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

K W Romański

doi:10.2754/avb200776010017

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.

Highlights

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 administration in the course of phase 2b of the migrating motor complex
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 minute rhythm (MR) in sheep
When the effects of CCK peptides on both phasic and tonic components were added, both higher doses of CCK-OP exerted significant effect while only the highest dose of cerulein was effective. Both CCK peptides significantly altered the myoelectric and motor responses examined in ovine duodenum

Summary

Introduction

Cholecystokinin (CCK) can affect phasic contractions and the minute rhythm (MR) in ovine duodenum but its effect on the tonic component remains unclear. Beside the migrating motor complex (MMC) and feeding pattern, it is one of the basic motility patterns and comprises one or even more consecutive contractions or spike bursts arriving cyclically, every around one-minute periods This pattern occurs mainly during the longest MMC phase and migrates through the upper small bowel or exhibits a stationary character (Romaƒski 2002). It seems likely that MR can exhibit phasic and tonic component and it may mean that the propulsive efficacy of the MR would be expected to be greater It appears that cholecystokinin (CCK) is able to affect the small-intestinal MR in sheep. Our aim was: 1) to determine separately the phasic and tonic component of mechanical activity before and after CCK-OP and cerulein administration (mainly for comparison of their potencies) and 2) to establish whether the MR exhibits its tonic component and whether the CCK peptides can affect both phasic and tonic components of the MR in the duodenum, where the MR is most precisely identifable

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