Effects of chronic morphine on biliary tract responses to cholecystokinin-octapeptide in female guinea pigs.

Acute and chronic opiates impairs the emptying of bile from the gallbladder of male guinea pigs. In view of the higher incidence of gallstone attacks in women, the aim of this study was to determine if this impairment would extend to female guinea pigs. Implantation of morphine pellets (400mg) in female guinea pigs did depress CCK-induced emptying of gallbladder bile. Likewise, gallbladder muscle strips isolated from the morphine treated animals showed depressed responses to CCK. The morphine treatment also antagonized CCK-induced cessation of bile flow present in female guinea pigs. In addition, the morphine treatment blocked both CCK-induced phasic contractions of the isolated isolated Sphincter of Oddi and the secondary cessation of bile flow observed following iv CCK. Thus this study demonstrates that opiate antagonism of CCK does extend to the biliary tract of female guinea pigs, and suggests that resultant biliary stasis could facilitate gallstone formation.