Synaptosomal action of thyroid hormone: changes in Na(+)-K(+)-ATPase activity in adult rat cerebral cortex

In view of the lack of knowledge on the thyroid hormone (T3) action in adult mammalian brain the present investigation was undertaken to assess the role of this hormone on synaptosomal function of adult rat cerebral cortex. Single injection of various doses of T3 showed dose-dependent inhibition of the synaptosomal Na(+)-K(+)-ATPase activity with its maximum effect at 24 hr in comparison to the untreated control values. The magnitude of the inhibitory response of T3 gradually diminished with the advancement of time (48 and 72 hr). Propylthiouracil (PTU) treatment caused stimulation of the synaptosomal Na(+)-K(+)-ATPase activity in comparison to the untreated control animals. T3 treatment to the PTU-treated animals showed inhibition of the Na(+)-K(+)-ATPase activity at a level very similar to that found in only T3-treated animals. The study indicates involvement of T3 in synaptosomal function of adult rat.