Intrathecal Drug Delivery in Rat Pain Model

Drugs were delivered intrathecally. The intrathecal catheterization was performed according to our previous method.^{22 (link)} In brief, a polyethylene-10 (OD, 0.61 mm; ID, 0.28 mm) catheter was inserted into the rat’s subarachnoid space through L5–L6 intervertebral space, and the tip of the catheter was located at the L5 spinal segmental level. The CXCR4-specific antagonist AMD3100 and the NF-κB activation inhibitor PDTC were purchased from Sigma (St. Louis, USA) and freshly dissolved daily in normal sterile saline prior to use. Anti-CXCL12 neutralizing antibody (Abcam, ab25117) and anti-IgG antibody (for control) were purchased from Abcam (Massachusetts, USA) and diluted with sterile artificial cerebrospinal fluid containing 126.6 mM NaCl, 2.5 mM KCl, 2.0 mM MgCl₂, and 1.3 mM CaCl₂. The specific MEK (extracellular signal-regulated kinase (ERK)) inhibitor PD98059 was purchased from Sigma and was dissolved in sterile saline containing 10% DMSO. The intrathecal injection of drug was performed on 8:00 a.m. daily, the time which was 30 min before behavioral test. The doses of AMD3100 (5, 10, 20 µg/10 μl),^{9 (link),13 (link)} anti-CXCL12 neutralizing antibody (4 µg/10 μl),^{8 (link)} PDTC (0.5 µg/10 μl),^{23 (link),24 (link)} and PD98059 (10 µg/10 μl)^{25 (link)} used in this experiment were based on those used in previous studies.