(A) Effects of γ-amino butyric acid (GABA) antagonists on clonidine-induced analgesia in spinal nerve ligated (SNL) rats. Animals received intrathecal injection of saline, clonidine (15 μg/rat), bicuculline (Bic, 0.25 μg/rat), CGP35348 (CGP, 15 μg/rat), or their combination. Withdrawal threshold in the paw ipsilateral to SNL is presented over the time. N = 6-8. * p < 0.05 versus saline. # p < 0.05 versus clonidine alone. (B) Microdialysis for spinal GABA release. Buffer or clonidine (30-300 μM) was perfused into the spinal dorsal horn through the microdialysis probe in normal and SNL rats. N = 7-9. Data are presented over time as percentage of baseline. * p < 0.05 versus buffer.