Effects of chlorpyrifos administered on GD9-12 (A,B), GD17-20 (C,D), PN1-4 (E,F) or PN11-14 (G,H), assessed in liver (A,C,E,G) and heart (B,D,F,H). Data represent means and standard errors obtained from 12–24 animals in each treatment group at each age; results from males and females were combined because of the absence of treatment × sex interactions. ANOVA appears at the top of each panel and asterisks denote individual treatment groups that differ significantly from the corresponding control group.