Effect of early life stress on behavior and neurotrophins of hippocampus in adult male rats

Objective To explore the effect of early life stress on behavior and neurotrophins of hippocampus in adult male rats.Methods Newborn male rats were randomly divided into early life stress group (n =12) and control group (n =12).The rats in early life stress group were deprived from their mother 3 h per day from postnatal day 2 to 14,and those in control group were given no treatment.When the animals grew up to 90-100 days,behaviors of these rats were assessed by sucrose preference test and open-field test.After behavior tests,rats were sacrificed and hippocampi were isolated.The levels of brainderived neurotrophic factor (BDNF)/cAMP responsive element-binding protein (CREB) mRNA and protein in the hippocampi were detected by using reverse transcription-polymerase chain reaction (RT-PCR) and Weston blotting.Results Behavior tests revealed that percentage of the sucrose preference,total distance,central total distance,mean velocity and erection in early life stress group were significantly less than those in control group [(66.6±6.6)％,(2793.33±945.66) cm,(194.34±86.10) cm,(5.25±1.47) cm/s,(9.25 ±4.49) times vs.(80.9 ±3.5)％,(4888.00±1112.47) cm,(483.09 ±324.45) cm,(8.90±2.02) cm/s,(14.92 ±5.16) times,P ＜0.01 ].Early life stress group showed a significant decrease in expression levels of BDNF/CREB mRNA and protein in hippocampi as compared with control group in their adulthood [(0.61 ±0.08),(0.55 ±0.06),(0.39 ±0.05),(0.44 ±0.06) vs.(0.86 ±0.06),(0.69 ±0.04),(0.53 ±0.05),(0.54 ±0.06),P＜0.01].Conclusion Early life stress could alter neurotrophins of the hippocampi in adulthod,resulting in changes in behavior and susceptibility to affective disorders. Key words: Early life stress; Behavior; Hippocampus; Neurotrophins