Changes of behavioral and serum inflammatory factors in rats with acute reserpine-induced comorbidity of pain and depression

Objective To investigate the effects of acute reserpine-induced pain and depression comorbidity model on behavior and related inflammatory cytokines in rats. Methods Twelve male 8-week-old SD rats were randomly divided into control group and model group, 6 in each group.Rats in the model group were intraperitoneally injected with reserpine(1 mg/kg/d)for 3 days to establish the model. Rats in the control group were injected with the same amount of distilled water. The pain threshold of rats was measured by Von Frey Hairs and Hot Plate Analgesia Test. The depression behavior of rats was evaluated by open-field test, Forced Swimming Test and Sucrose Consumption Test.Serum IL-1β, IL-6, IL-18 and TNF-α content were detected by ELISA. Results Compared with the control group(1d (15.00±0.00)g; 3d (13.20±4.03)g), the PWTs of the model group (1d (6.20±0.45)g; 3d (4.20±1.64)g) decreased significantly(t=44.00, 4.63, both P<0.05). Compared with the control group ((8.82±1.08)s), the PWTL ((3.16±0.24)s) was significantly reduced on the first day in model group, and the difference was statistically significant (t=11.48, P<0.05). Compared with the control group ((1 815.18±541.40)cm, (98.20±26.25)s, (87.78±9.38)g), the total distance of the open-field test ((948.91±494.35)cm)significantly shortened (t=2.64, P<0.05), swimming time ((143.60±21.45)s) was significantly prolonged (t=-2.65, P<0.05), and the sucrose consumption ((22.23±6.97)g) significantly decreased (t=12.55, P<0.05) in model group.Compared with the control group ((285.80±11.93) ng/ml, (233.07±8.47) ng/ml, (280.41±14.31) ng/ml, (213.10±33.87) ng/ml), serum levels of IL-1β, IL-6, IL-18, TNF-α in model group ((471.23±24.15) ng/ml, (364.82±17.16) ng/ml, (471.81± 28.98) ng/ml, (821.19±93.16) ng/ml) increased significantly(F=-15.39, -15.39, -13.24, -13.72, all P<0.05). Conclusion A large number of intraperitoneal injections of acute reserpine can cause hyperalgesia, depressive behavior and serum inflammatory factors in rats, effectively simulating the symptoms of pain and depression, and can be used as a model of pain and depression comorbidity for biological mechanisms and treatment research. Key words: Pain; Depression; Reserpine; Inflammatory cytokines; Rat