A Novel Long-Term Intrathecal Cannulation Technique in Rats: L5-L6 Approach With Cervical Externalization for Chronic...

Current intrathecal (IT) catheter techniques in rats are problematic due to complex surgical procedures and frequent blockages. This study developed a simpler, faster, and more reliable method for long-term IT catheter placement.

Fifty adult male Sprague-Dawley rats were randomly divided into three groups: IT group (n = 30), Sham group (n = 10), and Control group (n = 10). We inserted a polytetrafluoroethylene (PTFE) catheter (0.5-mm outer diameter, 0.3-mm inner diameter) into the cauda equina, reaching a depth of 0.5-1 cm via the L5-L6 intervertebral space. Then catheter was tunneled subcutaneously, exiting at the dorsal neck, and held in place with mechanical compression. We assessed safety and efficacy over 12 weeks through behavioral testing, functional evaluations, and immunofluorescence analysis.

Surgery took an average of 7.2 ± 1.8 min, with a 93.3% first-attempt success rate. Remarkably, all catheters remained patent throughout the 12-week study period (100% patency). Behavioral tests showed no changes in pain sensitivity, although rats did experience a temporary reduction in weight gain during the first postoperative week (p < 0.01). Lidocaine testing confirmed proper catheter function, with motor block occurring rapidly (onset: 30 ± 5 s), followed by complete recovery. Lipopolysaccharide doses of 3, 15, and 30 μg demonstrated clear dose-dependent inflammatory responses, confirming accurate drug delivery. Western blot analysis confirmed no chronic inflammation, with interleukin 1 beta (IL-1β), IL-6, and tumor necrosis factor alpha expression in the IT-Saline group comparable with controls (p > 0.05). Immunofluorescence analysis revealed no significant activation of microglia (ionized calcium-binding adaptor molecule 1) or astrocytes (glial fibrillary acidic protein) based on mean fluorescence intensity, with preserved neuronal density (NeuN-positive cells) comparable with controls.

Our L5-L6 approach effectively minimized the risk of spinal cord injury. The choice of PTFE material proved crucial, as it enabled 100% long-term patency, a result not achieved with other materials. Combined with the neck-mounted external design, this technique offers an improved approach for repeated IT drug delivery in rat models, but more studies are needed to confirm its effectiveness in a wider range of pharmacological applications.