Effect of neonatal thyroidectomy on nucleic acids and protein contents of the developing rat brain.

(1) Thyroidectomy at birth caused a temporal reduction of the DNA content only in the cerebellum during the periods from 7 to 21 days after birth, but not in the cerebrum and brain stem. (2) The ratio of RNA to DNA in cerebrum from the thyroidectomized rats was underwent a marked decrease from 14 to 56 days as compared with those of the normal controls. On the other hand, the effect of thyroid deficiency on the ratios of cerebellum and brain stem as a whole was very small. (3) The ratios of protein to DNA generally declined in the three brain regions during the periods from 14 to 56 days as a result of throid deprivation.