The influence of early environment on neuroglobin levels, learning and memory

Abstract

Objective To explore the influence of environment early in life on learning and memory abilities and neuroglobin (Ngb) expression. Methods Forty-five newborn,male,Sprague-Dawley rats were randomly divided into an EE (enriched environment) group,an EI (isolated environment) group and a normal control group,with 15 rats in each group.The EE and EI group rats lived in those environments for their first 28 days of life.The step-down test was used to measure the rats'learning and memory abilities on the 29th day.Ngb expression was examined using immunohistochemical methods. Results The step-down test showed learning and memory scores for the EE group rats of (9.67±0.49) and (9.80±0.56) respectively,significantly higher than those of the control group,(8.67±0.72) and (8.93±1.10).The learning and memory abilities of the EI group were the lowest among the three groups,with scores of only (7.07±1.98) and (7.67±0.98 ),respectively.The latency of the first electric shock was (166.33±36.08)s in the EE group and significantly shorter than that in the control group (108.93±73.26) s.The EI group showed the longest average latency (44.93±45.03)s.Average Ngb expression as reflected by the integrated optical density in the EE group was (224.56±89.09) in the frontal cortex and (127.70 ± 28.16)in the hippocampus,a significant increase over expression in the control group.The Ngb expressions of the EI group were the lowest among the 3 groups-(88.78 ± 18.84) and ( 63.42 ± 16.41 ) in the frontal cortex and hippocampus respectively. Conclusions Early exposure to an enriched environment can increase Ngb expression and improve learning and memory ability,but early isolation will reduce Ngb expression and learning and memory function. Key words: Early environment; Neuroglobin; Learning; Memory