Evidence for central neuropeptidergic control of rumination in sheep.

Effects of intracerebroventricular (ICV) vs. intravenous (IV) administration of tetragastrin, pentagastrin, CCK8 and gastrin 17 on rumination were investigated in conscious sheep. Administered at 26 pmoles/kg ICV both tetra and pentagastrin induced a premature short (15-27 min) period of rumination only 24 +/- 7 and 23 +/- 9 min after food distribution in place of 112 +/- 44 min in controls. Similar but less pronounced effects were observed for ICV administration of an equimolar dose of gastrin 17 whereas CCK8 did not promote an early period of rumination despite its anorectic effects. Administered intravenously tetra and pentagastrin but not gastrin 17 caused early rumination only for 10 times higher doses. It is concluded that gastrin 17 and its C-terminal tetrapeptide may play a physiological role in the central control of rumination in sheep.