Swim-stress induced changes of rat adrenal catecholamine level depending on metabolic state and different ambient temperature

Abstract

The simultaneous influence of swim and thermal stress on catecholamine (CA) content in rat adrenal medulla was investigated histofluorimetrically in satiated and 24 h fasted rats. It was found that the increase of adrenal CA synthesis rate occurs in both fasted and satiated rats in state of hypothermia after the swimming at 20 degree C and in the hyperthermia caused by swimming at 47 degree. Similar release-induced increase of adrenal CA synthesis rate was observed after the swimming performed at 25 degree C only in fasted, but not in satiated rats. This increase was associated with the better physical condition and the less marked hypothermia in fasted animals compared to the satiated ones. The ambient temperature of 4 degree C causing the extreme hypothermia in both groups of animals failed to cause the CA synthesis acceleration, evoking the evident CA exhaustion in adrenals. The possibility of hypothermia-induced impairment of acetylcholinergic regulation of CA synthesis in adrenals--have been suggested. The different results concerning the body temperature, physical condition and the adrenal CA level obtained in fasted and satiated rats exposed to swim-stress at 25 degree C and 37 degree C have been discussed on the basis of the possible influence of metabolism rate on the adrenergic reaction to stress.