Effects of Early Concurrent Protein Malnutrition and Environmental Stimulation on the Central Nervous System and Behavior

Abstract

A complex program of environmental and sensory stimulation was developed to study its potential effects in reversing some of the alterations produced by early protein malnutrition in the brain and behavior of rats. Litters (dam plus 6 male pups) were fed diets containing 8% (malnourished) or 25% (well-nourished) casein. After weaning, the animals were maintained on the same diets as their respective dams until 50 days of age. Environmental stimulation consisted of 3-min daily handling from birth to 50 days of age. Additional stimulation was provided from birth to 50 days of age by rearing the rats in an enriched living cage and exposing the animals to visual, auditory and olfactory stimuli. At 50 days of age the animals were submitted to locomotor and inhibitory avoidance tests. Animals of the same age were sacrificed, the brain removed and divided in telencephalon, brain steam and cerebellum. DNA and RNA were assessed in telencephalon and cerebellum. Protein malnutrition produced brain weight deficits that were partially reversed by environmental stimulation. DNA and RNA levels were reduced by protein malnutrition and increased by environmental stimulation. The behavioral measures showed lower locomotor activity and higher latencies in inhibitory avoidance for malnourished animals as compared to well-nourished animals. Environmental stimulation reduced the aversiveness in the inhibitory avoidance test as showed by lower latencies in the stimulated group of animals. These results suggest that early protein malnutrition impairs brain and behavior of rats and that a complex program of environmental stimulation is beneficial to reverse some of those impairments.