Distribution of intrathecal catheter positions in rat

Background: Although drug administration through an intrathecal catheter is widely used in the study of spinal pharmacology, the catheter positions in transverse plane that may cause a limited spread of a solution remain unclear In the first step to clarify this issue, the distribution of the intrathecal catheter position was investigated in rats. Methods: A polyethylene catheter (PE-10) was inserted intrathecally 8.5 cm through the atlanto-occipital membrane, aiming the tip of the catheter to the dorsal surface of the spinal cord. Three or four weeks after the implantation of the catheter, 83 rats were transcardiacally perfused with fixative solution. The catheter positions were investigated longitudinally and transversely by cutting the spinal cord segmentally through the intervertebral disk at different spinal levels. Results: Seventeen rats were excluded from further data analysis. Transversely, catheters were located in the left lateral subarachnoid space in 23 rats (35%), in the right lateral in 15 (23%), in the dorsal in 22 (33%), and in the ventral in G (9%). Longitudinally, catheter position was significantly higher in the ventral group (median, T9) than that in the dorsal group (T11/12) (P <0.01). Conclusion: Chronic intrathecal catheters were variously located in the rat spinal subarachnoid space in the transverse plane, and lateral subarachnoid placement of the catheter (58%) was frequently observed, whereas dorsal subarachnoid placement occurred in 33%.