INTRATHECAL CATHETERIZATION IN THE RAT - IMPROVED TECHNIQUE FOR MORPHOLOGIC ANALYSIS OF DRUG-INDUCED INJURY

Background: The authors previously described an in vivo model suitable for investigation of functional impairment induced by intrathecally i njected local anesthetic. However, meaningful histologic analysis coul d not be performed be cause catheterization, per se, induced morpholog ic changes in control animals. In the current experiments, the authors sought to identify ail alternative, less reactive, catheterization te chnique for intrathecal drug administration. Methods: Twenty-five rats received an intrathecal infusion of normal saline. through a catheter composed of either 28-gauge polyurethane, 32-gauge polyimide, 32-gaug e polyurethane, PE-10 polyethylene, or PE-10 polyethylene that had bee n stretched to twice its original length. Seven days after infusion, s ensory function was assessed using the tail-flick test, and the spinal cord and nerve roots were prepared for neuropathologic evaluation. Re sults: There was no significant difference in sensory function among g roups. Animals in which 28-gauge polyurethane, 32-gauge polyimide, PE- 10, and double-stretched PE-10 had been implanted had. moderate to sev ere nerve injury in 11%, 14%, 23%, and 8% of fascicles, respectively, whereas none of the animals in which 32-gauge polyurethane was implant ed had any evidence of moderate or severe damage. Conclusions: Morphol ogic changes induced by intrathecal catheterization in the rat can be minimized by the use of 32-gauge polyurethane tubing.