Interactive effects of genotype and early life undernutrition on the development of behavior in rats

Developing rats of 2 outbred stocks were either well-nourished or undernourished by underfeeding their mothers throughout pregnancy and lactation. All rats were well-fed from 25 days of age. Starting at 110 days male rats were observed first in an open field and then in a social situation; finally their motor performance was tested on a revolving drum. The social behavior test comprised pairing male rats of the same stock, 1 well-fed control with 1 previously undernourished rat. Analysis of variance of the results of the open-field and social behavior tests revealed main effects of Nutrition and of Stock for several measures of behavior in each test. There were also Nutrition X Stock interactions for 2 measures from the open field and 1 from the social situation. Motor performance was not impaired by early life undernutrition. The evidence of Nutrition X Stock interactions, together with that from analyses of the effects of nutrition performed separately for the 2 stocks, as if each stock had been investigated in a separate study, indicates that genotypic differences may be one of the reasons for the discordance often found between the conclusions of different early life malnutrition studies.