INTRADUODENAL FAT AND AMINO-ACIDS ACTIVATE GALLBLADDER MOTILITY IN THE RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

The effects on gall bladder motility of intraduodenal injections of fat (cod liver oil) and amino acids were investigated in rainbow trout, Onchorhynchus mykiss, in vivo. Fat (1 ml/kg, 15 min) increased basic tonus of the gallbladder by 79% and frequency of contractions by 53%; both effects were antagonized by pretreatment with atropine (1.2 mg/kg). The amino acid mixture similarly increased tonus and frequency of contractions of the gallbladder smooth muscle by 63 and 109%, respectively. The effects were mimicked by intraarterial infusion of cholecystokinin (100 pmol-1 nmol/kg-hr), It is concluded that the presence of oil and amino acids in the duodenum stimulates rainbow trout gallbladder motility and tension, possibly by a release of cholecystokinin, and that the effect of oil, as for cholecystokinin, involves a cholinergic pathway. (C) 1995 Academic Press, Inc.