Objective To dynamically observe the change of pain emotion in rats with chronic inflammatory pain induced by Freund's complete adjuvant (CFA), and explore the time difference of anxiety and depression in rats with chronic inflammatory pain.
Methods All experimental rats were randomly divided into blank control group and model control group. The model control group was injected CFA into the plantar to establish chronic inflammatory pain model. The changes of mechanical foot contraction threshold (PWTs) of rats in each group were dynamically observed before and 1,3,7,18 and 26 days after model establishment; The behavior changes of rats in open field test (OF), elevated O maze test (EZM), novel food inhibition test (NSF), marble burial test (MBT), sugar preference test (SPT) were observed 28 days after modeling, 29 days after modeling, 30 days after modeling.
Results The PWTs in the model control group were significantly decreased 1 day after the model was established (P<0.01), and were significantly lower than those in the blank control group throughout the experiment (P<0.01). Compared with the blank control group, the movement distance, stay time and entry times of the central area in the model control group were significantly reduced in OF (P<0.01); In EZM, compared with the blank control group, the open arm movement distance, the open arm stay time, and the number of open arm entries were significantly reduced (P<0.05); In NSF, the feeding latency was significantly increased compared with the blank control group (P<0.05), and="" there="" was="" no="" significant="" difference="" in="" food="" consumption="" p="">0.05); However, on the 31st day after MBT, the number of marbles in the model control group was significantly increased compared with the blank control group (P<0.05); there="" was="" no="" significant="" difference="" between="" the="" model="" control="" group="" and="" blank="" at="" each="" time="" point="" after="" spt="" middle="" p="">0.05).
Conclusion CFA induced chronic inflammatory pain model rats can show a variety of animal behavior changes related to anxiety like emotion after 4 weeks, but no animal behavior changes related to depression like emotion were observed within 5 weeks.