Environmental enrichment during adolescence reverses the effects of prenatal stress on play behaviour and HPA axis reactivity in rats

Abstract

Prenatal stress (PS) can produce profound and long-lasting perturbations of individual adaptive capacities, which in turn can result in an increased proneness to behavioural disorders. Indeed, in PS rats there is evidence of impaired social play behaviour, disturbances in a variety of circadian rhythms, enhanced anxiety and increased hypothalamic-pituitary-adrenal (HPA) axis reactivity. This study was designed to experimentally investigate the degree of reversibility of PS-induced disturbances of social play and HPA reactivity by assessing the effect of the enrichment of the physical environment on PS rats during periadolescence. PS subjects showed a reduced expression of social play behaviour and a prolonged corticosterone secretion in response to restraint stress, but both these effects were markedly reversed following environmental enrichment. Interestingly, the enrichment procedure increased social behaviour but had no effect on corticosterone secretion in nonstressed animals, indicating a differential impact of the postnatal environment as a function of prenatal background. As a whole, results clearly indicate that rats prenatally exposed to stress can benefit during periadolescence from the modulatory effects of an enriched environment. Moreover, they confirm that PS may well represent a suitable animal model for the design and testing of new therapeutic strategies for behavioural disorders produced by early insults.

The anxiolytic effect of environmental enrichment is mediated via amygdalar CRF receptor type 1

“…32,39 However, the majority of the studies concur that EE attenuates the hypothalamic-pituitary-adrenal response to acute stress 32,36 and is able to reverse the effect of past stressors on the hypothalamic-pituitary-adrenal reactivity. 37,38 In our study, EE decreased the basal and the stress-induced plasma corticosterone levels. However, although plasma corticosterone levels of SC mice returned to basal levels 90 min after stress initiation, the EE mice plasma corticosterone remained significantly elevated.…”

“…To date, no consensus on the effect of EE on resting plasma corticosterone levels is available. Although some studies have reported that EE decreased basal corticosterone levels, 35 others have reported no difference [36][37][38] or an increase in basal corticosterone levels. 32,39 However, the majority of the studies concur that EE attenuates the hypothalamic-pituitary-adrenal response to acute stress 32,36 and is able to reverse the effect of past stressors on the hypothalamic-pituitary-adrenal reactivity.…”

Environmental Enrichment Reverses Behavioral Alterations in Rats Prenatally Exposed to Valproic Acid: Issues for a Therapeutic Approach in Autism

“…Unfortunately, the effects exerted by environmental enrichment on social behaviors in animals have been poorly documented. To our knowledge, there are only two studies that have so far evaluated this issue and their results are inconsistent (Renner and Rosenzweig, 1986;Morley-Fletcher et al, 2003). In elucidating the attenuating effects of environmental enrichment in VPA rats, the known effects of enrichment on neurogenesis (Kemperman et al, 1997;Nilsson et al, 1999), neurotrophin gene expression (Torasdotter et al, 1996(Torasdotter et al, , 1998Young et al, 1999;Olsson et al, 1994;Ickes et al, 2000), and anatomical features (Diamond et al, 1964;Diamond, 1967;Rampon et al, 2000;Floeter and Greenough, 1979) should also be taken into account.…”

“…This pioneering observation generated a large number of studies, which have shown significant differences in animals' behavior associated with enriched living conditions. Environmental enrichment in rats leads to better performance in various learning tasks (eg Greenough et al, 1972;Mohammed et al, 1990;Nilsson et al, 1999;Rampon et al, 2000), enhanced social play behavior (Morley-Fletcher et al, 2003), increased exploration, lower anxiety, and ameliorated plasma corticosterone response to stress (Levine, 1962(Levine, , 1967. Experiments have shown that improvements in behavioral performances were accompanied with changes in various neurochemical and anatomical features in rat brains.…”

Non-genetic Inheritance of Behaviour and Stress Resilience

“…Importantly, enriched environment (EE) and cross fostering both are able to offset prenatal stress effects and normalize HPA axis function and affective states [82,97,98]. Notably, interactions by multiple treatments may cancel or enhance each other's benefit [99][100][101].…”