Sarkar_2001_Horm.Metab.Res_33_270

Despite the recently emerging notion of thyroid-hormone involvement in neurotransmission in the adult mammalian brain, adequate evidence for a cellular basis of the process is still lacking. The present study indicates the involvement of thyroid hormones in cholinergic system of the adult rat cerebral cortex. Administration of L-triiodothyronine (T3, 0.025 to 4 microg/g) in single doses increased the synaptosomal acetylcholinesterase (AchE) and Mg2+-ATPase activity maximally at 24 hours in a dose-dependent way. Propylthiouracil (PTU)-treated hypothyroid rats showed a significant increase in AchE and Mg2+-ATPase activity compared to euthyroid rats. T3-treatment on hypothyroid rats decreased AchE activity in synaptosomes compared to the hypothyroid synaptosomal values. Mg2+-ATPase activity found in (PTU + T3)-treated group and T3-treated group remained high. These results predict that T3 stimulates acetylcholine (Ach) metabolism by increasing AchE activity as well as uptake of the released Ach through an increase in synaptosomal Mg2+-ATPase activity. This indicates a positive impact of T3 on the cholinergic system in the adult mammalian brain.