ABSTRACT
Objective In order to study the difference of depression-like behaviours among three widelyused stress models in rats.Methods The new-born Spragne-Dawley rats were randomly divided into maternal deprivation(MD) group(n=27),chronic mild stress(CMS) group (n=29),dual stress(DS) group ( n=31 ) and control (C) group ( n =30) on postnatal day 1.MD rats only received maternal deprivation.CMS rats only received chronic mild stress when 10 weeks old.DS rats received both maternal deprivation and chronic mild stress.Control rats received no experimental handling.Behavior tests including forced swimming test and sucrose consumption which were carried out to evaluate rats' depression-like behaviors in the thirteenth weeks.The extend time of floating and sucrose preference ratio should be recorded in the forced swimming test and sucrose consumption test respectively to reflect the behavior of helplessness and anhedonia of rats.Results In the forced swimming test,the extend floating time of MD group( 119.30 ± 65.56) s,CMS group ( 145.00 ± 80.24) s and DS group ( 170.03 ±61.75 )s were longer than the control group(81.14 ± 52.40)s (F =11.53,P ＜ 0.01 ).In the sucrose consumption test,the MD group(0.32 ± 0.22) had a low sucrose consumption.The comparison of the MD group and CMS group (0.43 ± 0.28 ) to the control group (0.54 ± 0.28 ) had significant differences (F =4.33,P ＜ 0.01 ).In these four groups,no sexual difference was found in the forced swimming test and sucrose consumption test ( all P ＞ 0.05 ).Conclusion The results suggest that MD,CMS and DS may induce some kind of depression-like behaviors in rodents such as anhedonia or the behavior of helplessness and the depression-like behaviors induced by different stresses are similar in male and female individuals.
ABSTRACT
Objective To explore the effect of postweaning enriched environment and citalopram treatment during juvenility on the behaviour of male rats exposed to early adverse stress. Methods The newborn pups were randomly divided into maternal separation group (MS) and non-maternal separation group (NMS). Offspring were weaned on PND22 and housed in same-rearing groups under either standard or enriched conditions or citalopram treatment until adulthood. All of them were examined by sucrose consumption test, forced swimming test (FST) and morris water maze test (MWZ). Results (1) MS had significantly less consumption of sucrose intake (ml/g)(0.013 ±0.006, n = 10), compared with the following five groups (MS + EE (0.023 ±0.012, n = 8); MS + Drug (0.027 ±0.012, n = 9); NMS (0.022 ± 0. 007, n=11);NMS + EE (0.023 ±0.007, n = 7); NMS + Drug (0.032 ±0.011),n=7)), NMS + Drug had significantly increased the radio of sucrose consumption on NMS group. (2)The immobility in FST were longer in MS-experienced groups (MS (140. 19 ± 37.01) s, n = 8); MS + EE (129.41 ±29.50)s, n = 6) ;NMS + Drug (128.83 ±26. 11)s, n = 6)) than three non-MS groups (NMS (96.28 ±35.63)s,n = 7); NMS + EE (94.17 ±24. 87)s, n = 6) ;NMS + Drug (93.00 ±34. 21)s, n = 6)). (3) MS had shorter time and shorter percentage of distance spent in target quadrant in MWZ,citalopram treatment markedly improved spatial memory on NMS group. Conclusion Maternal separation applied in newborn rats induces a broad spectrum of behavioral changes reminiscent of depressive symptoms in humans, which might be reversed to some extent by EE and antidepressant in young adults.