Validation of a developmental swimming test using Swiss Webster mice perinatally treated with methimazole

The swimming method of Klaus and Hacker, developed for the AB/Jena and DBA2/Jena mouse strains, was evaluated for use with pre-weaned Swiss Webster (SW) mice. All SW mice completed the swimming pattern by postnatal day (PND) 16, but did not conform to all criteria depicted for each stage of the methodology. These swimming differences among strains required modification of the above method for the SW mouse. An expanded and revised swimming methodology included evaluation of limb movement and placement; body position; head position, including nostril and ear positions; and direction of movement. The revised methodology was validated on PND 4 through 20 with offspring of methimazole-treated or untreated SW dams. Methimazole, an antithyroid agent, was administered in drinking water (0.1 mg/ml; day 16 of pregnancy through day 10 postpartum). Untreated dams received tap water. Methimazole pups exhibited significant delays in swimming development on PND 9 through 16. This revised swimming methodology provides another preweaning test for the detection of behavioral teratogens for SW and probably other strains of mice.