Exposure to environmental enrichment elicits differential hippocampal cell proliferation: Role of individual responsiveness to anxiety

Abstract

Environmental enrichment (EE) is a largely employed behavioral procedure in which animals are exposed to high stimulation compared with conventional housing conditions. Animal exposure to an EE exerts beneficial effects on the performance of different learning tasks and induces a number of behavioral, neurochemical, and neuroanatomical changes including hippocampal cell proliferation. However, the importance of voluntary interaction with the environment in these changes has not been clearly resolved yet. Moreover, the effects of a complex environment on animal emotionality still remains questionable and has not been explored in detail under conditions that allow unmasking individual responses among subjects in a group. The present study was aimed at exposing groups of rats to an EE, and analyzing individual differences in activity levels during EE sessions. We observed differences with respect to the activity level displayed by rats during the enriched sessions, which correlated with differences in the rate of hippocampal cell proliferation. It is suggested that exposure to EE may reduce anxiety-like behaviors and may elicit individual differences on emotional reactions positively linked with hippocampal neurogenesis and testosterone levels.

Lifelong environmental enrichment in rats: impact on emotional behavior, spatial memory vividness, and cholinergic neurons over the lifespan

“…It is possible that, contrary to aged enriched rats, aged standard rats did not discriminate open from closed arms. Our observations in young and middle-aged enriched rats are in line with previous studies showing that environmental enrichment reduced anxiety-like behavior Leal-Galicia et al 2007Pena et al 2006).…”

“…Among factors that could account for the discrepant findings, the time of the light-dark cycle at which the samples were collected may be of major relevance (Cano et al 2008). Confirming previous reports in adult rats (e.g., Bakos et al 2009;Leal-Galicia et al 2007;Schrijver et al 2002; but see Moncek et al 2004), we observed that enrichment did not influence the basal corticosterone level, whatever the age.…”

Maternal postpartum corticosterone and fluoxetine differentially affect adult male and female offspring on anxiety-like behavior, stress reactivity, and hippocampal neurogenesis

“…Doublecortin is expressed for up to 21 days after the cell divides in rats (Brown et al, 2003), and it is possible that behavioral testing altered doublecortin expression. Environmental enrichment increases doublecortin expression in adult male and female rodents (Leal-Galicia et al, 2007;Ramirez-Rodriguez et al, 2014). Interestingly, environmental enrichment increased number of early immature neurons expressing doublecortin in adult male mice selectively in the septal (dorsal) region of the hippocampus (Tanti et al, 2013).…”

Antidepressant and Proneurogenic Influence of Environmental Enrichment in Mice: Protective Effects vs Recovery

“…The details of the antidepressant and proneurogenic effects of EE have been studied in different animal and disease models (eg see Leal-Galicia et al, 2007;Navailles et al, 2008;Schaeffer et al, 2009;Segovia et al, 2006;Sztainberg et al, 2010). However, there is still much to learn about the effects of EE in previously depressed and/or stressed animals, as well as the effect of pre-exposure to the same stressor.…”