CCKAR and gallstones: In spite of no sludge or gallstone formation at 6 months of age in either wild-type or CCK-1R(-/-) male mice fed CRF-1, the frequency of sludge and gallstone formation was substantially observed at 6 months of age in both wild-type and CCK-1R(-/-) male mice fed OA-2 [3 of 22 mice for wild-type and 5 of 18 mice for CCK-1R(-/-)].