Effect of Chronic Stress-induced Depression on Subcutaneously Implanted Walker 256 Tumors in Rats and Its Mechanism

Objective To observe the effect of chronic stress-induced depression on subcutaneously implanted Walker 256 tumors in rats,and to explore its possible mechanism.Methods Rat models of chronic stress-induced depression and subcutaneous implanted tumors were established in this study.Forty-eight female SD rats were randomly divided into four groups,with 12 rats in each group.Group A was only inoculated with Walker 256 carcinosarcoma cells,without stress before and after inoculation;Group B was given various stress treatments for 16 days after inoculation with Walker 256 carcinosarcoma cells;Group C was given various stress treatments for 16 days before inoculation with Walker 256 carcinosarcoma cells;Group D was given various stress treatments for 16 days both before and after inoculation with Walker 256 carcinosarcoma cells.The survival,behavior indexes,spleen weight,tumor weight,serum cortisol levels and interleukin-6(IL-6) levels were measured after inoculation.Results Compared with group A,movement time,movement distance and central regional movement time significantly decreased but rest time and peripheral regional movement time significantly increased in group B,C and D(P0.05).Compared with group B or C,movement distance significantly decreased in group D(P0.05).In addition,movement time,rest time,central regional movement time and peripheral regional movement time in group D were longer than those in group B or C,but differences were not significant(P0.05).Compared with group A,survival time and spleen weight obviously decreased but IL-6 levels obviously increased in group D(P0.05).However,no significant differences were found among group A,B and C(P0.05).Compared with group A,serum cortisol levels significantly increased in group B,C and D(P0.05).Compared with group D,serum cortisol levels significantly increased in group C and D(P0.05).There were no significant differences in tumor weight among the four groups(P0.05).Conclusion Chronic stress can induce depression,reduce locomotor activity and decrease exploratory behavior in rats,and the longer the stress-induced depression,the more serious depressive symptoms.Long time chronic stress-induced depression can reduced survival time in rats with implanted Walker 256 tumors,and the mechanism may be involved in immune organ atrophy,immune endocrine dysfunction and internal environment destruction caused by serum cortisol and IL-6 elevation.