| Objective: To explore the influence of early different environments onneurobehavioral development, neuroglobin (Ngb) expression and the regulation ofmelatonin (MT) and hypothalamic-pituitary-adrenal axis (HPAA) of rats.Method：(1) Animal grouping and evironmental interventions:45male SD pupswere randomly divided into three groups-the isolated environment (IE) group, theenriched environment (EE) group and the normal control (NC) group. There were15pups in each group (n=15). The isolated environment was a monotony cage withoutany object. The enriched environment was an early intervention with a rich visualenvironment.(2) The step-down test was performed to detected learning-memoryability of the rats and the handle-touch test was performed to assess anxious andnervous ability of the rats after postnatal29days (P29);(3) The levels of serummelatonin and corticosterone(CORT) of rats were tested by the emission immunologymethod before and after adrenocorticotropic hormone(ACTH) stimulation;(4)TheNgb expression in hippocampus and cerebral cortex were examined byimmunohistochemical method．Results:(1) In the step-down test, the score of learning ability and memory ofthe EE group rats were respectively (9.67±0.49) and (9.80±0.56); significantlyhigher than those in the NC group [(8.67±0.72) and(8.93±1.10); while in the IEgroup the score of learning ability and memory were the lowest among the threegroups, which were (7.07±1.98) and (7.67±0.98); The latency of first shock was[(166.33±36.08)s] in the EE group, which was significantly shorter than that in theNC group [(108.93±73.26)s]. And the latency of first shock in the IE group was[(44.93±45.03) s], which was the longest among the three groups, P＜0.05. In the handle-touch test, the scores of nervous and the pain in EE group were (1.13±0.35)、（1.87±0.83）, which was the least among three groups, P＜0.05. And the score ofnervous and the pain in the IE group wer（e2.06±0.76）and（3.47±0.64）, which werethe highest among three groups, P＜0.05;(2) Before the ACTH injection, the level ofserum melatonin of rats in EE group was [（49.67±6.76）ng/ml], which was more thanthat in control group [（45.81±4.09）ng/ml]. The level of serum MT in IE group was[(40.53±3.23) ng/ml], which was the lowest among three groups, P＜0.001. Aftergiven ACTH, the level of serum MT of rats among the three groups were nosignificantly different after stress (F=1.167, P>0.05); The level of MT in IE groupswas significantly increased (t=5.14, P＜0.001), but there was no significant difference(P>0.05) between the EE groups and the control groups after stress;(3) The basallevel of serum corticosterone of rats in EE group was（[32.56±9.05）ng/ml], which wasmore than that in control group[（24.96±6.19）ng/ml]. The level of serum melatonin inIE group was[（15.53±6.78）ng/ml], which was the lowest among three groups, P＜0.001. After given ACTH, the level of serum CORT of rats in EE group was（[18.24±5.53）ng/ml], which was less than that in control group（[21.71±6.05）ng/ml].The level of MT in IE group was [（28.09±6.51）ng/ml], which was the highest amongthree groups, P＜0.001.(4) Compared with the control group, the IOD of Ngb in EEgroup was (224.56±89.09) in rat frontal cortex and (127.70±28.16) in hippocampus,which showed significantly increased than those in the control group (P＜0.05). Andthe IOD of Ngb in IE group was the lowest among three group (P＜0.05).Conclusion:(1) Early isolation environment may disturb the function of HPAAand MT of rats, which may increase impulse-like and hyperactivity-like behavior andimpaired learning-memory ability by reducing the basis level of serum CORT/andMT, elevating the level of serum CORT/MT after stress, and decreasing theexpression of Ngb;(2) The rats in the early enriched environment can be maintainedtheir basis serum CORT/MT at a higher level, and show elevated MT level, anddecreased CORT level after stress, and increased expression of Ngb, which mayreduce impulse-like and hyperactivity-like behavior and promote learning-memory ability;(3) The function of HPAA and MT may be involved in the mechanism aboutthe affection of early environment on the unmature brain development and itslong-term developmental behavior. |
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