The effect of intracerebroventricular (ICV) administration of cholecystokinin-8 (CCK-8) (0.5, 1.0, 2.0, 4.0 µg) on plasma levels of. pancreatic polypeptide (PP) was studied in conscious dogs. ICV administration of CCK-8 (1.0, 2.0, 4.0 µg) produced a rapid and transient elevation in plasma concentrations of PP. Peripheral muscarinic receptor blockade with atropine or truncal vagotomy abolished PP secretion induced by ICV CCK-8. Pretreatment with ICV atropine also prevented the elevation in plasma PP induced by CCK-8. Plasma levels of CCK-33/39, CCK-8, and gastrin were not affected by ICV CCK-8. Our results indicate that central administration of CCK-8 selectively elevated plasma PP concentration. Since the effect of CCK-8 on plasma PP was abolished by central and peripheral atropine pretreatment, as well as by vagotomy, central and peripheral vagal cholinergic mechanisms appear to participate in release of PP that is induced by CCK-8 given by ICV injection.
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