(A) Complete Freund’s adjuvant (CFA) or saline injection to rat’s hind paw.
(B) CFA decreased withdrawal threshold (****p < 0.0001, two-way ANOVA with repeated measures and Sidak’s multiple comparisons test; n = 6 animals).
(C) Intracranial OT, compared SAL, increased the withdrawal threshold in CFA-treated rats (****p < 0.0001, unpaired t test; n = 6 animals).
(D) Conditioned place preference (CPP) assay on tonic pain in CFA rats. Rats had SAL delivered intracranially in one chamber and OT delivered in the opposite chamber.
(E) CFA-treated rats demonstrated a preference for the chamber associated with OT (**p < 0.01, n = 8 animals).
(F) Control rats that received subcutaneous saline injections to paw demonstrated no preference for OT treatment (p = 0.8976, n = 8 animals).
(G) CFA-treated rats exhibited a preference for the chamber associated with OT (*p < 0.05, unpaired t test; n = 8 CFA and saline animals).
Data are represented as mean ± S.E.M.