The Effect Of Early Environmental Enrichment On The Adult Rats’ Social Competitive Behaviour

Objective To observe the effect of early environmental enrichment on the adult rats’social competitive behaviour and detect whether the brain-derived neurotrophic factor (BDNF) is involved in this behaviour.Methods Apply physical and social stimulation to establish the early environmental enrichment model (EE group). At adulthood the animals were experienced in dominance tube test and competitive food foraging test to explore the effect of early environmental enrichment on the animal’s competitive behaviour. Then the animals that experienced environmental enrichment were infused with anti-BDNF serum into the lateral ventricle, while the control group was infused with saline,2h later the animals were carried out in the dominance tube test. The EE and control animals’medial prefrontal cortex and hippocampus were dissected for BDNF determination by ELISA and RT-q PCR.Results After early environmental enrichment, the rat show reduced hierarchy in the dominance tube test. The percent of win in the EE group were EE♂vs Nor♂:EE♂win=5%, Nor♂win=82%, draw=13%. EE♀vs Nor♀:EE♀win=14%, Nor♀in=82%, draw=4%. Moreover, in the competitive food forging test, the EE group forged significant little food than the Nor group (P<0.05). However, after infusion anti-BDNF serum into the EE rats’lateral ventricle, they did not show low hierarchy indicating by significantly increased time stay in the tube than before infusion (p<0.05) and increased percent of win. Compared with the Nor group, the EE group demonstrated significantly increased expression of BDNF protein (EE/Nor=1.35) and BDNF mRNA (EE/Nor=1.8) in the medial prefrontal cortex. While there was no difference in the expression of BDNF protein and mRNA level in the hippocampus between the EE group and Nor group.Conclusion Early environmental enrichment reduced the adult rat’s social competitive behaviour while infusing anti-BDNF serum into the lateral ventricle could reverse this behaviour deficit. Early environmental enrichment leaded to increased BDNF protein and mRNA level in the medial prefrontal cortex, which might be related to the reduced social competitive behaviour after environmental enrichment.