Spinal release of pro-inflammatory cytokines plays a pivotal role in the aberrant neuronal signalling that underlies neuropathic pain. This thesis sought to develop a methodology for monitoring spinal cytokine release in vivo using ‘high flux’ microdialysis sampling. In vitro studies characterising ‘high flux’ membranes Plasmaflo® (Poly-E), Prisma® (Poly-P), Terumo®(CUP-R) and commercially available probe, CMA/20 (nominal cut-off 3000,≈3000, 60 and 100 kDa respectively) revealed that Poly-E and Poly-P were significantly better in recovering IL-1β than the commercially available probe (58, 48 and 38% at 0.5 µl/min, n=4-5, respectively). Poly-E was identified as the most suitable membrane for in vivo studies. For future in vivo studies, disinfection of the membrane and blockade of non-specific peptide binding sites by siliconisation rather than conventional use of BSA, was shown not to adversely affect the dialysing capability of the Poly-E membrane. In rats with CCI-induced mechanical hypersensitivity intrathecal microdialysis was successful in measuring basal levels of IL-1β, IL-6 and TNFα (68±27, 5714±2451 and 638±175 pg/ml (mean ± SEM, n=10) respectively). Electrical stimulation capable of activating C-fibres was shown to induce IL-1β (≈ 3-fold), but not IL-6 and TNFα release in CCI animals compared to sham controls. In further studies, intrathecal microdialysis sampling was successfully performed in freely moving naïve animals. Atlanto-occipital catheterisation however, was associated with welfare concerns so a less invasive lumbar catheterisation technique was evaluated. This technique was well tolerated and may prove valuable in determining the spinal cytokine release in animal pain models.