The effects of intravenous cholecystokinin, secretin and pentagastrin on electromyographic activity of the rumen in sheep.

Several gastroenteropancreatic (GEP) peptides have been reported to alter ruminal motility. In the present study, we tested the effects of three of these peptides on ruminal myoelectrical activity in the sheep. We measured the effect of 10 min IV infusions of pentagastrin, secretin, and cholecystokinin, either alone or in combination, on the spike frequency of the rumen in conscious sheep. IV administration of 780 pmol/kg pentagastrin significantly decreased spike frequency within 10 min with a return towards control levels over the subsequent 30 min. Secretin decreased ruminal spike activity at doses of 120 and 180 pmol/kg. Finally, 13, 26 and 35 pmol/kg IV cholecystokinin all resulted in significant decreases of spike frequency, with virtual elimination of spiking activity at the highest dose. Administration of the lowest dose of secretin, or the single dose of pentagastrin, with the lowest dose of CCK resulted in a potentiation of their inhibitory effects. We conclude that one mechanism underlying the altered motility induced by these GEP peptides is a decrease of spike frequency which may contribute to overall contractile activity.