Effect of Cholecystokinin-Octapeptide and Cerulein on Phasic and Tonic Components in Ovine Duodenum with Special Reference to the 'Minute Rhythm'

Abstract

Cholecystokinin (CCK) can affect phasic contractions and the minute rhythm (MR) in ovine duodenum but its effect on the tonic component remains unclear. Thus, the aim of this study was to assess whether the hormone exerts significant changes on phasic and tonic components of the duodenal motor activity and on phasic and tonic components of the duodenal MR. Mechanical and electrical activities of the duodenum were recorded in four sheep before and after slow intravenous cholecystokinin octapeptide (CCK-OP, doses 20, 200 and 2000 ng/kg b.w.) and cerulein (doses 1, 10 and 100 ng/kg b.w.) administration in the course of phase 2b of the migrating motor complex. During 5-20-minute periods the area under contraction curve for phasic, tonic and total motor activity was measured for the whole curve and separately for the MR- related activity. It was found that both CCK peptides stimulate phasic and tonic components of the duodenal motor activity as well as both these components of the duodenal MR. The effect of CCK peptides on the tonic component was stronger than on the phasic component. These effects were similar in non-fasted and fasted animals. CCK-OP evoked slightly greater effect than cerulein. The effects of these CCK peptides on phasic and tonic components of the MR were similar. It is concluded that CCK-OP and cerulein stimulate both phasic and tonic components of the duodenal motor activity and phasic and tonic components related to the MR in sheep.