The Importance of Refractoriness in Ovine Antral Digestive and Interdigestive Motility


Abstract: The aim of this work was to find possible differences between the effects of anticholinergic drug administration during the duodenal phase 1 or phase 2a of migrating myoelectric complex on antral spike burst amplitude in fasted and non-fasted sheep. Eight adult rams possessing bipolar electrodes in the antrum and small intestine were used in the study. Feeding increased significantly the spike burst amplitude range from 60-110 to 80-160 µV. The effects of hexamethonium (2 mg/kg), atropine (0.1 mg/kg) and pirenzepine (0.5 mg/kg) given i.v. during phase 1 of the migrating myoelectric complex (expressed as per cent of control) in non-fasted sheep were 68 ± 18, P < 0.05, 69 ± 20, P < 0.05, 45 ± 18, P < 0.01, respectively. The effects of the same doses of these drugs given during phase 2a of the migrating myoelectric complex in non-fasted sheep were 54 ± 13, P < 0.01, 41 ± 12, P < 0.0001, 33 ± 11, P < 0.0001, respectively. In non-fasted animals, the anticholinergic drugs exerted a more pronounced effect than in fasted animals. These effects were partially dose-dependent. The effects of drug combinations were not additive. It is concluded that the effects of anticholinergic substances given during phase 1 or 2a of migrating myoelectric complex and under various feeding conditions on ovine antral spike burst amplitude can vary, partially due to the intensity of the refractory period.

Keywords: Sheep, abomasal antrum, myoelectric activity, feeding, anticholinergic drugs

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