GALLBLADDER PRESSURE-VOLUME RESPONSE TO GASTROINTESTINAL HORMONES

The pressure-volume (PV) response of the opossum [Didelphis virginiana] gallbladder was studied under basal conditions and after the continuous i.v. infusion of gastrin I, secretin and cholecystokinin (CCK). The hormone effects were examined individually and in combination. The unstimulated gallbladder was capable of accommodating increases in intraluminal volume with only slight changes in intraluminal pressure. Cholecystokinin significantly increased the pressure recorded from the gallbladder. The pressure generated depended on the concentration of CCK and the intraluminal volume. Gastrin I had no independent effect on the PV response of the gallbladder but reduced the stimulatory affect of CCK. Secretin, alone, decreased the PV response of the gallbladder. Secretin also antagonized the stimulatory response to CCK. The regulation of gallbladder motor function and pressure generation, exclusive of neural input, may depend on the interaction of CCK with gastrin and secretin and the intraluminal volume of the organ at the time of stimulation.