[Effects of hyper-and hypothyroidism on central nervous system with special reference to its effects on rectal temperature and brain norepinephrine levels in rats]

Infleunce of hyper-and hypothyroidism on amphetamine activity was observed by measuring the effects on hyperthermia and brain amphetamine and norepinephrine levels. Hyperthyroidism was obtained in rats injected with tri-iodothyronine 0.2 mg/kg i.p. every day for 5 days. Controls were treated with the vehicle 1.0 ml/kg i.p. for the same period. On the 6th day, d-amphetamine (10 mg/kg i.p.) was administered to the two groups of animals and the body temperature and brain amphetamine and norepinephrine contents were measured at 0 min, 15 min, 30 min and 60 min. Hyperthyroid rats showed a more marked hyperthermia than did the control animals. On the other hand "amphetamine-induced release of norepinephrine" of hyperthyroid rats was not so marked as in the control rats, however amphetamine levels did not differ in the two groups. Hypothyroidism was evident in the thyroidectomized rats. Controls for this group underwent a sham-operation. All animals were injected with amphetamine 21 days later. Amphetamine did not cause a hyperthermia in thyroidectomized rats. On the other hand, amphetamine levels were considerably higher than in the control rats, but the degree of norepinephrine release was comparable in the two groups.