Multigenerational exposure to dietary genistein has no severe effects on nursing behavior in rats

The phytoestrogen and principal isoflavone in soy, genistein, has adverse e ffects on reproductive physiology in rodents. Since physiology and behavior are both sensitive to perturbations by estrogens, genistein may produce be havioral alterations as well. This paper reports one aspect of a study in w h ich several adult rodent behaviors will be assessed following long term m ultigenerational dietary exposure to genistein. Since maternal care may aff ect offspring behaviors in adulthood, it is important to determine the pote ntial for genistein to affect maternal behavior. Here, rats (FU generation) were fed soy-free diets containing 0, 5, 100, or 500 ppm genistein (approx . 0, 0.4, 8, and 40 mg/kg/day for an adult) beginning on postnatal day (PND ) 42. Two generations of offspring (F1 and F2) were continued on these diet s and all treatment groups of the F3 generation were returned to 0 ppm at w eaning (PND 22). In the first 3 weeks after parturition (for each generatio n), darns were assessed on 6 occasions for the presence of the arched back posture with at least one pup nursing. Data were analyzed by 3 way repeated measures analysis of variance (ANOVA) with generation, treatment, and post natal day as factors, and p<0.05 required for significance There were no si gnificant interactions among treatment, generation, or day, and no overall effects of treatment or generation. As expected, there was a significant ov erall effect of day, with animals nursing less on later days (p<0.0001). As assessed here, these results suggest that lifelong and multigenerational e xposure to dietary genistein has no severe effects on nursing behavior in r odents. (C) 2000 Inter Press Inc.