The purpose of the study was to examine whether the underlying mechanism of the alteration of cognitive ability and synaptic plasticity induced by the housing environment is associated with the balance of excitatory/inhibitory synaptic density. Enriched environment (EE) and social isolation (SI) are two different housing environment, and one is to give multiple sensory environments, the other is to give monotonous and lonely environment.
Male four-week-old C57 mice were divided into three groups: CON, EE and SI. They were housed in the different cage for 3 months. Morris water maze (MWM) and novel object recognition were performed. Long term potentiation (LTP), depotentiation (DEP) and Local field potential (LFPs) were recorded in the hippocampal perforant pathway (PP) and dentate gyrus (DG). The data showed that EE enhanced the ability of spatial learning, reversal learning and memory as well as LTP/DEP in the hippocampal DG region. Meanwhile, SI reduced those abilities and the level of LTP/DEP. Moreover, there were higher couplings of both phase-amplitude and phase-phase in the EE group, and lower couplings of them in the SI group compared to that in the CON group. Western blot analysis showed that EE significantly enhanced the level of PSD-95, NR2B; however, SI reduced them but enhanced level of GABAAR.
These date suggests that the cognitive functions, synaptic plasticity and neural oscillatory patterns were significantly impacted by housing environment via possibly changing the balance of excitatory and inhibitory synaptic density.