A chronic arterial and venous cannulation method for freely moving rats.

A chronic arterial and venous cannulation method appropriate for pharmacokinetics studies in freely moving rats is described. Two catheters were implanted: one in the abdominal aorta, the other in the inferior vena cava. Passing subcutaneously, the catheters then emerged at the nape of the neck and were sealed by heating. In most cases (70%), 2-3 weeks after surgery, there were no problems of catheter patency. Twenty-four hours after surgery, all the animals were in good health as attested by normal behaviour and physiological parameters. Plasma corticosterone levels (544 +/- 219 ng/ml) determined at various times after an i.v. injection of saline, though 2.4-fold lower than in restrained rats (1330 +/- 292 ng/ml), were, however, indicative of a moderate stress. From a differential analysis of the factors involved in the relatively elevated circulating corticosterone as compared to basal levels, it is concluded that a prolonged postoperative period (7 days) and maintaining of the animals in metabolic cages are necessary conditions to obtain a minimal state of stress with this technique.