The mouse embryo culture technique is a valuable tool for assessing embryotoxicity of exogenous compounds as it excludes any confounding maternal and placental effects, allows for the selection of embryos that are at similar stages of development, and permits the control of exposure concentrations of exogenous agents and modifiers of interest. This chapter will use the anticonvulsant drug valproic acid as a model teratogen to describe the mouse embryo culture in detail. Briefly, mice are bred and the presence of a vaginal plug in a female mouse indicates gestational day (GD) 1. On GD 9 embryos are explanted from pregnant dams and embryos that are at similar stages of development (4–6 somite pairs) are cultured in CO2 saturated male rat serum for 24h at 37�C. After 24h embryonic morphological and developmental parameters, including anterior neuropore closure, are evaluated using a dissecting microscope. Additional biochemical analysis, including molecular approaches to assess embryonic signal transduction, as well as some limitations of the technique will also be discussed.
