Long-term intrathecal catheterization in the rat

We report an intrathecal (i.t.) catheter system that permits repeated administration of volumes of 10 microl or more in the awake rat over many months. A small skin incision is made and a 32 ga polyurethane catheter is inserted in the sacral subarachnoid space using a modified 22 ga needle. The other end of the catheter is tunneled subcutaneously to the flank and exteriorized through a titanium port. The device is well tolerated, does not cause sensory or motor deficits, and does not interfere with behavioral testing. Rats equipped with this device can be housed with other rats. Over the 9 month observation period the function of the catheter was verified by repeated injection of 15 microl of 2% lidocaine that caused temporary paraplegia. Out of 12 implanted rats, the number of fully functional catheters was 10 at 3 months, seven at 6 months, and six at 9 months. At 3 months, i.t. injection of anti-dopamine-beta-hydroxylase antibodies conjugated to saporin (DBH-SAP, 5 microg/10 microl) resulted in noradrenergic denervation of the spinal cord in all rats (n=10). We propose that intrathecal catheterization is well suited for long term behavioral and pharmacological studies.