The inhibitory effect of peptide YY on contractile activity in the innervated main stomach and the vagally denervated fundic pouch in conscious Heidenhain pouch dogs was investigated. Peptide YY was given in i.v. bolus injections of doses between 12.5 and 100 pmol/kg body wt. During the digestive state, 2-3 h after feeding, peptide YY was found to have no effect on contractile activity in either the innervated or the vagally denervated stomach. In the interdigestive state, it was found that peptide YY inhibited the interdigestive migrating contractions in the innervated main stomach dose-dependently for 1.2 +/- 0.1 to 5.8 +/- 0.3 min, but did not affect pouch contractions at all. This peptide, however, did not influence the cycle of the interdigestive migrating contractions. Pentagastrin, on the other hand, suppressed the interdigestive migrating contractions in the innervated main stomach when the bolus doses were greater than 300 pmol/kg body wt, but did not inhibit pouch contractions completely with this dose. Atropine (0.05 mg/kg body wt) suppressed contractions in both the main stomach and the vagally denervated pouch. Peptide YY inhibits the interdigestive migrating contractions in the stomach through the extrinsic nerves.