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.