Figure 2

The antinociceptive effects of DLT (10 μg, i.t.) were assessed in the tail flick acute thermal pain test. Rats chronically treated with morphine exhibited enhanced δOR-mediated analgesia as compared with controls and this enhancement was blocked by chronic co-administration of morphine with the glial modulatory agent, propentofylline. All testing was performed 12 h following the final morphine injection. A) The latencies to respond with a brisk tail flick were measured prior to and at 10 minute intervals following DLT administration for 50 minutes. Three pre-drug latencies were averaged to obtain a baseline latency value for each rat. B) Mean tail flick latencies at 30 minutes post-DLT injection were converted to % M.P.E. values. Statistical analyses of thermal latencies were performed by two-way ANOVA followed by Bonferroni post-hoc while statistics for transformed % M.P.E. data were accomplished by one-way ANOVA followed by Tukey's post-hoc multiple comparison test. Data represent means ± s.e.m. for n = 5–6 rats per group. The asterisk denotes a significant difference from saline-treated rats. * = p < 0.05. 0: Baseline prior to drug administration; MS: morphine sulfate; PF: propentofylline.