Effects of enriched environment on cognitive situation in senescence accelerated mouse prone/8 with mild cognitive impairment

Abstract

Objective To investigate the effects of enriched environment on cognitive situation in senescence accelerated mouse prone/8(SAMP8) with mild cognitive impairment (MCI) and the possible regulatory mechanisms. Methods A total of 20 healthy male SAMP8 mice in MCI (5-month-old) were randomly divided into enriched environment group (short for P8 EE group) and standard environment group (short for P8 SE group) with 10 in each group. Two groups of SAMP8 mice were subjected to the two different environments for 60 days. 10 5-month-old healthy male SAMR1 mice were selected as normal control group (short for R1 SE group) and subjected to the standard environment for 60 days. The cognitive situation of mice in each group before and after intervention was examined by the Morris water maze (MWM) test. The deposition of amyloid protein beta(Aβ) and expression of glial fibrillary acidic protein(GFAP) in hippocampal CA1 of mice in each group after intervention were determined by immunohistochemical staining and image analysis system. Results In the MWM test, there were statistical differences of latency and times of crossing the platform before and after intervention in each group(all P<0.05). The average latency ((81.22±11.82)s, (76.59±13.36)s, (70.74±8.73)s, (66.40±7.79)s) of P8 EE group after intervention were significantly shorter than that of P8 SE group on four consecutive days (P<0.01), while the times of crossing platform in P8 EE group after intervention (9.31±1.33) were more than that in P8 SE group after intervention (P<0.01). There were significant differences of escape latency and crossing times between P8 EE group and R1 SE group after intervention (all P<0.01). By immunohistochemical staining, the average absorbance of Aβ and GFAP((0.26±0.02), (0.26±0.03)) in P8 EE group after intervention were significantly less than that in P8 SE group after intervention (P<0.01). There were significant differences of Aβ and GFAP levels between P8 EE group and R1 SE group after intervention (both P<0.01). Conclusion Enriched environment can reduce cognitive impairment in SAMP8 mice with mild cognitive impairment, which may be associated with restraining the deposition of Aβ in hippocampus, reducing the expression of GFAP and inhibiting the activation of AST. Key words: Enriched environment; Learning and memory; Amyloid protein beta; Glial fibrillary acidic protein; Mild cognitive impairment