Effects of genetic and nutritional factors on post-natal reflex and behavioral development in the mouse

The development of a number of reflex activities, of the electrocorticogram (ECoG), and measures of brain and body weight were assessed at different ages from birth to maturity in mice belonging to Swiss-Webster stock and two inbred strains (C57BL/6J and SEC/1Re). The animals also were tested at 60 days of age for exploratory activity and avoidance behavior. These effects of postnatal undernutrition on the measures of reflex and ECoG activity, brain and body weight and avoidance learning were determined at different ages after birth and in adult animals following dietary rehabilitation. Undernutrition during suckling period was introduced by increasing the litter size from 4 pups to 8 or 16 pups per litter. The results indicate that early malnutrition delayed the development of the reflex and ECoG activities and permanently altered brain growth and avoidance learning. The effects were different, depending on the genotype considered. The data indicate that strains characterized by a slower development of brain function do not show early signs of brain malfunction following undernutrition.