Effects of early environment on emotional development and motor coordination ability of rats / 中华实用儿科临床杂志

ABSTRACT

Objeaive To explore the effects of the function of hypothalamus-pituitary-adrenal (HPA) axis on emotional development and motor coordination ability by studying the influences of early environment on long-term behaviors of developing rats.Methods Forty-five neonatal rats were randomly divided into 3 groupsthe enriched environment group (EE group),the isolated environment group (IE group) and the normal environment group (NE group),with 15 cases in each group.There were 15 rats nurtured separately in EE group,IE group or NE group.The rat motor coordination abilities were tested by straight walking test on postnatal day 28 (P28) and the emotional behaviors were evaluated by handling test at P29.The levels of serum corticosterone(CORT) of rats were detected by using emission immunology method.The morphology of neural cells in rat brain was examined by adopting HE staining.Results In the straight walking test,the motor coordination abilities of rats in EE group ＞ NE group ＞ IE group(F =49.30,P ＜ 0.000).In the handing test,the scores of reaction for stressful stimuli and painful stimuli in IE group were (1.14 ± 0.36,1.93 ±0.83) ＜ (1.47 ±0.64,2.60 ±0.91) in NE group ＜ (2.07 ±0.73,3.43 ±0.65) in IE group (all P ＜ 0.01).The base serum CORT levels were (32.56 ± 9.05) μg/L in EE group ＞ (24.96 ± 6.19) μg/L in NE group ＞ (15.53 ± 6.78) μg/L in IE group (F =19.71,P ＜ 0.001).After a lower-dose adrenocorticotropic hormone stimulation test,the concentration of CORT was (18.24 ± 5.53) μg/L in EE group ＜ (21.71 ± 6.05) μg/L in NE group ＜ (28.09 ±6.51) μg/L in IE group (F=10.25,P ＜0.000).The HE staining showed the number of neural cells in striaturn and amygdale of rats were[(72.80 ±6.81) cell/HP,(73.53 ±6.14) cell/HP] in EE group ＞ [(65.67 ± 8.98) cell/HP,(61.47 ±6.57) cell/HP] in NE group ＞ [(53.33 ± 6.84) cell/HP,(48.13 ± 6.53) cell/HP] in IE group (all P ＜ 0.001).Conclusions Early environment can affect emotional reaction,motor behavior and brain development of immature rats by regulating HPA axis function.Early isolation environment can lead to HPA axis dysfunction,which can make nerve cell damage and emotion and motor coordination ability dysfunction.On the contrary,early enriched environment can moderate the hyperactivity of HPA axis after stress and promote brain development and ameliorate long-term behavioral development.