The evaluation of the role of CCK in the opioid modulation of the motilityof the gastrointestinal tract in sheep

The participation of central cholecystokinin-8 (CCK-8) receptors in the mod ulatory effect of D-Ala(2), N-Me-Phe(4), Gly(5)-ol enkephalin (DAGO), a sel ective mu-opioid receptor agonist, on the spike burst activity of the gastr ointestinal tract (rumen, reticulum, antrum, duodenum, colon and caecum) in sheep was investigated. DAGO was infused intracerebroventricularly (i.c.v. ) at doses of 0.1-1 mu g/kg body weight (BW). It was shown that DAGO significantly inhibited myoelectrical activity of th e wall of the forestomachs, abomasum and colon but stimulated this activity in the duodenum (rate of myoelectrical migrant complex-MMC). The effects o f DAGO were prevented by CCK-8 antagonists (L-364.718 and L-365.260) previo usly infused at doses of 5-20 mu g/kg BW. The results of this present study indicate that central receptors of CCK-8 participated in the modulatory action of an opioid on myoelectrical activit y of the gastrointestinal tract in sheep. Furthermore, this result suggests that CCK-8 is released in response to mu-receptor stimulation, because CCK -8 antagonists (L 364.718 and L 365.260) prevented the modulatory action of DAGO on the gastrointestinal motility in sheep.