Effects of environmental stimulation during different periods of central nervous system development in malnourished rats subjected to the elevated plus maze.

Abstract

We compared the effects of environmental enrichment (EE) and tactile stimulation (handling [H]) during a critical period of development of the central nervous system (CNS) on behavior in malnourished (M; 6% protein) and control (C; 16% protein) rats in the elevated plus maze (EPM) on postnatal day 36 (P36) and P37. The stimulation occurred during two different periods of development: P8-21 (lactation period) and P22-35 (post-lactation period). The results showed higher exploration of the open arms of the EPM in the M group compared with the C group. Malnourished and stimulated rats presented lower exploration of the open arms compared with malnourished and non-stimulated rats and similar exploration of the open arms compared with control nonstimulated animals. The biochemical analysis showed that rats that were exposed to H during the post-lactation period, regardless of diet, had higher plasma corticosterone levels compared with non-stimulated rats and rats subjected to EE. Environmental enrichment during the lactation period appeared to protect animals from the effects of malnutrition on risk assessment behavior in the EPM. The type of stimulation may alter the stress response in the EPM during this critical period of CNS development.

Early-life maternal deprivation in rats increases sensitivity to the subsequent stressors: a pilot study

“…Moreover, the basal corticosterone level in plasma decreased in rats subjected to PSS after MD, paralleling the effects observed in patients with PTSD (Zoladz et al 2012(Zoladz et al , 2015Wilson et al 2014). These results are consistent with previous studies (Cruz et al 1994;de Oliveira Soares et al 2014) and suggest that, in rats, an early stress experience such as MD can aggravate some effects of exposure to a stressor during adulthood.…”

“…According to the results, MD led to only slight behavioral effects, which manifested as a general decrease in activity and impulsivity, and increased anxiety-like behavior (evaluated by the total number of entries, open arms entries and time spent in (Cruz et al 1994;de Oliveira Soares et al 2014), and the immobility time (Walf and Frye 2007). MD also resulted in decreases in unprotected SAP and grooming, which are indicative of increased approach avoidance conflict and/or risk assessment behavior (Fernández Espejo 1997;Rodgers and Dalvi 1997;Horii-Hayashi et al 2021).…”