<正> Changes of 5-hydroxytryptamine（5-HT）and 5-hydroxyindoleacetic acid（5-HIAA）levels in brain cortex and serum were studied using spectrofluorometer follow-ing brain injury in rats.Cyproheptadine

a receptor antagonist of 5-HT

was employedand its effect on alterations of 5-HT and 5-HIAA contents in brain cortex and serum af-ter brain injury was investigated.The results showed that after brain injury levels of5-HT and 5-HIAA in the brain cortex increased markedly

The increase of 5-HT in thebrain cortex reached its peak at 48h after brain injury

and its value was 4.29±0.44μg/g

which was 4.8 times of control value.The increase of 5-HIAA in the brain cortexreached its peak at 24h after brain injury

and its value was 5.48±0.41μg/g

which was5.8times of control value.The change of 5-HT in the serum was not significant

but thelevel of 5-HIAA in the serum was increased significantly.Cyproheptadine could reducelevels of 5-HT and 5-HIAA in this experiment.The value of 5-HT in the brain cortexdecreased to 1.32±0.09μg/g

and the value of 5-HIAA decreased to 1.36±0.10μg/g.Thelevel of 5-HIAA in the serum was also reduced significantly.It was 0.27±0.03μg/ml.