Abstract: Repeated exposure to acute hypoxia was performed on pentobarbital-anesthetized and coffeine-excited mice. The average tolerance time for first run in these two groups was 42 and 9 min, which was significantly longer and shorter than that of control group(13 min)respectively.The tolerance time of second, third and forth run in anesthetized and excited mice was 1.6 , 1.8 and 2 times longer than that of their own first run respectively. However, The results of both groups were all significantly shorter than that of control group which were 3, 5 and 7 times.These results indicate that the animal's anaesthesic and excited states may increase and decrease tolerance of the animals to first run of hypoxia respectively. However,the tolerance or adaptation to subsequent repeated hypoxia is markedly decreased in both groups.

Key words: tolerance to acute repeated hypoxia, sodium pentobarbital, coffeine, mice