[Iodine-containing thyroid hormones increases the motor activity of rats under stress]

It is established that alarm-stage of stress reaction (1 hour after the swimming of rats in a cage within 1 hour) is characterized by a decrease of total vertical motor activity (MA) and by the chan- ge of behavior structure--disappearance of racks without support on the board of "open field" and a central horizontal part of MA as well as an increase in physical endurance of rats; stage of resistan- ce (48 hours after the stress)--the restoration of motor reactions of animals, and stage of exhaustion (1 hour within 10 days of stress)--its oppression. Introduction of merkazolil (25 mg/kg, 20 da- ys) causes a fall of level of iodine-containing thyroid hormones (ITH) in the blood and causes a significant reduction of all types of MA and change of the structure of behavior in the alarm-stage, practically eliminating its normalization in stage of resistance and provokes its greatest violation in a stage of exhaustion of stress reaction. Introduction of L-thyroxine (1.5-3.0 μg/kg 28 days) does not change the ITH concentration in the blood, increases MA of rats, and provides its higher level and maintaining of the structure of behavior in all stages of stress reaction.