Duodenal acidification and intra-arterial injection of CCK8 increase gallbladder motility in the rainbow trout, Oncorhynchus mykiss.

A sensitive method for in vivo measurement of intra-gallbladder pressure in free swimming rainbow trout (Oncorhynchus mykiss) is described. The method gives information on changes in gallbladder pressure after either instillation of liquids into the duodenum or infusion/injection of agents into the circulatory system. Blood samples can also be taken. Duodenal acidification is a potent initiating factor for gallbladder motility in the rainbow trout. Intra-arterially injected sulfated octapeptide of cholecystokinin is also a potent excitatory agent for activating the gallbladder. Acidification of the upper intestine causes release of cholecystokinin, which affects gallbladder motility in trout as in mammals.