The present experiments examined the local effects of cholecystokinin-octapeptide (CCK-8) and related peptides on gastric motility of anesthetized dogs. Peptides were injected through the gastroepiploic artery at doses of 1.0, 2.5, 5.0, 10.0, and 20.0 ng/ml. CCK-8 and its analogues (Glt-CCK-8, pGlu-CCK-8, and Suc1-MePhe8-CCK-7) increased gastric smooth muscle contraction in a dose-dependent manner. ED50 of CCK-8 was 2.97 +/- 0.63 ng/ml. Administration of atropine (100-200 micrograms/kg) inhibited the effects of both CCK-8 and pentagastrin; however, hexamethonium (5 mg/kg) failed to block the contractile response induced by CCK-8 and pentagastrin. These results indicate that CCK-8 and related peptides can act as local modulators in controlling the neural regulation of gastric motility.