The project in general is aimed at investigating the molecular events underlying the mental dysfunction associated with hypothyroidism during early life and the regulatory role of thyroid hormones in the functional maturation of the brain. Specific studies are designed to localize and characterize the regional and subcellular recognition sites for thyroid hormones in the rat brain during development. By this approach it is hoped to provide some insight into the characteristic age-dependent sensitivity of the brain to thyroid hormones and the potential therapeutic effects of the hormones on nerve regeneration.