Effects of environmental stimulation on the expression of microtube associated protein-2 in hippocampus after hypoxic-ischemic brain damage in neonatal rats

Objective To study the effects of early and enriched environmental stimulation on learning and memory abilities,and on expression of microtube associated protein-2 (MAP-2) of hippocampal CA1 district after hypoxia-ischemic brain damage (HIBD) in neonatal rats. Methods Seven days old Sprague-Dawley rats were selected for this study. The HIBD models were established by ligation of left common carotid artery and then were exposed to 8% oxygen and 92% nitrogen mixture for 2 hours. The HIBD rats were randomly divided into two groups, intervention group and non-intervention group; the sham-operation rats were selected as control group. The rats in intervention group were kept in enriched environment in stimuli for 20 days; the rats in non-intervention group and control group were kept in a standard environment for the same period of time. Learning and memory abilities were measured by Morris water maze. The expression of MAP-2 was measured immuno-histochemically in paraffin sections of hippocampus. Results The learning ability of rats in non-intervention group was much lower than those of intervention group and control group (P0.01). The corrected optical densities (COD) of immuno-reactive products of the MAP-2 of hippocampal CA1 district were significantly decreased in rats of non-intervention group compared with those of intervention group and control group (P0.01). There was no significant differences in learning ability and amount of reactive COD of MAP-2 between rats in intervention group and those in control group (P0.05). Conclusions Early, enriched environmental stimulation can improve the learning and memory abilities of neonatal rats after HIBD. The changes of MAP-2 in hippocampus are possibly associated with the influence of environment.