Triiodothyronine increases desipramine with changing the concentrations of monoamines, in the brain of rat given imipramine.

After treatment with triiodothyronine (T3) for 5 days, rats received a single i.p. injection of imipramine. The concentrations of imipramine and desipramine decreased and increased, respectively, in the brains of T3-treated rats, and the elimination half-time of desipramine was increased. In rats that had received imipramine for 7 days, cotreatment with T3 also resulted in reduced imipramine and elevated desipramine concentrations in the brain. Coadministration of T3 with imipramine appeared to accelerate the desipramine-induced changes in norepinephrine and 3-methoxy-4-hydroxyphenylglycol concentrations in brain. Since T3 treatment elevated the 5-hydroxyindole acetic acid concentration in the brain, the concentration in rats receiving both drugs was equivalent to that of vehicle-treated rats.