Figure 5. Thyromimetic actions of TA3 in the developing mouse brain.

Pax8-KO mice and WT littermates were injected daily with TA3 (200 ng/g BW) starting at P1 and analyzed at P12. Control animals received saline injections. A, PCs in sagittal cerebellar sections through the vermis region were visualized by calbindin immunostaining, and the thickness of the molecular layer (ML) that comprises PC dendrites was determined on 3 consecutive sections of each animal (males; n = 4 per genotype). Whereas in saline-treated Pax8-KO mice, PCs showed a strongly reduced dendritic outgrowth and therefore a thinner ML, TA3 treatment of Pax8-KO mice restored normal PC outgrowth and consequently ML thickness. B, Coronal forebrain sections of the same animals were immunostained with an antibody against MBP and revealed a significantly reduced immunoreactivity in the cerebral cortex of saline-treated Pax8-KO mice. In contrast, TA3 treatment of Pax8-KO mice resulted in normal MBP expression. Scale bar, 50 μm. **, P < .01; ***, P < .001. Abbreviation: AU, arbitrary unit.