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. Author manuscript; available in PMC: 2013 Dec 3.
Published in final edited form as: Neuroscience. 2011 Mar 31;183:221–229. doi: 10.1016/j.neuroscience.2011.03.052

Figure 2. Anti-allodynic effects of i.t. deltorphin II in cancer rats.

Figure 2

(A) Mechanical thresholds were measured using von Frey filaments before (BL) and 14 days after MRMT-1 cell implantation. The paw withdrawal threshold (in g) was measured every 15 min (from 15 to 60 min) following i.t. injection of deltorphin II. Time 0 indicates the latency to paw withdrawal before i.t. injection of deltorphin II. Intrathecally-administered deltorphin II induced a dose-dependent (3, 10, 30 μg) reduction in mechanical allodynia in the ipsilateral hind paw (FTreatment=6.50 with P=0.002, two-way ANOVA followed by Bonferroni post hoc test). The anti-allodynia of deltorphin II peaked 15 min after the injection. Intrathecally-administered naltrindole (NTI), 10 min before deltorphin II (Delt II) injection (a 3:1 molar ratio of NTI/Delt II = 72/30 μg), antagonized deltorphin II anti-allodynic effects at both 15 and 30 min post-injection (FTreatment=32.15 with *** P<0.001, two-way ANOVA followed by Bonferroni post hoc test). (B) %MPE ± S.E.M. were determined 15 and 30 min after injection of deltorphin II ± NTI. Percentage MPE of deltorphin II administered after NTI are significantly different from %MPE in deltorphin II-treated rats, indicating that the effect of deltorphin II was DOPR-mediated (*** P<0.001, two-tailed unpaired t-test). (C) As compared with saline, by itself i.t. NTI (72 μg) has no effect on the cancer-induced mechanical allodynia (FTreatment=0.38 with P>0.05, two-way ANOVA followed by Bonferroni post hoc test).