CPA in control and CCK-8 infusion rats with or without CCK-A-R antagonist or capsaicin pretreatment. (A) For the CPA score the amount of time spent in the conditioning compartment on the post-conditioning days were subtracted from the amount of time spent in the same compartment on the pre-conditioning day. The rats spent less time in this compartment on the post-conditioning test day as compared with the pre-conditioning test day. Compared with control rats, intravenous infusion of CCK-8 after conditioning training markedly increased the CPA scores in post-conditioning day 1, 3 and 5, respectively. This effect was blocked by pretreatment of CCK-A receptor antagonist CR-1409. (B) Perivagal capsaicin treatment in control rats with saline infusion had no effect on CPA scores but eliminated the enhanced CRD-induced CPA in rats with CCK-8 infusion. For easy and clear comparison, the same control group and CCK-8 group were used here as in Figure 1 A. Results were presented as means ± SE. Statistical significance was determined by Two-way Repeated measurement ANOVA followed by Bonferroni posttests. * P < 0.05, ** P < 0.01 compared between CCK-8 treatment group and control group, n=5 for each group.