[Influences of deviations of thyroid functions on the effects of MAOI in rats--changes of 5-HT, 5-HIAA and norepinephrine contents and tyramine uptake by the brain and fluctuation of the rectal temperature].

Influences of hyper- and hypothyroidism on MAOI (tranylcypromine) were studied by measuring the effects on rectal temperature and 5-HT, 5-HIAA and norepiniphrine levels and tyramine uptake in the brain. Hyperthyroidism was accomplished in rats injected with triiodothyronine 0.2 mg/kg i.p. every two days for 70 days (long period group) or every day for 5 days (short period group) and hypothyroidism induced by feeding rats a diet to which 0.3% propylthiouracil had been added for 70 days (long period group) or 30 days (short period group). Those controls were treated with a triiodothyronine vehicle 1.0 ml/kg i.p. and fed a normal-balanced diet for each period. All the long period groups were decapitated on the last day and the brains were used for the determination of steady levels of above-cited monoamines. The 5-HT content in hypothyroid rats was considerably higher than euthyroid rats but other determinations in both hyper- and hypothyroid rats did not differ significantly in comparison with euthyroid controls. Each short term group was treated with tranylcypromine 10 mg/kg i.p. on the last day. Tranylcypromine brought about a marked hyperthermia in hyperthyroid rats but conversely hypothermia in hypothyroid rats, while "MAOI-induced 5-HT and norepinephrine increase, 5-HIAA decrease and tyramine uptake inhibition in the brain" of hyper- and hypothyroid rats were almost to the same in degree as in euthyroid rats.