The impact of chronic stress on the expression of IL-18 in the rats brain

Abstract

Objective To study the expression levels of interlukin-18(IL-18) in the CA1 region of the hippocampus and habenular of the rats with chronic stress. Methods Male Wistar rats (n = 30) weighting about 185～255g were divided into test group (T, n = 15) and control group (C, n = 15) randomly. The rats in group T were exposed to various types of stresses every day for consecutive 21 days. The rats in group C did not receive any stress during 21 days. Weighting and open-field tests were carried out on each rat before the test and on the 22nd day. On the 22nd day, brains were removed and cut coronally. Immunohistochemistry method was used to measure the expression levels of IL-18. Results After 21 -day stress, the body weight, erection time, rearing times, horizontal crossing numbers,modifying times and defecation in group T((297.33 ±25.83)g,(5.14 ±2.02)s,(19.00 ± 9.01), (9.47 ±3.64),(3. 93 ± 1. 87)and(4. 93 ± 1. 94)) were significantly different from those of group C((322.00 ±30.34)g,(1.97 ±0.93)s,(39.80 ±18.58),(14.80 ±5.88),(7.27 ±2.87)and(1.93 ±1.16)) (P < 0.01, P < 0.05). The average optical density values of IL-18 positive cells in CA1 region and habenular in group T ((0.3923 ±0.0084 and 0.4577 ±0.0234)) were higher than that in group C ((0. 3165 ±0.0063 and 0. 3400 ±0.0097)) (P<0.01). Conclusion The expression levels of IL-18 of the hippocampus glial cells and of the habenular neurons in the rats is increase after the chronic stress. Key words: Stress; Hippocampus; Habenular; Interlukin-18(IL-18)