incidence of the spike bursts was <10% (Code and Marlett, 1975).…”

“…The percentage of slow waves with spikes was calculated considering the slow wave frequency (cpm) in the given region. Phase 3 MMC started just after phase 2b MMC and was identified as the regular appearance of spike bursts which were superimposed on every slow wave and were of the relatively high amplitude (Romański, 2002b), as shown in Fig. 2.…”

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

“…The spike bursts of longer durations, that is, which last longer than the plateau phase of the slow wave (over 3 sec in the stomach), can occur independently of the slow waves and induce longer contractions (Sarna 2002 ). Slow waves arrive in the stomach and small bowel regularly, also in sheep (Roman´ski 2002a ). They are also present in the ovine gallbladder, although not always detected there (Roman´ski 2004a ).…”