Influences of early thyroid hormone manipulations: delays in pup motor and exploratory behavior are evident in adult operant performance.

The effects of thyroid hormone depletion and enhancement on litter size, survival, body mass, ambulation, quadrant crossing, home orientation, day of eye opening, and free serum T3 and T4 levels were examined in Study 1. In Study 2, the effects of the timing of prenatal insult and the level of thyroid hormone depletion on litter size, survival, body mass, and free serum T3 and T4 levels were examined. Upon the completion of Study 1, randomly selected pups were maintained on ad-libitum water and food for 2 years, and performance was evaluated on fixed and variable ratio schedules, fixed and variable interval schedules, and probability and reversal learning tasks (Study 3).