Different methods for producing neonatal undernutrition in rats cause different brain changes in the face of equivalent somatic growth parameters.

Similar degrees of undernutrition were induced in neonatal rat pups using a modified Slob technique and a large-litter manipulation. From birth, large litters and Slob litters were comprised of 20 and 10 pups, respectively. On days 2, 4 and 6, half of the pups in the Slob group were cross-fostered to nonlactating foster aunts, while the remaining half of each litter (controls), as well as the large-litter rats were cross-fostered to a lactating dam. On day 10, undernourished Slob and large-litter pups showed similar body weight and body length deficits compared with controls, but differences between the two undernourished groups emerged when regional brain weight and nucleic acids and proteins were examined. The acute intermittent undernutrition of the modified Slob technique had more severe consequences than the large-litter manipulation for brain growth and development. Therefore, two methods of inducing early postnatal undernutrition may yield equivalent somatic effects, but very different brain growth parameters.