Figure 1.

Inhibition of spontaneous neuropathic pain and evoked hypersensitivity can be dissociated by spinally administered drugs. (a,b) Spinal clonidine (10 μg, a) or ω-conotoxin (250 ng, b) reversed SNL-induced allodynia. * P < 0.05 (two-factor repeated-measure ANOVA, Student-Neuman-Keuls post hoc test versus pre-drug values). BL, baseline. (c,d) Spinal clonidine (c) or ω-conotoxin (d) increased the time the rats spent in their paired chamber, with a corresponding decrease in the saline-paired chamber. * P < 0.05 (two-factor repeated-measures ANOVA, Bonferroni post hoc test versus pre-conditioning values). (e) Spinal adenosine (10 μg) reversed SNL-induced allodynia. * P < 0.05 as above. (f) SNL rats did not increase the time that they spent in the adenosine-paired chamber. Sham-operated rats showed no chamber preference and no pre-conditioning chamber preferences existed (c,d,f). For all of the CPP experiments, pre-conditioning data was analyzed using two-factor ANOVA (chambers versus treatment). Statistical analysis for chamber preference before conditioning revealed no difference in the time spent in chambers between sham-operated and SNL-treated rats (P > 0.05), therefore baseline chamber data was pooled for graphical representation. For all analyses, significance was set at P < 0.05. All graphs represent mean ± s.e.m. (n = 6). All procedures involving rats were reviewed and approved by the Institutional Animal Care and Use Committee of the University of Arizona and were in accordance with the US National Institutes of Health guidelines.