Endogenous level and turnover of brain norepinephrine (NE), epinephrine (E), dopamine (DA), and serotonin (5-HT) in male Japanese quail were determined after acute (6 h) and chronic (5 wk) exposure to thermal (34 degrees C) and cyclic temperature (10--34 degrees C) stress. alpha-Methyl-p-tyrosine (alpha-MT) and p-chlorophenylalanine (PCPA) were used to study the turnover of the monoamine levels. The differences between the monoamine levels of drug-treated birds and control (22 degrees C) birds were regarded as changes in turnover. High ambient temperature (34 degrees C) stress for 6 h increased brain NE turnover. However, chronic exposure (5 wk) to 34 degrees C, and to cyclic temperatures (10--34 degrees C), did not increase turnover of brain NE. Also, acute and chronic heat exposures did not significantly change E turnover. High acute temperature stress had no effect on brain DA turnover, although chronic exposure of birds to 34 and 10--34 degrees C resulted in a retarded turnover. The central 5-HT turnovers increased when birds were subjected to acute 34 degrees C stress. Five weeks of exposure to 34 and 10--34 degrees C caused declines in 5-HT turnovers. Thus, the results indicate that NE and 5-HT turnovers increase during acute thermal exposure, but acclimation to thermal stress for 5 wk reduces the turnover of brain NE, 5-HT, and DA.