Computer-controlled flushing for long-term cannulation in freely moving rats.

An in vivo long-term perfusion system is presented, which is based on automated, computer-controlled high-frequency heparin (10 U/mL) flushing of the cannula inserted into the tail artery of freely moving rats. The short flushing intervals as achieved with this system guarantee stable conditions throughout an experiment of several days, and reduce blood clotting and the infiltration of fibroblasts. In addition, a specially developed software enables the periodical application of test substances into the blood stream under time-controlled conditions over long periods. The system can be used continuously to follow up blood parameters in single animals without significant elicitation of stress-sensitive plasma catecholamines for up to 12 days.