| Research Abstract |
Two types of CCK receptors (type A and type B) have been identified. We raised CCK-A,-B and AB receptor knockout mice, the role of these receptors in gastric functions and bile-pancreatic secretions was determined.
1. Basal gastric acid secretion was decreased in mice lacking CCK-BR. Administration of gastrin and histamine significantly increased acid secretion in all genotypes.
2. Lack of CCK-BR enhanced gastric emptying of a liquid load. The gastric emptying was inhibited by administration of CCK in mice with CCK-AR, but not in mice without CCK-AR. Atropine inhibited gastric emptying in all genotypes, however, larger doses were required to reveal a similar effect in mice with CCK-BR to in mice without CCK-BR. Therefore, autonomic nerve functions might be altered by the lack of CCK-BR
3. We confirmed that CCK did not induce gallbladder contraction nor pancreatic amylase secretion in CCK-AR(-/-) mice. Other stimulants such as acethocholine and neuromedin C could stimulated amylase secretion in CCK-AR(-/-) mice but could not produce gallbladder contraction. Secretin failed to increase bicarbonate secretion in mice, and CCK increased bicarbonate secretion via CCK-A receptor in mice. Glucose tolerance was not altered in CCK-AR(-/-) mice.
4. Age associated gallstone formation was induced by administration of a higher protein and fat diet in CCK-AR(-/-) mice, but not in wild type mice.
5. Anxiety related behaviors in the plus maze were increased in mice without CCK-BR.
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