Effects of neonatal undernutrition and cold stress on behavior and biochemical brain parameters in rats

This study was conducted to investigate the separate and combined effects of neonatal undernutrition (U) and cold stress (S) on the behavioral and cerebral development of postweaning rats. A severe U was imposed by feeding dams a low protein diet. Postweaning all pups were fed a control diet. S consisted of daily exposure to 5 degrees for 3 minutes from day 2 to 11. Behavioral data show that U animals, stressed (S) + nonstressed (NS), exhibited a significant deficit in reversal learning of T-maze at 21 days, an enhanced passive avoidance response, but no difference in active-avoidance at 35 days when compared to controls of the same age. S had no effect on behavior development. At death (110 days), the brains were dissected into five sections and assay for acetylcholinesterase (AChE) and cholinesterase (ChE) activities. Brain weights of U animals (NS + S) were significantly lower in all sections except dorsal cortex (DC). AChE and ChE activities were significantly higher in all sections (except DC) of U animals relative to controls. S resulted in lower cerebellar weight and ChE:AChE ratios in some sections. Our results suggest a delayed behavioral maturation in U animals and an association between early postweaning behavior and brain parameters in adult rehabilitated animals.