The role of muscarinic and nicotinic receptors in the control of the ovine pyloric antral myoelectric response to nutrients during individual phases of the migrating myoelectric complex

Abstract

The precise role of the muscarinic and especially of nicotinic receptors as well as the extent of the influence of individual phases of the migrating myoelectric complex (MMC) in the control of postprandial motility in sheep have been incompletely recognized. To gain further understanding of these, the antral and small-intestinal myoelectric activity was continuously recorded in six conscious sheep with implanted bipolar platinum electrodes. The amplitude of antral spike bursts observed during phase 1, 2a or 2b MMC in non-fasted animals gradually increased (77 ± 13, 87 ± 16 and 102 ± 9 μV, respectively), while in the fasted animals these values exhibited a similar tendency, although the values were lower (67 ± 12, 88 ± 14 and 91 ± 6 μV, respectively). Feeding performed during phase 2b MMC increased the antral spike burst amplitude in fasted and non-fasted animals, compared to the relevant pre-feeding value. When feed was administered during phase 1 or 2a of the MMC cycle, a significant response was recorded only in the non-fasted sheep. When feed was given following hexamethonium (2.0 mg/kg i.v.), atropine (0.1 mg/kg i.v.) or pirenzepine (0.5 mg/kg i.v.) administration, the response was still significant. Furthermore, the anticholinergic drugs often exerted more pronounced effect in non-fasted than in fasted animals. Thus, the muscarinic and nicotinic receptors contribute substantially, but not entirely to the control of the postprandial gastric motility in sheep and the roles of various MMC phases in this control can differ.