The effects of environmental diversity on well‐fed and previously undernourished rats: I. Body and brain measurements

Abstract

Rats were undernourished from the 16th day of gestation to 25 postnatal days of age and then weaned on to an ad libitum diet. Around 35 days of age, 12 previously undernourished (PU) male pups were assigned to an "enriched environmental condition" (EC) and 12 to an "isolated environmental condition" (IC). Well-fed controls were similarly assigned. After 30 days in these conditions all rats were killed by perfusion with fixative.Body and "forebrain" weights, and forebrain lengths and widths, were determined for each animal. The forebrains were subsequently embedded in paraffin wax and serially sectioned. Ten sections, identified by subcortical landmarks, were taken from each brain and used for cortical depth measurements. The whole experiment was carried out on two separate occasions.In both the well-fed and PU groups the EC rats were between 3% and 9% lighter in body weight and between 4% and 9% heavier in "forebrain" weight than IC animals. A two-way analysis of variance (two-way ANOVA) indicated significant effects of nutrition and environment on body and forebrain weights but no significant interaction. Nutrition, but not environment, also had significant effects on "forebrain" width and length measurements.For the well-fed groups, only one section out of all those measured from the two experimental series showed a significant effect of environment on the cortical depth measurements.For the PU groups, in experiment one the cortical thickness of the EC rats was significantly greater than their IC counterparts in four out of the ten sections analyzed. In the second experiment only two sections exhibited significant results. In contrast to experiment one, these showed that the IC rats had a slightly but significantly thicker cortex than the EC rats. A twoway ANOVA of the data on cortical depths showed no significant effects of, or interaction between, nutrition and environment.These observations are discussed in the context of previously published results on the effects of a differential environment on body and brain measurements.The developing brain may be influenced by a host of nongenetic factors. Some of these may have deleterious effects; others may be beneficial. One of the most important and well-studied factors which has a harmful effect on the developing brain is undernutrition during early life. For example, undernutrition of the infant at specified periods during the '%rain growth spurt," a period when the brain is going through its rapid phase of growth (Dobbing, '68) causes a permanent deficit in brain weight and DNA con- tent (Dobbing, '74) and in the cerebellar granule-to-Purkinje cell ratios (Bedi et al., '80a). However, the deficits in the synapse-to-neuron ratio (Cragg, '72; Thomas et al., '79; Bedi et al., '80b) observed as a result of undernutrition during early life disappear in later life following a period of nutritional rehabilitation. In addition to these morphological changes, undernutrition during early life also

Response threshold to aversive stimuli in stimulated early protein-malnourished rats

“…In fact, it has been reported that environmental stimulation produces changes in structural, neurochemical and functional parameters in the central nervous system of the rat (26)(27)(28)(29). It has been suggested that these effects of early protein malnutrition may be partially reversed by environmental stimulation offered during malnutrition, or later during the nutritional recovery period (26,(30)(31)(32)(33).…”

Effects of Preweaning Environmental Stimulation on Neuronal and Behavioral Impairment Produced by Undernutrition

“…Other reports have also shown that environmental enrichment reduces ncurobehavioral abnormalities pro duced by nutritional deprivation in both hu mans [16,17] and laboratory animals [18], In addition, some experimental studies suggest that polysensorial stimulation carried out when 'brain growth spurt' is completed, i.e. after weaning, partially compensates for neocortical structural deficits produced by nutri tional deprivation [19][20][21][22][23][24], However, under the former experimental conditions, it has not been possible to demonstrate modifications at the main locus of synaptogenesis: the dendrit ic tree. Thus, as the highest rate of cytodiffer entiation is reached during the suckling peri od [25,26], the aim of the present study was to evaluate if sensorimotor stimulation ap plied during that time ameliorates both struc tural dendritic impairment and deteriorated exploratory behavior induced by undernutri tion.…”