Growth patterns and complex maze performance:as a function of exposure to a protein- and tryptophan-deficient diet.

Abstract

Numerous correlational studies have reported that malnutrition experienced by humans during early development results in retarded physical growth and reduced mental functioning (Montagu, 1962; Kaplan, 1972; Winick, 1976; Dent & Caster, 1971; Cabak & Najdanvic, 1965; Cravioto & Robles, 1965) In response to the ethical restrictions on empirical evaluation of deficient diets upon humans, animal models of malnutrition have been developed. Several such studies have focused specifically upon protein-and tryptophan-restriction (Fernstrom & Hirsch, 1977; Segall & Timiras, 1976; Remley, Armstrong, Gilman, & Mercer, 1980). Diets most commonly employed in these studies utilized casein or corn as the main source of protein. Such diets have consistently produced animals with retarded brain weights (Forbes, Tracy, Resnick & Morgane, 1977) and body weights (e.g., Segall & Timiras, 1976; Remley et al. 1980). However, a complete picture of the growth curve for these tryptophan deprived animals does not exist. Effects of protein-and tryptophan-deficient diets upon learning ability in animals have been less conclusive, with deprived animals performing as well as or better than control animals on some tasks, and performing more poorly on others (Zimmerman, Geist, & Strobel, 1975; Remley et al. 1980; Cowley & Griesel, 1959; Caldwell & Churchill, 1967). In the present two studies a protein-and tryptophan-deficient corn grits diet was used to establish a more complete picture of growth and learning effects. Experiment 1 concluded that animals raised on the deficient diet from birth to 75 days of age were significantly lighter than animals exposed to this diet from weaning until 75 days of age. Both groups were significantly lighter than animals raised on a normal diet. Administering a normal diet to the grits-exposed animals resulted in weight gain. Experiment 2 concluded that differences in complex maze performance between grits-fed and normal animals existed for number and type of errors made, with grits-fed animals making fewer and less repetitive errors.