The Importance of Refractoriness in Ovine Antral Digestive and Interdigestive Motility.

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. [ABSTRACT FROM AUTHOR]