Pancreatic Response of Anaesthetized and Conscious Rats to Bolus Injection of Cholecystokinin-Pancreozymin

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Abstract
Pancreatic secretion was studied in anesthetized rats tested immediately after surgery or in conscious rats tested 48 h after the cannulation of the pancreatic duct. Pancreatic flow, protein output and enzyme output were measured over a 30-min period in the unstimulated state and after the i.v. injection of bolus doses of cholecystokinin-pancreozymin (CCK-PZ). Each animal received 3 doses of CCK-PZ, as ascending or descending doses. In anesthetized rats there was a linear relationship between the log-dose of CCK-PZ and the flow, protein and enzyme output with the ascending and descending doses. In conscious rats flow was unaffected by CCK-PZ and protein output was greatest after the 1st dose, whether this was given in the ascending or descending doses. At all CCK-PZ levels flow in anesthetized rats was less than that seen in conscious animals, but at doses of CCK-PZ > 5.00 CHRU (Crick Harper Raper Units) protein output was greater in anesthetized rats than in conscious rats. Ultrastructural studies of the pancreas showed areas of focal cytoplasmic degeneration and possible blockage of the duct with cellular debris after administration of high doses of CCK-PZ to conscious rats. These changes may be responsible for the reduced protein output with the 2nd and 3rd doses of CCK-PZ in these animals. No such changes were seen in anesthetized rats after similar doses of CCK-PZ. Fundamental differences in the response of the pancreas to CCK-PZ in anesthetized and conscious rats are shown. The mechanism for this difference is not clear, but it may represent a change in the normal response to CCK-PZ in the anesthetized rats as a result of the effects of acute operative trauma, possibly acting through changes in pancreatic blood flow.