Effects of Environmental Enrichment on Spatial Memory and Neurochemistry in Middle-Aged Mice

Abstract

The present study compared the effects of environmental enrichment on spatial memory, glutamic acid decarboxylase (GAD) activity, and synaptophysin levels in middle-aged male and female mice. Prior to testing, a subset of 18-month-old male and female C57BL/6 mice was housed with two to three toys and a running wheel in the home cage for up to 29 d. Adult mice (7 mo) of both sexes and the remaining middle-aged mice were group (social) housed, but not exposed to enriching objects. After the enrichment period, all mice were tested in a 1-day version of the Morris water maze, in which both spatial and nonspatial memory were assessed. Immediately after testing, the hippocampus and frontoparietal cortex were dissected, and GAD activity and synaptophysin levels were measured. Environmental enrichment reduced the age-related impairment in spatial acquisition and retention; relative to adult social controls, middle-aged enriched mice were unimpaired, whereas middle-aged social controls were impaired. This reduction was similar in middle-aged males and females. Enrichment did not affect cued memory in either sex. Although hippocampal GAD activity was increased by enrichment in males, all other neurochemical measurements were unaffected by enrichment or aging in either sex. These data suggest that environmental enrichment initiated at middle age can reduce age-related impairments in spatial memory in males and females, although the underlying neurobiological mechanisms of this effect remain unknown.

Effects of 900MHz radiofrequency on corticosterone, emotional memory and neuroinflammation in middle-aged rats

“…During this period, the onset of senescence is highly dependent on age, sex, species and strains (Frick et al, 2003;Hebda-Bauer et al, 2007). Since environmental factors and life style also play a key role in the progression of ageing, middle-aged models potentially display measurable reactivity to environmental challenges and may be a useful tool for toxicological investigations (Frick et al, 2003;Hebda-Bauer et al, 2007;Kohman et al, 2010).…”

“…Indeed, middle-aged biological systems are particularly sensitive to toxicological factors, as shown by exacerbated behavioral impairments in middle-aged animals, when compared to younger animals, in response to lipopolysaccharide administration and traumatic brain injury (Hoane et al, 2004;Kohman et al, 2010). In addition, enrichment or self food-restriction diet during middle-age may postpone the appearance of age-related memory decline and neurochemical modifications (Frick et al, 2003;Kollen et al, 2010).…”

Life-long environmental enrichment differentially affects the mnemonic response to estrogen in young, middle-aged, and aged female mice

“…Controls are group (social) or singly (isolated) housed and not exposed to enriching objects. Recent work has shown that enrichment improves hippocampal-dependent memory and enhances hippocampal morphology and plasticity in young-adult (Davis, Jones & Derrick, 2004;Duffy, Craddock & Nguyen, 2001;Kempermann, Kuhn & Gage, 1997;Rampon, Tang, Goodhouse, Shimizu, Kyin & Tsien, 2000), middle-aged (Frick, Stearns, Pan & Berger-Sweeney, 2003;Kempermann, Kuhn & Gage, 1998), and aged (Frick et al, 2002;Nakamura, Kobayashi, Ohashi & Ando, 1999;Soffié, Hahn, Terao & Eclancher, 1999;Winocur, 1998) rats and mice.…”

The influence of enriched environment on spatial memory in Swiss mice of different ages

“…While some found significant positive effects on spatial memory only in aged mice 7 , other studies also demonstrated such effects in middle-aged mice 6 . Still, some studies have reported improvement on spatial task execution by both young and young adult mice groups 8,9,10,12 .…”

“…On the other hand, those studies with significant results in relation to spatial memory, despite using similar enrichment protocols, maintained the EE for longer periods, from 2 to 21 months 9,10,12 . Some of the groups that reported significant results with an EE period and enrichment protocol similar to this study 6,7,8 evaluated middle-aged and aged mice.…”