Brain indole and catecholamines of turkeys during exposure to temperature stress

Turnovers of dopamine (DA), norepinephrine (NE), epinephrine (E), and 5-hydroxytryptamine (5-HT) were determined in the brains of male turkeys during acute, chronic, and posttemperature stress. Changes induced in the depletion of endogenous monoamine levels 6 h after tyrosine hydroxylase or tryptophan hydroxylase inhibitions were regarded as changes in turnovers. High or low ambient temperature had no effect on brain DA turnover, whether the temperature stress was acute (6 h) or chronic (5 wk). Brain NE turnover increased upon acute exposure to either a cold (5 degrees C) or warm (32 degrees C) environment. Chronic exposure (5 wk) to such temperatures reduced significantly (P less than 0.001) the elevated NE turnover. The central E and 5-HT turnovers of birds kept at 32 degrees C for 6 h decreased and increased, respectively, whereas determination of E and 5-HT of birds kept at 5 degrees C showed an opposite pattern. Five weeks of continuous exposure to high and low environmental temperatures did not alter the changes in E and 5-HT turnovers from those observed during acute stress. Exposure of heat- or cold-reared turkeys to 24 degrees C reversed the changes in E and 5-HT turnovers. Thus the results indicated an increase in NE turnover only during acute exposure to thermal stress. However, the changes in E and 5-HT turnovers persisted during chronic exposure.