Vulnerability of Developing Brain: Relative Effects of Growth Restriction during the Fetal and Suckling Periods on Behavior and Brain Composition of Adult Rats

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Abstract
Growth restriction was achieved by underfeeding mother rats during pregnancy and lactation. Offspring were either (i) adequately nourished during the fetal and suckling periods, (ii) undernourished during both, or (iii) and (iv) undernourished during one or the other period. All rats were fed ad libitum from weaning. The postnatally underfed animals were the most efficient at running a maze for a food reward. Differences in levels of motivation were sought using a Skinner box in which rats learned to press a lever for food. Normal rats had the lowest lever-pressing rate and those restricted both pre- and postnatally had the highest. The tendency to inhibit movement to avoid an electric shock was weakest in normal rats and greatest in the doubly deprived animals. As in the Skinner box test, rats undernourished during only one period occupied intermediate positions. This is taken to indicate that, with respect to these two measures of behavior, the effects of undernutrition in the fetal and suckling periods were additive. Evidence for an additive effect on physical brain growth is confined to fore-brain DNA-P content, which was substantially reduced by both periods of growth retardation. Cerebellum DNA-P and weights of cerebellum and forebrain were all much more affected by the postnatal treatment.