Abstract 1. 1.|Adult feral pigeons of both sexes were exposed either to 32° or 2°C for 5, 15, 30 or 60 min, respectively. 2. 2.|Acute heat or cold stress increased total 5-HT content in the diencephalon-mesencephalon region of the brain. 5-HIAA level was decreased immediately after exposure to heat. However, after PCPA treatment the increased 5-HT metabolism in heat was seen. 3. 3.|Total NA content in the same brain region was increased immediately after exposure either to cold or heat levelling out within 15min. NA and DA levels fell significantly both in heat and cold after treatment with α-MpT. 4. 4.|Both cold and heat stress increased MAO activity in the same brain region.