CARBAMAZEPINE AFFECTS TRIIODOTHYRONINE PRODUCTION AND METABOLIZATION IN RAT HIPPOCAMPUS

The effects of subchronic administration of carbamazepine on thyroid h ormone metabolism were investigated in the hippocampus in adult male r ats at two different measuring times (4 a.m. and 8 p.m.). Carbamazepin e enhanced the activity of 5'II-deiodinase, which catalyzes the deiodi nation of the prohormone T4 to the active compound T-3, at 8 p.m., but not at 4 a.m. The activity of 5III-deiodinase, which catalyzes the fu rther deiodination of the active hormone T-3 to its metabolite 3,3'T-2 , was inhibited at 4 a.m. but not at 8 p.m. These effects of carbamaze pine on intracellular thyroid hormone metabolism in the hippocampus sh ould theoretically lead to a rise in T-3 production. It remains to be investigated whether they are somehow involved in the as yet unknown m echanisms underlying the anticonvulsant/mood-stabilizing effects of ca rbamazepine.