Environmental enrichment improves hippocampal function in aged rats by enhancing learning and memory, LTP, and mGluR5-Homer1c activity

Abstract

Previous studies from our laboratory have shown that environmental enrichment (EE) in young rats results in improved learning ability and enhanced metabotropic glutamate receptor-dependent long-term potentiation (mGluR-dependent LTP) resulting from sustained activation of p70S6 kinase. Here, we investigated whether 1-month EE is sufficient to improve hippocampus-dependent learning and memory and enhance hippocampal LTP in 23-24 month-old Fischer 344 male rats. Aged rats were housed in environmentally enriched, socially enriched, or standard housing conditions. We find that aged rats exposed to 1-month of EE demonstrate enhanced learning and memory relative to standard housed controls when tested in the Morris water maze and novel object recognition behavioral tasks. Furthermore, we find that environmentally enriched rats perform significantly better than socially enriched or standard housed rats in the radial-arm water maze and display enhanced mGluR5-dependent hippocampal LTP. Enhanced hippocampal function results from activity-dependent increases in the levels of mGluR5, Homer1c, and phospho-p70S6 kinase. These findings demonstrate that a short exposure of EE to aged rats can have significant effects on hippocampal function.

Environmental Enrichment Rescues Visually-Mediated Behavior in Ten-m3 Knockout Mice During an Early Critical Period

“…A beneficial effect of EE on hippocampal function could, therefore, have contributed to the behavioral recovery in Ten-m3 KOs. The early, narrow time window of sensitivity to EE seen here does not fit well with hippocampal changes being the primary driver, however, as there is strong evidence that exposure to EE from weaning (Bernstein, 1973;Kempermann et al, 1997;van Praag et al, 2000) and even into old age (Speisman et al, 2013;Neidl et al, 2016;Cortese et al, 2018) can have a beneficial impact on spatially-dependent hippocampal function.…”

Social enrichment reverses the isolation-induced deficits of neuronal plasticity in the hippocampus of male rats

“…In fact, environmental enrichment may promote adult hippocampal neurogenesis (Kempermann et al, 1997), the integration of new-born cells into functional circuits (Tanti et al, 2013) and, in general, more neuronal plasticity. Moreover, several reports highlight the importance of such kinds of enrichment especially when applied early in life, towards improving cognitive ability in a similar manner to that observed when animals were enriched environmentally during the lifespan (Cortese et al, 2018;Fuchs et al, 2016;Harati et al, 2011).…”

Synaptic Plasticity Shapes Brain Connectivity: Implications for Network Topology

“…Accordingly, higher levels of education, cognitive abilities, occupation and physical activity have been correlated with reduced functional impact of brain structural damage as demonstrated in healthy aging subjects and in neurological patients [103][104][105][106][107]. In preclinical studies, environmental enrichment with physical, cognitive, and social stimuli improved the performance in different behavioral tasks exploring memory and learning [108] and enhanced LTP induction [109][110][111][112][113].…”