The Effect of Diet Manipulation on Learning, Memory and Anxiety

Abstract

The focus of this research was on the effects of both autoclaving lab feed and soy content in lab feed. Autoclaving sterilizes and cleans equipment through heat and steam. However, autoclaving animal feed can not only affect key nutrients, but also increase the “hardness” of food pellets and produce toxic and carcinogenic products. An additional dietary factor that is often overlooked is soy (phytoestrogen) content. Evidence has found that phytoestrogens have anxiolytic effects in both males and females when assessed in an elevated plus maze (Lephart et al., 2002) and open-field testing (McCarthy et al., 1997). Therefore, it is important to consider both autoclaving and soy content in animal feed when conducting behavioral neuroscience research. Ninety-five C57BL/6J male and female mice were assigned to one of four diet groups prenatally: (1) a non-autoclaved standardized Teklad 7012 (containing soy); (2) an autoclaved standardized Teklad 7012; (3) soy-free Teklad 2020SX; and (4) low-soy Teklad 2018SX. Neither the soy-free nor the low-soy diets were autoclaved. At 4 months of age, the mice were examined on behavioral tests including: Morris water maze (MWM), fear conditioning (FC), nesting, elevated zero maze (EZM), open field (OF), and grooming. Collapsed across sex, there were no significant differences in MWM, EZM, and OF between dietary groups. However, animals on Teklad 7012 and autoclaved Teklad 7012 extinguished the learned tone/shock pairing in FC significantly slower than animals on low-soy and soy-free diets. Animals on the standard Teklad 7012 diet created significantly better nests than the animals on any other diet. Additionally, animals on standard Teklad 7012 diet groomed less than the animals on low-soy and soy-free, but more than the animals on the autoclaved Teklad 7012. These data show that the dietary effects including autoclaving feed and amount of soy in diet have a significant effect on behavior and are therefore an important factor for behavioral researchers to consider.