A new system for long-term vascular access in the unrestrained rat (n
= 380) is described that combines low cost with high reliability and f
ree movement. It consists of a polyurethane catheter that is placed in
the right atrium via the external jugular vein. A leather harness is
applied to the animal and the catheter passed subcutaneously to the ne
ck into the harness. The harness is connected to the outside of a swiv
el joint via a silicone tube in which the catheter runs. The catheter
is connected to the inside of the swivel. The swivel is a modified con
ventional 5-mL glass syringe and is positioned in ball bearings and Jo
hnson joint. Swivel, ball bearings, and the Johnson joint are counterb
alanced and can move up and down. With this system all catheter functi
oned well until they were electively removed after 28 days. Four cathe
ter dislocations resulted from harness failure and three from a twiste
d catheter. Seven cases of septicemia and eight of thrombosis cccured.
All animals gained weight (3.53 +/- 0.37 [SEM] g/d) during the time t
he system was in place. The entire apparatus is simple and inexpensive
to construct. The rotary portion of the swivel and the Johnson joint
avoid twisting of the catheter, and the counterbalance enables the ani
mal to move up and down. The low thrombogenicity of polyurethane furth
er reduced complications. This system reduces stress for the animal du
ring long-term investigations.