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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 3. Anti-allodynic effects of i.t. deltorphin II in CFA rats.

Figure 3

(A) Rats were injected with CFA in the plantar surface of the left hind paw. Six days after CFA injection, the 50% paw withdrawal threshold (in g) was measured using von Frey hairs every 15 min over a period of 60 min following i.t. injection of deltorphin II (Delt II; 3, 10, 30 μg) alone or following naltrindole (NTI; 72 μg) injection. BL indicates the baseline for 50% withdrawal threshold just before CFA injection, and time 0 indicates the paw withdrawal threshold immediately before deltorphin II injection. Intrathecally-administered deltorphin II induced a dose-dependent (3, 10, 30 μg) reduction of mechanical allodynia of the ipsilateral hind paw of CFA-treated rats (FTreatment=15.83 with P<0.0001, two-way ANOVA followed by Bonferroni post hoc test). The anti-allodynia induced by deltorphin II peaked 15 min after the injection. Intrathecally-administered naltrindole, 10 min prior to deltorphin II injection (a 3:1 molar ratio of NTI/Delt II = 72/30 μg), reversed the anti-allodynia induced by deltorphin II at 15 min post-injection (FTreatment=25.53 with P<0.0001, two-way ANOVA followed by Bonferroni post hoc test). (B) The %MPE ± S.E.M. was determined 15 and 30 min after injection of deltorphin II alone or in combination with NTI. The %MPE for deltorphin II injected after NTI was lower than the %MPE of deltorphin II-injected rats, indicating that the effect of deltorphin II was DOPR-mediated (* P<0.05 at 30 min, two-tailed unpaired t-test). (C) As compared with saline, by itself i.t. NTI (72 μg) has no effect on the CFA-induced mechanical allodynia (FTreatment=3.13 with P>0.05, two-way ANOVA followed by Bonferroni post hoc test).